Single-speaker podcast explaining why heat pumps make loud noises during defrost: the system briefly reverses into AC mode and engages electric heat strips to prevent indoor cooling while blowing house heat outside to melt frost. The speaker advises against switching to auxiliary/immersive heat except when the outdoor unit is iced over, noting it is roughly three times more expensive.
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 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 is 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. Like it was summertime. So that's how you melt that frost. So it does make quite a 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. And some folks have asked too, you know, when it's really cold outside, should I just turn my unit to immersive heat only? And the answer is no, do not do that. There is still heat in the air. The heat pump can still function with the immersive heat. If you go straight to immersive heat, that is three times more expensive than regular heat. So that is not a good option unless you 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 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.
