Why Is My Heat Pump Blowing Cold Air?

When a heat pump is blowing cold air, the unit might be in defrost mode which is completely normal. The presence of cold air for a prolonged period, however, is not normal and can be caused by issues with the reversing valve, a dirty filter, and low refrigerant levels. 

What should you do, if your unit is blowing cold air? Below you’ll find a few useful tips, but first let’s figure out if there’s even a problem (your body might be tricking you).

Is Your Heat Pump Actually Blowing Cold Air?

Heat pumps deliver air that is colder than our body temperature. That’s why it might feel like the air is ‘cold’, but the truth is that the unit is actually making your house warmer.

Another important thing to bear in mind – a lot of homeowners are used to gas and oil furnaces. These units are able to deliver air that is 130-140 degrees, while a heat pump can warm the air up to only around 85-92 degrees.

So, if you have switched to a heat pump not that long ago, then the temperature of the air transferred by the unit might come as a surprise to you. 

Read: What Is The Difference Between A Heat Pump And A Furnace?

How to find out if your heat pump is actually blowing cold air?

Don’t trust your body when it comes to identifying whether the air coming out of the vent is cold or not, use a thermometer.

Hold the thermometer up to the supply vent and then – the return vent. The latter is the one that sucks the air in, while the first one is used to blow out the heated air.

If there aren’t any problems with your heat pump, then the air coming out of the supply vent should be 15-30 degrees hotter than the air that is getting sucked into the return vent. The actual difference will mainly depend on the outdoor temperature.

Why Is My Heat Pump Blowing Cold Air?

If there is no difference between the temperature next to the two vents, then it looks like your heat pump is actually blowing cold air.

Here are the things that might be causing this:

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The Thermostat Settings

The first thing that you should check is the thermostat settings. You might have accidentally switched the device to ‘cool’, so, simply put ‘heat’ on.

Tip: in winter, try to keep your thermostat settings between 68 and 72 F. This will prevent the heat pump from working at full capacity all the time.

The thermostat might also be incorrectly calibrated. In such a case, the device will be reading the wrong temperature.

  • Use a thermometer to check the thermostat’s accuracy.
  • Gently clean the device and check the wiring connections.
  • If you have a programmable thermostat, all you would have to do is access the calibration setting, adjust the temperature change, and go back to the main screen.

Read: Why Does Home Thermostat Say HEAT ON But There Is No Heat?

Issues with the Reversing Valve

A refrigerant is a chemical mixture that allows heat exchange to occur. It can flow in different directions and switch the function of the indoor and outdoor coils.

Thanks to this mixture, your heat pump can be used in both heating and cooling modes.

The reversing valve is an element that sits right on the refrigerant line. Once a current is applied to the valve, it switches the flow of the refrigerant and the unit starts cooling instead of heating (or vice versa).

However, there might be an issue with the reversing valve that will make the heat pump switch to cooling mode (even if you don’t need that).

For example, the valve can get stuck.

It is better to call a professional to deal with the problem, but if you feel comfortable working with electricity, then there are a few things that you can try out:

  • You would have to make sure that the valve is energized. Use a voltmeter to check the voltage at the solenoid coil and hold a screwdriver next to the coil to confirm the presence of a magnetic field.
  • After that, ensure that there is a pressure difference between the high side and the low side (when the heat pump is running). If there is no pressure difference, the valve won’t be able to operate.
  • If you think that the valve is stuck, you can take the handle of the screwdriver and gently tap it on one side of the valve. This might free the element.

If nothing helps, then you would have to replace the reversing valve.

The Filter Might Be Clogged

Your heat pump can have one or more air filters that help keep the unit clean and increase the quality of the indoor air.

The air filter is usually located on the return duct – it is a rectangular or square door that can be found on the ceiling or the wall close to the center of the house.

Multi-zone systems have two or more return ducts and, consequently, more filters. Some systems might also have an air filter at the bottom of the air handler cabinet.

A dirty filter will restrict the airflow into the unit. As a result, your heat pump might simply not have enough air in it to be heated.

Tip: make sure to change your air filter once every 1-3 months.

  1. Turn off the thermostat.
  2. Unlatch the air return grill.
  3. Remove the old filter and wipe off any dust from the return grill.
  4. Install the new filter (pay extra attention to the airflow arrows).
  5. Close the door and turn your thermostat back on.

Low Refrigerant Levels

A refrigerant is a substance that can both cool and heat the air when needed. But if there is not enough refrigerant in the system, the heat pump won’t be able to effectively function.

The substance is not consumed during operation, so if there is not enough refrigerant, it means that your system has a leak.

You should definitely call a professional who knows how to safely work with different refrigerants

Here are a few signs that indicate that your system has low refrigerant levels:

  • The heat pump is experiencing a drop in cooling or heating output.
  • If you hear gurgling sounds, it means that there is a refrigerant leak. Air bubbles can get in the refrigerant line and start making these noises.
  • You have noticed liquid pooling or dripping around the unit.

A Dirty Outdoor Unit

Your heat pump won’t be able to draw any warm air from the outside if the coils in the outdoor unit are dirty.

Dirty coils can reduce energy efficiency by up to 60% and increase compressor power by up to 70%.

If you decide to clean the outdoor unit yourself, be extremely careful.

  • Turn off the power to the unit.
  • Put on gloves and remove any large pieces of debris (there should be a 2-foot clearance around the unit).
  • Remove the cover and vacuum the fins with a soft bristle attachment.
  • Use a screwdriver to remove the fan and top grille. Wipe the unit down with a special coil cleaner.
  • Rinse the unit off and give it time to dry.
  • Put the covers back in place and turn the power on.

The Fan Is Set to ‘On’

Your thermostat has a fan setting and you have to make sure that it is set to ‘auto’, noton’. The latter will make the fan constantly blow air, while the ‘auto’ setting turns the fan on only once the air has been heated.

The Heat Pump Isn’t Right for Your House

If this is your first winter with a heat pump, you might find out that the unit is not exactly the right fit for your house. 

If the system is too small or hasn’t been installed properly, it will fail to warm up the house. 

When choosing a heat pump, you should take the climate, the size of the house, the windows, the quality of insulation, and the number of people living in the house into consideration.

Read: What Size Heat Pump Do I Need?

Heat Pump Blowing Cold Air During Defrost

If it gets too cold outside, your outdoor unit can freeze. This will make the heat pump go into defrost mode.

In a nutshell, the defrost mode makes the unit switch to the cooling mode. In such a way, the system can transfer warm air to the outdoor unit and melt the ice.

To find out, whether your heat pump went in defrost mode, take a look at your outdoor unit. If the fan had stopped and the unit is producing a puff of steam, then it’s defrosting.