rattle and roll

[self employed 1]

i have a reach in freezer with a tecumsi semi hermetic pumping 408-a. a several months ago i installed a valve plate kit, new liguid line dryer and sight glass. the unit runs and cools beautifuly. recently unit started with a knocking noise on start up and gradually goes away. i have not been called back on this, i just noticed it the other day while working on a adjacent cooler. when i left it last amp draw, superheat, sightglass, all good. condensor is clean. any ideas of posible causes?

[R12rules]

tecumsee dont make no semi hermetic. They make a bomb-proof belt driven unit. Dairies used to use them a lot.

They also make pots. But nothing you can service with a valve plate. Heck, even to change the oil is a tough challenge in one of them tecumsee's.

Maybe you mean a copeland?!
A copeland semi-hermetic ... a coplematic... something like that ....

are you getting a liquid return after the off cycle or defrost?

Pull your screens and check for metal down there. Maybe your washing away your lubrication and this will show up in tiny sparkles in the sump.

They sure are pretty to look at, unless it's your job to service and maintain that system.

Check your oil screen.

[condenseddave]

It's probably a Copeland K body that will always make that noise on startup...

[beau]

sounds like an oil problem. Is the nooise continuous or just at startup. Is this an old R502 box running on R408A?
Are you slugging back liquid to the compressor ?

[jhd1234]

I'm with Dave on this, It's probably a piston pin with some wear. I've seen small, noisy, Copelands like that run forever.

[jeffcolledge]

Check the Kanuten valve...