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Resolved Dometic Heat Pump - what's the loud grinding noise?

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Neal

Staff member
RVF Administrator
Joined
Jul 27, 2019
Messages
11,477
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
Chassis
Freightliner XCR
Engine
Cummins 400 HP
TOW/TOAD
2017 Chevy Colorado
Fulltimer
No
With overnight lows around 45-50 I'm using the heat pump for heat instead of furnace (convectors). It seems that the heat pump actually puts out more heat and more effectively if in the temp range that they work (above 45'ish). The unit over my bedroom typically sounds fine but at times it sounds like a friggin car parked on the roof, something loud, almost a vibration or grinding noise. I'm not sure if this is part of the heat pump system or if something is loose and I need to get up there and inspect to make sure all parts within are secure. I'll probably check it anyways as I need to get on the roof for something else.

I'm not too familiar with heat pumps as I don't have it in my S&B but it seems there is a phase of its run, sometimes, that gets annoyingly noisy. Is this normal or something I need to check?
 
Peace of mind comes with the ladder. Heat pump is an A/C in reverse, rather than pump the heat out it pumps the heat in. The compressor is running as it would when cooling. is that the kind of noise you are getting?
 
Peace of mind comes with the ladder. Heat pump is an A/C in reverse, rather than pump the heat out it pumps the heat in. The compressor is running as it would when cooling. is that the kind of noise you are getting?
Yep, gonna have to take a look and make sure all is secure. It sounds like a vibration harmony type thing, just a cyclic vibration of some sort.
 
Depending on the atmospheric conditions where you are, it could be going thru a defrost cycle. Is it putting out normal airflow when it is making this noise?
 
Last edited:
Yep, something you need to check. A heat pump is the same as an air conditioner. The only difference is the unit is trying to cool the outdoors instead of the inside. About the only thing to make noise like you describe is the fan motor. Most likely (in my mind) you will find something stuck in the squirrel cage blower wheel that is causing an imbalance issue or something similar.
 
It's hard to appreciate the loudness being over the bed but here is the noise.

 
It may very well be a defrost cycle as it's not a consistent situation. But I need to check. Ugh, it just kicked in again, it was running as expected then this obnoxious cycle harmony started.
 
? Sounds JUST like mine...that's why I prefer the furnace (can't hardly hear it)...everyone says it's like the air conditioner in reverse...yup! The air conditioner is loud too! Just don't use it at night (except on few occasions). Good luck...in my (humble) opinion, it's the nature of the beast (i.e., nothings wrong with your unit). Blessings
 
I think the consensus is most use the furnace for this reason, as you stated. I wanted to give the heat pump a try as it does put out some good heat. I think for the bedroom it's just too noisy. Maybe I can try zone 1 heat pump and zone 2 (bedroom) furnace.
 
Neal, Sounds to me what you are hearing is the harmonics of the fan running and the compressor running at the same time. The sounds are somewhat close together and when the two sound waves cross they cancel each other out somewhat. Totally normal and totally a PITA.
 

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