Glossary
Definitions of the terms used across Home Climate Journal, each on its own page.
A
- A2L refrigerantAn A2L refrigerant is one classed under ASHRAE Standard 34 as lower toxicity (A) and lower flammability with slow flame propagation (2L); R-454B and R-32 are examples.
- AFUEAFUE (annual fuel utilization efficiency) is the federal rating of how much of a furnace's fuel becomes heat for the home over a year, including standby and off modes; an 80% AFUE furnace turns 80% of its fuel into delivered heat.
- Auxiliary heatAuxiliary heat is the backup heating a heat pump system uses when the heat pump alone cannot meet the load, most often electric resistance strips in the indoor air handler.
B
- Balance pointA heat pump's balance point is the outdoor temperature at which its heating output equals the home's heat loss; below it, the heat pump alone cannot keep the home at the set temperature.
- BtuA British thermal unit (Btu) is the heat needed to raise the temperature of one pound of water by 1 °F; one kilowatt-hour equals 3,412 Btu and one therm equals 100,000 Btu.
C
- CADRCADR (clean air delivery rate) measures how much particle-free air a portable air cleaner delivers, in cubic feet per minute; the higher it is, the larger the room the unit can serve.
- Coefficient of performanceThe coefficient of performance (COP) is the heat a heat pump delivers divided by the electricity it uses, measured at one set of conditions; electric resistance heat has a COP of 1.
- Cold-climate heat pumpA cold-climate heat pump is an air-source heat pump certified to keep delivering useful heat at 5 °F (−15 °C); under ENERGY STAR it must keep at least 70% of its 47 °F capacity there at a COP of at least 1.75.
D
E
G
H
- Heat pump water heaterA heat pump water heater is a storage water heater that heats water by moving heat from the surrounding air into the tank; ENERGY STAR integrated models are rated at UEF 3.30 or more, against 0.95 for a standard electric tank.
- HEEHRHEEHR (High-Efficiency Electric Home Rebates) is the federally funded, state-run rebate program for electric home upgrades such as heat pumps, capped at $14,000 per household and limited to incomes up to 150% of area median income.
- HSPF2HSPF2 (heating seasonal performance factor 2) is the federal rating of a heat pump's heating efficiency over a whole season, in Btu of heat per watt-hour of electricity, measured under DOE's Appendix M1 test procedure.
M
R
- R-410AR-410A is the HFC refrigerant blend that replaced HCFC-22 as the most common refrigerant in new U.S. home air conditioners; EPA lists its global warming potential as 2,090 and its ASHRAE safety class as A1.
- R-454BR-454B is a lower-GWP refrigerant blend used in many new U.S. home air conditioners and heat pumps; EPA lists its global warming potential as 470 and its ASHRAE safety class as A2L.