help with trane comm

[cool jag]

hey i'm working on trane commercial heat pump 2 stage .i was changing out the txv on the outside .i had started it up while it was running the indoor fan stopped . i looked into the problem and found the 3 pole contactor not pulled in i then pushed in contactor it started to run but chattering it has a aux contactor . voltage 208 pulling 210 high voltage 24 volt coil pulling 21v. i have never seen this before could you please help with twa180

[GoColts]

Does it have a muli tap transformer? If so make sure it's wired to the 208v terminal. Is this the only contractor that as 21v at the coil?

[cool jag]

i don't think so but it worked for years with no change.what are you thinking voltage drop or maybe weak coill? i'm all ears

[jpsmith1cm]

Moved to Tech-to-tech Commercial.

[GoColts]

When doing start-up, one of the things you are supposed to do is set the line voltage on the transformer. With that said I have seen many units started up with 208v incoming power and the tap left at 230v. The unit will run fine for a while, eventually the coils weaken on your contacts and thats when the service calls start. Low coil volotage with make your contacts chatter, if this goes on for to long you will start to damage componets ie compressors or motors. Check the transformer and check your line voltage and your low voltage. It could be set correctly, and your transformer is going bad or you have a bad IDF contactor.