Vibration Help (Long)

[behrend]

Hello, I have posted here a few times before and appreciate the feedback. Here is my latest problem. I have a Bryant 265ANA, 36000BTU that is mounted outside of the bedrooms. Here is some background. Since it was set before the ground was solid and settled, the HVAC company constructed a plastic base and attached it to the block foundation and backfilled under it. This was done March 2007. By June 2007 I noticed that it was no longer level. I let the HVAC company know, they said it is fine. By November 2007, the ambient was cold enough for it to hit defrost. It was really loud, it almost sounds like a locked rotor. I called, again they said this is normal. Then everytime it would switch stages, about 30 seconds after the compressor restarts it gets extremely loud. It vibrated enough to loosed the majority of the sheet metal screws. Finally they sent someone out and they relevled the unit and level. This did not help. A Bryant service rep come in 3 hours to look at the unit. He agreed there was a lot of vibration on the vapor line inside of the unit. He loosened the compressor dampers that were cranked all the way down. He measured the pressures and found they are a 'little low', maybe 4 ounces low on 410A. They did not add any though because it was like 'shooting in the dark' when it was that cold out. We measured the delta T around the A coil and found only a 12 degree delta - he stated he would expect a 18-20 degree delta T. Anyhow, the my problem is still this low frequency groan that eminates through the house at night. The bryant tech recommeneded a compressor change becuase the unit was out of level for so long that I could have wore a bad spot on the armature. I decided to turn off the HP at night so I can get some sleep. I have done my best to isolate the lineset from the structure of the house. I am not sure if the vibration is being transfered through the compressor, into the cabinet, into the base and into the foundation (because the base is mounted to the foundation) or if it is being projected into the home. When I go into the basement and put my hand on the block wall directly inside from where the HP sits, I can feel the vibration on the block. I was thinking about cutting the support members away from the house to see if this helps. Has anyone gone through this and is there a recommeneded isolation system? I am pretty sure I will end up pouring a thick concrete pad for this to sit on in the spring to eliminate this setup. Thanks.

[Wizzard of Oz]

We use a lot of porta pads in new home construction here, and while they do seem to be a bit louder than a cement pad that usually only exterior noise. If you feel a vibration in the wall its most likely the line-set is making contact with some portion of it and transferring the compressor vibration into the wall. Here we mostly build stick on slab homes so we would open the drywall and re secure the line-set and make sure theres insulation around them. Check to see if your line-sets are touching the penetration where they run into the house. Where is your air handler located? Remember the "vapor line" in a heat pump is the discharge line in heat so it's pumping hot gas directly into your air handler coil. Also if your pad is in direct contact with the foundation that could also add to the noise transfer.

[behrend]

Thanks. I am going to try to 'free' the pad from the house tonight. The low frequency rumble is one step away from Chinese water torture. Right now, I have a 22' lineset. Is it possible to push the HP down the hill, run the lineset through conduit and bury it? I would hate to pour a pad only to have the same issue. I checked the lineset last night and isolated it the best I could. It is coming through the cap plate so it doesn't even contact the block. I don't know how to isolate this other than to open up the hole larger and fill with silicon.

[Wizzard of Oz]

Yes you can have the unit moved away from the home, and if they bury the line-set it needs to be in PVC. Talk with your installing HVAC contractor, since they did the original install the may give you a good deal on relocation. You might also ask them about widening the wall penetration too, they are the ones who should know how it was installed.

[behrend]

How long of a lineset can I go within reason? Is there a tradeoff between performance and lineset length?

[tinknocker service tech]

has anyone put isolation pads under the unit yet.

[keep2kool]

We had several problems with noisy Bryant systems and excessive vibration when running in heating mode. After looking hard at several installation issues, we checked the refrigerant charge and found it to be overcharged by over 3 lbs of refrigerant. The systems were installed by another contractor and none were properly charged. (eight in a row)

Another issue causing vibration was poor oil return. The air handlers were three stories up and were not properly trapped. If there is excessive line lengths, or the air handlers are over 20 feet up you need to read the installation manuals and check out the procedure for long line sets.