Why Your Heat Pump Does Not Reach The Set Temperature

There are reasons why your heat pump does not reach temperature set on your thermostat. If you set your thermostat to 71 degrees in the winter and your house only get up to 69 degrees, it does not mean your heat pump isn’t functioning properly. This problem/situation is extremely common and it generates many service calls. Sometimes there is a genuine problem, but more often than not, there is nothing wrong. Unfortunately, in extremely cold weather, even a properly working heat pump does not reach temperature set on thermostat.

Why does this happen? When it gets below 35 degrees, a heat pump loses its efficiency and cannot keep up with the heat loss of the structure. When the temperature in the house drops approximately 2 degrees below the room temperature, supplemental heat comes on to assist the heat pump (usually in the form of electric resistance heaters). When its gets with 1.5 degrees of room temperature, the back-up heat cycles off and the heat pump continues to run trying to keep up to reach temperature, but it cannot. This happens most often when it is cold – less than 30 degrees.

This is, however, the way heat pumps are designed to operate. Even though they don’t put out a lot of heat in to the house, and they run for long periods of time, they are still quite efficient. So, if it is very cold outside and your heat pump does not reach temperature set on your thermostat, you might have to raise your thermostat a few degrees to maintain it.

Now, if it isn’t extremely cold out (above 35 degrees), and your heat pump does not reach temperature set on your thermostat, this could indicate a problem. Here is a list of possible causes: items in blue need to be addressed and can be fixed by homeowner – items in red require a licensed profession like those here at LHT!

• Outdoor unit iced up
• Outdoor unit not running
• Duct leakage – pulling in cold air
• Open windows/poorly insulated house
• Thermostat not calibrated/faulty
• Low refrigerant
• Needs service or cleaning
• Bad reversing valve
• Bad compressor valves
• Compressor not running

So if your heat pump does not reach temperature set on your thermostat, don’t despair Spring is just around the corner!