View Full Version : Liebert challenger 3 High head pressure
06-12-2007, 06:03 PM
The unit keeps going into High Head Pressure.(HHP) It is a water cooled (Coil) unit incoming water is 77 deg F. I start the unit. Fan comeís on and the liebert calls for cooling. The Compressor comes on and I hear the Solenoid Valve click and for that 2 seconds the unit goís to HHP. I do have my by-pass valve Open for the water Reg valve.
I am thinking it may be the Expansion valve w/bulb that has gone bad.
06-12-2007, 06:10 PM
What is the actual head pressure? what (if there is one) is the water regulator set for, about 180-225 lbs is normal.
06-12-2007, 06:26 PM
The water reg valve is set for 200 but for testing I have the By-Pass open. I have 30-50 psi of water flow with in coil codenser that is at 77 Deg F
It could be a bad head pressure switch!
06-12-2007, 07:02 PM
You need to know what the actual pressure is. If water is flowing, could be refrigerant blockage, fouled condenser, bad pressure switch, etc.. You can't make a diagnosis on intuition, it doesn't work. If you dont have a port, add one, no gauge, buy one.
06-12-2007, 07:33 PM
Is the actual High Pressure Cut-Out opening or are you just getting the alarm on the panel? If the pressure switch is opening after 2 seconds of operation, I would say that it is likely a bad switch. Put your gauges on it to see what is happening.
06-12-2007, 07:41 PM
The unit was running at 77 deg room with the high pressure side of the gauge at 225 psi and the low side was at 75 psi. The unit was working normal. Water Supply at 77 deg F and the Return Water was at 89 deg F with the by-pass valve closed. The unit was running for 20 minís and I walked away from the unit when the control panel beeped for high head pressure. The compressor shut down and the gauges do what is normal and a compressor shuts down. So I didnít really get a reading before the compressor shut down.
06-12-2007, 07:54 PM
Did you manually have to reset a high pressure switch? 225 head is not a reason to think that txv is an issue. Sounds like a faulty pressure switch, but make sure there is nothing else in the same alarm circuit.
06-12-2007, 08:02 PM
Yes i had to manually hit the High pressure switch every time I try to restart the unit.
Thermal expansion valve w/bulb. I would think that this might be the case but I going to change out the compressor high pressure switch first. I just wanted to run it by you guys first.
06-12-2007, 10:34 PM
From what you are saying, i wouldn't suspect the TXV.
Loss of hydronic flow would be my first guess, but you gotta be there gauged up to really tell for sure.
Usually there is a pair of wires leaving the unit to signal the pump controls or a dry cooler pump. I've seen units added into a system where they didn't bother to hook that up, and then when the other units all satisfy at once...
Find out what controls the loop pump, for a start.
06-14-2007, 09:21 PM
Isolate the condenser and backflush it.
That condenser is in the bottom of that Challenger and often works as a trap for the systems' trash.
Couple of times. Checking the flush water will tell the tale.
06-15-2007, 12:45 AM
With a bad TXV on a water condenser I would think that the unit would go off on low pressure before it tripped out on high head. Almost like it was pumping down.
As long as you have strong flow on the OUTLET of the condenser I'de be looking at that TXV bulb too.
Look for breaks or bends on the bulb line or rub-outs on it. Look for the suction side to never make it over 60psi too if that is the case.
06-15-2007, 01:12 AM
I have found this many times when multiple hands have been on the machine and it has been mysteriously overcharged. Verify charge first.
06-15-2007, 06:34 AM
Welding slag will go right thru a Y strainer.
06-15-2007, 12:39 PM
If the unit goes out on high head almost as soon as the compressor starts, but when it does run all seems to be normal and has "Scroll" compressor the unit is overcharged. Liebert has a service bulletin out on this. Also in the late 90's some water/glycol cooled Challengers had the wrong R22 charge on the data plate. If the unit runs normal for awhile then the head pressure climbs or it goes out on hi head after a short rest look at the coolant piping. The coolant inlet should be hooked up where the condensed R22 comes out of the condensor coil. Don't trust your strainer to be correctly installed on the inlet supply. Check your coolant temperature in and out to confirm flow.
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