PDA

View Full Version : Cpr?



cretan
19-08-2008, 05:08 AM
Why do some walk-in freezers have CPR valves and others don't?Can't figure this one out.

WINJA
19-08-2008, 06:49 AM
The ones that dont have a CPR might have a MOP tx valve

cretan
19-08-2008, 07:32 AM
Thats right too.I thought they were only used on smaller systems.Any pro's or con's to using cpr or mop txv?

old gas bottle
19-08-2008, 05:35 PM
i like cpr,s you can set them up as you require, MOP,S you cant,just the price of buying them.;)

philfridge
19-08-2008, 07:52 PM
Why do some walk-in freezers have CPR valves and others don't?Can't figure this one out


Depends, the ones without cprs probably have l.l.s.v to stop h.b.p after defrosting periods :)

WINJA
20-08-2008, 08:11 AM
Thats right too.I thought they were only used on smaller systems.Any pro's or con's to using cpr or mop txv?
MOP valve is just a cheap substitute for a CPR , its only slight advantage is it dont have the PD of a CPR during normal loads but this is usually neglegigable , the MOP valve works buy starving the evap during start up and pull down , this results in high superheat at a time when the compressor least needs it and generally a longer pull down and recovery time compared to using a CPR , its hard to beat a CPR which has been set up with an HP gauge fitted and an amp meter , the MOP valve is quite crude as far as control goes after all its usually just made of a normal TX valve with an undercharged element, still they are good if a CPR is not in the budget