Silencing a House's Resonating Air Conditioner

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DaveLessnau
Posts: 192
Joined: Mon May 22, 2006 7:01 am
Location: USA

Silencing a House's Resonating Air Conditioner

Post by DaveLessnau » Fri May 06, 2011 6:30 pm

This is a weird one. We recently had the central air conditioner in our house replaced. Unfortunately, since then, we've been hearing a pulsing resonance at about 85 cycles/minute at various points in the house (several of the loudest spots are in our master bedroom). At first, I thought the noise was coming from the compressor down through the pseudo-concrete slab it's sitting on and then through the soil (sand) and up into the foundation. We called the people who installed the unit, and they came out and looked things over. The guy found that the coolant pipes entering/leaving the brick wall were pulsing (I guess the high pressure coolant they currently use transmits vibration more readily than the old freon systems) and that the brick was picking that up, amplifying it and transferring it to various points in the house. He removed some brick from around the pipes (so they were no longer touching it) and used foam insulation to fill the gap. The noise went away. But, once the foam hardened (the next day), the noise came back (somewhat reduced).

I'm wondering if anyone has any other suggestions for isolating those pulsing pipes from the resonance board that is our brick wall. I was thinking that maybe some soft rubber around the pipes might help. But, I'd guess that that rubber would not last long in that environment (the compressor is in the 10 foot space between our house and the neighbors', both houses have brick walls, and the sun spends a lot of time down here in Florida shining into that area -- I'd guess the daytime temperatures in that space run at least 10 degrees hotter than the open-space temperatures). Digging away some of the foam insulation around the pipe and leaving an air gap might work, but I'm worried about the external environment reaching the house's interior (but then, I'm not sure if that would be any difference from those weeping holes they leave in brick walls). I'd appreciate any suggestions that I could pass on to the company.

Arbutus
Posts: 234
Joined: Wed Jun 02, 2010 9:15 pm
Location: Calgary, Alberta, Canada

Re: Silencing a House's Resonating Air Conditioner

Post by Arbutus » Fri May 06, 2011 11:14 pm

Homer Depot sells 2 kinds of foam in handyman spray cans. One type expands more and cures harder and the other expands less and is very soft when cured. I strongly suspect that the softer foam conducts much less vibration the the harder foam.

jhhoffma
Posts: 2131
Joined: Mon Apr 25, 2005 10:00 am
Location: Grand Rapids, MI

Re: Silencing a House's Resonating Air Conditioner

Post by jhhoffma » Sat May 07, 2011 4:54 pm

You can also try wrapping some thin layers of fiberglass mat around the pipes transmitting the vibrations. Some stores might even carry pipe-wrap that might work.

jamesmartin
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Joined: Mon May 19, 2014 8:26 pm
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Re: Silencing a House's Resonating Air Conditioner

Post by jamesmartin » Mon May 19, 2014 9:06 pm

Definitely rubber is not the solution of this problem. There is one thing more you can do. That's little strange but it will do the perfect job you just need right now. Instead of filling foam take few pieces of useless cloths and try to fill the whole by using them. After filling clothes in the whole check the sound if you are still hearing it then you use some plaster of Paris to fix them properly.

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