Brochure

134
Hoffman Specialty
®
Glossary of Terms
Glossary of Terms
Glossary of Terms (cont’d)
Coefficient of Heat Transmission (Over-all)-U-: The
amount of heat (BTU) transmitted from air to air in one hour
per square foot of the wall, floor, roof, or ceiling for a
difference in temperature of one degree Fahrenheit
between the air on the inside and outside of the wall, floor,
roof, or ceiling.
Column Radiator: A type of direct radiator. This radiator
has not been sold by manufacturers since 1926.
Comfort Line: The effective temperature at which the
largest percentage of adults feel comfortable.
Comfort Zone (Average): The range of effective
temperatures over which the majority of adults feel
comfortable.
Concealed Radiator: See Convector.
Condensate: Water formed by cooling steam. The
capacity of traps, pumps, etc., is sometimes expressed in
Ibs. of condensate they will handle per hour. One pound of
condensate per hour is equal to approximately 4 sq. ft. of
steam heating surface (240 BTU per hour per sq. ft.).
Condensate Pump: A pump that is controlled by a switch
mounted on the condensate tank. It adds water to the
boiler when the condensate tank becomes full, whether
the boiler needs water or not.
Condensate Return Rate: The rate at which condensate is
returned to the boiler
Condensate Return (unit): A pre-packaged system
consisting of a tank, pump, and usually a float switch that is
used to pump condensate back to the boiler or boiler feed
unit.
Conductance (Thermal)-C-: The amount of heat (BTU)
transmitted from surface to surface, in one hour through
one square foot of a material or construction for the
thickness or type under consideration for a difference in
temperature of one degree Fahrenheit between the two
surfaces.
Conduction (Thermal): The transmission of heat through
and by means of matter.
Conductivity (Thermal)-k-: The amount of heat (BTU)
transmitted in one hour through one square foot of a
homogenous material one inch thick for a difference in
temperature of one degree Fahrenheit between the two
surfaces of the material.
Conductor (Thermal): A material capable of readily
transmitting heat by means of conduction.
Convection: The transmission of heat by the circulation
(either natural or forced) of a liquid or a gas such as air. If
natural, it is caused by the difference in weight of hotter
and colder fluid.
Convector: A concealed radiator. An enclosed heating
unit located either within, adjacent to, or exterior to the
room or space to be heated, but transferring heat to the
room or space mainly by the process of convection. A
shielded heating unit is also termed a convector. If the
heating unit is located exterior to the room or space to be
heated, the heat is transferred through one or more ducts
or pipes.
Convertor: A piece of equipment for heating water with
steam without mixing the two. It may be used for
supplying hot water for domestic purposes or for a hot
water heating system.
Cooling Leg: A length of uninsulated pipe through which
the condensate flows to a trap and which has sufficient
cooling surface to permit the condensate to dissipate
enough heat to prevent flashing when the trap opens. A
thermostatic trap may require a cooling leg to permit the
condensate to drop enough in temperature to permit the
trap to open.
Degree-Day: (Standard) A unit which is the difference
between 65° F. and the daily average temperature when it
is below 65°F. The “degree day” on any given day is equal
to the number of degrees F. that the average temperature
for that day is below 65° F.
Dew-Point Temperature: The air temperature
corresponding to saturation (100 percent relative
humidity) for a given moisture content. It is the lowest
temperature at which air can retain water vapor.
Direct-lndirect Heating Unit: A heating unit located in
the room or space to be heated which is fully or partially
closed. The enclosed portion is used to heat air which
enters from outside the room.
Direct Radiator: Same as radiator.
Domestic Hot Water: Hot water used for purposes other
than house heating such as laundering, dishwashing,
bathing, etc.
Down-Feed One-Pipe Riser (Steam): A pipe which
carries steam downward to the heating units and into
which heating units drain condensation.
Down-Feed System (Steam): A steam heating system in
which the supply mains are above the level of the heating
units which they serve.
Dry-Bulb Temperature: The temperature of the air as
determined by an ordinary thermometer.
Dry Return (Steam): A return pipe in a steam heating
system which carries both condensation and air.
Dry Saturated Steam: Saturated steam containing no
water in suspension.
Equivalent Direct Radiation (E.D.R.): The amount of
heating surface which will give off 240 BTU per hour when
filled with a heating medium at 215°F. and surrounded by
air at 70° F. The equivalent square foot of heating surface
may have no direct relation to the actual surface area.
Extended Heating Surface: Heating surface consisting of
ribs, fins, or extended surfaces which receive heat by
conduction from the prime surface.