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View Full Version : MCQUAY RPS rooftop solenoid problems


hvacdoctor
07-11-2005, 04:25 PM
Have a Rps20BA rooftop not getting power to pump down solenoids for some reason? Wiring diagram is missing, we got a copy of a orginal OM manual but can't read the print. Unit looks modified control wise with relays and wires. I understand that Mcquay might had a tech bulletin on these units to bypass the pump down solenoids due to problems?
jemawalton
07-11-2005, 05:19 PM
Try this site

http://mcquay.hvacrcat.com/mcquay.asp?SID=lizlMcPdcpklikhj,112437&w=r

Type in RPS and look for the IM (instalation manual) for the RPS Vintage B. You can download a manual there. I will look for a service bulletin on the subject.
jemawalton
07-11-2005, 05:27 PM
That link isn't doing what I wanted it to do. I will try again shortly.
jemawalton
07-11-2005, 05:31 PM
I'm not sure downloading the manual from McQuay is worth the effort. It is a poor scan that you can barely read. Anyone else have any suggestions?
wasp
07-11-2005, 11:12 PM
Got to love those "modified" units. Sounds like to me that it is an older machine. Ain't nothin' to rewire correctly, I have done it numerous times with excellent results and running better than the way it was running before I got there.

When you say "no power" to the solenoids, do you mean it stays in a pump down mode or will not de-energize to pump down?

Either way it could be a bad wiring problem or a relay that is not working correctly. Trace wires back from solenoids and see which relay(s) are controlling it and then find the control that controls the relay.

It is possible that the coil itself is bad, getting power and not energizing.
hvacdoctor
07-12-2005, 10:25 AM
No power to solenoids at all. We will have to trace wires and tag them/label.
johnnyc
07-13-2005, 04:04 PM
You might want to check on the output board, next to the relay for the LLSV the mini 5 amp fuse,it looks like a resistor and pulls out with a pair of tweezers/pliers.
refrtech
07-13-2005, 08:40 PM
Originally posted by johnnyc
You might want to check on the output board, next to the relay for the LLSV the mini 5 amp fuse,it looks like a resistor and pulls out with a pair of tweezers/pliers. BINGO !:) There have been problems with some of the older solid state relays on the board (black ones with screw in the middle). Do not rely on the red light to tell you it is powered.