the density of a substance usually increases as its temperature increases.. true or false
false
heat applied to the lower part of a fluid will cause ...
convection
two cloumns of the same liquid are of equal height, but at different temperatures. the column with the higher temperature will have..
THE lower pressure at the bottom
for gravity circulation, the boiler should be _____ the heat transfer units
below the level of
the heat transfer units of a gravity system are usually hooked up in parallel. true or false?
true
flow stopped in one element of a series circuit will stop flow in the rest of the ciruit. true or false?
true
To ensure that there is enough water in the system and sufficient room for thermal expansion, a gravity system has an..
expansion tank
pipes need to be sloped for the elimination of air..
even when a circulation pump is used
in a ____system, the flow through one heat transfer unit cannot be shut off without stopping the flow in the other heat transfer units
series loop
A _____ system, is a one-pipe system in which flow can be stopped to individual heat transfer units
monoflow
a_____ system is a balanced two pipe system
reverse return
A ____ system is only used for commmercial and industrial applications
direct return
a monoflow tee induces flow in the branch by use of a
venturi
The first heat transfer unit to receive the water is the last to return it is the characteristic of a _____ system
reverse return
A boiler is used to provide
hot water and steam
The area of a water chamber is increased in order to
heat the water more quickly and efficiently
Large water tube boilers are normally used for
producing high pressure steam in large volumes
Fire tube boilers are well suited for
hydronic or steam heating
The operating pressure of a hot water heating system is
normally 12 psi
Boiler ratings indicate output capacity in
kilowatts (Btuh)
A cast iron boiler is made of
modules operating at different temperatures
sections of a cast iron boiler are connected together with
push nipples
steam boilers are controlled by
pressure switches only
hot water boilers are controlled by
temperature switches only
steam boilers are ____ filled with water
only partially
steam is usually forced through a piping system by means of a steam circulating pump.. true or false>
false
steam is called high pressure steam at 15 psi. true or false?
false
low pressure steam boilers can reach 135 c or 275 dg f .. true or false
false
boilers in hot water heating systems usually operate at
1120 kpa and 121 c ( 160 psi and 250 deg f
package boilers
are fully assembled and tested at the factory
the original package boilers were____boilers
fire tube
the water supply system to the boiler is usually called the
boiler makeup
the water supply system adds water to a hydronic heating boiler when
pressure gets too low
the pressure reducing valve is
part of the water supply system
an aquastat measures the _______ of the water
temperature
after making its measurment, the aquastat
opens or closes a switch
when a diaphragm compression tank is installed
an air purger should be routed to it
the vent on a boiler
expels burnt gases to the outdoors
the vent for a boiler is made of
steel or masonry
heat travels by conduction, convection, and by..
radiation
heat travels quickly through a good
conductor
heat moving through space without heating is called
radiation
heat travel in water from a boiler to heat transfer unit is called..
conduction
rough, black objects make the best
radiators
heat transfer surfaces which heat an area by the circulation of air through heated fins are called..
convectors
heat transfer surfaces emit more heat, the larger and ____ that they are
hotter
gravity, forced air, or blower fan cirulation is used to direct the air through the fins of convectors for better heating of the surrounding area,.. true or false?
true
copper and steel are conductors; air and plastic are..
insulators
grids of nonmetallic pipe enclosed in concrete floors are used to provide the most comfortable residential heating ever developed .. true or false
true
a convector basically heats a room by heating the
air
convectors with fans mounted near the ceiling are called
unit heaters
a convector which does not depend on gravity for circulation uses a
fan
convector cabinets are usually made of
steel
convectors should be installed under windows. true or false?
true
the heating element of a convector is usually made of__pipe
finned
the amount of heat given off by a hot gravity circulation convector is usually regulated by an adjustable....
louvre
the two types of unit heaters are
vertical heaters and horizontal heaters
convectors which replace baseboards are called
baseboard convectors
heat loss through the back of a convector should be minimized by the installation of insulation.. true or false?
true
radiant heat travels through
rays
cast iron radiators give off heat by..
both radiation and convection
one difficulty with pure radiant heating is that the heater must be..
in sight of the objects to be heated
freestanding radiators were
sectional
the most comfortable room is slightly warmer
near the floor
the most efficiently heated space is warmer
near the floor
radiant heating panels are best located
in the floor
radiant heating panels can provide extra heat to parts of an area by
closer spacing
in radiant panels, supply and return piping should be run side by side.. true or false?
true
clamped or threaded pipe joints should not be buried in concrete.. true or false
true
piping runs in a hydronic heating system should
be almost level or have a slope of 4mm/m 1/2"/10'
the fittings in a swing connection are
either all 90 degree elbows or a combination of 90 deg and 45 deg elbows
small circulators can lift water
4 feet or 1.3 meters
piping runs should not be placed in outside walls. true or false
true
pump circulation can be stopped by air bubbles accumulating at a high point.. true or false?
true
drops to downfeed heat transfer units should connect from the______ of the mains
bottom
downfeed baseboard heat transfer units usually require __ air vents
no
Baseboard heat transfer units with upfeed stubs usually require __ air vents
two
if a heating system contained 100 litres of water, the volume change from cold to hot would be about..
1 litre
open systems, where pressure cannot build up above static pressure, accomodate volume expansion by the use of a
compression tank
adding fresh water to a heating system increases
flow through the system
closed systems with cirulators accommodate volume expansion by the use of a
expansion tank
if volume expansion is properly accommodated, the pressure will not not increase in a closed system when the water is heated .. true or false
false
A boiler fitting
is used to connect a diaphragm compresssion tank
flow control valves prevent
excessive flow through a piping run
an altitude gauge measures
pressure in psig
air contained in fresh water
immediately separates and rises to the top
mixed air separates more quickly when..
the water is heated
air vents on a heating system
maintain the correct water air mixture
a serious accumulation of air can cause
gurgling sounds from the system
automatic air vents open when..
more air is required
high points in a heating system should be
vented and supported
High volume locations, such as mains and unit heaters, should hav an
air volume control
a thermostat originates a demands for heat by ___and closing a switch
sensing air temperature
an aquastat senses
water temperature
a sensing device with a normally closed switch that opens when reaching a set temperature or pressure is said to be
direct acting
the circulator is usually switched on and off by a
relay
when a bimetal strip experiences a temperature change, it
bends
a boiler burner is turned on and off by a
aquastat
a thermostat should be located __ above the floor on an inside wall away from heat sources
5 ft
a zone valve is controlled by a ..
thermostat
a zone valve controls the flow of
water
a releif valve senses and reacts to water
pressure
a high limit burner safety switch with a manual reset button is an
aquastat
RELIEF VALVES OPEN AT
30 psi
EPDM piping material is not used in HRF systems because it..
