Scotsman Ice CME1656R, CME1356R specifications March

PTCR

The “D” series cubers use a PTCR (Positive Temperature Coefficient Resistor) in place of a conventional start relay and start capacitor.

Power from the contactor connects to the PTCR and to the Run Capacitor

A wire connects the other terminal of the PTCR to the compressor’s start winding.

CME1356R and CME1656R

Diagnosis:

1. Disconnect electrical power.

2. Check if the PTCR is cool enough to handle safely. If not, wait 5 minutes for it to cool off.

3. Disconnect both leads to the PTCR and measure its resistance with an ohmmeter. If the PTCR reads less than 21 ohms or more than 39 ohms, replace

Another wire connects the run capacitor to the start it. winding.

A parallel circuit connects power from the contactor to the Run winding of the compressor.

A PTCR changes resistance sharply when its temperature changes. When the PTCR is cold, it connects full current to the compressor’s start winding. After a very short time, the PTCR heats up and shuts off the current flow. Under normal conditions, the PTCR’s case is at about 180oF. At that temperature the PTCR has very high resistance and will not allow current to flow. It must cool down to about 120oF. Before current will pass through it again.

March 2003

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