bitzer screw compressor

[joe magee]

I have a hussmann rack that has open drive bitzer screw compressors. Somtimes the compressors go off on the motor starters. I reset and check my amp draw is fine . Two days later I am out again. Some have drives others dont. I am thinking a possibly voltage drop? maybe I need to put a recorder on them. voltage checks out ok 480.

[LRAC]

Hi joe magee

If the units are within name plate perameters when you are testing them i.e during start up and running it may be wise to record over 48 hrs what exactly is happening are the loads increasing at specific times of the day or after defrost, unloading and loading etc.

This may give you an idea for a full diagnosis.

Regards
Lrac

[TSK]

How old are the starters? The conacts could be burnt & pitted, on start up the current will be off the scale of your clip-on for a moment, during this time the voltage & current can be out of balence across the phases, with bad contacts the starting conditions can be different each time.

[Andy]

I have a hussmann rack that has open drive bitzer screw compressors. Somtimes the compressors go off on the motor starters. I reset and check my amp draw is fine . Two days later I am out again. Some have drives others dont. I am thinking a possibly voltage drop? maybe I need to put a recorder on them. voltage checks out ok 480.

Hi Joe
check the oil solinoides, if they pass on off cycle this will happen. Also the oil solinoide should only be energised when your compressor goes to delta

hope this helps

Kind Regards Andy

[joe magee]

Hi Andy. Why do the compressors trip if oil soleniod sticks open? possibly heavy load on start up? It's 480 across the line. Thanks I'll check that

[Andy]

Hi Andy. Why do the compressors trip if oil soleniod sticks open? possibly heavy load on start up? It's 480 across the line. Thanks I'll check that

Hi Joe
take a look at the bitzer web site.
www.bitzer.de
and download the application manual. One of the first things Bitzer say to look out for
It's a compressor not a pump, if you get oil in there the only way to clear it is by turning the compressor over by hand, it is quite difficult and you can feel how the excessive load would feel like on a motor.

Another possibilty would be liquid refrigerant coming back from the cases, this would trip them, but you would have multiple other faults also

Kind Regards Andy