Copeland tandem compressors over amping.

[acguy951]

Having a problem with copeland tandem scroll compressors. The compressors are over amping and tripping breakers in machine. They will run but the amps at startup are 100 + then fall back to 60 amps then gradually climb to over 100 amps before tripping breakers. Checked subcooling and superheat. 12 degrees SC & 17 degrees SH. The compressors also sound like theyre binding up inside sometimes. The oil color is light gray. Plan on having oil analysis performed. This is the second set of compressors replaced on a just installed new 60 ton Mcquay air cooled condensing unit. The 2nd circuit of compressors on the machine have no problems. We removed 2 o6e compressors and water cooled condensers and a cooling tower. This was a retrofit from R-22 to R407C. We drilled holes at the bottom of the refrigerant traps located at the air handler and tried blowing out and residual mineral oil. Checked txv's and they are labeled for R407c or R-22. Hooked up nitro during brazing. When we had the first set of compressors doing the samething we turned to our local reps service dept for answers. We never got any feedback and were given new replacment compressors. Hoping we can save these!

[ryan1088]

The oil color really bothers me. Did you already get the oil sample out? Have you tried changing the oil in the sumps?

Also what are the RLA on the compressors?

[acguy951]

I plan on doing oil analysis on monday. I did drain some oil. That was when I noticed the color. The RLA are 58 amps. Changing the oil in the compressors is going to be my first attempt at saving these along with changing drier and flushing system.

[hands]

Sounds like there is metal in the oil and the compressors are damaged from a lack of oil. I would say you will be replacing them soon. It could be there was still mineral oil in the system. What is the oil pressure and how does it compair to the compressors that are running good. After adding the 407c was there any leaks. If so you would have to recover the charge and add all new.

[ryan1088]

Metal in the oil is what I was just sitting here thinking. What was the oil level in the crossover tube?

[ascj]

Is this a 2 circuit condenser with 2 sets of 2 scrolls?
I have never seen that from McQuay is R407C.

[acguy951]

Metal in the oil is what I was just sitting here thinking. What was the oil level in the crossover tube?

The compressor oil level was half way when they were off. While running one compressor the sight glass was full when both compressors run they both are below the halfway mark on the sight glass. Oil is a milky gray. When we changed the first compressors the oil color was normal. I did perform acid test on oil and refrigerant. No acid.

[ryan1088]

That doesn't seem too out of the ordinary. You have a real mess on your hands....

[socotech]

Grey oil. Sounds like aluminium in the oil.

[GoColts]

What are the refrigerant pressures doing when the amps climbed? When these compressors were installed was the system properly flushed and cleaned? The milky color in the oil could be moisture, there is definitly metal in the oil. You should get you answers with an oil sample.

[Push It]

What is the amperage draw of the other compressors on the second circuit? If you are drawing 60 amps on a RLA of 58, with all else you descibed you are changing those compressors. What was the ambient, head pressure at time of amperage readings? I would look at your piping and verify that with 407c you have the correct velocity for oil return with the staging. How many stages of cooling is there? You stated 1 compressor does run at once. What about your air flow? What kid of AHU system is it? Constant volume? VAV?

Good luck man I agree with Ryan

[flange]

go to the parts store and buy a bunch of oil and driers. start cleaning the system up. in the meantime, ask whomever did this if they considered the effect of going to a higher condensing temp when they sized it....

[jayguy]

...The oil color is light gray. Plan on having oil analysis performed...

save your money and time on the oil analysis. your compressors are toast. there is a lot of clean up to perform now and you can not do it with these compressors as they are just filling the system with more garbage.