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Ak900 Negative superheat

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#21 ·
jtrammel said:
The dew point of the refrigerant is the suction saturation temperature, the bubble point is the condenser saturation temperature. This comes into play when you use blends that have a temperature glide. Dewperheat and Bubcooling.
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LOL. Got it.:whistle:
 
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#26 ·
If it is 22 or 410 There is a error with the way you are connected where you are not taking temp and pressure at the same spot or there is a calibration issue.
 
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#28 ·
In theory you can't have negative superheat because it would be subcooling.
However these gauges do display a negative superheat normally when the system is overcharged or the TXV has failed and the suction line is flooded.
I own a set and have witnessed it myself due to the above reasons.
 
#29 ·
marc5180 said:
In theory you can't have negative superheat because it would be subcooling.
However these gauges do display a negative superheat normally when the system is overcharged or the TXV has failed and the suction line is flooded.
I own a set and have witnessed it myself due to the above reasons.
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I've seen a few degrees negative but not -22*SH unless I had my probe not on the pipe while reading static pressure or something.
 
Discussion starter · #30 ·
jtrammel said:
I've seen a few degrees negative but not -22*SH unless I had my probe not on the pipe while reading static pressure or something.
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obviously at this point i should post a photo. i'll try to get to work a little earlier tomorrow and setup my gauges on one of the test systems we have. i know its low on 410a i think since it has a leak on that system. and ill post tomorrow evening when i get home.
 
#33 ·
Your superheat is fine, your subcooling is bad. Condenser clean? Fan working? High ambient? Could be overcharge, but it's late and my brain isn't thinking too well.

I had this the other day, kinda. I had a discharge temperature well below condensing temp (only warm to the touch), problem I had was a serious overcharge (80% more than it should be) causing liquid to flood into the compressor jacket and cool the discharge well below condensing (as well as an inefficient compressor).
 
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