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Proudly Serving Yakima, Ellensburg, Cle Elum, and the Surrounding Areas Since 1998


ThermAll Heating, Cooling & Electric Blog

I See Smoke Coming From My Heat Pump! What’s Wrong?


First, take a deep breath. Your heat pump is almost certainly not on fire. In fact, it’s probably working just the way it’s supposed to.

If this is the first winter you’ve used a heat pump to provide comfort to your home, then we’re not surprised that you might find this sight alarming. A heat pump works similarly to an air conditioner, and if you see smoke coming off your air conditioning system’s outdoor unit, that’s a big problem, likely some kind of electrical fire. This is extremely rare, but not impossible.

However, that “smoke” you see rising from your heat pump isn’t smoke at all, as we’ll explain.

The Defrost Cycle of the Heat Pump

What you are actually seeing coming from your heat pump is steam. This is part of the heat pump’s defrost cycle, which is an essential part of how it works during the winter. 

If you know a bit about how a heat pump works, you’ll know that when in heating mode it absorbs thermal energy from the outside air by evaporating cold refrigerant in the outdoor refrigerant coil. This heat then goes indoors, where it’s released via condensation in the indoor coil. During evaporation, water vapor in the air condenses along the coil, which is something you’re used to with an AC or a heat pump that’s working in cooling mode: you’ll hear the sound of condensate water dripping off the coil of the indoor cabinet.

But when water condenses along the outdoor coil, it can freeze. On the coldest days of winter, ice will quickly start to form along the outdoor coil of a heat pump. Ice insulates the coil and will make it harder for the heat pump to draw thermal energy from the air.

To combat this, heat pumps have a built-in defrost cycle. Periodically when the heat pump is in heat mode, it will temporarily switch the direction it moves heat so that the refrigerant in the outdoor coil is hot instead of cold. The heat melts off the ice on the coil, and steam billows into the air. That’s what you’re seeing happen with your heat pump in winter.

Actual Heat Pump Defrost Malfunctions

There is a problem you may encounter with the defrost cycle, which has nothing to do with fires. The defrost controls may malfunction and not cause the heat pump to periodically switch to defrost mode. This will allow ice to continue to develop along the coils. 

When this occurs, you’ll notice the heat pump losing energy efficiency. It will need to run for longer trying to effectively warm your house, and you’ll see your energy bills going up. These could be symptoms of other problems, but no matter the case, you’ll want to call for heat pump repair in Yakima, WA from our team. We’ll investigate and discover what’s hurting your heat pump’s performance and then find the right solution. We’ll see that your heat pump gets back to work, effectively handling both parts of its job.

Call ThermAll Heating & Cooling, Inc: We are “Your Home Comfort Hero!”

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