Superheat

[moonman]

Im new to this forum and ive been going through a lot of them and i find them very helpful i would like to say thanx! but i have a question regarding superheat. i got this W/I cooler R22 system i cant get the superheat right my head pressure is 200psi suction 44psi full sightglass TXV bulb is about the 4 O' clock position, i know on coolers superheat should be 8`F to 10`F. i got to 10 but then it just dropped to -18`F the closest ive got it was 2`F. could it be faulty TXV? or oversized orfice? or what else could it be? what do you suggest i check for?

[dan wong]

Im new to this forum and ive been going through a lot of them and i find them very helpful i would like to say thanx! but i have a question regarding superheat. i got this W/I cooler R22 system i cant get the superheat right my head pressure is 200psi suction 44psi full sightglass TXV bulb is about the 4 O' clock position, i know on coolers superheat should be 8`F to 10`F. i got to 10 but then it just dropped to -18`F the closest ive got it was 2`F. could it be faulty TXV? or oversized orfice? or what else could it be? what do you suggest i check for?

One of my guy call in with almost identical problem as you describe. Negative super heat?? I couldn't beleived my ear.

I went to site. it turned out, Suction valve was broken - split in the middle, sometime it will pump down to negative, sometime not. (it was a semi-hermatic compressor, we take the head apart and replace the valve. problem solved).

Do a pump down test, see if you have the same problem.

[marc5180]

As Gary says, you can't have negative superheat, more like subcooling which suggests that you have liquid floodback to your compressor.