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pakblogger2012
07-06-2017, 06:54 PM
Dear forum fellows;

We have TRANE chiller RTWA-216 and one of its motor is having high RLA (about 400% ~ 700 A ) at start-up followed by breaker trip.
It is worthy to mention that in last season it operated normally .Motor Megger results are also not bad.

It remained shut-down for many months and the only work that has recently been done is replacement of its cable from main panel.

Please guide what possible reasons may be and how to troubleshoot it.

Thanks in advance

Grizzly
07-06-2017, 07:19 PM
Hi.
Is it possible the motor has got Damp?
Sometimes warming the motor to dry off any Moisture absorbed whilst standing idle, will resolve a tripping motor.
You say Megga readings are not Bad?
Care to elaborate?
Grizzly

pakblogger2012
07-06-2017, 07:33 PM
Hi.
Is it possible the motor has got Damp?
Sometimes warming the motor to dry off any Moisture absorbed whilst standing idle, will resolve a tripping motor.
You say Megga readings are not Bad?
Care to elaborate?
Grizzly

Every time compressor heaters have been run for sufficient time before getting motor started. I wanted to say that motor insulation resistance values /Meggering results are greater than 700 K ohms.

what are possibilities of mechanical seizure of compressor ?

al
08-06-2017, 11:23 PM
Is there only one compressor having an issue? If not i would look at the new cable...

PaulZ
09-06-2017, 07:47 AM
Hi
You say the mega results are greater than 700 k ohms. What test voltage did you use, 500 or 1000?
I would normally say anything below 2 megohm would be suspect and as Al suggested the cables could be at fault.
We are presuming you meggered from the board, if so disconnect at the motor and redo, this should confirm whether it is motor or cable.
Regards
Paul

RANGER1
09-06-2017, 09:22 AM
Assuming a screw compressor
Was it direction tested after new cable was installed?
If so how & by whom.
If not it could be at risk.
Is it at minimum load?

RANGER1
10-06-2017, 03:47 AM
Single phasing for some reason?

AlexG
10-06-2017, 11:48 AM
Is 700A real amps or reading on display?

chemi-cool
10-06-2017, 04:30 PM
Typical result for a phase lost.
Check motor protector and contactor. At such high amps, they both need replacing.