crazy train

[cborgs]

I am working on a train car with a 15 ton copeland discuss compressor on r22 refrigerant. They have been having problems with this unit for some time now. When the unit is fully charged the suction pressure is around 30-35 psi and the liquid pressure is running around 380-425 psi depending on the temperature outside or in the building the train is stored in. I have washed the condenser and the evap, adjusted the txv's...etc. I have done everything I can think of except recover and evacuate the system. I think it may have non-condensables in it, I am going to recover, evacuate, change the core dryers and recharge the system hoping to drop the head pressure, is there anything I may have not thought of? Any tips may solve the problem.
Thanks

[troubleshootin]

It definetely sounds like there is a restriction somewhere. Driers are a good start. If you do pull the system down check the strainer in front of the txv to make sure it is not plugged, also make sure the txv setting is right and the bulb is mounted correctly on the right suction line (if there are 2) and the external equilizer line is downstream of the bulb. Then make sure your powerhead hasnt lost its charge by taking the bulb and dipping it in hot and cold water with the system running and watch for a change in suction pressure. Check for airflow issues, amp draw on blower motor. also check superheat and subcooling and post it. Make sure all king valves are totally back seated. See how that goes and please keep us posted, i would like to know what you find!

[mustardman]

I am working on a train car with a 15 ton copeland discuss compressor on r22 refrigerant. They have been having problems with this unit for some time now. When the unit is fully charged the suction pressure is around 30-35 psi and the liquid pressure is running around 380-425 psi depending on the temperature outside or in the building the train is stored in. I have washed the condenser and the evap, adjusted the txv's...etc. I have done everything I can think of except recover and evacuate the system. I think it may have non-condensables in it, I am going to recover, evacuate, change the core dryers and recharge the system hoping to drop the head pressure, is there anything I may have not thought of? Any tips may solve the problem.
Thanks

You have a restriction somewhere plain and simple could be a failed txv but likely a plugged liquid line drier

[mustardman]

It definetely sounds like there is a restriction somewhere. Driers are a good start. If you do pull the system down check the strainer in front of the txv to make sure it is not plugged, also make sure the txv setting is right and the bulb is mounted correctly on the right suction line (if there are 2) and the external equilizer line is downstream of the bulb. Then make sure your powerhead hasnt lost its charge by taking the bulb and dipping it in hot and cold water with the system running and watch for a change in suction pressure. Check for airflow issues, amp draw on blower motor. also check superheat and subcooling and post it. Make sure all king valves are totally back seated. See how that goes and please keep us posted, i would like to know what you find!

Just beat me to it

[HVAC/R Man CO]

AH the old choo choo.

[HVAC/R Man CO]

AH the old choo choo.

See about installing an unloader on the compressor.

[HVAC9900]

I like the idea of pulling the charge,changing drier(s) as a start.
As it's been worked over many times, may have had some non condensables introduced.
Check your superheat and subcooling when that's done,will provide a lot of info.

Does this have a headmaster,crankcase pressure regulator,pressure limiting txv?

Would also pay close attention to fan rotation and operation on both ends.

Is this used for ac?

[cborgs]

I pulled the charge, changed the core dryers, did a leak check of the system and pulled a vacuum on the system. I returned the next day to find the system had not pulled down, upon further inspection of the unit I traced the refrigeration lines under the train. They are both wrapped in insulation and have a protective cover around them so it is hard to see them. I noticed a slight bow in the lines under the fuel tank. The train must have hit something because the suction line which is 2 1/8" was kinked to the point where there the pipe was only about 1 inch thick. I changed the piece of pipe and hooked up the vacuum pump again. I'll return tomorrow to finish up the job. Ill keep you posted on the results, but I'm willing to bet that is going to be the cause of my problems.

[cborgs]

here are a couple of pictures of the pipe I cut out. One picture is the old pipe lying next to the new pipe.

[troubleshootin]

Is this a split system or packaged unit? And did you find a refrigerant leak anywhere? The crimped piping may cause those pressures, but the discharge pressure is not as likely to climb that high with something like that. See how many microns you get it down to and if it holds, did you check the txv??

[Dowadudda]

my experience tells me that although that pipe is indeed kinked, I am saying that aint the problem. That is a suction line. And your problem is upstream of that.

High Head. Low suction. The head aint high because it's not rejecting heat that is for sure. It aint picking any heat up in the evaporator with that low suction.

We aint getting any Refrigerant out of the condenser, She is stacked with Liquid. I wonder what your subcooling measurement is?

[Randy S.]

Unless you felt a TD at the drier, I would suspect the TXV head is dying, and agree with dowadudda.

The old timer's rule of thumb is air cooled condenser pressure is around 30 degrees above ambient, or entering air. For subcooling, 10 degrees, and for suction superheat 12-15.

[cborgs]

I pulled the system down to 320 microns held the vaccum for 24 hours, this is used for comfort cooling on the train. It is a split system. The txv's are good. There was a small pin hole in the suction line where it was kinked. I charged the unit back up and my subcooling was 10 degrees, suction pressure was 68 psi and the head pressure was 255. Just about perfect for r-22 air conditioning. Before, the suction pressure was 30-35 and the head was 385-425. Part of the problem was their maintance guy kept adding refrigerant to the unit because it had low suction pressure, he thought it held around 80-100 pounds. but once I had everything straigtened out it only held about 36 pounds. In the building where the train was, the temp was 90 degrees with 70% humidity. I'll continue to monitor it for the next few days.

[HVAC/R Man CO]

I pulled the system down to 320 microns held the vaccum for 24 hours, this is used for comfort cooling on the train. It is a split system. The txv's are good. There was a small pin hole in the suction line where it was kinked. I charged the unit back up and my subcooling was 10 degrees, suction pressure was 68 psi and the head pressure was 255. Just about perfect for r-22 air conditioning. Before, the suction pressure was 30-35 and the head was 385-425. Part of the problem was their maintance guy kept adding refrigerant to the unit because it had low suction pressure, he thought it held around 80-100 pounds. but once I had everything straigtened out it only held about 36 pounds. In the building where the train was, the temp was 90 degrees with 70% humidity. I'll continue to monitor it for the next few days.

I can't belive a maint guy would add refrigerant!!! HA!! HA!!