Dometic AC dissection for Noise reduction

[rotorbudd]

Originally Posted by dana mcdaniel

Removed the ac cover this morning to compare our set up to the photos. So, if I understand you replaced the existing cushion washers with softer ones from Isolateit. I looked those up and found three levels of density 30,50,and 70 with 30 being the softest. So, I suppose softest might be quietest.

However the current cushion washers seem soft. These are approximately 1” tall and secured by a metal washer and cotter pin on top. No hard rubber anywhere I saw. Wondering if this system has been in use for a while or if this is a change Dometic has made in the last few years ( our trailer was completed 12/19) in order to try to quiet the compressor rumble. If these stock cushion washers are softer than those previously in use, swapping them out may have little effect. If rotobudds set up is as I have described on our ac I’ll give the washer replacement a try.

Hoping I don’t have to depend on long term hearing loss as the solution. Maybe we are just too sensitive to noise. A real possibility.

Here's the parts that I've just installed:
Isolate It!: Sorbothane Vibration Isolation Bushing 50 Duro (.25" ID - 1" OD - .6" Deep) - 12 Pack
Isolate It!: Sorbothane Vibration Isolation Washer 50 Duro (.45" ID - 1" OD - .19" Deep) - 12 Pack

They are the softest I've tried so far and the drumming I have when laying in the bed is almost unnoticeable.
As far as the metal washer and safety clip I just left them off because the added bushing that I used cover most of the hole for the clip helped in reducing vibration. I guess I might put a couple of wraps of safety wire thru them. But I've never had a problem with the compressor moving.
Just be aware that you will want to enlarge the hole in the top stock rubber so that the last silicone bushing fits up into it. You don't want any part of the compressor mount touching the mount post.Isolating the compressor won't make a huge difference in noise, just vibration. The noise reduction comes from the addition of the sound proofing.
I was a aircraft mechanic for 45 years so my sensitivity to vibration is much, much, higher than to sound.
My wife is very sound sensitive to sound. Which is why I started this mod, and she says it has made a major improvement.

Let me know if you have any other questions,
Richard Budd

[dana mcdaniel]

Thanks again for all your information

[TTMartin]

Our Escape 19 was new September 2020. Heading north out of Florida this month we stayed at state parks with electric hookups. When we turned on the AC it made unusual noises.

I thought maybe something had built a nest in the AC over the winter. Upon removing the cover nothing seemed amiss on the roof. My wife was doing the looking as our ladder required someone to climb on the roof to see. Since she weighs almost a 100 lbs less than me, I figured having her do the looking was a better choice.

I then took off the interior cover and saw that the blower fan was loose. I lifted the blower barrel from below and she saw that the entire blower motor that drives both the inside and outside fans on the Dometic air conditioner was loose.

One bolt had completely fallen out and the second was loose. She located the missing bolt in the AC reinstalled it and tightened the other one.

I restarted the AC and the noise was gone and it was much quitter than before just like new. I plan on getting some loctite and getting up on the roof with a longer ladder now that we're home and reinstalling the two bolts on the motor so the problem doesn't repeat itself.

Moral of the story check the two bolts that hold the blower motor to the housing and make sure they are tight. If they are loose even if not to the point where the blower fan is rubbing against something, the noise of the vibration would be multiplied.

[TTMartin]

Originally Posted by rotorbudd

BTW I also isolated the fan motor. Let me know if you're interested in that project.

Thank you for your post.

Yes, I am interested in the fan motor isolation.

[rotorbudd]

Originally Posted by TTMartin

Our Escape 19 was new September 2020. Heading north out of Florida this month we stayed at state parks with electric hookups. When we turned on the AC it made unusual noises.

I thought maybe something had built a nest in the AC over the winter. Upon removing the cover nothing seemed amiss on the roof. My wife was doing the looking as our ladder required someone to climb on the roof to see. Since she weighs almost a 100 lbs less than me, I figured having her do the looking was a better choice.

I then took off the interior cover and saw that the blower fan was loose. I lifted the blower barrel from below and she saw that the entire blower motor that drives both the inside and outside fans on the Dometic air conditioner was loose.

One bolt had completely fallen out and the second was loose. She located the missing bolt in the AC reinstalled it and tightened the other one.

I restarted the AC and the noise was gone and it was much quitter than before just like new. I plan on getting some loctite and getting up on the roof with a longer ladder now that we're home and reinstalling the two bolts on the motor so the problem doesn't repeat itself.

Moral of the story check the two bolts that hold the blower motor to the housing and make sure they are tight. If they are loose even if not to the point where the blower fan is rubbing against something, the noise of the vibration would be multiplied.

There are 2 horizontal bolts that thread thru a plastic shouldered nut and 2 vertical bolts that thread thru motor mount plate into the A/C base.
Make sure all 4 are tight. Those fans are heavy and spin kinda fast!

[dcgrout]

I am considering installing a RecPro 13.5 with heat pump in my 21C. Is that too much AC for the size of the 21? Don't know if we will ever see a RecPro 9.5 again. They have been out of stock for many months.

[cpaharley2008]

I think the larger 13.500 is too large and will freeze you before chilling you, that has been my experience with a half a dozen other trailers with the 13.500 units. The smaller 9.5 unit is quieter and a lot more enjoyable.

[rubicon327]

Originally Posted by dcgrout

I am considering installing a RecPro 13.5 with heat pump in my 21C. Is that too much AC for the size of the 21? Don't know if we will ever see a RecPro 9.5 again. They have been out of stock for many months.

For perspective I installed a 9,000 BTU mini-split for an owner of a 21 and it has worked perfectly for him. Been across the country and back twice. I think the 9,500 BTU Rec Pro is the perfect size. It will run long enough to dehumidify instead of short cycling and leaving you cold and clammy. If you can I would wait for it to come back in stock.

[Hollybee]

Originally Posted by cpaharley2008

There is a fan control switch on the thermostat for a lower speed setting.

CPAC, I was going to see about this problem too until I read YOUR post..we are so used to the old Casita w AC controls up in the ceiling , that I completely 4got about the digital thermomstat which HAS a low setting for fan!!! Will try that b4 tearing into AC unit!!!

[Tford]

Well I tried this fix today doing only the INSIDE using the Noico flexible insulation and the soundproofing pads. Using an iPhone decibel app, it improved the noise level with low fan A/C by about 3 decibels both directly below the unit and up in the 5.0 bedroom….
Glad I did it, but might still replace the top unit with a back bumper, upper cabinet ductless unit.

[dana mcdaniel]

Hi rotorbudd, Wanted to thank you for your input on quieting the noise and vibration from our Dometic AC. Bottom line is much improved noise and vibration. We essentially used the materials you suggested (Noico sound absorbing sheets, 150 mil, self-adhesive from Amazon) and Dura50 washers and bushings from the Isolateit website (1 package of 12 bushings - 50-0510002-50-12 and 2 packages of washers 50-0510001-50-12. ) No critical order to these washers and bushings. Just need to build a stack of approximately the right height. We stacked these to approximately the height of the standard bushing we removed. Finished atop the metal top mounting plate with 1 more soft washer and the standard metal washer and cotter pin. Seemed to work out. Softer ride for the compressor. Again, we think it is considerably quieter. Fan is a bit quieter and hardly notice when the compressor kicks on.