This article is a collection of questions about cold-weather heat pump problems that we’ve received at HomeTips, along with the answers we’ve offered.Get a heat pump repair pro fast! Brenda: We have a heat pump with our AC unit. It works fine until the temperature drops outside. The temp outside is now 11 degrees and no heat at all will come out. It just blows cold air. We have cut it off, left it off for an hour or so, turn it back on and all that comes out is cold air. Can you advise the problem? Richard: I just bought a house that has gas heat with heat pump. I have always had an electric heat pump. Will the outside unit function when the temperature is below 40 degrees? I noticed it hasn’t been running. Is this a problem? Don V: In general, heat pumps can be poor at heating when outside temperatures get really cold. Here is an article on another site that discusses this: Heat Pump Effectiveness In Cold Weather Then again, any of several components could be malfunctioning.

It may pay to have a pro come out and check your system. central ac unit calculatorYou can get bids from local pros through this free online service: a heat pump repair technician.build roof over ac unit Jimmy: I’ve bought a home and it has a 7 year old Bryant Heat pump/Gas furnace combination unit. stand up ac dc downloadWe have only lived here 1 month. The home heats fine, but I did notice at late last night that the outside unit looked like it only ran for a few minuets. I got up twice later in the night and the furnace was running on gas and the unit outside was not running. In other words, the gas side had kicked in as needed. Should the outside unit ever come on when temp is below say freezing? Last night it was 10 degrees here in IN. When we had warmer days, say 35 or warmer, the unit did run outside.

When the heat pump runs outside it is rather quiet for a 3 ton unit. Should I be concerned that the unit ever comes on when temp is so cold or is it just trying to cycle and then it realizes it is too cold so it stays then shut off until outside temp recovers above freezing or in the 30’s?? Don V: Though the unit may need servicing, I think your speculation at the end of your question is right on target. I’m guessing that the outside temperature is so cold that the auxiliary heat is doing all of the work. Unfortunately, this is not very efficient—heat pumps are not at their best in super cold weather. Bettina: Hello, My Heat Pump unit outside is frozen and has a thick block of ice on it. I have turned my unit off. What can I do to thaw out the unit outside? Don V: It isn’t unusual for a heat pump to freeze up in cold weather, but it should kick into “defrost” mode and melt the ice periodically. Here are some conversations on other sites that might be helpful.

Be sure to read the second one after you read the first one. A Frozen Heat Pump Is Normal What To Do If Heat Pump Is Frozen More About Frozen Heat Pumps Roy: I have a standard “air source” type heat pump. It’s only a year old so it’s in great working order. Living in Michigan it gets well below 32 degrees in the winter. Is it wise or not to run it at such cold temperatures. Or should I stick with $2.00/gal.propane? Don V: In general, heat pumps —both gas and electric—can be poor at heating when outside temperatures get really cold. Here is an article on another site that discusses this: Heat Pumps and Cold Weather If the auxiliary heat has to kick on, it uses electricity to heat your home—and that gets very pricey. $2 propane as a heat source is probably much more affordable. Nikko: We have a heat pump that has trouble heating the house below about 40 degrees. Right now the temperature is below freezing and the house is more than ten degrees colder than outside, even with auxiliary heat on.

We paid to have the ducts and coils cleaned, and it helped but did not fix the problem. We looked at our ducts as best we were able and noticed that the system is pulling air from BETWEEN our basement ceiling and ground level floor. There is a big opening, about 1.5 ft2. Should we close it off? There is a normal register on the first floor (but not heated basement level) that is also pulling air. Don V: If I understand your description, the return-air is traveling in a chase between the ceiling and floor above it. Sometimes return-air ducts are designed that way—no actual metal duct, but rather a boxed-in chase. That’s okay, because it’s just drawing room air back to the heating appliance through that chase. You wouldn’t want to deliver heated or cooled air to rooms through a chase, however (too much heat loss). In general, heat pumps can be poor at heating when outside temperatures get really cold. Do heat pumps make sense with Minnesota winters? Also, can they be used with a radiator heating system?

Don V: Typical air-source heat pumps are not normally used for radiant heating systems, but ground-source heat pumps are. In general, heat pumps can be problematic in really cold climates. Here are a couple of discussions about this on two other sites: Heat Pumps In Cold Weather Discussion #1 Heat Pumps In Cold Weather Discussion #2Welcome to the Brewer HVAC Heating, Air Conditioning, and Utilities Blog A freeze stat is a temperature sensing device for HVAC that monitors a heat exchanger to prevent its coils from freezing. Freeze stats can be used on both freon-to-air, and freon-to-liquid type heat exchangers and serve different purposes with similar goals for each. The purpose of an air coil freeze stat is to keep the refrigerant-to-air heat exchanger (commonly called air coils) from freezing. This kind of freeze stat is typically used for heating coils which are exposed to outside air and is usually installed on the supply air side of the coil.[1] To accomplish this, they typically shut down the flow of outside air to a mixing box when the temperature reaches a predetermined setpoint.

The setpoint for air coil freeze stats is typically about 38 degrees Fahrenheit which is approximately when the dew point temperature of the air starts to drop below freezing point. The water coil freeze stat performs a similar function to the air coil freeze stat, but is used on a different type of HVAC system. Its function is to keep the freon-to-liquid heat exchanger (commonly called liquid coils) from freezing. In practical situations, when an air coil freeze stat is not used, bypassed, or defeated, the air coil can freeze, and this causes a lack of air flow to the facility.[3] By contrast, when a water coil freeze stat is not used, the water coil can get so cold that it can freeze the cooling liquid in the exchanger and burst the exchanger.[5] A ruptured heat exchanger mixes contaminants such as freon and oil into the coolant. The intrusion of coolant into the delicately balanced refrigeration system can cause expensive damage to components such as the freon compressor, and the reversing valve.

Conceptually, mechanical freeze stats are constructed with a diaphragm, a capillary tube and bulb, and an electric switch.[6] The capillary tube allows gas movement to and from the capillary bulb and the diaphragm with a fall or rise in temperature, respectively. When the temperature reaches a specific setpoint, the pressure in the diaphragm will trip a switch which typically shuts down the flow of outside air while the capillary bulb's temperature is at or below the setpoint.[6] Mechanical freeze stats can have more than one set of contacts, and the contacts can be NO or NC. Digital freeze stats, also known as electronic or solid state freeze stats, use an electronic circuit, microprocessor, or microcontroller in place of the mechanical freeze stat's diaphragm and switch. They also use one or more electric or electronic sensors in place of the capillary tube and bulb for temperature sensing. Digital freeze stats utilizing microcontrollers or microprocessors can also perform more advanced functions than simply opening or closing switch contacts.