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Thread: TXV Powerhead Lost Charged
05-29-2012, 11:12 PM #1
TXV Powerhead Lost Charged
I have a chiller and I believe that one of the circuits has a failed powerhead on the TXV but I am not 100% on this diagnosis.
About 2 months ago I removed the filter dryer and replaced it and charged the system to the manufacturers specs. Today I found this compressor locked out on a low pressure alarm. I reset the alarm and the compressor ran less than 5 seconds. In that time the suction pressure dropped to 25 psi (its a R22 system) and the head pressure rose to 200 psi. This leads me to think that the TXV powerhead lost its charge and is more or less working like a pump down solenoid. Am I missing something here or am I correct in my diagnosis?
05-29-2012, 11:19 PM #2
could be.. may be valve itself... are you sure its got enough refrigerant.. is there any liquid line solenoids...it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair
05-29-2012, 11:45 PM #3
There are no LLSV. I am not positive on the charge, it just seems like a lot to lose in a short period, not impossible. I have leak checked it with an electronic leak detector and got not hits. I will find out if it has enough once I pull the charge, I am just leaning towards the TXV. What in the valve would cause it to act this way?
05-29-2012, 11:46 PM #4
It could be. It could be the valve itself, or a liquid solenoid valve. Is there icing on the leaving side of the TXV ??
That would pretty much tell you where the restriction is.
05-30-2012, 12:14 AM #5
5 seconds of run time doesn't allow for much icing, or diagnostics for that matter.
05-30-2012, 08:04 AM #6
05-30-2012, 05:14 PM #7Professional Member*
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05-30-2012, 05:18 PM #8Originally Posted by carmon
The symptoms sure sound like a bad element...
05-30-2012, 07:48 PM #9
I pulled the charge today, had the same amount I put in. Took off the power head and found a small pinhole in the diaphragm with my eye glass. I took apart the rest of the valve and found no debris. Put it back together, replaced the power head, charged it up, and now its running like a champ.
05-30-2012, 10:30 PM #10
Certainly sounds like a restriction in the liquid line; whether a dead element keeping the TEV closed, a plugged filter-drier, etc.
Once you remove the power head, take your thumb and attempt to push the disphragm in. If there' no charge (or a weak charge) you'll be able to move the diaphragm with your thumb.
Also, when you screw the power head back onto the valve, you'll feel it come in contact with the pushrods and start to depress the pushrods during the last half turn or so.
If you're seeing something different than this, then the power head has lost its charge.