Why Is My Heat Pump Not Heating the House?
A heat pump that seems not to heat is often working fine. Its air comes out cooler than a furnace, and it blows cool for a few minutes while it melts frost off the outdoor unit. Real problems include wrong thermostat settings, a dirty filter, an outdoor unit packed in ice, or low refrigerant. Check the mode and the filter first.
What makes a heat pump stop heating?
Air that feels cool but is actually normal
A heat pump sends out air around ninety to one hundred degrees. That warms the house steadily, but it feels cool on your skin next to a gas furnace. People new to heat pumps report this as a failure every winter. If the house holds the temperature you set, the system is doing its job.
Safe to check yourselfIt is melting frost off the outdoor unit
In cold, damp weather the outdoor unit frosts over, so the system reverses itself for a few minutes to melt it off. While that happens, the outdoor fan stops, steam rises off the unit, and the indoor air turns cool. That is the system protecting itself, not breaking.
Safe to check yourselfThermostat set wrong for a heat pump
A heat pump thermostat has a HEAT setting and an EMERGENCY or AUX setting, and picking the wrong one changes everything. Emergency heat runs only the electric backup coils, and those cost far more to run. Checking that the mode is HEAT is safe and takes a moment.
Safe to check yourselfDirty air filter
Low airflow hurts a heat pump both ways. Rooms get weak, lukewarm air and the system works harder for less heat. Changing the filter is safe to do yourself. It matters more on a heat pump than on a furnace, because a heat pump runs many more hours a day in winter.
Safe to check yourselfOutdoor unit packed in ice
A unit buried in thick ice that never clears cannot pull heat out of the air. That points to a failed frost control, a bad sensor, or low refrigerant. Do not chip the ice or pour hot water on the coil. This one needs a technician.
Technician repairLow refrigerant
Refrigerant is the fluid a heat pump uses to carry heat, and a leak cuts its heating the same way it cuts its cooling. Long run times, lukewarm air, and heavy icing outside are the winter signs. Leak repair and recharging need a license.
Technician repairStuck valve
A heat pump uses one valve to switch between heating and cooling. Stuck in cooling, it blows cold air on a heat call no matter what the thermostat says. Getting to that valve means opening the sealed refrigerant side, so it is technician work.
Technician repairFailed backup heat
On the coldest nights, electric backup coils carry part of the load. When those coils or their controls fail, the house slowly loses ground even though the heat pump itself is running. Testing those circuits is professional electrical work.
Technician repairWhat can you check yourself?
- Check that the thermostat is set to HEAT, not EMERGENCY or AUX, with the temperature above the room.
- Change the air filter if it is dirty.
- Look at the outdoor unit. Light frost that clears now and then is normal. Thick ice that stays is not.
- Clear snow, leaves, and debris from around the outdoor unit, and check that roof runoff is not dripping on it.
- Measure instead of guessing. Note the indoor temperature, wait an hour, and see whether it is holding or climbing.
Safety note: Never chip ice off the outdoor unit or pour hot water on it. The fins and the refrigerant lines damage easily, and a heavy ice-up needs a technician.
When should you call for repair?
Call when the house keeps losing ground in ordinary winter weather. Call when the outdoor unit is packed in ice that never clears. Call when the vents blow truly cold air on a heat call. Call if your electric bill jumps because the system has been running on emergency heat. A heat pump that runs long hours in deep cold is normal. A house that cannot hold its temperature is not.
Most Potomac houses run two or more systems, split by floor or by wing, and the two are almost never the same age. So one part of the house can go cold while the rest is fine. Zone dampers are common here too, and a failed damper motor gets read as a failed heat pump. Below a certain outdoor temperature, often somewhere in the low thirties, the backup heat runs alongside the heat pump. Long run times and cooler air at the vents during a January cold snap are normal.
Related questions
At what temperature does a heat pump stop working?
A heat pump does not stop all at once. It puts out less heat as it gets colder outside. Below a certain point, often in the twenties to low thirties for systems here, the electric backup runs alongside it to cover the gap. Newer cold-weather models hold useful output well below zero. Running constantly in deep cold is expected.
Why does my heat pump blow cool air sometimes?
Two normal reasons. Heat pump air comes out around ninety to one hundred degrees, which feels cool on your hand while it still warms the house. And every so often the system reverses for a few minutes to melt frost off the outdoor unit, so the air turns cold and steam rises outside. Cool air is only a real symptom when the house stops holding its temperature.
Should I switch to emergency heat when it is cold outside?
No, not as a routine answer to cold weather. Emergency heat shuts the heat pump out and runs only the electric backup coils, which cost far more per hour. The system already blends in backup heat on its own when it needs help. Use emergency heat only when the heat pump has actually failed and you are waiting on a repair.
Why is my heat pump running constantly in winter?
Running almost nonstop in cold weather is usually by design. A heat pump gives moderate heat over long cycles, and in real cold it may run nearly all the time while holding the house steady. The thermostat tells you which it is. If the temperature holds, the run time is fine. If it keeps slipping, book a visit.
If your heat pump cannot hold the house at temperature, call Mora Heating & Air and we will tell real faults apart from normal winter behavior.
Or tell us what your system is doing
Send us the details and we will call you back. If the house is very hot or very cold right now, calling is faster.