pressure unloaders on reciprocating compressors are pretty common the higher the horsepower. used mostly as a sort of "idle" when between stages of a process during production runs. Injection unloaders are used on a lot of the racks now especially with scroll units. A lot of vapor recovery units run 24/7, they idle nost of the time, load-up only when product is introduced to the system or it gets very warm for a long time. Staging of compressors is most common way to control capacity, but hot gas injection on production lines will keep a big evaporator at a consistent temp. without much change for the compressor. Never saw anything negative about unloading low temp. provided you have good oil management. Can't say i've "installed" any just kept the OEM ones working. I would be interested If you find something.
Hello y'all, sorry been busy...thanks for the replies
Talking mainly about supermarket/commercial refrigeration. Was talking to someone who had taken the CMS test and said there was a question relating to this. Found some literature that may support this, if I figured out how to upload.
I believe the 5H is an open drive??? No motor cooling needed???