AFUE |
Annual Fuel Utilization Efficiency:
A measurement of the seasonal energy efficiency of gas heating
equipment. It is the annual output energy of the equipment divided
by its annual input energy, expressed in consistent units (i.e.
Btu-out per Btu-in). Thus, the resultant value of AFUE is unitless.
AFUE includes any input energy required by the pilot light but
does not include any electrical energy or fans or pumps. |
BTU/H |
British Thermal Unit/per hour. One of the
two (watts-hours is the other) standard units of measure ( IP
System) for the amount of energy consumed by a process, the amount
of energy transferred from one location to another, or the amount
of embodied energy (such as the heat contents of fuels). Specifically,
it is the amount of energy required to raise the temperature of
one pound of water by one degree Fahrenheit. The term ‘kbty’
stands for “kiloBtu” or 1,000 Btu. The term of ‘Mbtu’
stands for “MegaBtu” or 1,000,000 Btu. One Btu/his
equal to 0.293 watt-hours (Wh). |
Capacity |
The rate at which the heating or cooling load
can be satisfied by a given equipment system designed to heat
or cool and dehumidify a conditioned space or heat service hot
water. Heating and cooling capacity is normally given on equipment
nameplates in units of Btu/h. The air conditioning industry often
uses units of “tons” to refer to equipment capacity.
One ton of capacity equals 12,000 Btu/h. |
Compressor |
A reciprocating or rotary pump for raising
the pressure of air or another gas; this may be a single-stage
or multistage unit. Reciprocating Compressor: a machine that compresses
gases, composed of one or several cylinders; each cylinder contains
a piston that is moved by a crankshaft through a connecting rod.
Rotary Compressor: a machine having a rotating member that directly
compresses fluid in an enclosed housing; the fluid pressure rises
as the volume of the closed space decreases. |
COP |
Coefficient of Performance: A measurement
of the instantaneous efficiency of heating or cooling equipment.
It represents the steady-state rate of energy output of the equipment
divided by the steady-state rate of energy input to the equipment,
expressed in consistent units(i.e. watts-out per watts-in or Btu/h-out
per Btu-in). Thus, the resultant value of COP is unitless. Most
vapor-compression heating and cooling equipment has COPs greater
than unity. That means it delivers more heat energy than it consumes. |
Heat pump |
A heat pump is a heat transfer machine, collecting
heat from one area (where it is not wanted) and depositing it
in another (where it is wanted). Therefore, it can act as a heating
as well as a cooling device. |
HSPF |
Heating Season Performance Factor: A measurement
ot the seasonal efficiency of an electric heat pump using a standard
heating load and outdoor climate profile over a standard heating
season. It represents the total seasonal heating output in Btu
divided by the total seasonal electric power input in watt-hours
(Wh). Thus, the resultant value for HSPF has units of Btu/Wh. |
Humidifier |
A device for adding moisture to the air or
another gas. |
Load |
The quantity of heat that must be added to
or removed from the building (or the hot water tank) to satisfy
specific levels of service – in other words, to keep the
space temperature or hot water temperature at a specified thermostat
setting ( see also the definitions of energy and thermostat). |
(S)EER |
(Seasonal) Energy Efficiency Ratio: A measurement
of the instantaneous energy efficiency of cooling equipment. It
normally is used only for electric air conditioning equipment.
EER is the steady-state rate of heat energy removal by the equipment
in Btu/h divided by the steady-state rate of energy input to the
equipment in watts. Thus, the resultant value for EER has units
of Btu/Wh. The EER of a given system is always higher than the
COP of that system by a factor equal to the number of Btu/h in
a watt, or 3.413. |
Thermostat |
A control device that measures the temperature
of the air in a home or the water in a hot water tank and activates
the heating or cooling equipment to cause the air or water temperature
to remain at a pre-specified value, normally called the set point
temperature (see also the definitions of load and energy). |
Ton |
A term used primarily by the air conditioning
industry to characterize the cooling capacity of air conditioning
equipment. One ton equals 12,000 Btu/h. |
