Heat pump not heating
Heat pump not heating: aux, emergency heat and power outages
Stop first
If the backup heat is a gas or oil furnace (dual fuel), or anything else in the home burns gas or oil, these come before anything else on this page.
If you smell gas
Leave the building now. Do not touch light switches or use a phone inside. From outside, call your gas supplier, or the fire department if you cannot reach them.
If a carbon monoxide (CO) alarm is sounding, or someone feels sick
Get everyone outside into fresh air now, then call 911 or the fire department from outside.
The U.S. Consumer Product Safety Commission's words:
- "Never ignore an alarming CO alarm! It is warning you of a potentially deadly hazard."
- "If the alarm signal sounds do not try to find the source of the CO:"
- "Immediately move outside to fresh air."
- "Call your emergency services, fire department, or 911."
- "After calling 911, do a head count to check that all persons are accounted for. DO NOT reenter the premises until the emergency services responders have given you permission. You could lose consciousness and die if you go in the home."
- "If the source of the CO is determined to be a malfunctioning appliance, DO NOT operate that appliance until it has been properly serviced by trained personnel."
If the furnace itself shows flame while the thermostat is not calling, or a reset button on it tripped again, its stop checks and its light or code are on furnace codes by model.
Pick the brand on the outdoor unit and say how long the power was off. A restart rule is held here only where that maker's own manual prints one (York, Luxaire, Coleman; Lennox), and it is read from that manual, never another's; for any other maker the page says none is held. Then pick the thermostat to see what its aux and emergency heat do, in its maker's words where the page holds them.
1. The outdoor unit
2. After a power outage
Pick the brand on the outdoor unit above.
3. What aux and emergency heat mean
Pick the thermostat to see its maker's words.
Next
If the backup heat is a gas or oil furnace
Where the thermostat makes the switch from the heat pump to the furnace, it does so from one or two lockout settings, depending on the thermostat; some systems make it in another control instead. This page prints no setting: the dual-fuel switchover calculator works them out for your equipment and your thermostat.
Questions
My heat pump lost power. Can I just turn it back on?
It depends on the maker, and the makers held here print different rules, so use your own maker's. York, written for the homeowner (York 1183508-UUM-O-0121, user's information manual, outdoor split-system air conditioner or heat pump, page 1): "Should the main power be disconnected or interrupted for 8 h or longer, do not attempt to start the system for 8 h after the power is restored to the outdoor unit. If heat is needed during this 8-h period, use emergency heat." Lennox, written for the technician (Lennox 508406-01, EL16KP1 heat pump installation manual, page 17): "Emergency heat is usually used during an outdoor unit shutdown, but it should also be used following a power outage if power has been off for over an hour and the outdoor temperature is below 50°F (10°C). System should be left in the emergency heat mode at least six hours to allow the crankcase heater sufficient time to prevent compressor slugging." Lennox, written for the homeowner (Lennox 508406-01, EL16KP1 heat pump installation manual, page 20): "If power to your unit has been interrupted for several hours or more, set the room thermostat selector to the EMERGENCY HEAT setting to obtain temporary heat without the risk of serious damage to the heat pump. In EMERGENCY HEAT mode, all heating demand is satisfied by auxiliary heat; heat pump operation is locked out. After a six-hour compressor crankcase warm-up period, the thermostat can be switched to the HEAT setting and normal heat pump operation may resume." No restart rule is held here from Carrier, Bryant, Payne; ICP; Allied; Goodman, Amana, Daikin; Rheem, Ruud; Trane, American Standard; Nortek, and York's and Lennox's do not carry over to them.
What is the difference between aux heat and emergency heat?
In the thermostat makers' own words. Google (Google Nest help article 9276120 (emergency heat)): "Emergency heat must be turned on manually while Nest thermostats can use Auxiliary Heat automatically as needed." Resideo (Resideo 33-00462-08, T10 / T10+ Pro Smart thermostat product data, page 106): "Emergency Heat runs when you manually switch the thermostat to the Em Heat mode. When the thermostat is in Emergency Heat mode, the heat pump is locked out." Pick your thermostat on this page to see its maker's words.
Should I switch to aux or emergency heat if the heat pump reports a refrigerant leak?
Not as a fix. Carrier's owner's manual for its R-454B heat pumps (Carrier OG-HPR454GEN-02, owner's manual, split-system heat pump using R-454B, page 1) says: "If a refrigerant leak is detected, the dissipation system will turn off the outdoor unit, turn off supplementary heat and turn on the indoor blower." Leave that to the system and call a technician.