woman sitting on couch with dog covered in blanket because heat pump is blowing cold air

Is your heat pump blowing cold air in winter? While heat pumps are excellent at removing heat and humidity in summer, they also effectively heat homes during the cold months. Air-source heat pumps transfer heat between indoor and outdoor air similarly, whether they are in cooling or heating mode. Refrigerants absorb the air’s heat at one of the system’s coils and release it at the other.

It’s concerning if your heat pump supplies cold air when the heat is switched on. Heat pumps are complex systems, and several issues can affect their operations. Luckily, some problems can easily be resolved by homeowners. Before you schedule a service call for your heat pump blowing cold air, investigate the cause. You might quickly fix it and save some money!

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Reasons Why Your Heat Pump is Blowing Cold Air

Heat pumps in cooling mode operate like air conditioners, absorbing heat from the indoor air and transferring it outside. But how does a heat pump work in winter? Heat pumps work the same way in heating mode but in the opposite direction. The refrigerant in the outdoor coil absorbs heat from the environment and transfers it inside the house. Thermal energy is always available for harnessing, even at below-freezing temperatures. Standard heat pumps are inefficient at capturing heat below 40°F, so heat pump systems often include backup heating. Although heat pump systems can supply heat in winter, there are several explanations for why cold air is coming from your vents.

1. It’s not actually blowing cold air

Heat pump heat has a lower temperature than furnace heat and might feel cold if unused to it. While furnace heat is between 110 and 140°F, heat pump heat is about 85 to 90°F. This temperature is also several degrees lower than the average body temperature and might feel cold.

The good news is that there might be nothing wrong with your heat pump. To be sure, alternately hold a thermometer near a supply and a return vent. The supply air should be 15 to 30 degrees hotter than the air entering the return vent. If there is no difference, one of the following issues could be to blame.

2. Incorrect thermostat settings

A few thermostat issues can cause cold air to blow from the vents. First, the thermostat might be set to “cool” instead of “heat.” This is a common mistake considering the heat pump provides heating and cooling, and the outdoor unit runs for both functions. Second, the fan setting might be incorrect. Cool air blows from the vents between heating cycles if the fan is turned on. A final possibility is improper thermostat calibration that causes it to misread temperatures.

If the thermostat is set to “cool,” switch it to “heat.” Setting the indoor temperature between 68 and 72°F prevents the heat pump from overworking and reduces energy bills. Next, ensure the fan is set to “auto” so only heated air blows from the vents. Setting the fan to “on” causes it to run constantly and circulate cool indoor air between cycles. Then, check the thermostat’s calibration. Tape a thermometer to the wall near the thermostat and compare temperature readings. The calibration can usually be adjusted in a programmable thermostat’s settings. Finally, gently remove dust from the thermostat and its wiring, and carefully check its electrical connections.

3. Refrigerant leak

Heat pumps circulate refrigerants through their systems to transfer heat between indoor and outdoor air. Low refrigerant levels diminish the heat the system can absorb from the outside air and deliver to your home. Low refrigerant also affects the heat pump’s cooling abilities.

Refrigerants exist in a sealed system and don’t diminish over time. Low refrigerant levels indicate a Freon leak. Gurgling sounds and liquid pooling around the outdoor unit are additional signs of refrigerant leaks. Call a professional to check the refrigerant’s charge, repair leaks, and recharge the system.

4. Dirty coil or cabinet

Refrigerants in the heat pump’s coils absorb heat from the air, and dirt on the coils reduces the heat absorbed. The outdoor coil in the condensing unit accumulates grime from the elements, and the cabinet that houses the coil can become blocked by leaves, twigs, and other organic matter that falls or is sucked into it

Regular heat pump maintenance ensures the system runs efficiently. Winter is not the best time for a thorough cleaning, but removing debris from the unit might be enough to resume normal functioning. First, cut power to the outdoor unit at the circuit breaker panel. Then, examine the unit for debris obstructing airflow through the metal fins and remove it. Gently vacuum the fins with the brush attachment of a shop vac, being careful not to bend or damage them. Straighten previously angled fins with a butter knife, but don’t insert the knife beyond ½ inch. Clean the unit thoroughly with a hose or coil cleaner when the weather is favorable, or schedule a professional cleaning.

5. Dirty air filter

The air filter traps contaminants before they enter the indoor unit to improve air quality and preserve the HVAC system’s cleanliness. Air filters are typically located at the point where the central return duct feeds into the air handler or furnace, but some systems have additional air filters. Air filters that aren’t regularly replaced fill up with contaminants and restrict airflow, reducing the amount of heated and cooled air. Severely restricted airflow overworks the HVAC system and damages it.

Remove the air filter and assess its cleanliness. Replace the filter with a new one if it’s coated with dust, hair, or other fragments. Regularly check and change the filter to avoid heat pump issues. How often should you change the air filter? Change the filter when it appears dirty, about every 30 to 90 days.

6. System is in defrost mode

The heat pump defrost cycle removes frost from the outdoor coil to preserve heat pump efficiency. Heat pumps automatically switch to defrost mode when sensors detect ice on the coil or low coil temperatures. Defrost mode operates similarly to cooling mode so that cold air might flow from the vents during the cycle. The indoor coil absorbs the home’s heat and transfers it to the outdoor coil to melt the frost. The heat pump returns to heating mode when the coil’s temperature increases. Defrost cycles recur as needed or at timed intervals.

Go to the outside unit to check if the heat pump is running a defrost cycle. The fan should be inactive, and steam might waft from the unit. Defrost cycles lasting longer than 15 minutes or recurring more often than every 30 minutes typically indicate defrosting problems and can be alleviated by switching the thermostat to the air conditioning mode for 20 to 30 minutes. Follow up with a service call to avoid future defrosting issues.

7. Failing reversing valve

The reversing valve allows the heat pump to switch between heating, cooling, and defrosting by reversing the refrigerant’s flow. A faulty reversing valve prevents heat pumps from switching modes. If cold air blows from the vents, your heat pump might be stuck in cooling mode.

Professionals should handle reverse valve repairs, but homeowners can attempt to unstick the valve. First, cut power to the outdoor unit at the circuit breaker panel. Locate the reversing valve in the outdoor unit, and tap it with a hard plastic object, such as a screwdriver handle. If heating doesn’t resume, call a heat pump-savvy technician.

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8. Buildup of ice and/or snow

Heat pumps transfer the environment’s heat indoors in heating mode, and ice and snow on and around the outdoor unit affect the system’s ability to do so.

Remove snow around and on top of the unit with a broom or brush to avoid damaging it. The defrost cycle should melt frost, but thick ice from freezing rain or gutter leaks must be manually removed if the heat pump is freezing up. Turn off the power supply to the heat pump, and pour warm water over the ice to melt it. Don’t use a sharp object to chip away at it. Repair the gutter if it leaks onto the unit.

9. Auxiliary heat isn’t working

Most heat pumps in cold climates include backup, auxiliary heat systems. Electric heat strips are installed in the air handler and supplement the heat pump’s heat when the heat pump loses efficiency in cold weather and during defrost cycles. The backup heating system is also used for emergency or EM heat. It can be manually activated and independently provide the home’s heat if the heat pump is inoperational.

Cold air from the vents could signal a problem with your auxiliary system rather than your heat pump. Call a professional to repair or replace the system.

10. Tripped circuit breaker

Circuit breakers are electrical safety mechanisms that interrupt electrical currents to protect equipment and prevent fires if abnormal conditions occur. A tripped circuit breaker cuts off the heat pump’s power supply and might be to blame if the heat pump is not turning on.

Check the circuit breaker panel for a switch that’s out of line with the others and between the “on” and “off” positions. Verify that it’s the circuit leading to the heat pump. Move the switch to “off” and then to “on.” It’s essential to diagnose and rectify the cause of the breaker tripping. It could be a dirty filter or a buildup of ice and snow that forced the system to overwork. If the breaker trips again, call a professional.

Is it time to replace your heat pump?

It might be time to replace your heat pump if it’s continually problematic and nearing the end of its lifespan or out of warranty. How long heat pumps last largely depends on how well they’re maintained. The average lifespan is about 15 years.

Several signs indicate that a heat pump is close to total failure:

  • Frequent repairs

  • Inability to control indoor temperatures

  • Higher energy bills

  • Unusual operational noises

How to Handle a Heat Pump That Blows Cold Air

There are several things to check when your electric heat pump blows cold air in winter. First off, there might be nothing wrong with the system. Heat pump heat has a lower temperature than gas furnace heat and your normal body temperature. It might simply feel cold. Compare the supply and return air’s temperatures to verify that the supply air isn’t 15 to 30 degrees warmer than the return air. If there is little to no temperature difference, check your system for these common issues with do-it-yourself solutions:

  • Incorrect thermostat settings

  • Dirty coil or cabinet

  • Dirty air filter

  • System in defrost mode

  • Build up of ice or snow

  • Tripped circuit breaker

If you can’t locate the problem, schedule a service call with an HVAC company specializing in heat pumps. The cause could be one of the following issues that professionals should handle:

  • Refrigerant leak

  • Failing reversing valve

  • Auxiliary heat isn’t working

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