mcquay tandem oil level.

[hvac17011]

I am workimg on mcquay splt systems that have had alot of service issues(long story). My question is the tandems have a oil crossover between compressors. Should the compressors have the same oil level. We have units that the one compressor is normal to high and the other compressor you can barely see any oil. Whatr is the real purpose of the oil crossover tube. These units have had return issues and have exvs. I am just looking for some general input.

[Six]

on the off cycle their shouldn't be a distinction in level unless it's giving you a false indication. It's just for oil equalization.

If you're having oil return issues then it could be your running under low load too long or you have a control problem with the EXVs.

Their should be specific data on those comps for oil level during run and off cycles.

[hvac17011]

We dont agree with how the units are being controlled. if both compressors are running should oil level be the same

[Six]

Close if not the same. I don't see how you could have a distinction in oil level with a cross over tube.

Unless it's blocked. That basically makes that tandem assembly one compressor. The cross over tubes on a Carlyse 06E for example are huge.

I have seen ball valves installed in them before. Right in the middle of the equalizing tube.

[ryan1088]

Are both compressors running when you made your observation?