Trane RTAC300 Question

[todouble]

Ive got a Trane Rtac air cooled chiller that tripped out today on high liquid level in evap on ckt 1. Reset and ran fine, looked in my IOM and read that the high liquid level setpoint was reached and was above this point for 80 minutes. Does anybody know what this actual high level number is??? Seems like it was just a nuisance trip but out of curiosity I would like to know what is considered high level???

[Tech Rob]

I'm not sure about the specifics of "high liquid level", but I'm sure Jayguy can help when he arrives.

I think you should look at the cooler water flow and pump(s). EEV problems are also a possibility.

[fixerup]

1.0 is top of range.I believe it tries to maintain 0.0 level. I would try to run your EXV in test mode to see if it is closing 100%.I had one give me this alarm periodically ended up finding the EXV would not close off all the way.Changed EXV and its been running good ever since.

[Healey Nut]

Fixerup is right about the level specifics . it tries to maintain zero but it is not unusual to see it run at -.02/3 " depending on load etc . check the exv and also check that the copper lines have not been bent accidentally ,which would cause a liquid trap and give a false reading . Graham

[mtntom]

Quick check for EXV: Cycle circuit off, watching the sight glass at exv, if you see any flow right at or just after shutdown, its leaking by.

[cw0682]

You should be able to do a pumpdown using the Techview and the LL King Valve. Your LL sensor should read -1.0 or -1.1 after the pumpdown is complete. Then you can drive your EXV closed with techview and open the LL King valve. No refrigerant should get pass your EXV. If your LL sesor climbs after trying this you would have then verified a leaking EXV.

[nun]

If this unit runs for long periods at a time it could be that the EXV is loosing it position. Then it floods the evap. Try cycling it off once a day to recalibrate its self.

[jayguy]

another item to watch is the liquid level...(duh!). does it drift around or is it pretty stable? your setpoints may be set such that the EXV can not respond fast enough.

good luck.

[todouble]

Yes ive cycled the machine off then back on, and manually drove the valve thru techview. Liquid level is running anywhere from -.02 to +.03. This is were I usually see it run. I know its looking for 0.0 but it runs a point of two high or low. Anyways it has been running fine since, but I just wanted to know if anybody knew what the magic number was that the microprocessor considers high liquid level. Thanks for all the help guys!!

[jimbob73]

If this unit runs for long periods at a time it could be that the EXV is loosing it position. Then it floods the evap. Try cycling it off once a day to recalibrate its self.

Long periods of time or conditions that cause higher then normal condenser pressures like walls, other units,etc. The permanent fix for this is to replace current EXV motors with the high torque motor.

[nun]

80% of bit count corresponding to +.8mm or more liquid level for 80 minutes.

[Manu1]

What is the circuit tonnage? and the chiller serial number? There was a problem with the EXV motor torque on circuits with 2 compressors where if the chiller stays on line for long periods of time the EXV looses track of it's own position, the controller believes it's fully closed and stops any attempts to keep closing it eventually the EXV is fully open and the liquid level is above 1" and CH530 calls for high liquid level diagnostic, but when the chiller is reset the EXV calibrates it self and the problem is gone.

You have two solutions, one is to replace the EXV motor for a new one, or stop and start the chiller once every 24 hrs or every 12 depending how long does it take for the problem to show up. :cool:

[ON-CALL]

Fixerup is correct it is 1.0 and nobody has added oil to system lately.

[jmshrmn]

Manu1 is right. I have a customer with (12) RTAC5004's that had the same problem. (That is 6000 tons) The problem is, generally when the head pressure is high, the stepper motor on the EXV misses steps because the stepper motor is not strong enough to close down against the higher head pressure. As there is no feedback potentiometer on the valve, the CPU does not know the actual valve position. It only knows where it is supposed to be. So, after a hot day, the load diminishes and the valve is open further than it should be. The barrel level goes up. The chiller shuts down due to a high liquid level in the evaporator. You get called the next morning. Shutting down the chiller resets the valve to a known position at 0%. It will allow the chiller to operate until it misses steps again. Trane is aware of the problem and has a new valve with a stronger stepper motor. And it works. By the way, large tonnage air cooled chillers is a very bad idea! This is only the beginning of your problems with these chillers. Good luck to you.

[19c357]

Great thread. Nobody said the chiller is junk. Nobody responded by saying "ive never seen one of these,but here is whats wrong. Just guys knowing what they are talking about.This is the way the forum should work. Thanks for sharing Trane experts.