HVAC Central

Chillers

A fluid that absorbs heat by evaporation at a low temperature and pressure and releases heat by condensing at a higher temperature and pressure

Water or glycol mixture that is cooled by a refrigerant, which is then circulated by pumps throughout the refrigeration system to absorb heat.  (a secondary refrigerant is used because it is cheaper and safer, as opposed to circulating refrigerant).

Variable Frequency Drive

Pie shaped dampers, used on centrifugal compressors used to direct gasses into the compressor and used for capacity control.  (The compressor will start with guide vanes closed=unloaded position)

Know a dry type evaporator, this evaporator will boil a refrigerant and superheat that refrigerant before leaving the evaporator.

An evaporator that has water in the tubes and the tubes are submerged in refrigerant.  This allows for better heat transfer.  A flooded evaporator will use more refrigerant than a dry type evaporator.

A water box on a chiller or condenser with a removable cover.

The difference in temperature between the refrigerant and the leaving ater in a chilled-water system.

The process by which one substance is absorbed by another

A term used to adjust the charge in an absorption chiller

Lithium-Bromide, a type of salt solution used in an absorption chiller.

Pumps

Rotating part of a centrifugal compressor, pump or other machine which uses centrifugal force to move or compress a fluid.

This is the housing that surrounds the impeller and guides the water through the water through the pump.

Centrifugal pump which has its inlet and its discharge in a straight line.

Raises fluid pressure within the piping system, used to overcome resistance within the piping.

These pumps recirculate water throughout the system and coil/terminal units to transfer more heat from the water.

These types of pumps are mounted directly to the motor shaft.

These types of pumps are mounted on an impeller shaft connected to the motor by a flexible coupling.

Water within this system will come in contact with the atmosphere.  An example would be an open cooling tower.

Water within this system will not come in contact with the atmosphere.  Most chilled and hot water systems are closed systems.

Air Handling Units and Piping systems

This converts energy from electricity or fuel and is the source of hot or chilled water.  These are boilers and chillers within a system.

This is known as the distribution system.  This delivers the heating or cooling throughout the building.

Return Air

Exhaust Air

Outside Air

Mixed Air

Are devices that are used to transfer heat from the stream or water to the surrounding air.  THis would be baseboard, radiator, unit heater, fan coil, or any other device that exchanges heat.

This is the simplest design, all water flows through each terminal unit.

This system is designed with supply and branch pipes and valves seaperate each terminal unit from the main supply line.  These systems require diverting tees to help with flow through the terminal units.

This design uses a supply line and a return line to improve terminal unit efficiency by having each terminal unit receive water directly from the supply line.  The firs supplies, is the first returned.  (Water tends to cycle with design).

This design is where flow resistance is directly proportional to the pipe length.  This is a better balanced system.  The first supplied is the last returned.

A system where one pipe supplies chilled water and another supplies hot water and uses one pipe to return the water.  There are also three pipe systems that are changed over in the mechanical room.  This allows the system to supply heating or cooling by changing over the primary source.

A system that supplies hot and chilled water all season long with each having their own return line to their primary source.  This allows the most flexibility for a building, but is the most expensive to install.

Make-up Air (MUA)

This Type of make-up air allows the air to come in contact with the flame to exchange heat.  This style does not have a heat exchanger.

This type of make-up air has a heat exchanger.  The products of combustion do not come in contact with the make-up air.

A system that allows an additional item to get and/or become energized when needed.

A thermostat that is installed in a make-up air to prevent incoming air that is below freezing to continue to be supplied to the space.

The temperature of the air entering a make-up air unit.

The temperature of the air leaving the make-up air

Boilers

Maximum Allowable Working Pressure

A boiler design with water in the tubes surrounded by fire. 

A boiler design with fire in the tubes surrounded by surrounded by water. 

American Society of Mechanical Engineers

Normal Operating Water Level

WWSD

A valve on the boiler used to release air from the boiler when filling the boiler.

A system that "feed" water to the boiler at the correct pressure and temperature.

Removers sludge build-up from the bottom of the boiler.

Allows a continuous trickle of blowdown water from the boiler.

Removes impurities from the surface water of a boiler system.

Cooling Tower
When water and air come into contact and sensible heat is exchanged for latent heat.

When air comes in direct contact with the water being cooled.

Whenever a wetted surface is used to faciltate heat transfer to another medium. 

When air and water flow is in the same direction while traveling through the tower.

When the water flows from the top to the bottom of the tower.  Fans draw in from the sides of the tower and discharge it from the top.

The flow of the water is opposite the flow of the air as they travel through the fill section.

When air is moved by pulling it through the tower.

When air is blowing into the tower by mechanical means.

When a amount of water is drained from the tower sump to remove minerals left behind as a result of water that has evaporated.

Is a column of moisture rising in the atmosphere.

Is the undesirable loss of water within the atmosphere.

A type of control that is used for towers, with or without fans, as a means of controlling the cooling tower at low ambient conditions.

Is when when a portion of the water is directed two inlets and one outlet.

A whirlpool action action in the sump of a cooling tower.

Fire/Smoke Dampers-Fans

Temperature rate link used on fire dampers.

A fan that forces the air in a radical direction perpendicular to the fan shaft.

A design which air enters and exits the impeller along the same axis paralles to the fan's shaft.

A fan in which it discharges its air upward.

Air station and pneumatics
Lines that supply supply air from the air station to the controller.

Lines that supply air from the controller to actuator.

When the temperature is increased pressure is increased.

When the temperature is increased pressure is decreased.

A range in which in which an actuator will move from the full open  or closed position.

A compressor and associated parts needed to supply clean dry air for pneumatic control.