copeland semi hermetic run on

[ikpucool]

hi all..I am new to this site and am trying to get an answer to a weird situation.
I have a single phase compressor for a commercial refrigeration unit that continues to run briefly after shut down, and shakes a lot also. I've replaced the capacitors and potential relay, voltage is within rated and amp draw is also within rated..
During operations the unit is quiet and amp draw normal, start up amp draw normal also.
I am starting to think it may be due to worn bearings that allow crank shaft to shift upon de energizing voltage.....??????
Any one have any ideas?? any help would be great
thanks

[Brian_UK]

Hi and welcome to the forum.

What type of compressor is it?

Some machines will run backwards during pressure equalization.

[monkey spanners]

I would try turning it off by the main isolator to see if it still does it, i've seen faulty contactors and wiring faults do strange things.
If it still does it then maybe its a mechanical problem, maybe its snaped a rod or something.

I once had a condenser fan motor that run backwards for five seconds and off for ten then on again and this was due to faulty control circuit wiring.

Jon

[powell]

continues to run briefly after shut down

Could you define this statement?

LLSV shutdown, T'stat shutdown, LPC shutdown, contactor shutdown....... etc.

Also, give us the compressor model number.

[ikpucool]

Could you define this statement?

LLSV shutdown, T'stat shutdown, LPC shutdown, contactor shutdown....... etc.

Also, give us the compressor model number.

the compressor is shut down by contactor that controls one line of power.....second line is fed live at all times....the contactor is controlled by voltage from electronic controller....ive checked the contactor and contacts as well as voltage and all is checking out normally....this is what makes it a weird problem....
copeland semi hermetic....not sure of m/n at time of this reply...sorry

[powell]

the compressor is shut down by contactor that controls one line of power.....second line is fed live at all times....

I'll assume a H/K/EA or 3A (1/2 thru 3 HP) model that's 115v?

Verify that neutral is connected to terminal "R" and the hot leg is connected to "2" (feeding the overload).

Then verify that the contactor is breaking the "hot" leg.