AAON Heat Pumps HELP

[xnetfly]

We are having some trouble with the rooftop units that were installed when the new facility opened a few years ago. The units are three AAON rooftop heat pumps. Two units are split, one is a package unit. All have dual compressors. The first stage compressor in each system has hot gas bypass.

We have had five (5) compressors and at least 10 contactors fail since the facility opened. Another compressor appears to be failing, it "megs" bad according to the 3rd party Contractor who looked at it. Every single one of the 5 failed compressors has been the first stage compressor on the split units. In other words, one split unit has had 3 compressors go bad, the other split unit has had two compressors go bad. The sixth compressor that is dying slowly is the first stage compressor on the package unit.

The 5-6 Trane split systems also used at the Facility have given us absolutely no problems at all.

Have you guys ever used this type of equipment before? The vendor is being of very little help. He blames everything from the power to the building to the filter change intervals. Our consultant is good but she has only specified one other system like this and it is also having similar as-yet unsolved problems.

 

[NCDesign]

As far as the splits are concerned I would be looking at the refrigerant piping, sizing, layout etc. I would also take a look at the hot gas bypass set-up. Have any of the failed compressors been sent for testing to find the actual cause of failure, overheating, low oil, arcing, etc.. The last time I was involved in something like this the manufacturer, as well as the owner and contractor, had had enough that after the 3rd compressor the parts people sent it back to the factory for a little forensic analysis. The compressors where dying due to lack of oil flow which was traced back to an oversized accumulator (actually unnecessary) that the manufacturer had recommended installing in the first place. The contractor removed the accumulator and had no further problems.