Okay I have a walk in freezer with two units in it i had one system freeze up on the evap pretty bad. We got it thawed out changed the faulty clock and checked the sysyem out unit was good. but it was a little low on oil. I asumed it would bring the oil back after we removed the ice but after a few days it didn't it is actully lower now its a 404a system and my suction in around 11psi the evap coil is under the condensor. what can i do to get the oil back to the system with out taking out the valves. i did add a little oil to help the compressor but now im concerned about it having to much. someone did replace the compressor about a year ago not sure why though. oh it does have a crank case regulator and but no suction acumalator. and it is a pump down system. thanks and you all can call me an idiot lol
What's your charge look like?
Is it properly charged for low ambient operation?
yeh it seems to be just fine it cools great and hold temp just fine. back pressure is aound 11 psi for mp 66. sorry i said it was 404a after 2 weeks im still not getting any oil back to the compressor
11 psig with R401B (MP66) would correspond to a +4ºF SST, which is pretty high for a freezer. What's the box temperature at this condition?
Originally Posted by lurch12
It's possible the system just needs a bit more oil, but in my experience, you can sometimes get oil return issues with MP66 if it's running with straight mineral oil.
I'd drain the existing oil and refill with 200TD alkylbenzene, which will result in better oil return, so watch the level for a while afterwards because you may get a lot back that's been sitting out in the system.