Derek ColeGM, Simmons One Hour Heating & Air · AI HVAC Answers

Noise from My Heat Pump HVAC Unit

26 Jan 2018 · 2 min

Watch on YouTube

1:48

In this video, Derek Cole explains that the loud noise heard from a heat pump during its defrost cycle is caused by the refrigerant flow reversing as the system temporarily switches to air‑conditioning mode and activates electric heat strips to melt frost on the outdoor unit. He describes how the heat from the house is expelled outside, producing a "Brrr" sound. Cole also advises homeowners not to switch to emergency heat in cold weather because it is three times more expensive than normal heat pump operation, and should only be used when the outdoor unit is completely iced over and inaccessible. The overall message is that the defrost noise is normal and the heat pump should remain in its regular mode for cost‑effective heating.

Chapters

When it goes into defrost, it has to go on that cycle. It actually reverses the flow of refrigerant. So instead of being in heat mode, it switches to AC mode and it turns on those heat strips so you don't get cold in the house. So the reason it makes that loud noise is all that gas and refrigerant is saying, "Brrr," back the other way. So that is the noise you're hearing. A lot of folks don't know that and probably don't need to know that, but it's actually going into AC mode because because it's burning off the frost on the outdoor unit. So it's actually taking the heat that's in the house and blowing it back outside like it was summertime. So that's how you melt that frost. So it does make kind of a loud noise, and especially if it's at the bedroom or wherever the outdoor unit is, it'll probably wake you up, or at least until you get used to it, wake you up. But it's nothing to worry about. Some folks have asked too, you know, when it's really cold outside, should I just turn my unit to emergency heat only? And the answer is no, do not do that. There's still heat in the air. The heat pump can still function with the emergency heat. If you go straight to emergency heat, that is 3 times more expensive than regular heat, so that is not a good option unless that unit is just packed with snow and ice and you can't get to it and can't defrost, and that's a good reason. But to, uh, have the unit work less by not having to go to defrost cycle is actually going to cost you more money. So just a little tidbit there, but the noise is the defrost cycle.