Copeland 5 Ton 3ph Compressor Trouble

[David40]

Would appreciate some advise on troubleshooting this system.
Got a call about a straight cool A/C system not running up to snuff after I replaced the compressor two weeks ago. When I got there I heard a loud hissing noise like a large refrigerant leak, only there was no leak. The noise was coming from the compressor. Pressures were 90 low and 140 High. I would normally expect 76 low and 250 high with 85 degrees outside. At first I thought it might be an expansion valve stuck open but discovered the system does not have one.
I'm assuming the sound I am hearing is an internal bypass of some sort that is stuck open. I tried reversing the rotation for about 30 seconds just to see what would happen and it ran with a bit of noise but the pressure remained equalized. (no pumping action in reverse at all)
Is this compressor defective or did I screw something up?
Additional information:
-Customer says old compressor worked fine for 5 years up to the time it quit.
- Old compressor had a locked rotor, no burn out.

Thanks for any suggestions or comments.

[sedgy]

hi dave , eather internal pressure releafe valve , or valve plate gone ?
happy stripping ,

[David40]

Thought I had mentioned it but I see I didn't. This is a scroll compressor not a piston type.

[serviceman]

check the expansion device, the compressor is a scroll

[David40]

That was the first thing I thought of, but no joy. It has no expansion device. It is a fixed orifice / cap tube system. I also considered that someone might have replaced the Air Handler that could have the wrong sized orifice, because I have seen symptoms like this in a mismatched system before, but that's not the case here.

[monkey spanners]

Some of those scroll comps have an internal doodad which bypasses discharge pressure and temp refrigerant back into the suction part of the compressor if they get too hot, which would give similar symptoms to what you describe.

Is it a copeland?

Might be worth letting it cool right down and see if it runs ok then, if so it would be worth looking for reasons for it to overheat, low refrigerant charge, blocked filters/coils, blocked drier, restricted capiliary/orifice, etc.

Was this comp the same type as the old one?

Do a search on here for scroll comp problems, i'm sure i read something on here about a similar fault.

Jon

[lawrence1]

Sounds like the reversing valve switching over.

[David40]

I had not considered overheating as a cause. Most units I have worked on have an electrical overload that cuts power to the motor not a bypass.
Air flow in the handler is good.
Before I jump into replacing it I think I'll take your advice and try it again tomorrow when it's totally cool and see what happens.

No reversing valve, straight cool with electric heat.

[David40]

monkey spanners
Was this comp the same type as the old one?


Yes, exact replacement.

[Magoo]

David40.
take the replacement compressor supplier to site and show the problem.
I would think the internal releif has failed.

[goshen]

Would appreciate some advise on troubleshooting this system.
Got a call about a straight cool A/C system not running up to snuff after I replaced the compressor two weeks ago. When I got there I heard a loud hissing noise like a large refrigerant leak, only there was no leak. The noise was coming from the compressor. Pressures were 90 low and 140 High. I would normally expect 76 low and 250 high with 85 degrees outside. At first I thought it might be an expansion valve stuck open but discovered the system does not have one.
I'm assuming the sound I am hearing is an internal bypass of some sort that is stuck open. I tried reversing the rotation for about 30 seconds just to see what would happen and it ran with a bit of noise but the pressure remained equalized. (no pumping action in reverse at all)
Is this compressor defective or did I screw something up?
Additional information:
-Customer says old compressor worked fine for 5 years up to the time it quit.
- Old compressor had a locked rotor, no burn out.

Thanks for any suggestions or comments.

Hi :
this sounds like a typical symptom of scroll comps that overheat or work at very high head pressure,
u could try and cool down comp and hope for the internal relief valve to close or u might have to change comp !!this seems to happen on copeland comps pretty often .
good luck!

[nike123]

Hit it hard with BIG rubber/plastic hammer few times when cooled. It may help.
Then search for cause of internal relief action.
What is compressor full model #?

Loud, very loud, relief sound coming from the compressor.

Some model scrolls have an internal pressure relief (IPR) valve. This valve opens at a discharge to suction differential of 375 to 450 psi (R-22) or 550 to 625 psi (R-410A). Check for restrictions in the discharge line, overcharge of refrigerant or a faulty component.

http://www.hvacrinfo.com/scroll_trouble.htm

[David40]

Model is ZR57K3-TF5-930

Can't be high head pressure because the thing never went over 150 psi even when I first fired it up. Outdoor temp was very cool that day so I didn't give it a second thought.
Now that I have all these suggestions I'll have plenty of experiments to do today.

[serviceman]

notes that the warehouses of expansion is correct and is positioned correctly

[David40]

notes that the warehouses of expansion is correct and is positioned correctly

Not exactly sure what that means.... BUT, I wanted to thank everyone for all the suggestions and references. I decided to check the pressure right at the pump. so I installed a piercing valve on the pipe right out of the pump. Pressure instantly spiked to over 300psi. I shut it down immediately. Upon further investigation I discovered the factory installed filter/dryer was almost completely clogged. This surprised me since it was not a burn out, but apparently the old pump was spitting out very small metal filings that finally clogged the filter. System is running great now. Customer is very happy.
So, I never got to take the new compressor off the truck, and I returned it.
Again, My thanks to all of you.

[goshen]

hi :
now that is good to hear,
good luck!
Dont forget the hammer it actully did work once!

[cadillackid]

Not exactly sure what that means.... BUT, I wanted to thank everyone for all the suggestions and references. I decided to check the pressure right at the pump. so I installed a piercing valve on the pipe right out of the pump. Pressure instantly spiked to over 300psi. I shut it down immediately. Upon further investigation I discovered the factory installed filter/dryer was almost completely clogged. This surprised me since it was not a burn out, but apparently the old pump was spitting out very small metal filings that finally clogged the filter. System is running great now. Customer is very happy.
So, I never got to take the new compressor off the truck, and I returned it.
Again, My thanks to all of you.

whenever I do a compressor replacement of any type burnout or locked rotor i always replace the factory installed filter dryer with a new one AND flush the system...

having done a lot of work on automobile systems ive found that any compressor failure can slop a bunch of junk through a system and I like to flush out as much of the old oil and junk as I can get out before fitting a new compressor.. just to help the longevity of the new compressor...
-Christopher

[David40]

That's good advice. I'm going to adopt that procedure myself.

[surenuff]

From what I hear you saying, it is the interanal relief valve that is bypassing. But if it is bypassing, then you won't see any pressure very high on your guages. I have seen these valves be bad before, but if they were bad, you would see it right away. Other times I have seen a scroll bypassing, but it was doing it's job. Is there a chance maybe you charged the unit on a cool day, and might have gotten too much in it?? NOt trying to question your skills, just making suggestions. I do not believe any of the internal pressure relive valves were a one time valve, so if it is not resetting, you are probably going to have to change it again. Auto reset, or one time, it does not matter if it is not resetting,

[surenuff]

whenever I do a compressor replacement of any type burnout or locked rotor i always replace the factory installed filter dryer with a new one AND flush the system...

having done a lot of work on automobile systems ive found that any compressor failure can slop a bunch of junk through a system and I like to flush out as much of the old oil and junk as I can get out before fitting a new compressor.. just to help the longevity of the new compressor...
-Christopher

I also will change a factory filter dryer anytime I open up a system. I can see no reason why it would be a bad thing to flush every system before changing a compressor. But at the same time, if my test shows no acid, and the oil is not really dirty looking, I will blow out the lines install dryer, compressor, vaccuum, put back online. Of course a burnout is a different story.