TXV Replacement

[naifmbo]

Hi,
i am trying to replace unknown model txv of 75ton trane chiller(one circuit),i fixed a 55ton (ove55-cp100- nominal)txv which is running in 125ton york chiller (two circuits),but parameters were:
suction pressure : 45 psi (very low)
leaving and return water temp: 40 c
condensing pressure : 220 psi
no buubles in sight glass
compressor 33% loaded
do you think the new txv is small,why it is running with that york chiller.
i also replaced liquid line solenoid valve befor that txv.
i am in saudi arabia with 47c ambient temp.
thanks.

 

[Yorkman]

Are you running R-22 in that York? Is the machine an air cooled screw, recip, or scoll? What is your chilled water setpoint. If the TXV in the York was a direct replacment, the valve should be right. Your pressuers indicate that something is wrong, for an R-22 system the suction should be a lot higher if the water temp is 40[°]C maybe 100 psig or a bit higher, There may even me some suction limiting or load limiting going on depending on the machine. Your discharge pressure should be a lot higher too maybe 320 to 350 psig at 47[°]C again depending on design. Are you sure you have the chilled water flow, a damaged flow switch may indicate flow and you actually have none. What is your sub-cooling. Are you sure you are looking at a clear sight glass and not an empty one,it almost sounds like you might be short of charge. Do you see any temperature differential across your liquid line? This might indicate a restriction. Is it possible that the cap. tube or bulb were damaged on the TXV when it was soldered in place. Those are a few things to check. Let us know what you find.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[Yorkman]

Naifmbo,
I misinformed; There may even me some suction limiting or load limiting going on depending on the machine. I meant discharge limiting or load limiting not suction limiting. Although at 45 psig and R-22 that maybe the case, what is your low pressure cut out? It has to be pretty closed to that for comfort cooling chill water.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[naifmbo]

Thanks Yorkman for your replay,
Both chillers are air-cooled reciprocating compressor.
Trane chiller has 325psig high-pressure cutout,but for york chiller it is around 360psig.
Trane compressor suction temperature 30-35c.
How can i inspect the txv's cap.tube?
note: If there is no flow compressor suction must be very low but it is not.

 

[Yorkman]

There are a couple of ways, the one that I use most often is to remove the TXV bulb from the suction line and warm it with my hand while the machine is running this should drive the valve open. And you should see a rapid response in the suction line noted by a rise in suction pressure and a drop in suction line temperature. Next if you can get to some ice water submerge the bulb in ice water this should drive the valve closed. You should see a drop in suction pressure and a rise in suction temperature.
That's a pretty quick and easy method.
Let me reveiw your data; suction pressure is 45 psig, suction temperature is 30-35[°]C, water temperature is 40[°]C, ambient air is 47[°]C, discharge pressure is 220 psig. What is the temperature of your liquid line you should have about 15[°]F of sub-cooling. If the TXV is not working I would expect a high sub-cooling value. If it's low or zero I would suggest that your under charged. Before replacing a perfectly good TXV verify your charge.


I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI