Data Aire with scroll's

[joe magee]

I worked on a thirty ton two circuit downflow air cooled Data Aire unit. The one circuit with a scroll compressor was tripping on the hpc. There was no rhyme or reason as to why or when it would trip. Cold outside,warm out etc. The discharge pipe came out three feet horizontal and fifty up the wall to the aircooled condenser. There was traps on the liquid line so liquid would not migrate back to the compressor, the crankcase heater was working. After checking all the common problems I decided to install a checkvalve on the outlet of the discharge line. That worked.

I know scrolls have checkvalves in the compressors and usually when they go bad you can here the scroll spin backwards when the compressor shuts down but not in this case. This was a new install. So my question is why did this work?
We have thirty other units piped the same way and no problems. Is it possible a check valve was never installed on this compressor and at start up it would trip. It never did it while I was there. The other circuit never tripped

[stufus]

Anything is possible but most likely a duff NRV . Would the comp hold a pump-down before the new valve was fitted?
If all is well now and stays that way , well spotted.
Alternatively if you have the time and the comp has rotoloks swap it onto the other circuit to see what happens.
Or sit back and pat yourself on the back for a job well done
OH nearly forgot get onto the manufacturer and give them both barrels and an invoice for your time..
Cheers
Stu

[NoNickName]

a duff NRV

Recently is happening more frequently than not. We had 12-14 compressors with broken scrolls by liquid return from the discharge.

[joe magee]

Thanks for the feedback.