what should the presures be r22 unit
Starts high and gets low at the end of the dry cycle.
Look in the Manufactures Book for that piece of equipment. The book that came with the machine.
what made the r-22 pressure change from its orginal charge
They don't provide much useful information in the books that come with the machine.
When the dry cycle starts and the steam is being added the suction will be high, maybe 85-95#
As the cycle nears completion and the steam is off, the solution is condensing and the suction will be low, maybe 50#.
It depends on the machine.
If the filters are dirty it will freeze up and slug in the regeneration cycle.
I've been doing this crap since 87". Never in my life have I set foot in a dry cleaners. I didn't know the machines used refrigeration.
I've just found something new "to me" to research.
What will your legacy be ??
There is not much info available but you can check a couple of companies on the interent;
Forenta & Sailstar
The refrigeration is a part of the still. When you heat the cleaning solution up to evaporate it out of the clothing, it is condensed back into a liquid by a cold coil.
Various companies make water chillers used to cool the condenser on the refrigeration unit of some models of these machines.