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john-hvac-new 11-02-2009 07:26 PM

Loud vibration of indoor coil in heat mode
 
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Hi guys. Any helpful ideas on the following situation will be appreciated.

We have a Goodman dual fuel, split heat pump system. The indoor part is suspended from the floor joists in our crawl space. The indoor coil started leaking and was recently replaced. Nothing else about the system was changed.

Now, there is a loud vibration in the structure of our house, above the indoor HVAC components, any time the heat pump is in heat mode. It’s worse when the outdoor temperature is near 65, but still very significant at 40F.

The vibration becomes audible 15 seconds after the outside unit kicks on, in heat mode. After another 15 seconds, the vibration is at maximum loudness. The vibration is coming from the indoor coil. It and the line-set are vibrating at the same rate as the compressor.

Since the vibration started immediately after the coil was replaced, I have to believe that either something was damaged or not done properly during the coil replacement - or - we just have a loud, but in-spec coil that is asserting itself - and our old coil was laid back and quiet.

Maybe there is a 'third way' - some sort of adapter kit that can calm the vibrations in a system that is in-spec, but on the loud side. Maybe the newer coils have to be supplemented with other parts/techniques so they don't 'upset' the older system.

I am concerned about system damage that may be caused by this excessive vibration – plus, its an irritating noise.

The furnace model is GMV950704CXA, serial 0601773716.
The condenser is GSH130421, serial 0605212296.
The new indoor coil is aluminum = Model CHPF3642C6CA, serial 0907129414. The old coil was copper.

My installing contractor has “thrown up his hands” on this one. “Nothing is bad enough to be covered by the Goodman warranty” he says.

I had a Tech from a different Goodman authorized company come out to check the system. It was more than 10% over charged. He pulled all refrigerant into the condenser unit, checked the orifice at input to coil – it was OK, pulled a long, strong vacuum on system, the vacuum held, he put system back on line and checked for leaks. Then, he reduced the refrigerant charge to the correct level, while the system was in cooling mode.

Readings – after charge reduced:

1. Indoors: S/A = 52º, R/A = 74º, delta temp = 22º, cooling mode
2. Indoors: Enter air wet bulb = 59º, cooling mode
3. Indoor temp = 76º, cooling mode
4. Out of doors: Condenser entering air temp 62º
5. Out of doors: Low side pressure 60 psi, High side pressure 130 psi, cooling mode
6. Out of doors: super heat 13º, sub cooling 10º
7. Out of doors: Low side pressure 74 psi, High side pressure 317 psi, compressor drawing 15.4 amps, heating mode, after 15 minutes in heat mode.

There was no noticeable improvement in the vibrations.

Technician’s comments:

1. New coil fits properly, installed exactly as it should be.
2. Short line set (~ 15 feet) lets vibration from compressor hit the coil hard.
3. Called local wholesaler – no vibration problems reported on aluminum coils.
4. Furnace is not supported properly.
5. Similar vibration case was “fixed” by changing the support from floor joist suspension (like mine) to blocks on the ground beneath the unit. Line set/coil still vibrated, but vibration not transmitted into house.
6. Vibration of my line-set/coil in heat mode is not dysfunctional = won’t cause any premature failure.
7. Not concerned by lack of outside, fresh air intake pipe to furnace.
8. Condensate drain arrangement (coil + furnace) looks OK.
9. Could not explain why vibration occurs with the new coil and not the old one.
10. Don’t run heat pump in heat mode when outdoor temp is above 65º.

HPGui 11-03-2009 02:27 AM

Faced the same issue with my Amana dual fuel system. Have them replace the stock muffler in the OD unit with a larger one. That will stop the line set vibrations that are being transmitted into your home.

john-hvac-new 11-03-2009 09:23 AM

Quote:

Originally Posted by HPGui (Post 348616)
Faced the same issue with my Amana dual fuel system. Have them replace the stock muffler in the OD unit with a larger one. That will stop the line set vibrations that are being transmitted into your home.

That sounds promising. What does "OD" stand for? Some part, or all of the outdoor unit?

Thanks.


New understanding: I Googled around and learned that the OD is the condenser unit. I also saw, on an HVAC professional forum, that wholesalers carry discharge mufflers. Now the thing is to get Goodman to make this upgrade happen.

SKIP4661 11-03-2009 10:27 AM

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