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.
David A. Lessnau
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