Hi,

I've been servicing a couple of 4' open display merchandisers - each individually served by a dedicated condensing unit.

The system employs an evaporator pressure regulator and cycles on pump down via liquid solenoid valve.

I am concerned about proper pump-down control setting. The EPR is set at a minimum 18degF evaporator temperature (R-22). At times, when the EPR modulates, the suction pressure back to the compressor can drop to 15 to 20 psi so the cut-out is needed to be set lower than such occurance.

On pump-down (cut-out set at 5 to 10 psi) and cycle off, the suction pressure will rise to the 18degF SST pressure plus the superheat setting of the expansion valve (approx. 45 psi). Some short-cycling is evident during off-cycle, and obtaining satisfactory shut-down of the condensing unit under the cool ambient conditions that now exist is somewhat tedious.

I slept on it last night, and considered perhaps more satisfactory results would be obtained with use of a suction stop solenoid valve, as opposed to the liquid line solenoid valve in conjunction with the application of the EPR.

Any thoughts or observations?