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

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Joined
Jul 27, 2019
Messages
5,237
Location
Midlothian, VA
RV Year
2017
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Newmar
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Ventana 4037
RV Length
40' 10"
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?
 
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AZ
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Alpinelite
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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?
 
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Location
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2017 Chevy Colorado
Fulltimer
No
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.
 
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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?
 
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Joined
Nov 13, 2019
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595
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Where ever I park it
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Salem
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Hemisphere 346RK
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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.
 
Joined
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Location
Midlothian, VA
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Newmar
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Ventana 4037
RV Length
40' 10"
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2017 Chevy Colorado
Fulltimer
No
It's hard to appreciate the loudness being over the bed but here is the noise.

 
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2017 Chevy Colorado
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No
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.
 
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Central Coast of California
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😊 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
 
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2017 Chevy Colorado
Fulltimer
No
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.
 
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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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2017 Chevy Colorado
Fulltimer
No
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.
Agreed. Used furnace last night. Done with the heat pump nonsense. Too loud right over the bed. Someday I may try turning zone 2 off and only use zone 1 and see how that heats the bedroom as the duct work seems to pass zone 1 through to zone 2.
 
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Since I don't like a lot of heat and appreciate less noise, at night, I run zone one on the heat pump and leave zone two off. If I really need more heat I will run a small electric heater in the living room only. I do use he heat pumps during the day sometimes, but the small electric heaters do a good job without the noise.

Hey if you think it is loud in a Newmar, try one of the other brands that has the A/C unit extend through the ceiling. It is like parking next to a busy runway.
 
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There is still a possibility of an unbalanced squirrel cage wheel contributing to the noise. Only way to tell is pull it apart and clean it since you are in there anyway.
 
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sound about like mine. Maybe louder but no context.
I have trouble finding a use for my heat pumps. Too loud and slow.
 
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Agreed. Used furnace last night. Done with the heat pump nonsense. Too loud right over the bed. Someday I may try turning zone 2 off and only use zone 1 and see how that heats the bedroom as the duct work seems to pass zone 1 through to zone 2.
Our bedroom unit is somewhat noisy on defrost. My solution is to set the bedroom a 2-3 degrees cooler than I want the night temperature to be and set the living room unit 1-2 degrees warmer than it would otherwise be for night. I can barely hear the front unit when in the bedroom and it has to get really cold for the back unit to kick on (down to pretty near needing to use the furnace).
 
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Heated floors are nice and quiet! Just sayin’.

TJ
 
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