Determining Target Superheat & Target Subcooling
Determining Target Superheat & Target Subcooling
(OP)
In determining target superheat and/or subcooling is it best to have the HVAC/R (A/C unit) manufacturer's chart or will the generic/universal target superheat charts or hand calc's suffice? I have not yet been able to locate a target subcooling universal chart. Thank you. Jon





RE: Determining Target Superheat & Target Subcooling
RE: Determining Target Superheat & Target Subcooling
In any case, to check/commission a unit properly, both superheat and subcooling readings are essential. With fixed metering, superheat will vary widely with load and head pressure. With a TXV, superheat will be much more consistent over a variation in load and head pressure, provided the system is charged properly and airflow is good. Subcooling tends to be more consistent with a TXV as well, as the device has the ability to "stack" refrigerant in the condenser coils (granted we're talking a/c vs. a system with a receiver) if the evaporator heat load is reduced.
If you have no charging chart, there are apps available for smart phones/tablets that can assist in approaching correct superheat or subcooling values. I've used these and find them pretty accurate. Any time you get out a psychrometer and measure wet bulb temps and go from there, you're going to get closer than the guy who goes by "beer can cold" methods.