gibson unit: air handler noise during heating

[oldranger]

I hope someone out there can help. I just bought a house and was told that the Gibson unit in it was a "contractor" model (low end). I read on this site where Gibsons seem to be noisy, which this one fits in perfectly. There is a very annoying buzz that seems to drone in the same rythm as the compressor outside. There is no hum when it is on fan only or emergency heat, only in heat pump mode. The unit is probably 3 years old. I guess it is a harmonic from the piping. I have plans to put rubber mats under the outside unit to see if this helps some, but here is possibly a clue: It warmed up the other day and I was able for the first time to put in A/C mode and there was no buzzing at all, plus the unit cooled well. So why would it buzz on heat pump and not on air conditioning?
Air handler is a Gibson Mod# GB38M-042K-B-1B, ser# GBD050207582.
Exterior Unit is a Nordyne Mod JT3BA-042KA, ser# JTD050361853.
Anybody have experience with this sort of problem so I can tell my a/c guy? Evidently there aren't too many Gibsons in this neck of the woods.
Thanks

[beenthere]

Could be ovecharged.
Could be several things.
Your service tech wil have to run it in heating mode, and hear the noise himself to determine what is actually causing it.

[BaldLoonie]

That's not a problem exclusive to Gibson, that's not unusual with any scroll heat pump. Had the same complaint from a Rheem owner last week. In the winter, the hot gas is shot directly into the home. Need to be sure the refrigerant lines aren't up against a beam or duct causing transmission of this noise. In my house, I had to put the indoor coil on rubber pads to get rid of the noise.

[oldranger]

Thanks, beenthere. If the unit is only 3 years old and is overcharged, does it mean that it has already been "serviced" by someone?

[oldranger]

Thanks, Baldloonie, the refrigerant lines go directly into the slab and come up straight from the slab. Obviously I don't understand these things...why would it only do it on heat and not on cool?

[air2spare]

buzzing noises are usually electrical in nature

[dash]

If the buzzing niose,is more of a pluszation from the refrigerant lines,the smaller line should be run above the indoor coil,before going down into the slab.

[BaldLoonie]

In the cool mode, the hot gas directly off the compressor goes to the outdoor coil then liquid comes in. In heat mode, the hot gas goes straight inside so it can transfer noise along the way. I tried various methods of stopping my noise until I discovered the indoor coil right behind the couch was the noise. Putting it up on little rubber feet stopped it.

[beenthere]

Some times when heat pumps are installed in teh winter, they don't get charged right from day one.
It could be as Baldies says.

This is why you really need someone to come out and find what the problem is.
We can only guess.

[oldranger]

Baldloonie, beenthere,air2spare and dash:

Thanks for all the input and knowledge. Don't worry...there will be no DYI on this end...HVAC is one of those mysteries in life. Being that Gibsons don't seem to be too popular around here, the tech was scratching his head and suggested the rubber under the outdoor coil. He also said that being that if it had been recharged too high at 3 years...it might indicate that it was already needing work and that was not a good sign. My father had a saying that optimists just aren't paying attention.

Installation in winter makes sense, as do the rubber footings on the interior coil. If I put my hand on the coil itself while it is operating, would that be enough vibration absorbtion to see if the rubber feet would be the route to go, or no?

I know you guys probably have some real HVAC problems to solve, so I really appreciate all your help. Any other things I could look for to give my tech other clues. I also like a suggestion on a similar problem on another post that was to go outside and kick the unit several times

Again, Thanks a million

[beenthere]

Most techs will prefer to check the unit out for themselves without advise from the internet right away.
Give your tech a chance on his own first.
Then if he doesn't locate the cause, give him our suggestions.