McQuay ALS312

[Luce]

McQuay ALS312

I have problem with start comp 3. After Recycle Time, I have Starting, Prepurge, Auto 25% and Off Alarm (Transition Alarm). I don't have 110AC in contactor KM65. Do you have any idea what can be cause of that?

[heatingman]

Is this unit w/ soft starter, of wye delta, or across the line start?

[refrtech]

Is this an A , B , or C vintage ? I am guessing it is across the line with the 2 contactors . There is a 2-3 second timer that pulls in the second contactor . See if you are getting power to it .

[Luce]

It is wye delta start. KM3 is line contactor, KM65 is wye contactor and KM4 is for delta. All coils are deenergized for all time while I have Recycle Time, Starting, Prepurge, Auto 25%. I checked all fuses and that is OK. I suspected to controller (maybe relay output for start), because I see moisture in card near Tyco Shrack Relay. I don't know how I can check that?

[heatingman]

It is wye delta start. KM3 is line contactor, KM65 is wye contactor and KM4 is for delta. All coils are deenergized for all time while I have Recycle Time, Starting, Prepurge, Auto 25%. I checked all fuses and that is OK. I suspected to controller (maybe relay output for start), because I see moisture in card near Tyco Shrack Relay. I don't know how I can check that?

The biggest trouble w/ wye-delta is auxilary contact problems. ie; not opening or closing, poor contact from dirt etc...

[refrtech]

OK there is an output board with like 20 relays down the right side of it . If you look inbetween the relays you will see what looks like a green resistor , it isn't . They are 5 amp fuses . Check across the fuse with your meter and make sure you have 120V on each side of it . The fuses are replaceable , just grab it with a pair of needle nose pliers and pull it out . If you do , look for the red light to be on . If it is on and the relay is open then you have a bad relay . If the compressors have dedicated breakers for each then I would shut off the breaker for the compressor and jump out the terminals on the output board for the relay that energizes the contactor coil and see if it pulls in . If I had to take a stab in the dark here I would say that you probobally have a bad output relay for that contactor .

[refrtech]

The biggest trouble w/ wye-delta is auxilary contact problems. ie; not opening or closing, poor contact from dirt etc...

This is a very good point also . It has been so long since I have see an ALS that does not have a soft starter that I forgot about the aux contacts .

[Luce]

Thank you guys,

McQuay' s servicer was diagnostic problem with control board. I don't know what component was wrong, but definitely, coil had not 110VAC because bad board. Do you know settings for dip switches in the new board?