SUMMARY
Micro processor - Dual Compressor Lag Lead. Understanding how it works.

SYMPTOMS
On a dual compressor system CP2 may start on a first stage cooling call.

CAUSE
The chillers micro-process controller logs total run hours of each compressor. From a NO call condition, when process fluid gets to SP1 + dif1 the micro-processor will perform a call for cooling. At this time it will review the compressor that has less running hours. For that cycle, the compressor with less running hours will be the LEAD compressor.

Technician should be aware of the automatic lag lead function of our micro-processors when performing diagnostics. During service, to assure that both compressors run, we recommend setting both SP1, SP2 at the same temp.

Note: Compressor hours can be seen in the micro-processor review mode as the "HR" parameter. Keep in mind that compressor run hours will be the displayed digits x 10. For example: An HR reading of 10 indicates 100 hours of compressor run time.