View Full Version : high head pressure
07-07-2005, 08:21 AM
HELP!! I evacuated a semi hermetic compressor with R12 as I put the r12 back in the system the head pressure will go 300 to 400psi and trip the pressure switch. what is going on ?
07-07-2005, 08:45 AM
discharge valve on compressor closed???? if not that something very very very bad to get those pressures with r-12
07-07-2005, 09:04 AM
It sure sounds like a valve on the high side is closed or a blockage, bad txv.
You either had non-condensibles or added them by mistake, most likely. Easy way to check:
- Close liquid line solenoid and let the system pump down.
- Remove a control wire from the compressor contactor.
- Jump out the condenser fan and let run for 1/2 hour.
- Get high side pressure.
- Get ambient temperature.
- Look at P/T chart for the ambient temperature measured. If the pressure is more than a pound or two higher than what it should be (which allows for the gauge to be off a little), you have non-condensibles.
Hope this help.
07-07-2005, 06:30 PM
What was the reason for the "evacuation"??
Did you change a system part or something?
07-07-2005, 09:09 PM
Back seat your discharge service valve stem and attach your hi side gage to the liquid line at the receiver.
THEN and only THEN ... restart your compressor.
07-07-2005, 11:44 PM
overcharge or restriction on high side of system.
Have you checked water/airflow whichever applies over the condensor coil?
[Edited by dnt on 07-12-2005 at 03:35 PM]
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