Failed temperture sensor in Copeland

[NH3LVR]

A Industrial guy needs a little help.

We have a older 30 HP, 3 phase, 480V Copeland at work. It operates a falling film chiller. Unfortunately I left the exact model number at work.
This morning when I arrived my number one was trying to find why it did not start.
The overheat protection control was open, preventing the machine from starting. The 3 sensors located on the motor were all showing open from common to the sensor leads. And then we got a reading of 1250 Ohms or so on each one. Scratching our heads we started the machine and it ran a few hours. Then the compressors stopped and we found the sensor leads open again.
It did not take long to determine that the common lead was opening in the compressor. A decision was made to bypass the switch for the moment.
I talked to a local Copeland re-builder I know and he said we could bring the compressor in and he most likely be able to fix the problem. It would be a small problem to get it out of it's location, and I would like to avoid the downtime.
I am well familiar with sizing and using overloads to protect a external motor, but thought a refrigerant cooled motor might have other requirements. A Phase Monitor could also be included. I do not wish to risk a burnout and the required cleanup. Hot gas flows continuously to the evaporator on this chiller so I would have a excellent chance to contaminate the system if a burnout would occur.
Any thoughts?

[mad fridgie]

I would look at Phase protection at the compressor terminals (after contactor and overload), discharge overheat stat. Short timed oil protection pressure switch and oil level.