(Long) Carrier Specialists--Scroll Compressor Noise Level?

[newbie_home_owner]

What's the reasonable level of noise for the compressor of a new Carrier YX38030 2.5 Ton Heat Pump? It was recently installed this past April and matched with a Carrier FV4BNF002 Fan Coil. It works great and cools the house like a charm. My only concern is the noise emanating from the compressor.

I keep comparing the noise level that I'm hearing now--a constant buzzing--to the noise level, or lack of noise, the heat pump gave the first few days after installation. During the cooling test run really marvelled at how quiet the whole unit was at first. All I could hear was the turbine/fan on the heat pump.

Now that summer is here and I've been running the system pretty consistently, is it normal for the compressor to generate a consistent buzzing noise that was not present at installation? Or, should I expect this specific heat pump to be as quiet as I first heard it after installation? That is, hearing only the sounds of the turbine/fan?

I had the business who installed the system send out their tech a month ago to check it out and interestingly, the moment he hooked up his gauges to the unit, the buzzing sound ceased. He mentioned that the noise could be due to liquid slugging back into the compressor. He then identified the problem as the install guys incorrectly hooking up the connections to Y1-Low Speed Compressor instead of Y/Y2 Single or Hi Speed. Once this was corrected, the sound diminished.

Now, the sound is present again, but not as loud as before the service call. Before I think of calling them to come out again, I want to check with the pros on this board to see if I'm being too sensitive/unreasonable.

I may go to Radio Shack and get a noise meter to measure the decibels and compare the reading to the noise level Carrier claims.

Much appreciated.

[Toolpusher]

My Bryant is loud also,
It's a twin to your unit.

I'm going to switch it out with a Lennox,
they have a seperate compressor compartment to help with the noise levels.

[pmurf1]

Does it make the sound when the compressor is off? If it's still making a buzzing noise with the thermostat set to cool, but not calling for cooling, that would make me suspect the reversing valve coil. If it buzzes loud enough for you to hear while the unit is running, I'd start looking at the contactor. Those are the two things that will really create a "buzzing" noise in a heat pump. Of course different people describe noises different, but that's where I'd look first. Compressors don't usually get described as buzzing.

[fireship1]

If all else checks out and you still have the noise try a sound blanket. They are sold to fit various kinds of Scroll and recipro compressors. Thy slip on the compressor like a small coat and hat. Thy will drop the sound level by quite a bit. I always offer them on the Armstrong units that I install. Or like someone else said in this thread, step up to a Lennox. They put their compressors in sound shielded boxes. All you will hear is the fan on those models. http://www.brinmar.com, They manufacture and sell the sound blankets for compressors. Don't believe people who try to tell you that a sound blanket will overheat a compressor. It's cooled by refrigerant vapor and not by surface air.

Good luck

[docholiday]

IF its truley the compressor then I would say your guy needs to check for slugging again. A slight airflow problem can cause refrigerant to not boil off like it should, this can make compressors noisy as it would with a slight overcharge. A sound blanket may help also. 9 times out of 10 compressor noise is a result of the refrigerant system not being correct.

If its not the compressor itself, it may indeed be a contactor or reversing valve solenoid making that noise. On a cooler day, run it in heat and see if its still there. If it goes away, then at least you'll have the piece of mind that the compressor is not the problem. I've seen alot of techs rip out perfectly good compressors and replace them only to find that they are much more comfortable with their brazing techniques than their refrigerant charging and troubleshooting practices.

[Swampfox]

Ive seen this a lot, might be your problem as you state hooking up the gauges stopped the noise....

the compresoor vibration carries down to the service valve and then is transmitted through the entire unit making some of the metal panels vibrate, Ive found the fix is to start loosening the panel screws all over the unit slightly until the noise goes away, they are 5/16" by the way, worth a try