I have a chiller that I helped overhauled and have some questions. Hopefully somebody might have seen this before.

CVHE045, Serial # L00H04317

So the chiller was overhauled and a service first motor was installed. Chiller was known to have oil return problems before overhaul. All orings replaced, all flat gaskets replaced, however oil pump not not inspected or disassembled. Solenoid vent valve replaced and charge was weighed back in.

Chiller started and logged. No problems noticed. Left site and 3 weeks later customer called and said chiller went down on low differential oil pressure. Figured it might be oil filter or something simple. Installed new filter and manually turned on pump. Oil pressure was good so the chiller was started and after having run for a few minutes it tripped on differential oil pressure.

Unfortunately I was not there when the customer called and was not part of the oil pressure diagnosis but since I was there for the overhaul I am very interested in finding an answer.

All this to say, the other technician performs a variety of tests and determines that the chiller isn't making oil pressure across the journal bearing! Unit was disassembled and the journal bearing is found to be very wiped.

This time the motor is sent to a local rebuilder and is found to have shaft damage. We have had trouble in the past with service first motors and so we felt confident that we originally received a motor that was properly rebuilt. We believe after the local shop rebuilds the motor and the chiller is reassembled we should be good to go.

So now we are having a similar problem with the most recent overhaul. Upon closer investigation, it is found that the oil sump/oil is foaming each time the drive re optimizes and the chiller surges. When this happens the chiller loses most of the oil from the site glasses and the differential oil pressure drops off to about 12 psi. The surges seem more violent than the other chiller in the room which is the same setup. We set the oil trip point to 10 psi (same as the other chiller) and this has helped.

My question is why is the chiller unable to operate with the surges? Why does it lose the oil so quickly.

For what it is worth, I am an apprentice who is really curious about the reason behind problems like this and I have yet to be able to find an answer. Sorry for the long post, please ask me for any information that would help in diagnosing the problem...I may not have all the information but I have a lot.