# bad TXV ?



## wetbar (Jun 5, 2012)

So this has happen 3 times today, and it is blowing my mind. I get to the first customer and I hook up my gauges and the high side is way to high like 130 degrees Lsat on a 75 degree day, but the low side is 5 degrees Vsat. Then the second call is the same then the third. 

Call 1 R-22 Split 2 ton (I think) The head was 205.00 and the suction was 45. I added a little R-22 just to see if the suction would come up and it did not but the head shot up. Subcool went to 26 and the super heat stayed at 50 or so. Im thinking TXV is stuck shut, I take the bulb off the pipe, and out of the case and my numbers are absolutely perfect. My subcool and super heat comes down, the suction goes to 70 PSIG the high side comes down to 210.00. So the TXV is opening and closing, when I hold the bulb in my hand the suction goes up and if I hold it long enough I can get super heat down to 6 or so. 

Call 2 - R410 package heat pump less than 1 year old! When I get there Suction is 75 and 235 head ODDB is 69 degrees at this point. I add a little freon to see if the suction comes up, but no. I changed guages and start over, but same numbers. The subcool is 26 or so and the super heat is 50 or so. Same thing pull the bulb out of the evap and put it next to discharge(but not strapped) numbers look awesome suction comes up to 112 and head drops to 286.3 sub cool comes down to 22 and the super heat comes down to 8. So now I am thinking I over charged the unit a little.


Call 3 Piston split R 22 Same freaking thing! this time I pumped it down and blew nitrogen through the lines. to make sure the piston was not clogged. My numbers did get better but still the head is high and the suction is low with high subcool and superheat. I thought maybe I had noncondensables so I pulled a vac and weighed in charge of R-422D. Once again the number got better but my head was still high for a 35 degree Vsat. When I left the numbers were: 60.0 suction and 242.8 head. I was getting a delta T of 15 degrees. 

I am out of ideas, I cant believe I have 3 bad metering devices in one day. 

Any clues?


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## heatingrepairchicago (Nov 8, 2014)

are your line set sizes proper?


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## HVAC Service Mentor (Sep 24, 2016)

*3 in a row... possible but suspicious.*

Very interesting that all three units, two splits and one package with different refrigerants show similar problems and similar symptoms. First question: What was the complaint from the customer? Were these "not enough cooling" calls or PM calls? 

Are you starting with no refrigerant in your gauges and your gauges zeroed out? Your gauges may be out of calibration. I know you switched gauges at one point, but make sure just the same.

When you remove the txv bulb and expose it to warmer temps, the txv should drive wide open, flooding the evap. In this condition, with subcools in the 20s, the superheat should drop to zero. A superheat of 8 doesn't add up. This suggests that something in your technique may be off. 

What kind of thermometer are you using for your suction line, liquid line, and air temperature measurements? When was the last time you calibrated it? Are your probes in firm contact with the pipe and insulated from the ambient air? 

While it is entirely possible that all of your diagnoses are correct, there is not quite enough detailed information to be sure from here. Whenever something like this comes up, always question your measuring techniques! If you are using a digital manifold, question them twice!

Last, why recharge the R22 unit with R422d? In the event of poor cooling, switching the refrigerant would not provide a solution.

Good Luck!


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