Design I - Key Concepts

In the construction process, there are three traditional principal roles: owner (primary role), design professional (secondary role), & contractor (secondary role). Each of these roles can include one or more individuals or organizations.

• -Supplying the project concept and requirements
• -Acquiring the land
• -Obtaining municipal approvals
• -Providng and arranging financing
• -Contracting the architect and/or engineer
• -Awarding contracts in connection with the work
• -Furnishing property surveys
• -Providing certain insurance
• -Making periodic payments
• -Securing and paying for necessary easements

The most vital contribution of the owner is financial resources, including the ability to obtain funding for the project.

• -Representing the owner
• -Advising and consulting with the owner
• -Coordinating, communicating, and working with other disciplines
• -Generating a complete set of drawings and specifications
• -Coordinating all drawings and specifications. A cross-sectional diagram that shows all building systems to scale is encouraged during the facility design and is required in mechanical rooms, chases, and areas where building systems intersect.
• -Participating in the bid process and conractor selection.
• -Verifying that the workmanship and the materials conform to the requirements of the drawings and specifications.
• -Inspecting the project periodically
• -Preparing punch lists

• -Giving personal attention to the work
• -Complying with laws and ordinances concerning job safety, licensing, employment of labor, sanitation, insurance, traffic and pedestrian control, and other aspects of the work
• -Following the drawings and specifications
• -Taking responsibility for all materials and workmanship
• -Supervising all subcontractors
• -Alerting the building owner of discrepancies in the design
• -Putting together a bid
• -Acquiring performance and payment bonds
• -Following the contract

In speculative development, a building is built without a commitment from a user, but with the belief that a demand exists for the space and that the space will be rented within a reasonable time after the building is completed. Speculative development with little or no preleasing of the space was common in major metropolitan areas from World War II until the early 1980's.

This caused overbuilding in many markets through the 1970's and 1980's, forcing developers in the 1990's to sign major users for speculative buildings, because lenders would not agree to finance the projects without committed users. Preleasing reduces the risk of speculative development.

Build-to-suit development is the design and construction of a building to meet the specific needs of a user who is committed to the project. The user can be a business that will own and occupy the building (owner-occupied). Or, the user can be a tenant who signs a long-term lease - usually 20 years with an option to renew - for all or a major portion of the building. Many build-to-suit buildings are single-purpose structures, like a research laboratory or a computer operations center.

Renovation involves the basic ingredients of new construction and can include rehabilitation, modernization, and remodeling.

All new construction must comply with the standards established in the ADA (unless it is structurally impracticable to do so). Alteratiosn to buildigns must also comply with the ADA (to the maximum extend feasibile). As of July 1, 1994, existing public accommodations - as defined in the ADA and which include most multitenant commercial buildings - must remove architectural barriers to the extent removal is readily achievable (as defined in the ADA).

In addition, alterations to a primary function area in a public accommodatino or a commercial facility must remove barriers from the path of travel to that primary function area.

Space utilization standards identify the space needed for each job title, function, or level within an organization. New approaches to integrating people and technology into the workplace should be made part of the space utilization standards.

Building codes are regulations that promote general safety by regulating the design and construction of the building's components. In the United States and Canada, each municipality establishes its own building code, usually by adopting a model building code and adding amendments to accommodate local conditions.

1. Performance: state what the final outcome of the project should be. These standards leave the method used to achieve that outcome up to the contractor.

2. Prescriptive: tell the contractor exactly what to do and how to do it.

A punch list is a list of deficiencies in construction compiled by the project manager or the architect near the end of a job. The list should record all incomplete, missing, or substandard items, and the action to be taken by the contractor to correct each problem.

As-built drawings are an accurate record of the placement of construction components and the routing of other components such as cables,, pipes, and ducts that indicate how a buildign was actually built, ratehr than how it was designed to be built. As-built drawings are submitted by each trade (e.g. mechanical, electrical). They document a building's systems and components, as observed and documented in the field.

Site coverage is the percentage of the lot that can be covered by the structure. Some urban sites permit 100 percent site coverage; but most jurisdictions require the structure to be set back from property lines and a percentage of open space.

Floor area ratio (FAR) is the ratio of the total floor area of all buildings on the lot to the area of the lot. This ratio varies by local code. IN urban areas, the FAR is greater than 1.00. An FAR of 10.00 permits 255,000 SF of floor area on a 25,500 SF lot. In suburban areas, FAR is less than 1.00. A FAR of 0.40 permits 32,000 SF of floor area on a 80,000 SF lot.

An agreement that confers on an individual, company, or municipality the right to use a landowner's property in some way is an easement or right-of-way. An easement grants the rights and partially restricts an owner's use of those portions of land affected by the easement. Public and private right-of-way is the fraction of the gross land allocated for vehicular circulation through public and private right-of-way dedication and/or paved easements.

A market supply and demand study begins with a listing of existing buildings and available space. For leased space, this listing includes occupancy percentages, rental rates, typical lease terms, and descriptions of the buildings. The market study continues with a review of the demand for space as indicated by space vacancy, space absorption, adn rental rate statistics and trends. These market study data indicate the marketability of the proposed project, the rental rate the market will pay, and the time it will take to achieve full occupancy.

Life Cycle Costing (LCC) is a process used to determine the sum of all costs associated with an asset, including acquisition, installatino, operation, maintenance, refurbishment, and disposal costs. LCC is pivotal to the asset management process.

A cost-benefit analysis is the calculation of payback to determine the desirability of investing in an item that will produce savings. Cost-benefit is used more frequently than LCC. This technique can help you determine how long it will take for the savings of installing a more energy efficient device would take to pay back the added cost.

• 1. Design-Bid-Build
• 2. Design-Build
• 3. CMAR (Construction Management At-Risk)
• 4. Multiple Prime Contract

Under this traditional method, an architectural firm is hired and serves as the owner's agent. Although the firm may have numerous responsibilities, including the selection of consultants, its primary responsibility is to provide and manage the design and construction documents for the project. As the design progresses, the architectural firm and external cost estimators periodically prepare cost estimates. Once the construction documents and specifications are completely finished, and other requirements of the owner have been met, the project is bid and subsequently awarded to the general contractor with the lowest responsible bid.

Some architectural firms have an in-house team that may include engineers, interior designers, planners, and landscape architects. If not, the architect hires independent architects and engineers to provide the specialized design services needed to complete the design phase. The architect advises the owner when determining the owner's space and building needs, administers the contract, and monitors the progress of construction.

The decision about which of the four project delivery methods is appropriate depends on the nature of the project (size, diversity, cost), the capabilities of the owner, and what best serves the owner's objectives.

Large, complex building types or difficult sites require the multiple prime contracts approach to effectively coordinate the interrelated phases.

When the project has constraints that will affect cost, schedule, and resources, or the project requires collaboration between the design an construction, they will use the design-build approach.

• 1. Cost Plus Contract
• 2. GMP-CM (Guaranteed Maximum Price-Construction Management)
• 3. Lump Sum Contract
• 4. Fixed Price

A cost plus contract is usually between an owner and contractor, design professional, or construction manager. Under this contract, the contractor - design professional or construction manager - is reimbursed for his or her direct and indirect costs and is paid a fee for his or her services. The fee is usually stated as a stipulated sum or as a percentage of the cost.

• 1. Provides maximum flexibility to owner
• 2. Minimizes contractor profits
• 3. Minimizes negotiations and preliminary specifications costs
• 4. Permits choice of best-qualified not lowest-bidding contractor
• 5. Usually permits use of same contractor from consultation to completion
• 6. Increases quality and efficiency.

• 1. No assurance of final cost.
• 2. No final incentive to minimize time and cost
• 3. Permits specification of high-cost features by owner's staff
• 4. Permits excessive design changes by owner's staff, increasing time and cost

A fixed price contract has a set contract amount for all labor, materials, equipment, and services and contractor's overhead and profit for all work being performed for a specific project. A fixed price contract includes fixed prices for services, material, labor, and local costs reimbursable.

• 1. Bid bond
• 2. Payment bond
• 3. Performance bond
• 4. Ancillary bond

A bid bond is a written form of security executed by the bidder as principal and a surety. The bond guarantees that the bidder will sign the contract if awarded the contract for the stated bid amount. The surety is a third party that makes a pledge to pay liquidated damages to the owner if the bonded contractor declines an award offered by the owner. The damages are the difference between the bonded contractor bid and the next highest bidder but do not exceed the face value of the bond.

A payment bond protects certain laborers, material suppliers, and subcontractors against nonpayment. Since a mechanic's lien cannot be placed against public property, the payment bond may be the only protection these claimants have if they are not paid for the goods and services they provide to the project.

A performance bond is a written form of security form a surety (bonding) company to the owner on behalf of a acceptable prime or main contractor or subcontractor. This bond guarantees payment to the owner of the face value performance bond if the contractor fails to perform all labor, materials, equipment, or services in accordance with the contract. The surety companies generally reserve the right to have the original prime or main or subcontract remedy the claims before paying on the bond or hiring other contractors.

RFI (Request for Information): A written request from one party to another for clarification or information about the contract documents following contract award.

RFP (Request for Proposal): A type of bid document used to solicit proposals from prospective practitioners of products or services. This is a request for uniform, detailed information from prospective practitioners being screened for a project.

Critical path method, or CPM, scheduling is a simple but powerful tool in the science of project scheduling. Delay is always measured by its effect on the project's critical path. Even if the owner causes a delay to noncritical path activity, the contractor may still be entitled to the additional cost from disruption to the activity. This is the most commonly used schedule, and when used properly can give a snapshot of a project's health at any given moment. It is also a valuable tool for "what if" questions. Sometimes a slight change in the sequence or duration of one event can have a dramatic impact on the overall schedule.

CPM identifies critical tasks. Critical tasks are those items that must be done in sequence before the next critical task can be done. They cannot be done at the same time. There is a line or path that runs through a job schedule made up of critical tasks that determine the amount of time the job takes. Activities that take less time than a critical task and can be done at the same time are called noncritical tasks. The leftover time available for noncritical items is called slack, or float, time.

Commissioning is the initial start-up and verification of proper operation of the original design specification.

Building commissioning is of greatest value to the owner when it provides, throughout the many phases of design and construction, a means of continuously communicating building systems criteria and rigorously verifying compliance of these systems.

Conduction is the mechanism of heat transfer in opaque, solid media, such as through walls and roofs. Conduction is the direct flow of heat through a material resulting from physical contact. The transfer of heat by conduction is caused by molecular motion in which molecules transfer their energy to adjoining molecules and increase their temperature.

Convective heat transfer occurs when a fluid becomes in contact with a surface at a different temperature, such as heat transfer taking place between the air stream in a duct and the duct wall. Convection is the transfer of heat in fluid, such as air, caused by the movement of the heated air or fluid. Convective heat transfer can be divided into two types: forced convection and natural, or free, convection. In a building space, warm air rises and cold air settles to create a convection loop called free convection. Convection can also be caused mechanically (forced convection) by a fan or pump.

Thermal radiation is the form of heat transfer that occurs between two separated bodies as a result of electromagnetic radiation, sometimes called wave motion. Thermal radiation is the transfer of heat by electromagnetic waves from a warm substance to a cooler substance without heating the medium in between.

R-Value, or insulating value, is a numerical index that indicates the resistance of a material to heat passing through it. The higher the R-Value, the higher the resistance to heat transfer through the material. c

The R-Value of a wall or other building segment composed of several elements can be found by adding the R-Values for each element. If the effect of the studs in a wall is considered, the overall R-Value is smaller because the studs are not as effective an insulator as fiberglass. R-Values are determined in laboratories an can be found in many construction reference books.

Concrete is a homogeneous mixture of portland cement, sand, gravel, and water, which may contain coloring pigments. Concrete, brick, block, and mortar all use cement. Concrete is only as strong as its weakest aggregate. The aggregate materials are generally some combination of gravel, crushed stone, and crushed furnace slag. The characteristics of the concrete depend on the type of cement used as well as the type of aggregate. The aggregate generally constitutes 60-80% of the volume of concrete and provides low-cost rigidity and dimensional stability to the concrete.

A cold joint is a defined interface between concrete poured at two different times. A cold joint at a surface appears as a crack and allows water to migrate easily through the concrete.

Spalling is a defect that occurs when pieces of masonry or brick split or flake off a wall surface. It is a rapid separation of the surface material from the main body of the concrete. This is followed by a gradual separation of layers of surface material, called sloughing off.

Epoxies are added to concrete to enhance the properties of the concrete or to correct problems in the concrete mixture. When added to concrete, epoxies provide high compressive and tensile strength, superior chemical resistance, and good wear resistance. When added to concrete mixture, the cost of the mixture is increased and will require longer curing times.

Epoxies have been used for various purposes such as bonding concrete, filling cracks, and anchoring bolts. Epoxies are thermosetting resins that cure by adding a hardener or catalyst.

A thin space is left at the top of the brick wall segment to allow for expansion. This space should be caulked with a flexible silicon sealant to prevent moisture from getting into the cavity wall. The flexible caulk will lose its elasticity and will have to be replaced on a 10- to 15- year cycle. The caulking on the exterior of the building should be closely inspected at least every 5 years.

• 1. Roofing Slate
• 2. Blackboard Slate
• 3. Countertop Slate & Sill Slate
• 4. Flagstone Slate

Most metals are subject to some degree of galvanic action. Galvanic action occurs when two dissimilar metals are in contact with the presence of an electrolyte. An electrolyte is a liquid that can conduct electricity.

The thermal, or heat transfer, properties of steel vary for different types of steel. In general, steel is an excellent heat conductor and, therefore, a poor heat insulator. To minimize the adverse effect that steel will have on energy efficiency, steel can be insulated with materials such as fiberboard, styrofoam, and spray-on mineral fibers.

The acoustical properties of steel are similar to those of nonacoustical (for example, stone aggregate) concrete. It is an excellent sound reflector and should be used with sound absorption material in spaces where steel is abundant. However, this same reflective property of steel can be valuable on the exterior of a building because it will reflect unwanted sounds back to the outside.

While steel does not burn, the strength of structural steel is tremendously reduced at temperatures that are commonly reached in fire. To protect steel members during a fire, they can be cast in concrete, encased in a thick layer of metal lath and plaster, sprayed with lightweight mineral insulation in cementitious binders, or have preformed slabs of mineral insulation attached to them.

Aluminum is a soft, nonmagnetic, and corrosion-resistant silvery metal. It has a low melting point, high thermal and electrical conductivity, and light weight - which is one-third that of iron, brass, or copper. Aluminum's conductivity is surpassed only by silver and copper. Aluminum has a fairly high coefficient of expansion and oxidizes readily.

Aluminum is a versatile construction material. Its various alloys are strong, corrosion resistant, ductile, heat resistant, or a combination of these characteristics.

The most notable characteristic of aluminum is its corrosion resistance. Aluminum is made corrosion-resistant by the transparent film of aluminum oxide that quickly forms upon exposure. This film causes the aluminum to be fairly impervious to further chemical action. When aluminum comes in direct contact with metals other than zinc, cadmium, magnesium, and nonmagnetic stainless steel, it is subject to various types of galvanic action. Therefore, aluminum should be directly insulated from other metals.

Commercial aluminum is an alloy of pure aluminum with varying but small amounts of iron and silicon that increase its strength and decrease its corrosion resistance. The joining of commercial aluminum is done by welding, brazing, resistance welding methods, inert-gas shielded arc processes, soldering, and adhesive bonding.

Aluminum is not an effective sound absorber and is not generally used in wall, floor, or ceiling applications as a sound reflector. The use of acoustical tiles in combination with aluminum can compensate for aluminum's poor acoustical properties.

Laminated wood is a wooden member made up of several layers of wood. Some references make a distinction between laminated timber (pieces are joined with the grain of each piece running parallel to make a thick beam) and plywood (adjacent layers have grain running at right angles to each other to make a thin sheet).

Laminated Timber




Laminated Wood

Gypsum is a soft, hydrous calcium sulfate used in construction materials such as wallboard and sheathing.

Reflective insulation must be installed with an air space of at least 3/4 in. between the reflective surface and the interior wall.

Dead loads are the permanent loads on the structure. They include the weight of structural members and all attachments that remain throughout the life of the building, such as pipes, electrical conduits, air-conditioning and heating ducts, lighting fixtures, flooring, permanent partitions, suspended ceilings, and roofing.

• Live loads move on and off the structure and vary in magnitude and location. The indeterminate nature of the weight, location, and density of live loads makes it difficult to realistically estimate the mangitudes and positions of these loads. The following are considered live loads:
• -occupants (people)
• -furnishings
• -machinery
• -movable partitions
• -rain, snow, and ice

The greatest wind forces are near the building's corners and roof edges.

• 1. Tensile stress
• 2. Compressive stress
• 3. Shear stress

Compressive stress is the stress applied to materials resulting in compaction, or decrease of volume. Usually compressive stress applied to items such as bars and columns leads to shortening.

The structural system and its individual members must meet the fire-resistance standard of the local building code, usually specified as either a two- or three-hour fire rating. Underwriters Laboratories, Inc., an independent testing agency established by insurance companies, has developed fire testing procedures and fire ratings for structural systems.

Cellular steel floor systems are commonly used in office buildings, hotels, and apartment buildings.

Open web joists are commonly used to support the floors and roofs of commercial buildings, apartment houses, hotels, and schools.

• 1. Exterior walls
• 2. Curtain walls
• 3. Interior walls

• 1. Loadbearing Wall
• 2. Frame
• 3. Long Span
• 4. Combination Steel & Concrete

Office building atriums, auditoriums, theaters, hotel ballrooms, field houses, and airplane hangars are examples of structures requring a long span steel system.

Most high-rise buildings erected today use a combination of reinforced concrete and structural steel. Steel column shapes surrounded by and bonded to reinforced concrete are commonly used and are referred to as composite columns.

• 1. Fireproofing costs
• 2. Maintenance costs

Where small tensile strength would limit the load-carrying capacity of a concrete member, steel rods or bars, which have high tensile strength, can supply reinforcement. This reinforcement, usually in the form of round steel rods with appropriate surface deformation to allow it to interlock with the concrete, is placed in teh forms before the concrete. When completely surrounded by the hardened concrete mass, the steel reinforcements become an integral part of the member. The resulting combination of the two materials, known as reinforced concrete, combines many of the advantages of each. Concrete's relatively low cost, good weather and fire resistance, good compressive strength, and excellent formability are added to steel's high tensile strength and much greater ductility and toughness.

Reinforced concrete is poured on site. To pour concrete on site, both formwork and shoring must be used.

Precast concrete is reinforced concrete that is cast and hardened into desired shapes away from the building site, then positioned in the building as a rigid component similar to structural steel. Steel forms are used, providing an excellent finished surface to the concrete.

Plywood is a building material made by laminating several thin layers of wood together. Plywood is used both structurally and decoratveily in construction. Structural benefits result from plywood's thin, crossbanded veneer sheets that are glued together into panels. This construction tends to provide uniformity in the plywood's strength, improve dimensional stability, and increase resistance to both cracking and splitting.

• 1. Moisture Content
• 2. Permeability
• 3. Shearing Resistance
• 4. Particle Size
• 5. Liquid Limit

• 1. Augered-in-Place Piles
• 2. Tapered PIles
• 3. Caissons

• 1. Corrosion
• 2. Abrasion
• 3. Loosening of Connections
• 4. Fatigue
• 5. Impact

• 1. Cracking
• 2. Spalling
• 3. Disintegration

• 1. Temperature
• 2. Humidity
• 3. Air Movement (Wind Speed & Direction)
• 4. Precipitation (Rain, Hail, Snow, Dew)
• 5. Cloud Cover
• 6. Solar Radiatio

Water infiltration is the most important factor in premature building decay.

• 1. Gravity
• 2. Kinetic Energy
• 3. Surface Tension
• 4. Capillary Action
• 5. Air Currents
• 6. Pressure Drops

Weatherstripping ensures a weathertight seal around widows and door frames.

In a window assembly, air leakage between the sash and frame is controlled by weatherstripping. Air leakage between a window frame and the building wall or between sections of a curtain wall assembly is controlled by joint sealants and gaskets.

Air infiltration through a curtain wall can set up a pattern known as the stack effect. This occurs when air enters the building at the lower floors, rises within the building, and exits at the upper floors. This pattern of infiltration and exfiltration adversely affects heating and cooling costs and the comfort of building occupants. Proper building envelope design, correct installation of sealants and weather striping, and effective maintenance will prevent the stack effect. Infiltration and exfiltration cause humidification to form in the walls and could cause molds and mildews.

Wind acting upon the curtain wall produces loads that largely dictate the wall's structural design. On taller structures in particular, the structural properties of the framing members and panels and the thickness of the glass panels in windows are determined by the design wind loads.

A curtain wall has both dead-load, or fixed, anchors and wind-load, or movable anchors. Between the fixed points of dead-load anchors, the wind-load anchors allow for thermal movement, floor-to-floor relative deflections, building sway or drift, and other movements in the plane of the wall. Both wind-load and dead-load anchors resist the pressures and vacuums perpendicular to the plane of the wall.

Between the fixed points of dead-load anchors, the wind-load anchors allow for thermal movement, floor-to-floor relative deflections, building sway or drift, and other movements in the plane of the wall. Both wind-load and dead-load anchors resist the pressures and vacuums perpendicular to the plane of the wall.

U-Value is the ability of the measure of heat conductivity of a material or structural unit, expressed as BTU per square foot per degree differences per hour; lower U-Values provide greater resistance to heat transmissions. U-Value is the ability of the curtain wall or window assembly to transmit heat (its thermal transmittance). A lower U-Value indicates the curtain wall or window assembly is well insulated and resists heat transmission. In a cold climate, a low U-Value can be a significant energy conservation measure.

R-Value is a measure of thermal resistance of a specific material; the higher the R-Value, the greater the resistance. R-Value is the reciprocal of the U-Value.

A thermal break in metal curtain walls keeps the inner face from losing heat to the exposed outer face and thus prevents the condensation of interior humidity on cold metal. Condensation has more severe consequences than heat loss and therefore can be a more important reason for using thermal breaks. Thermal breaks prevent condensation on interior surfaces by preventing the rapid cooling of metal curtain wall members. If a metal component has no thermal break, condensation or frost could form on its inner surface during the winter.

Summer solar heat gain increases the cost of air conditioning and can be controlled by selecting a glass with a low shading coefficient. A shading coefficient indicates the total amount of solar energy that passes through a glass relative to a 1/8" thick clear glass under the same design conditions. Lower shading coefficient values indicate better performance in reducing summer heat gain and, in turn, reduced air conditioning loads.

The shading coefficient indicates the total amount of solar energy that passes through a glass relative to a 1/8" thick clear glass under the same design conditions.

Glass tinting and coating reduce the shading coefficient; reflective coatings are the most effective. These coatings are not suitable where clear visibility through glass is desired. Reflective coating obscures visibility into the building during the day and out of the building at night. However, tinted and reflective glass reduces solar glare as well as the shading coefficient, thereby increasing the comfort of building occupants.

In high-rise curtain walls, the spread of fire from floor to floor is prevented by firestops, fire-resistant materials placed in the concealed hollow spaces of the building frame. Firestops are required by code and should be maintained and inspected according to a regular schedule. The location of required firestops will depend on the location of wall anchors. Close cooperation between the architect and the builder in the early stages of design is essential to ensure that proper firestops are provided and potentially hazardous conditions are eliminated.

• 1. Monolithic Glass - a single, flat piece of glass of constant thickness.
• 2. Insulating Glass - the most energy efficient of the three applications. It consists of 2 glass lights with 1/4" to 1/2" between them.
• 3. Double Glazing - similar to insulating glass, but with a wider space of 1" to 4" in between the glass lights. Double glazing is two layers of glass installed at the job by glazers, as if two monolithic glass installations were placed one in front of the other.

Typical problems with the exterior building envelope are failure of glazing compound or sealant,m corrosion of steel supports, clogged weep holes, loss of sealant adhesion, dislodged glazing gaskets, deterioration of mortar joints, and improper installation of flashing membranes.

Designs of operable windows that minimize the movement of sash against the frame generally provide a tighter seal and longer-lasting weatherstripping. Hinged windows (casement, hopper, and awning) typically outperform their sliding-sash counterparts (single-hung, double-hunt, and horizontal sliders). Hinged sashes usually employ interlocking weatherstripping techniques that can last almost indefinitely. Sliding sashes can wear down weatherstripping, eventually causing questionable performance.

Aluminum windows share the problems common to metal windows: they corrode, are difficult to refinish, and have poor heat flow resistance.

Anodization is the most common coating for aluminum. Anodization is a process which makes aluminum harder, nonporous, and more durable. Anodized aluminum will not chip, crack, or peel and can withstand lots of abuse from the elements.

1. Adhesive failure is the failure of the sealant to bond with the substrate. This is the main cause of sealant failure. where this occurs, the cause of the failure should be determined so that the reseal project can correct the problem. The lack of adhesion is usually caused by improper preparation of the surface receiving the sealant.

2. Cohesive failure is failure of the sealant to bond to itself. This condition causes cracks and splits in the center of the material. This type of failure is a sure indicator that the movement of the joint was greater than the sealant could allow.

• The most frequently used types of roofing construction are:
• -BUR (built-up membrane roofing)
• -fluid-applied membrane
• -single-ply membrane
• -metal sheet and metal panel
• -shingles, shakes, and tile

Bitumen is the generic term for a semisolid mixture of complex hydrocarbons derived from petroleum or coal after distillation. In the roofing industry, there are two basic bitumens: asphalt and coal-tar pitch.

The presence of asbestos or other controlled materials will add containment or abatement to the scope of the work.

During reroofing projects, environmental and ecological concerns (such as how debris will be unloaded and discarded, espeically if existing roofing is to be removed) cannot be overlooked. Disposal problems and the potential for long-term litigation should be anticipated with certain hazardous materials. The presence of asbestos or other controlled materials will add containment or abatement to the scope of the work. Replacing a damaged roof deck or wet insulation influences the logistics of the reroofing project. Access to the roof may be limited, by time of day or by type of access equipment. Rooftop equipment can either be worked around or must be removed for the project.

Interference with building operations may affect the reroofing schedule or require closing sectors of the building's interior over which work is being done. Occupant concerns about fumes, dust, noise, flames, and visibility of workers may affect scheduling. The expected remaining useful life of the building should also influence the cdecision to reroof - especially in a life cycle cost analysis of reroofing alternatives.

• -roofing design considerations
• -building location
• -building use
• -building aesthetics
• -owner's preferences

Watershed Approach: Relies on positive and rapid drainage away from overlapped units, such as roofing shingles, on stee-sloped roofs.

Waterproof Approach: Used on low-sloped and nearly flat roofs and requires a completely waterproof roofing membrane with seals at all terminations and penetrations.

The location of the building will influence roofing system selection. Climate conditions, including rain, hail, wind, snow load, and thermal load must be taken into account. The presence of mildew, pollution, salt conditions, birds, and vermin and additional environmental factors related to location, as are ease of roof access and the potential for vandalism. Local weather conditions determine the lenth of the consruction season. Local practices, including the experience of contractors and their installation crews, also influence the materials and installation methods used.

Since heat rises, considerable heat loss can occur through a roof. However, because the ratio of roof area to total building volume is considerably less for high-rise buildings than for low-rise buildings, the relative heat loss through the roof of high-rise buildings is also less.

Insulation reduces heat transmission through the roof, prevents condensation on the underside of the roof deck, and may furnish a better substrate for application of the roofing system. It also tends to stabilize deck components by reducing temperature variations and subsequent differences in expansion and contraction through the roofing system. This can relieve stress between the plies of the memberane. If a vapor barrier is installed beneath the insulation, the insulation must be vented to allow any water vapor that penetrates the roofing membrane to escape. Continuous venting is a cost-effective solution in certain climates and must be evaluated based on location and climate.

Thermoplastic means capable of softening or fusing when heated and of hardening again when cooled.

Flashing is various connecting devices that seal roofing membrane joints at expansion joints, drains, gravel stops, and othe rplaces where the membrane ends.

Gravel stops are metal flashing attached to the edge of the roof to protect and secure the edge of the roof membrane. When gravel is placed on the roof, the profile of the gravel stop prevents the gravel from rolling or washing over the edge of the roof.

Pitch pockets are pockets usually formed of aluminum or copper and fastened to the roof deck. They enclose a pipe or series of pipes that penetrate the roof surface. This pocket, or dam, is then filled with pitch, a black viscous tar that cold flows to seal the spaces around the penetrations. Pitch pockets require periodic inspections to ensure tha the pitch levels are maintained.

Expansion joint covers are used when a large expanse of roof is constructed. Allowance must be made for expansion and subsequent contraction. Various types of bellow or slip-joint expansion joints can be installed, and, depending on the configuration, might require additional flashing to make them watertight.

A cant strip is a triangular cross-section of fibrous or wood material, generally in 3-foot lengths. At the junction of the roof with a wall or equipment curb, a cant strip is used to split the 90-degree angle into two 45-degree angles. Cant stirps provide structural strength to bituminous flashing memberanes but are often omitted in elastoplastic systems.

A coping is a cover for the walls extending above the roof. Coping metal serves as a miniroof, keeping water out of the building parapet wall and acting as a counterflashing to the wall base flashing. The coping should slope toward the roof so that rain or melting snow is shed away from the coping joints.

Five rules to observe when using metal in flashings and other accessories on bituminous and modified bituminous roofing systems are:

• 1. Metal always goes on top of the completed roofing membrane but may go under stripping plies.
• 2. Metal flanges (the parts of a roofing detail used to attach accessories to the roofing system) should be set in a solid bed of flashing cement or supplied sealant, depending on the material.
• 3. Horizontal metal flanges should be nailed to treated wood nailers with fasteners 3"-4" on center, staggered front-to-rear of the flange.
• 4. Horizontal flanges should be stripped-in with a minimum of two plies of felt (in some climates, the minimum may be three or more plies) feathred onto the roofing surface and set in bituminous mastic or hot steep asphalt. One layer of modified bituminous membrane extended a minimum of 4" onto the roofing membrane can also be used. Alternatvely, use the flashing material supplied by the manufacturer.
• 5. Continuous metal cleats should be used on the face (side) of coping, gravel stop, and curb flashing.

It is best to place mechanical equipment somewhere other than on the roof. However, when equipment is mounted on the roof, planning and detailing is necessary to provide adequate clearance for maintenance and eventual replacement on the roofing membrane beneath the equipment. Avoid pitch pockets, because they require refiling to stay watertight; use curbed openings or premolded boots instead.

• Roofs typically consist of the following supports and penetrations:
• -equipment curbs
• -equipment stands and other mountings
• -equipment piping
• -equipment drains

The most important reason to establish a program of regular roofing inspection and maintenance is to protect the investment in the building and its contents. An effective maintenance program will not only add years to the life of the roofing, but will also detect minor problems before damage is widespread and the internal functions of the building are interrupted. You should not wait until the roof is leaking to begin a roofing maintenance program.

Interior walls, or partitions, may define individual offices and support areas (such as conference rooms or work rooms), create boundaries between a company's various departments, or create a demising wall between unrelated tenants on a floor of a building. Walls can also isolate areas that have environmental or security functions, such as separating a research laboratory from adjacent office space or defining a SCIF (Secure Compartmentalized Information Facility) from other parts of the building. Partitions can also provide the required fire rating between tenant spaces.

• Interior walls may serve many functions including:
• -Separating and defining spaces
• -Controlling sound
• -Resisting fire
• -Bearing loads

A slab-to-slab partition, generally fire-rated, that separates a tenant/occupant's space from that of neighboring tenants, departments, or companies. Also called demising partitions.

Thermal barriers are used to maintain a temperature range in a room or area. This barrier protects the space from the exterior of the building or an adjacent area that requires a different temperature range. As an example, a temperature sensitive computer server room may need to maintain a temperature that is 20 degrees cooler than an adjacent, general office space. Thermal barrier partitions, extending from slab to slabl will need to be constructed on all sides of the room.

To serve as a thermal barrier, a wall must be well insulated. Insulating wallboard made with lightweight, thermally resistant aggergates such as perlite or vermiculite, backed with bright aluminum foil, and finished with insulating plaster can minimize energy loss through an interior wall. Using fiberglass, rock, wool, expanded polystyrene, or other suitable insulating materiasl between the wall panels increases the thermal effectiveness of a studded wall.

• 1. Blowing wool, cellulose, or other types of loose insulation into the cavity, if there is one.
• 2. Removing the gypsum board sheathing from one side of the wall and adding insulation blankets between the studs.
• 3. Buidling a new adjacent wall or adding resilient channels and drywall with proper insulation.

• 1. Predecorated wallboard
• 2. Insulating wallboard
• 3. Fire-resistant (Type X) wallboard
• 4. Water-resistant (Type W/R) wallboard or green board
• 5. Gypsum sheathing
• 6. Gypsum lath

Demountable partition systems can be progressive or nonprogressive. Progressive systems require you take down a row of panel secxtions so you can replace a section in the middle of a run. A nonprogressive, demountable partition system allows you to replace a panel section in the middle of a run without any disruption to the adjacent wall sections.

Glass-fiber-reinforced gypsum is now used extensively in construction to create the special architectural shapes formerly produced by the ornamental plasters of the past. This material is commonly found in reproductions of ornamental moldings, archways, columns, and mantels that may be found in more traditional, high-end settings.

• -Superior fire-retardant properties
• -A variety of shapes similar to those previously available only in plaster or precast plaster
• -Installation with minimal field labor using drywall techniques
• -LIght weight for use on ceilings

• 1. Pigment: Provides the paint color.
• 2. Solvent: This the paint by dissolving or dispersing the binder.
• 3. Binder: The glue that combines the pitment and solvents and allows for surface adhesion.

A prime coat, or primer, applied to the bare surface seals proes in the surface and provides adhesion to the surface. The udnercoat covers up the surface, builds up film thickness, and furnishes an even sufrace for the final coat. The finish coat, or topcoat, provides teh final appearance, both color and glossiness. In high-class paintwork, such as automobile finishing and other commercial paint uses, multiple-coat paint systems are used. Multiple secondary and final coats are used to provide a mirror-like light reflecting quality.

Preparation of the surface to be painted is the most important phase of the painting process. Correct preparation produces a smooth, clean, hard, and dry surface that will enable the paint to bond.

To ensure cohesion, clean all surfaces, use the appropriate paint, and follow the manufacturer's instructions. Thorough preparation will be reflected in teh appearance and the durability of the finished job.

Zinc-rich primers act as sacrficial anodes; that is, the zinc in the paint corrodes instead of the iron or steel surface to which it is applied. Sacrificial anodesare very effective in protecting metal against corrosion.

• Defects in the paint film are usually caused by:
• 1. improper paint formulation
• 2. substandard materials
• 3. inadequate surface preparation

Flammable materials are used in the manufacture of many paints. Ignition can occur from autoignition, as well as the presence of an ignition source. Autoignition seldom occurs in the normal use of solvents. When the solvent dries by oxidation, it gives off heat. If the heat cannot escape, the temperatrue rises and can cause fire.

To replace deteriorated lead-based paint, perform a complete removal and refinishing.

Because of the ease in which they can be cleaned and their resistance to wear, vinyl wall coverings have a longer useful life than wallpaper.

Ceiling panels are produced from a variety of materials, including metal, wood, particle board, mineral fiber, and glass fiber. Most lay-in ceiling panels are made of acoustically absorbent materials such as wood, vemiculite, herculite, perlite, and fiberglass. Lay-in ceiling tiles can be ceiling tiles or ceiling boards.

Tegular-edge ceiling tiles have finished edges that drop down about 1/4" below the ceiling grid in order to create visual interest by creating a 2' x 2' pattern in the ceiling. There are 2' x 4' tegular-edge ceiling tiles that create a 2' x 2' appearance by incorporating a reveal in the middle of the ceiling tile that simulates the width of the adjacent ceiling tile grid. This system gives the appearance of a 2' x 2' tegular-edge ceiling system without the cost of the additional ceiling T.

The exposed grid system is the most common ceiling system and is typically found in shopping centers, general office areas, nonpublic spaces, and storage spaces.

The concealed grid, or concealed spline, system presents a flush, monolithic appearance and controls sound transmission as well. This system was popular during the 1960's and 1970's. The problem with this system is that it is a progressive system which makes it difficult to remove tiles and replace or reinstall them. Tiles are frequently damaged when the ceiling system is handled or modified.

The concealed grid system is able to receive partitions while maintaining effective acoustical control because of the flush ceiling surface. However, the finished tile surface is often marred by a ceiling-high partition fasteners. The cost of the concealed grid ceiling is 50-75% more than the cost of an exposed grid ceiling with mineral tile. The unit cost of the ceiling is related to the percentage of cutting and fitting at the perimeter and around interruptions in the ceiling.

• The following are typical applications of the access tile system:
• -general office areas
• -areas with limited access to the plenum space above the ceiling
• -areas requiring minimum changes of partitions, lighting, telephone, etc.

• Popular in restaurants, the snap-in metal pan system is typically used in:
• -areas requiring very high sound absorption
• -areas under exterior soffits and entrance canopies
• -areas of high moisture or grease content
• -area that need more elaborate stepping, special features, bulkheads, or core lighting

• The integrated modular ceiling provides a well-organized and efficient acoustical, lighting, air diffusing, and partition-receiving membrane. Integrated modular systems are used in the following areas:
• -general and private office areas within modular office buildings
• -office areas that have a rigid space standard based on the module of the ceiling system for partition layout, lighting and air distribution
• -as part of an integrated partition and ceiling system

• Several considerations that guide the selection and use of flooring:
• -function and cost
• -appearance and style
• -durability and noise
• -comfort and safety
• -installation and maintenance
• -weight and measurements

The type of flooring dictates the installation method. All flooring requires that there be some preparation of the subfloor. Carpeting is tolerant of some subfloor problems; it can bridge small cracks and hide other imperfections. Most vinyl flooring products need a smooth application surface. Subfloor imperfections , such as gaps between sheets of plywood and improperly set nail heads, are often transmitted, or telegraphed, though vinyl flooring. Broadloom carpet can be directly glued to the floor or can be stretched over a hair and jute or synthetic foam pad.

All flooring requires that there be some preparation of the subfloor. Carpeting is tolerant of some floor problems; it can bridge small cracks and hide other imperfections.

• 1. Resilient
• 2. Wood
• 3. Hard
• 4. Textile

• 1. Backed vinyl is a vinyl wear layer bonded to a backing material.
• 2. Homogenous vinyl consists of vinyl resins, plasticizers, fillers, stabilizers, and coloring matter mixed into a hot dough, which is passed between heated, polished steel rollers that squeeze it into sheets of the desired thickness. After cooling, the sheets are sanded on the back side, polished, and cut into tiles.

The important difference between the backed vinyl and homogenous vinyl is the wear layer. Homogenous vinyl, sometimes called solid vinyl tile, has a uniform, continuous-wear surface throughout the thickness of the tile, while the backed varieties have a thin, high-performance surface-wear layer. Homogenous vinyl has excellent indentation resistance and is good for high traffic areas. Backed vinyl has a lower resistance.

Terrazzo is a mixture of tow parts course aggregate and one part portland cement. Its smooth surface is obtained by grinding down the rough surface after the mixture hardens. The aggregate is typically composed of waste marble, granite chips, or crushed gravel. Many colors and designs can be incorporated into a terrazzo floor. Terrazzo combines the durability of marble with the strength and economy of concrete. Because of its durability, attractive appearance, natural sheen, and easy maintenance, terrazzo is used extensively in high-traffic lobbies of many buildings.

Acrylic fiber is long wearing.

Nylon has good stain resistance, and no longer fosters a significant static electricity condition.

Olefins are suitable for outdoors and for walk-off mats because they are not absorbent and do not fade.

Polyesters have abrasion resistance and a luxurious feel, but are not easy to keep clean.

Rayon do not perform like the other synthetics and are used only in the cheapest carpet.

Carpet is installed directly on the floor or over carpet padding. It can be loose-laid, stretched and tacked, or glued down.

Direct glue-down has become the most popular installation method for commercial carpet.

The overall quality of air in an enclosed space, accounting for factors such as temperature, humidity, odor, clarity, and absence of toxins or other agents that impair human health.

Heat that, when added to or removed from a particular substance, causes a change in temperature, but not a change of state.

Heat that, when added to or removed from a particular substance, changes the state of the substance (e.g., solid to liquid, liquid to gas) without changing its temperature.

The temperature of air as measured by an ordinary thermometer.

A temperature measurement that takes into consideration the moisture content of the air.

The ratio of the actual amount of water in the air compared to the maximum amount of water that the air could hold at the same temperature.

The temperature at which air is fully saturated with moisture and condensation can occur.

A measurement expressing the quantity of heat possessed by an object. One BTU is equal to the amount of heat requried to rais the temperature of one pound of water one degree Fahrenheit.

A means of expressing cooling capacity. One ton equals 12,000 BTU/hour (or 288,000 BTU/Day or 200 BTU/Miniute) of cooling.

The measure of heat conductivity of a material or structural unit, expressed as BTU per square foot per degrees differece per hour. Lower U-Values provide greater resistance to heat transmissions.

A measure of the thermal resistance of a specific material. Under steady conditions, the mean temperature difference between the two surfaces separated by the insulation. The higher the R-Value, the greater the resistance.

The average temperature of all the surfaces to which a person is exposed, exchanging infrared radiation.

The resistance that a system must overcome to accomplish the job it was designed to do.

Movement of air into a building or from one space to another space within a building, using a fan.

The uncontrolled leakage of unconditioned air into a building; generally caused by wind loads, or by a negatively pressured building.

A setting within an air-handling system that allows the use of cool outside air or water and less mechanical cooling.

The total heat content of the air as measured by its temperature and humidity.

The general discomfort, adverse reactions, or nonspecific sicnesses that appear to be linked to the time people spend in a particular building. Symptoms may include headaches, rashes, burning, teary eyes, or other irritations.

Specifically, diagnosible illness whose symptoms can be identified and whose cause is directly attributed to airborne building pollutants (e.g., Legionnaires' disesase, hypersensitivity pneumonitis).

The temperature, humidity, and air cleanliness range within which one is comfortable.

To control the spread of fire through ceiling plenums and ducts that penetrate fire walls, fire dampers are required. The fire dampers are typically held open by a low temperature alloy, like tin, which melts in the event of a fire. The damper then slams shut and seals off the opening, preventing further spreading of the fire.

• There are six basic components in the air cycle of a comfort air-conditioning system:
• 1. a duct system to convey the circulating air
• 2. a terminal device to distribute the air
• 3. a fan to move the air
• 4. a filter to clean the air
• 5. an air cooler to cool and dehumidify the air
• 6. an air heater to heat the air

The pressure of the air in HVAC distribution duct systems is only slightly above atmospheric pressure. The gauge pressure in these systems seldom exceeds one-half pound per square inch, or 13.85 in. wg, and is often one-half of this figure.

A manometer is an instrument for measuring the pressure of gases and vapors.

Terminal devices are the end points at which air dumps into the room.

The aspect ratio of a duct influences the initial expense and operating costs of high-velocity duct systems constructed with rectangular ducts. The aspect ratio of the long dimension to the short dimension at the cross section of the duct.

As aspect ratios increase, higher air pressures are required to deliver a given quantity of air through a duct system. This results in higher energy input to the fan, increased air temperature because of frictiona s the air moves from the inlet to the outlet, and greater transmission of heat through the walls of the ducts.

Therefore, net effect of ductwork with a high aspect ratio is increased energy consumption. Unless constrained by the geometry or the aethetics of the application, ductwork should be designed with a low aspect ratio.

Ducts with high aspect ratios have greater perimeters, requiring more sheet metal to construct them and resulting in higher friction-induced pressure losses. The additional material required for ducts with high aspect ratios causes higher construction costs for fabrication and installation.

A fire damper is a damper designed to close automatically when excessive heat is detected. A fire damper is required in a duct system where the duct penetrates a fire wall, floor, or other fire-zone barriers. The fire damper prevents the spread of fire and smoke from one area to another through the duct system. The location and construction of fire dampers is normally dictated by local, state, or provincial codes.

The two types of fire dampers are curtain and blade. Both types can close by gravity or can be spring operated. Most fire dampers are activated by a fusible leink that melts when subjected to abnormally high temperatures. Some fire dampers close because of a signal from the buidling's fire alarm system. Other systems include smoke dampers that are activated by a signal from teh building's fire alarm system.

The design of the HVAC system provides for specific quantities of air to be delivered to each room so that comfortable conditions can be maintained. The size of ducts, terminal devices, fans, and other system components is based on the quantities ofa ir to be handled. To make the system perform to its design, the system is subjected to TAB (testing, adjusting, and blancing), or T&B. TAB technicians examine the completed air-handling system to confirm proper installation and to verify that all equipment is performing as specified. Each register, grille, terminal device, and volume damper is adjusted to properly distribute the design airflow within 10% of the design specifications.

Rebalancing should be done for each new occupancy and whenever the conditioned space or the duct system is otherwise modified. This rebalancing should rely on updated internal load calculations. Many comfort and air-delivery problems are resolved through proper air balancing. Because the air balancer is reviewing the installation work of others, hire an independent air-balancing firm rather than make air balancing par tof the HVAC installation contract.

• 1. Dual duct (mixing boxes)
• 2. Single duct
• 3. VAV (variable air volume)
• 4. Induction

Dual-duct terminal units (mixing boxes) receive hot air and cold air through spearate supply ducts and discharge hot, cold, or mixed air to satisfy the requirements of the space.

Single-duct terminal units either receive air at a variable temperature that is adjusted to take care of the cooling load or are supplied with constant temperature cold air and use a heating coil to reheat the cold air to the required temperature.

In VAV terminal units, also called VAV boxes, temperature is controlled by regulating the volume of air first rather than by controlling the temperature of the air introduced into the sapce. A VAV box typically delivers 55-degree air to all spaces at all times. When the room temperature is satisfied, the VAV box will hold the last volume of air delivered. This means the box output volume of air remains the same. If the room temperature continues to drop, the VAV box would reduce the amount of air flow into the space. There are many types of VAV controls. When minimal air (referred to as a set poitn) is needed, a damper closes, or throttles, down the air leaving the VAV box, or duct reliefs that bypass excess supply-air to the return-air plenum. Minimum air volume is required on all VAV boxes. VAV terminal units are an energy-efficient temperature control system, especially when combined with variable speed fans. Some VAV boxes have either a hot water or an electric reheat coil. If the VAV box has reduced the air flow to a minimum level and the room temperature continues to drop, the heat turns on to warm the space.

• 1. Finned-tube coils
• 2. Air washers
• 3. Sprayed coils

Air particles are measured in microns. Particle sizes range in diameter from less than 1 micron to 5,000 microns. 1 inch = 25,400 microns. Air filters can remove particles ranging from 0.1 microns to 200 microns in diameter.

Viscous impingement filters use a coarse filtering medium constructed of fiber, wire mesh, or metal stampings. This medium is coated with a viscous substance, such as oil. As the airstreams change direction through the filter, dirt particles are thrown against the medium and adhere to the oily coating.

Fibrous media filters use media of mats or blankets of varying thickness, fiber sizes, and densities. The medium is usually cellulose or glass fiber, treated paper, cotton batting, wool felt, or synthetic material. The medium is commonly supported by a wire frame formed in pockets, bags, or V-shaped pleats, or it may be self-supporting or held of medium area to airstream area and creates a reasonable pressure drop for high-density media. Extended-surface fibrous media filters are available in bag-and-cube (cube is prefilter for bag) configurations for greater efficiencies without higher pressure drops, where the filter section of the air-handling unit is long enough.

Gaseous contaminants, including odors, can be absorbed from the air by activated carbon filters. The effective life of activated charcoal depends on the type and concentration of the gaseous matter. The carbon eventually becomes saturated and loses its capacity for further absorption. The saturated charcoal is then replaced or reactivated.

• -Toilet Rooms
• -Kitchens
• -Parking Garages
• -Below-ground Storage Spaces
• -Equipment Rooms
• -Special Use Areas

A refrigerant is a fluid that picks up heat by evaporating to a gas at a low temperature and pressure and gives up heat by condensing to a liquid at a high temperature and pressure. While various refrigerants have been used, such as water, ammonia, and carbon dioxide, the most common are members of the fluorocarbon family.

Desirable properties of a refrigerant include non-corrosiveness and the ability to alternate between the gaseous and liquid states at practicable temperatures and pressures.

CFCs were developed in the 1930's and have unique properties. They are low in toxicity, nonflammable, noncorrosive, compatible with many materials, and offer the thermodynamic and physical properties that make CFCs ideal as refrigerants. However, the stability of these compounds with their chlorine content has linked them to depletion of the earth's protective ozone layer.

Phased-out refrigerants are not obsolete; they are just no longer manufactured. If they are in use and the system functions well and is not leaking, they can be used if monitored.

A retrofit is a renovation of an existing system to update outmoded features to current standards of usability and code compliance.

Liquid refrigerant passes through an evaporator, a heat exchanger between the building interior air and the refrigerant. The refrigerant absorbs sufficient heat to change its state from a liquid to a gas. this gas enters the compressor, a motor-driven pump (or, in a large chiller, a stem-driven turbine) that increases the gas pressure and raises the temperature at which the refrigerant will condense. The high pressure gaseous refrigerant then enters the condenser, a heat exchanger between the refrigerant and the exterior environment. In the condenser, a cool fluid, such as water, absorbs enough heat from the refrigerant for it to condense into a liquid so that the refrigerant is ready to return to the evaporator. The condenser water is pumped through a cooling tower or other unit to release the waste heat to the atmosphere.

• 1. Compressor
• 2. Condenser
• 3. Liquid Metering Device or Expansion Valve
• 4. Evaporator

The high-pressure side of the system is on the discharge side of the compressor and includes all components at or above condensing pressure. Service people call the pressure on the high-pressure side head pressure, discharge pressure, or high-side pressure.

The low-pressure side of the system is on the suction side of the system and includes all components operating at or below evaporating pressure. Service pople call the low side pressure back pressure, suction pressure, or low-side pressure.

1. Reciprocating - The reciprocating compressor uses a piston that travels back and forth in a cylinder, like in an automobile engine.

2. Rotary - The rotary compressor uses gears or an eccentric rotor with vanes that rotate within a cylinder.

3. Centrifugal - The centfifugal compressor uses a high speed centrifugal impeller with many blades that rotate within a housing.

4. Helical Screw - The helical screw compressor uses positive rotary displacement.

The hermetic compressor is driven by an electric motor connected directly to the crankshaft. The compressor and motor are mounted within the same housing, eliminating the need for shaft sealing. The housing is sealed by welding, so service in the field is not possible. When the compressor fails, it is removed and replaced. To allow cooling of the motor windings, the low-temperature refrigerant vapor drawin from the evaporator is passed around these windings before it enters the suction of the compressor. The sealed hermetic design is applied mainly to low-capacity compressors used in appliances such as refrigerators, freezers, and air-conditioning units.

A centrifugal compressor is a relatively high-speed machine in which a continuous stream of refrigerant gas is compressed by centrifugal force. Since it develops a purely rotational motion, it is possible to obtain a high degree of balance with minimal vibration. The centrifugal compressor operates with less vibration than a reciprocating compressor. However, the centrifugal compressor operates at a higher noise level than other compressors, primarily due to its size and capacity.

• There are two basic types of centrifugal compressors:
• 1. open centrifugal compressors
• 2. hermetic centrifugal compressors

Inlet guide vanes are devices used for capacity control on centrifugal compressors. The vanes are located in front of the impeller and regulate the flow of the refrigerant into it.

• 1. Air-Cooled
• 2. Evaporative
• 3. Water-Cooled

The shell-and-tube condenser consists of a welded steel shell containing a number of straight tubes fastened in tube sheets that close the shell. HOt refrigerant gas from the compressor is admitted through the inlet and flows downward over the tubes. Cold water from the cooling tower is circulated through the tubes and absorbs heat from the hot gas. The gas condenses on the surfaces of the tubes and collects on the bottom of the shell. The liquid refrigerant leaves the condenser through the liquid pipe at the bottom of the condenser shell and flows to the evaporator.

Many cooling systems use evaporation to remove heat from the condenser water that has absorbed heat from a refrigerant. When a water-cooled condenser is used in a medium or large refrigeration system, the warm cooling water leaving the condenser is not discharged to the sewer. To conserve water, the condenser water leaving the system is cooled in a cooling tower and recirculated through the systm

• Cooling towers are divided into two classes according to the method of air circulation:
• -Natural-Draft: Depend on natural wind movements for air circulation
• -Mechanical-Draft: Use one or more fans to either induce or force the air through the tower

Fill is the part of the cooling tower over wheich water is distributed and exposed to outside air to cool through evaporation. Most fill is composed of FRP, PVC, & wood.

The fan in an induced-draft cooling tower is located at the top of the tower, thus the air is drawn upward through the bottom of the tower. The water is introduced into the upper part of the tower through spray nozzels and falls downward. Since the water and the air flow in opposite directions, this tower is called a counterflow cooling tower. The fill allows the water follow a long downward path, increasing air exposure time and resulting in an increased heat transfer efficiency.

Drift eliminators are used in the upper part of the tower to separate any water droplets from the air before the air leaves the tower.

• 1. bare tube
• 2. plate surface
• 3. finned tube
• 4. shell and tube

The finned-tube evaporator with forced air circulation is the most widely used evaporator in air-conditioning applications. The air to be cooled is forced between the fins and gives up its heat to the vaporizing refrigerant in the coils.

In place of the compressor, it has an absorber, a generator, and a heat exchanger and pumps to cause the fluids to circulate.

The refrigerant in this system is water; it is interesting to see how the absorption system cools water with water. Like refrigerants used in compression refrigeration, water will boil or vaporize at a lower temperature if the pressure is reduced below atmospheric pressure. For this reason, the system operates in an extremely high vacuum in which water will boil at 40-degrees Fahrenheit.

1. Convection - Convection is the transfer of heat through a liquid, such as water, or a gas, such as air. When heated, the liquid or gas expands and rises because it is less dense. This movement of heated air spreads the heat to surrounding air and to objects with which the heated air comes in contact.

2. Conduction - Conduction is the transfer of heat in solid material. For example, the handle of a steel rod that has its other end in a fire becomes hot as the heat is conducted from the hot end to the cool end.

3. Radiation - Radiation is the transfer of heat by electromagnetic waves. These energy waves move from a warmer surface to a cooler surface without heating the space in between. Thus, the sun warms our bodies while we stand in cold air.

• 1. High Pressure
• 2. Low Pressure
• 3. Hot Water

In firetube boiilers, the hot gases from the burned fuel pass through steel tubes immersed in water, which is enclosed within a steel shell. The firetubes are arranged to make one or more passes through the steel shell, thereby maximizing the heat transfer from the hot gases through the steel tubes to the water.

Watertube boilers have a lower water-filled drum connected by water-filled tubes to an upper drum, into which steam rises. The hot combustion gases from the burned fuel pass around the outside of the water-filled tubes, transferring heat to the water. Watertube boilers are primarily used in industrial applications to generate steam.

• 1. Packaged boilers
• 2. Erected boilers

Packaged boielrs are fully assembled in the boiler manufacturer's shop. When delivered to the installation site, a packaged boiler includes all of its components: shell, external insulation, fuel burner, piping, valves, gauges, and control panel. Only connectinos to water, fuel, electricity, flue stack, and heating distribution piping are needed to put the boiler in service. As part of the package, the entire boiler is mounted on a structureal base, facilitating shipment and final positioning at the site. A packaged boiler is standardized, pretested, space efficient, and readily available fromone manufacturer. Responsibility for all of the package's components rests with that manufacturer.

In hot-water heating systems, the minimum pressure must be high enough to prevent water from flashing into steam. Consequently, the maximum desirable tempreature for water systms with direct space heat transfer equipment is 220 degrees Fahrenheit. Most hot-water heating systems in commercial buildings operate at low temperature ranging from 180-220 degrees Fahrenheit.

• 1. High-pressure
• 2. Medium-pressure
• 3. Low-pressure
• 4. Vapor
• 5. Vacuum

• 1. Mechanical
• 2. Impulse
• 3. Thermostatic

• 1. Air vents
• 2. Condensate tanks
• 3. Flash tanks
• 4. Drip legs

• 1. Proper chemical treatment
• 2. Daily blowdown
• 3. Proper inspections

Blowdown is the discharge of water from a boiler that contains a high proportion of dissolved solids.

Electric heating requires no fuel usage or storage, making it cleaner, safer, and easier to maintain than fossil fuel systems. In addition, maintenance and insurance costs are lower. Electric heat is simple to distribute and control, and electric heating equipment is compact and has a lower installation cost. However, electricity is relatively expensive, costing more per BTU than fossil fuel. Electric heating has a fundamentally lower efficiency than fossil fuel systems, because the electric utility typically achieves only 35% efficiency in electricity generation and transmission to customers.

• 1. Step controllers
• 2. Rectifiers

A heat pump is an electric device that uses a compressor to drive refrigeration cycles to move heat from one medium to another. A device capable of providing heating or cooling by reversing its operation.

Most heat pumps uses electric motors to drive their compressors.

When an adequate external heat source is available for heat pump operation, the savings in operating costs over electric heat are considerale.

Many buildings generate excess heat within their interior areas, even in the winter. In most buildings, this heat is rmeoved from teh building because it is not transferable to the areas that require heating. Therefore, a large office building may require simultaneous heating and cooling. Heat is requried to offset the heat loss through the exterior walls and roof; interio cooling may be necessary to remove excess heat from people, equipment, and lights. In many buildings, the internal heat gain from lights may be sufficient to heat the building through most of the winter season. Thus, the principal heating or cooling requirements are due to heat losses or gains through the exterior walls of the buildings and through infiltration of outside air.

A heat recovery system extracts excess interior heat and transfers it to areas of the building that require heat.

The heat energy from condensate normally spilled as waste may be used to heat/preheat domestic water or temper outside air.

• 1. Heat wheel
• 2. Runaround coil
• 3. Heat pipe

Cogeneration, frequently called total energy system, applies a single energy source to multiple uses, ideally supplying the total energy needs of a facility. Cogeneration is the sequential production of electrical or mechancial energy and thermal energy. By this method, more energy is extracted form each unit of fuel, resulting in higher efficiency.

The design of HVAC systems is based on the estimated maximum heating and cooling loads within a building envelope.

The intent is to provide comfort as it relates to temperature, humidity, and the air quality.

• 1. all air
• 2. all water
• 3. air-water
• 4. DX

In the single-duct, constant-volume, variable-temperature system, variations in loads are offset by reheating the previously cooled air supplied to each zone. The branch duct feeding each room or area is fitted with a thermostatically controlled reheat coil that addes enough heat to the supply air to offset the lack of cooling load in the space. This is especially necessary for perimeter zones in the winter. The source or reheat may be steam, hot water, or electricity. The sytem may serve interior or perimeter zones of a building.

A diffuser is an outlet that spreads and circulates the flow of air from an HVAC system over a large are of a room.

Plenum is an air-filled space in a structure, espcially one that receives air from a blower for distribution.

The single-duct, constant-temperature, variable-volume system uses large central air-handling equipment to filter, cool, and deliver air of constant tempreature to a single-duct distribution system. The quantity of air is based on the maximum instantaneous building heat gain. This maximum is less than the sum of the individual quantities required for each space at its maximum load, since the maximum zone loads are not concurrent throughout the building. Variations in individual space loads are offset by reduing the amount of air that is supplied to that space. The branch duct feeding each zone is fitted with a thermostatically controlled volume damper or VAV (variable air volume) box, usually with DDC (direct digital control), which regulates the amount of air supplied in accordance with the heat gain in the zone.

An economizer cycle is an energy-saving process that discontinues the operation of the mechanical cooling system when the outdoor temperature falls below a predetermined temperature setting, normally between 50-60-degrees Fahrenheit.

Dry-bulb tempreature is the temperature of air as measured by an ordinary thermometer.

All-water systems generally use fan-coil terminal units, or, in the case of educational buildings, a larger version called unit ventilators. Generally, fan-coil terminal units consist of a small electrically driven fan with a heat transfer coil or coils for cooling and/or heating and a low-grade replaceable or cleanable filter. The entire unit is within a steel cabinet and is usually located along the exterior wall of a building.

By far the most common fan-coil system arrangement is a two-pip system; it is the least expensive design. In the two-pipe system, cold water is supplied to the unit for summer cooling and hot water for winter heating. Minimum ventilation is normally supplied by a system serving the interior zones of the building. However, in mild climates, ventilation can be supplied through a wall opening to the fan coil

Three-pipe and four-pipe arrangements overcome the disadvantages of poor space temperature control inherent in the two-pipe arrangement. Three-pip and four-pipe arrangements make heating and cooling available simultaneously; therefore, excellent dry-bulb temperature control can be maintained thruogh all seasons.

• -An air-hanlding unit, which supplies primary air conditioned to offset building transmission losses or gains
• -A high-velocity duct system
• -An induction unit for each room or office
• -A secondary water system, which is supplied from a central boiler and chiller - the secondary water system consists of either hot or chilled water, depending on the time of year and the requirements of the space being served/
• -Two sets of coil (one heating, one cooling), or one coil controleld by a two-way or three-way valve that provides both heating and cooling.

• -Through-the-wall units
• -Cabinet units
• -Rooftop units
• -Split Systems

• Rooftop units are self-contained assemblies with the following components:
• -Refrigeration Section: Containing an air-cooled condenser, refrigerant compressor or compressors, and automatic controls
• -Air-handling Section: With a supply fan, DX cooling coil, filter, return-air plenum, and outside air plenum
• -Optional Heating Section: With a self-contained gas-fired or oil-fired furnace and an electric heating coil or steam or water coil connected to a remote heating plant.

Rooftop units are usually installed on the roof of low profile buildings - typically three stories or less - including housing, industrial, commercial, and office functions.

In split systems, the evaporation section is located away from the air-cooled condensing section. The evaporator section is usually located inside the building, and the condensing section is usually placed outside the building.

• 1. Establishes a final condition
• 2. Provides safe operation of equipment
• 3. Eliminates the need for ongoing human attention
• 4. Ensure economical operation

Sensors are devices that transmit a signal by way of pneumatics, electronics, or resistance to a control device such as a damper or valve. A sensor can be installed in any location where a tempreature, pressure, or flow reading is desired.

• 1. Pneumatic Control Systems
• 2. Electric Control Systems
• 3. DDC Systems

Steam boilers are typically controleld by packaged controls (for start up and flame control) installed at the point of manufacture. A field contractor typically adds controls for start/stop, off/on status, steam pressure, and lead/lag operation. Additional controls include flue gas monitoring and analysis, stack temperature, and condensate temperature.

Set point is the desirable level of a variable at which a controller is set to maintain.

• Cooling towers reject (or release) heat from the building. Whether they contain one cell or several cells, they are typically controlled by one of four methods.
• 1. bypass control
• 2. fan control
• 3. damper control
• 4. a combination of any or all of these methods

Energy management systems are stand-alone, single-function systems that limit the use of energy by controlling the unneeded capacity of HVAC systems and responding to prevailing conditions. Control is achieved by connecting sensors to points - wire terminals - on a panel board. A series of boards placed close to individual clusters of equipment, away from the head-end (central) computer, are referred to as field points.

• 1. Whether analog or DDC is used
• 2. Whether the data processing is centralized or distributed

BASs are a fmily of separate, electronically interfaced building systems. BASs offer centralized control through the use of a common signaling system for all base building functions. This integration allows quick (automated) response to fire, intrusions, and mechanical failures because systems are linked. For example, when fire suppression systems are activated, elevators are automatically switched to emergency oepration and HVAC fire dampers are closed. BASs, also known as facilities management systems, are available in various configurations (for example, DDC or analog, centralized or distributed) depending on the type, condition, and number of separate systems conbined into one BAS.

• DDC technology has several advantages over analog controls. These include:
• -direct signal reading
• -better control
• -ability to anticipate
• -user-friendliness

Coaxial cable and a twisted pair of wires may be the least expensive and easiest type of communication link to install. However, these are subject to electrical interference, such as lightning, which can damage components and cause a loss of data.

Fiber-optic cable provides high quality transmission. Telephone lines can trasnport data long distances to integrate remote buildings into a single BAS network. They are, however, expensive to use and are subject to the same failures as normal twisted-pair telephone lines. Connections of fiber-optic cable to copper are very expensive and must be used sparingly. Fiber-optic is used mostly for backbones (primary trunk lines).

The OST is the latest possible time to start the HVAC system in order to reach comfort levels by occupancy time.

The duty cycling feature can significantly reduce overall electrical consumption by stopping (shedding) certain electrical equipment (loads) for predefined amounts of time periodically through the day. Duty cycling is sometimes called load cycling or load rolling.

Many fans, pumps, and other HVAC system components in a building are operated continuously during occupied periods to provide the heating, cooling, and ventilation for which they were designed. Because the capacity of this equipment is large enough to maintain ocupant comfort during the peak load conditions on the hottest and coldest days of the year, it is possible to turn off some of the equipment for short periods of time with no loss of occupant comfort.

Unlike the duty cycling feature, demand limiting can create savings by shedding deferrable loads. The demand limiting feature monitors the rate of electrical consumption and starts shedding (turning off) loads when usage exceeds a predefined demand limit (demand target).

An economizer switchover cycle is an energy-saving process that discontinues the operatino of the mechanical cooling system when the outdoor temperature falls below a peredetermined temperature setting - normally between 50-60 degrees Fahrenheit.

A VAV system optimizes energy consumption by changing the amount of air being supplied to the space to maintain comfort levels. A VAV system has the potential for greater energy savings than a constant-volume system. This is because fan horsepower requirements drop as the system throttles back during part-load conditions, thus reducing electrical usage.

The VAV system compensates for varying cooling loads by regulating the volume of cool air provided by the central supply fan. A terminal unit supplies each space. Each unit opens and closes to allow enough airflow in each space to satisfy cooling requirements, varying the static pressure in the main duct. The computer or controller reacts to the changes in static pressure and adjusts the fan speed to maintain the correct static pressure in the duct. Minimum setting of VAV systems is required to ensure minimum airflow enteres the space at all times. If necessary, reheat coils in terminal units can provide conditioning for any psaces that may require heating.

The condenser water reset feature saves energy by lowering the condenser water temperature set point based on the ambient wet-bulb tempreature and the actual load being handled by the chiller. Cooling the condenser water to the lower set point requires the cooling tower fans expend more energy. However, when properly implemented, lowering the condenser water temperature by one degree, for example, can save more energy. The system ivnests msome energy to save more energy.

• 1. The amount of time a particular status was in effect
• 2. The number of times an event occurred
• 3. The number of pulses recorded at a pulse sensor
• 4. THe quantity used (calculated using the current rate of consumption)

Preserving the intended performance of HVAC equipment begins with keeping records of system operation data on a daily basis.

Data from temperature and pressure indicating insturments can confirm proper control set points, warn of performance problems, and provide a basis for troubleshooting.

• -Improved building performance and reliability
• -Maximum facility productivity through reduced downtime
• -Efficient use of energy and labor resources
• -Protection of capital investment through extended equipment life
• -Compliance with government and industry codes and regulations

The ATC (automatic temperature controls) are the brain and nervous system of the HVAC system. Of all the HVAC components, the ATC are a major cause of discomfort and inefficiency and require the most attention. Wear, dirt, and vibration cause these controls to lose accuracy or fail. They should be inspected, calibrated, and tested at least semiannually (in the fall and spring). This work should not be attempted by anyone other than a certified or highly experienced technician. Allowing an inexperienced technician to work on these systems can cause more hamr and lead to system shutdown.

Troubleshooting is the diagnostic process to determine the cause of a suspected abnormal condition. To troubleshoot effectively, a technician must have a clear understanding of how each piece of equipment relates to other pieces in the system, and of the troubleshooting processes. The technician must also understand the normal operating and design conditions of the equipment.

To achieve the rated life expectancy, equipment has to be properly operated, repaired, and maintained. This includes being kept free of dirt, foreign material, corrosion, and unnecessary wear. Poor maintenance reduces both efficiency and useful life. Maintenance is necessary to ensure continuous performance and minimize operating costs.

• -Dirt
• -Heat
• -Wear
• -Improperly trained technicians

• Dirt deposits on air filters, air passages of motors, contacts of electric switches, and open-type bearings. Accumulated dirt and/or foreign material and corrosion can cause the following problems:
• -loss of capacity of individual components or the entire system through interference with heat transfer functions
• -an increase in energy consumption to compensate for higher temperature differential than originally designed
• -unnecessary repairs and replacements
• -reduced useful life of components

Dirt or foreign matter that affects the interior of mechanical systems may be airborne, may enter with a system fluid such as water, or may have been left during construction. Airborne dirt can enter the condenser water at the cooling tower. Water contains dissolved solids, such as calcium and magnesium, that can deposit on interior piping surfaces if the water is not treated properly. Foreign matter left by construction can include sand, stone, welding chips, drywall dust, mill scale, soldering paste, and oils used for pipe threading or gasket seals.

• 1. Breakdown maintenance
• 2. Service maintenance
• 3. Preventive maintenance

Service maintenance consists of lubricating equipment, changing filters, adjusting and replacing belts, and keeping equipment clean. Service maintenance meets the manufacturer's basic recommendations and requires a minimum level of skill. Service maintenance should be done quarterly, semi-annually, or annually. Service maintenance tasks are within the capabilities of most on-site operating and maintenance staff.

• 1. scale
• 2. corrosion
• 3. microbiological growth
• 4. dirt/silt fouling

PPM is a measure of the concentrations of various water impurities, such as calcium, silica, iron, and alkalinity.

pH is a mesaure of the strength or intensity of an acid or alkalai. The pH scale runs from 0-14. A pH of 7 is neutral; lower values are acidic, and higher values are alkaline.

Conductivity is the ability of a water to conduct electricity (sometimes expressed as mhos). In water treatment, conductivity can be measured indirectly by determining the TDS (total dissolved solids) in water. The greater amount of TDS in the water, the greater the level of conductivity. Control of conductivity is necessary to keep dissolved solids from precipitating to form heat-insulating deposits.

High concentrations of TDS can contribute to scale, sludge, foaming, and carryover.

Cycles of concentration determine the buildup of dissolved solids in water. This indicates the efficient use of water as well as its scaling and/or corrosion potential.

Dissolved solids of calcium and magnesium become less soluble as temperature increases. This means that as the temperature of water increases, teh scaling tendency of dissolved calcium and magnesium increases. These deposits tend to be the most common and troublesome on heat exchange surfaces. The potential for corrosion also increases as the temperature of water rises.

Blowdown is the periodic flushing of dissolved and suspended solids from an open recirculating water system.

Bleedoff is the removal of water from a cooling tower to reduce the concentrated solids in an air conditioning cooling tower.

Corrosion can be minimized. The most effective, practic al, and economical method is a total corrosino control program designed specifically for your particular cooling or heating system. These programs use corrosion inhibitor chemcials that form a protective film on metal surfaces of properly cleaned and pretreated cooling and heating water. This barrier is effective only if water characteristics such as pH and conductivity are maintained within recommended ranges. HVAC systms in a buildign consist of several processed metals, such as mild steel, stainless steel, and copper. These metals will corrode; the extent of corrosion depends on their natural characteristics and how they are processed.

• -reduced heat transfer efficiency
• -increased maintenance and cleaning
• -equipment repair and replacement
• -unscheduled shutdown

Microbiological growth differs from scale and corrosion in that it does not create problems in high-temperature systems - steam and hot water - because most microbes cannot survive at temperatures above 140-degrees Fahrenheit.

• 1. slime forming
• 2. corrosive
• 3. iron depositing
• 4. nitrifying

Living, active, occurring, or existing in the absence of free oxygen.

The water distribution system of a building connects a source (municipal water main, storage tank, well water, or natural body of water) to various points of use in the building. This water distribution system conveys water through pipes and other equipment, collectively called plumbing.

• 1. Velocity - the speed at which the water flows through a pipe.
• 2. Water Pressure - The force of the water in the plumbing system that causes water to flow.
• 3. Pressure Drop -The loss of energy in water flowign through a pipe. This is head pressure plus the turbulence caused by friction between the water and the pipe.
• 4. Pipe Size - Affects the pressure drop in a piping system, depending upon the quantity of water flowing through the pipe.

• Water flow is usually measured in gmp (gallons per minute), but can be expressed in cubic fee per minute or per hour. There are 7.5 gallons in 1 cubic foot. The two classifications of water flow that make up the peak demand load - that is, the instantaneous demand - are:
• -Constant Load: The regularly recurring flow of water to equipment (such as a cooling tower).
• -Intermittent Load: The maximum flow that could occur at any instant from the periodic use of plumbing fixtures, hose connections, and laundry and dish-washing equipemtn. Intermittent load is difficult to predict, because people, not fixtures, use water. To estimate this load, the fixture unit and a probability curve are used.

• 1. Constant-speed pump
• 2. Variable-speed pump

Water hammer is a turbulent vibration accompanied by a loud banging noise and is caused by oscillations in the pressure of water when valves are rapidly opened or closed. Water flow that is stopped suddnely causes a momentary pressure surge that may damage pipes and fittings, especially on waterlines containing high-velicyt water flow. This action is more severe in long mains - that is, the principal supply pipes. The presence of air in the system will cause more oscillation to occur. Air is released from water when it is heated; the air can cause the water pressure to fluctuate, and noise can result.

Water hammer is eliminated by the use of slow-closing valves and/or by designing the piping to have low velocities. However, slow closing is not desirable for an automatic urinal or water closet flush valve designed to limit water use. The solution with flush valves is the installation of water hammer arresters, also called shock absorbers, in the system.

• 1. gravity systems
• 2. constnat pressure with suction tank pressure

The hydropneumatic pressure systme boosts a water supply of adequate flow, but limited or varying pressure to ahigher and more uniform pressure so that a continuous water supply will be available at all fixtures on the system. The pressure system uses a pump to supply water to a pressurized tank, compress air stored in the tank, and adjust the pressure by changing the volume of air in the tank in conjunction with the water level.

A check valve is designed to allow liquid or gas to flow in one direction only.

High-limit energy cutoffs: Prevent stored water temperatures in excess of 210-degrees by stopping the flow of fuel or energy.

Temperature Relief Valves: Prevent stored water temperatures in excess of 210-degrees by discharging the hot water so it can be replaced with cold water. Temperature relief valves contain a thermally sensitive element that opens at a set temperature, allowing water to spill out until the temperature has been corrected.

Pressure Relief Valves: Relieve excess wate pressure. Pressure relief valves also permit water to spill out until excessive pressure is relieved.

Pressure relief valves protect systems against damage caused by escessive water or air pressures.

Globe valves are designed for use in waterlines where regulating the flow (throttling) is required. Throttling, flow measurement, and shutoff can also be accomplished by a globe-style circuit-balancing valve with flow-metering ports. This valve eliminates the need to install three separate valves at each indicated section and thus saves on labor and material.

Gate valves are designed for use in the full open or closed position, where the valve is used for turning water on and off for servicing. When a gate valve is partially opened, the ggate can vibrate, causing noise and damage to the seat.

Butterfly vavles can be used partially opened or closed. Needle valves are recommended for air lines. All manual valves should be left approximately one-quarter turn from full open to prevent them from being stuck open.

• 1. sanitary drainage for the disposal of waste
• 2. storm drainiage for the disposal of rainwater

Systems that are not properly vented are sluggish or nonfunctional; symptoms include a wash basin that takes forever to empty or insufficient water left in the bowl after a toilet is flushed. When these malfunctions occur repeatedly, the solids in the system may settle out. When solid waste deposits in the pipe, blockages occur.

Traps act as a seal between the piping system and outlets from any fixture, preventing sewer gases and vermin from entering occupied spaces through the drainage system and teh fixture outlets. Traps retain some water to form a liquid seal between the drain connectino of the fixture and the drainage piping system.

• 1. electrical pumping systems
• 2. pneumatic ejectors