Hey guys and gals, I have an RTAA200 built in 92', I got sent out on the job for the 1st time a couple days ago and this is what I found. The relief valves had been replaced, the coils cleaned, some refrigerant leaks repaired, the EWT, LWT, Sat EVAP/ref. temp sensors had been replaced, and the oil filters replaced. The unit was not running due to a LWT sensor alarm. I trace this back to the board and find where the other tech just didn't have a good connecton in the plug. After that I fire up the unit to a very high pitched sound on Circuit A. I found some condenser fans running backward, fixed that. Then checked the oil level and found it was severely low. I added 4 gal of oil(system holds 8) and calibrated the differential switch. The oil level is good now and I have about 15-25psi of oil pressure diff. from my angel valve to my low side Tee on the oil line going into the comp. All this made the sound less but still there. As it starts up I am looking at 40% RLA and it loads up correctly from there, the thing is after about 30 seconds of running the high pitch noise returns until the fans stage on(15 seconds or so) and it loads up, then it goes away and runs fine. The refrigerant charge is correct to my knowledge. My question is, what else could be causing this sound? I have heard there is a check valve inside the discharge side of the compressor, could that be it? Has the damage been done due to running on a low oil level? I sent in an oil analysis and I am awaiting results. but in the mean time I turn to the pro's(you).

Also to make matters worse I have an alarm for Compressor overload setting. I went through the dip switches and into level 5 and all settings were correct. Tech support lady told me it is a faulty board at this point. Anyone else see this before? I know that when that alarm is present it puts the settings at factory default of "00000" but how will that effect my compressor? The chillers next to it are RTAA185(2) and had the same alarms, I went through and corrected the dip switches and display settings and alarms went away so I am confident I did that part right.

Also the Chiller with the noise does not have the EPROM upgrade FWIW. Thanks .