View Full Version : TXV question
10-02-2008, 07:45 PM
I am trying to diagnose a problem with an R-22 system that was just retrofitted to R-410a after a major compressor burn out. The system has a 4 ton evap coil and 3 ton TXV and condensing unit. The system was flushed of contaminants, piston orifice removed, condensing unit replaced, suction and liquid dryers installed, and TXV added. After the retrofit/repair was complete I started the system and it ran at normal pressures for a good amount of time. After a few minutes, the suction pressure stood still, but the head pressure climbed and climbed and climbed, until it was up to about 575 to 600 psig. At this point I pulled the disconnect, waited, and tried again. Same deal. I have a few ideas but I'm trying to get some other opinions before I have to go back to the job tomorrow. I figured there was a restriction or a jammed shut TXV, but in that situation I would expect to see the system pumping down the low side but it didn't. The low side stays at about 140 psig but the high side just keeps going up. So, I'm lost for now. Contaminated system? Bad TXV? Sensinb bulb location? Help would be greatly appreciated. Thanks.
10-02-2008, 08:18 PM
need to go to pros forum for that.
10-02-2008, 08:58 PM
Did you happen to check thetemp drop across your liquidline drier?Stop the indoor fan for an equal frost pattern? How long does it take until the pressures sky rocket? There`s a few to start.
10-02-2008, 10:05 PM
10-02-2008, 10:05 PM
probalby overcharged. you need to take subcooling and superheat readings for a good diagnosis.
best thing to do is take a clean recovery drum and dump most of the refigerant into it. then charge unit untill proper subcooling is obtained. then check superheat. If superheat is low then check for low air flow if superheat is high then check txv, driers and of course if superheat is good then your ok.
10-02-2008, 10:12 PM
Could be a condenser fan motor failing, but I would tend to lean towards a failing headmaster.
10-02-2008, 10:44 PM
you hooked up a new 410 unit to an old 22 coil and it don't work????:rolleyes:
10-02-2008, 10:46 PM
Are you using the old R22 evap coil.
Brand and model numbers of both indoor coil/air handler, and outdoor unit would help.
10-02-2008, 10:52 PM
i hope he meant changed out a 22 "system" with a 410a "system"
10-02-2008, 11:25 PM
Yes, it is a 4 ton R-22 coil inside of a Carrier fan coil unit with a 3 ton Bryant Evolution condensing unit. 3 ton 410a TXV. Model and serial numbers are not handy right now. If I remember correctly the condensing unit is a 187ANA. If I had it my way this job would have not been done this way, but I was not the one who set it up, but was the one who got stuck doing it. I appreciate the help, I'll try out these suggestions tomorrow and see what I come up with. Thanks.
10-02-2008, 11:31 PM
is it a heat pump? if so run the heat and see what happens ;)
other than that, you need some pro help and this is not pro section :)
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