Running, moving air, but the house isn't warming. What's normal for a heat pump, and what isn't.
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Heat pump problems
A heat pump fails differently than a furnace, because it moves heat rather than burning fuel for it: which means some things that look broken are actually the system working exactly as designed.
The same equipment does both jobs
A heat pump is mechanically an air conditioner that can also run in reverse, moving heat from the outside air into the house instead of the other way around. That single fact explains a lot of the patterns in this section: why heating-mode air feels warm rather than furnace-hot, why the outdoor unit does real work even on a cold day. And why a periodic defrost cycle is normal rather than a fault.
Heat pump guides
Long runs in extreme weather are normal. Running nonstop in mild weather without catching up is not.
No response at all when you call for heat is a different problem than a system that runs but doesn't warm up. Start with power.
"HVAC heat" covers two different systems with different failure points. Identify yours before you troubleshoot.
Find which half is dead, wait out the restart delay, then check the breaker and the outdoor disconnect.
No heat, cool air or a house that never catches up: match the symptom to the right check.
Separate defrost mode and fan settings from a real fault, and know when to call a technician.
Defrost and restart delays look like failure. Check the thermostat, breaker and disconnect before you call.
Gentle air is normal. Judge by whether the house warms up, then check filter, airflow and backup heat.
When the outdoor condenser stays off, start with the thermostat, the delay and the breaker.
What the compressor does, the warning signs of a failing one, and the checks that are safe to do yourself.
Tell a normal defrost cycle from real icing, and thaw it without damaging the coil.
The main parts of a heat pump, what each does, and the few you can safely look after.
How a dual fuel system switches between electric and gas heat, and who it suits.
What sets a heat pump's low-temperature limit, and when backup heat should take over.
Normal pauses, safe checks and the point where a still fan is a job for a licensed pro.
The four ports, the solenoid, and why this sealed part is never a DIY repair.
How to tell a heat pump fault from a furnace fault and the safe checks to run first.
Which one you choose, which one switches on alone, and when to call a pro.
What each one can do in winter and what should decide your choice.
How much heat you get per unit of electricity, and why the number drops in the cold.
Why square footage rules fail and what a proper load calculation checks.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- ENERGY STAR. Air-Source Heat Pumps
- ENERGY STAR. Energy Savings at Home: Heating & Cooling