SCT: 125 - 180F
TXV SH delta 5-8F
The compressor is a variable capacity type with constant target suction pressure.
I'd like to get some input on drop-in installation of R134a bellow TXV into a R12 system.
The vapor pressure difference between HFC134a and CFC12 in the evaporator temperature range given above will cause TXV to respond as if sensing bulb is 2F cooler than it really is compared to a matching bellow charge & system charge pair.
This MVAC TXV has an adjustment screw at the liquid line entry but to tweak it, the system has to be opened. Since getting it adjusted right on first try isn't guaranteed, so this would be just as, if not more time consuming than replacing the bellow charge with R12.
Anyways, uncompensated, my speculation is that R134a TXV would cause the SH to increase from 5-8 to 7-10(as measured at evaporator outlet, not compressor).
If my speculation is right how much relative capacity loss can it be expected?