SRL Service Manual
Revision 00
July 2007
Page 34 of 56
8.2 Cycling Mode
When Parameter C7 is set to “CYC” the dryer operates in cycling mode. In this mode the
microprocessor reads the dew point, the temperature of the evaporator, and the time since the
compressor was last turned off, and cycles the refrigerant compressor on and off as required to keep
the temperature of evaporator between preset upper and lower temperature limits.
As the temperature in the evaporator decreases, these three values are fed into an algorithm which
calculates whether or not to turn the refrigerant compressor off. This algorithm is designed to maintain
a minimum dewpoint, while ensuring maximum energy savings, and protecting the compressor from
excessive starts and stops.
When these three goals have been met, the compressor is turned off and the “Energy Saving” light
turns on indicating the compressor is stopped and the dryer is saving energy.
It should be noted that there is no specific temperature at which the compressor will turn off. The
microprocessor must also consider other factors such as the amount of time since the compressor
was last turned off, and therefore may delay turning the compressor off regardless of the temperature
of the evaporator. In these cases, the Hot Gas Bypass Valve will ensure the temperature in the
evaporator is maintained to avoid freezing.
While the compressor is off, the temperature in the evaporator will begin to rise. This is due to heat in
the air flow (or, if there is no airflow, due to the ambient). When the evaporator reaches a preset
temperature value, the compressor is turned back on.
The purpose of the “cycling” mode is solely to save energy. Dewpoint will fluctuate moreso in Cycling
mode than in Continuous mode so it is suggested that if energy costs are not a concern, the dryer is
operated in continuous mode for optimum performance and reliability.
Note: Cycling mode is not available on the SRL-250.
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