Quote Originally Posted by MeanMack
The efficiency of "all" industrial compressors degrades as they operate at a fraction of full load capacity.

For screws this is true, for recip.'s not so much. You should not categorize all compressors as the same. Now if you said it's a general tendency for all screw compressors to behave this way (some have different variations of what you described) then I would agree.

Another obvious attempt at low defrost pressure is to find the minimum pressure needed for adequate defrosts and then use a dedicated compressor to supply the hot gas for defrosts. That way you only penalize the system power for a much smaller compressor instead of the whole system.