McQuay SWP045 question

[menmycbrf4i]

I have a building full of the McQuay SWp045's and i'm having problems with two of them. They run great but a few times a day the 2 keep coming up with a motor protection alarm on compressor 1. The 1st and 4th compressors do not have motor protection on them. I've replaced the CCB1 board and the R1 relay per McQuays advice. Alarm still happening. These are 2 units on seperate floors and its random when they happen. Any help would be great.
Thanks

[captinsano]

Bit confusing if it in fact has a motor protector on the compressor and you changed the module and it is still occuring jump the module and put a good ohm meter w/ a hi resistance scale on the thermistor leads inbedded in the winding you may have to watch it for a while I have had a problem w/ those going haywire before.If I remember right these are scrolls w/ no pumpdown and no crankcase heater I have a theory on this but no one from copeland would entetain it!

[flange]

short cycling could cause that.

[Tech Rob]

I'm not really up to speed on what McQuay is using on their self contained units these days, but the last microtech 2 units I worked on had copeland scrolls with "tele-make-it-cheap" manual reset overloads. The days of the klixon and texas instruments solid state modules are gone.

I'll go out on a limb and assume that you have verified that the motor is not actually being overloaded and that the current draw is within reason.

If that is the case, you've replaced the ccb1 and the r1, then you probably have a conductor or connector problem. Check the pins and plugs and the wiring in the circuit.

It's possible that the overload relay is at fault, too.

[McQuayUser]

The alarm indicates that the controller commanded the compressor to start but the contactor did not pull in. I suspect that the auxiliary contacts on the compressor contactor are not making a good connection or the CCB is not seeing that the contacts closed. In some cases A BAS system can be delaying the information long enough (BAS asking for a lot of data) that the alarm gets generated. There is a 10 second timing for the MCB to receive confirmation from the CCB that the compressor contactor pulled in.

[richper]

This problem may ormay not be control related.You need to do much more trouble shooting. The compressor may be off on internal overload at the time it is being called to run due to a mechanical problem such as a refrigerant related issue,there could be an electrical problem in or suppling this unit.Alot more information is required such as pressures,temps,amps,volts,etc. for anyone to make a determination about whats going on here.Anything less is just shooting from the hip.