Why Is My Heat Pump Not Blowing Hot Air? A Portland Tech Answers

If you’ve double checked that your thermostat didn’t accidentally get set to COOL or the fan set to ON (it happens), your heat pump could be blowing cool air for 2 reasons:

  1. It’s in defrost mode
  2. It needs to be repaired or serviced

We’ll explain those situations in more detail below. But first, let’s go over how a heat pump works.

Think there’s really something wrong with your heat pump? Call us at 503-538-1950 or schedule an appointment online. You can count on our techs to figure out the problem and repair your heat pump system as soon as possible.

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Keep in mind: Heat pumps don’t blow super hot air

See, unlike furnaces that generate heat, heat pumps only transfer heat. To put it simply, heat pumps absorb heat from the outside air and move it into your home. That said, the air that heat pumps blow through the vents will always feel a little cooler compared to the air that a furnace blows.

Heat pumps normally blow air that’s around 80–95°F. If you’re comparing that temperature to the air that a furnace produces, which can range from 120°F to 155°F, the air coming from a heat pump will feel much cooler.

Plus, our body temperatures run at approximately 98°F, which means the 80–95°F air coming from your vents will feel cool (compared to our body temperature), even though the unit is working as it’s supposed to.

Now that you know how the air from a heat pump should feel, we’ll go over why your heat pump could actually be blowing cold air.

Reason #1: Your heat pump is in defrost mode

When in defrost mode, your heat pump will blow cold air for a few minutes to allow frost on the outdoor coils to melt.

While we don’t get a lot of sub-freezing temperatures here in Portland, it can drop into the high 20s on winter nights. The low temperature, combined with the humidity, can cause frost to build up on the outdoor coils—which can kick the heat pump into defrost mode.

During a defrost cycle, your heat pump temporarily goes into cooling mode (that explains the cool air coming from your vents). This allows the outdoor coils to warm up, melting the frost. How long the unit will run in defrost mode depends on how long it takes to melt the iced over coils, but it shouldn’t take longer than 10 minutes.

How can you tell if your unit is in defrost mode? Go take a look at your outdoor unit. If the outdoor fan has stopped running and the unit is releasing puffs of steam, it’s in defrost mode.

Reason #2: Your heat pump needs to be serviced

If your system isn’t heating your home and you notice cold air coming from the vents for long periods of time, you may need to get your heat pump repaired or serviced.

A heat pump blowing cold air could mean:

  • Reversing valve problems. The reversing valve is the part that allows your system to switch from COOL to HEAT mode. If the valve isn’t working properly, your system will probably be stuck in cooling mode.
  • A refrigerant leak. Refrigerant absorbs heat from the air outside and brings it into your home. A leak in the refrigerant lines means there won’t be enough refrigerant to properly draw heat, causing cooler-than-normal air to blow from your vents. If your system does have a leak, we recommend having a professional do the hazardous job of repairing the line and refilling the refrigerant.
  • The system is losing efficiency. A system that’s running inefficiently won’t heat your home as well as is should. We recommend getting annual tune-ups to help your heat pump run more efficiently, making your system last longer and reducing energy costs.

Think you need a heat pump repair? Call a Portland pro.

Give us a call at 503-538-1950 or schedule an appointment online and we’ll send one of our best Four Seasons pros to diagnose why your heat pump isn’t blowing warm air.

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