Hi Gary, it’s been a long time since we had lunch in Michigan at Bob Evans :-) Hope you have been well.
Quote:
Originally Posted by Gary

Coil outlet superheat varies with type of system. Generally speaking, a freezer should have 6-8F/3.5-4.5K superheat, a cooler should have 8-10F/4.5-5.5K superheat, and an A/C should have 12-16F/6.5-9K superheat..


We installed a Russell freezer system last week and I thought of you. They are saying Copeland now wants 30F superheat at the compressor MINIMUM. They don't seem to care about the superheat outlet at the coil. What happened to Copeland’s 12F standard?


On the high side the sub cooling should be no more than 15F/8.5K because this is the point at which liquid will start to back up into the condenser.


I have yet to see a system that can obtain a 15F sub cooling, the most I have seen ever was 10 and the newer systems seem to be around 4f. Is this due to a design issue? I always test a system before leaving to make certain it can pump down under load and not be a problem. Over 10f sub cooling I have yet to see possible. ?????

Also, I'd like to mention to newbie’s that these numbers may not be obtainable on converted systems. On a converted system you may have an overly charged system trying to obtain even small sub cooling temperatures. Also, one must be concerned with pump down capacity where LONG liquid lines are used and the solenoid valve is located inside the condenser. I have one customer with a 7/8 liquid line where the original installer put the solenoid valve at the unit and the line was over 100 actual feet. Needless to say, we moved the solenoid valve to the evaporator and the systems pump down capacity was ample since we didn't have the entire refrigerant in the liquid line pumping into the condenser.



......Additional refrigerant can then be added to bring the sub cooling up to 15F/8.5K. This is the maximum charge.


Is this a new standard? Like I stated, I've seen systems overcharged at 10 Sub Cooling.

Eagerly waiting for your guidance.

Richard