Contactor Coil Burning

Nothing fancy here< but I replaced a contactor 3 times! I know, stupid me. Well, here is the situation: 3 pole 220v coil 30Amp contactor. Found coil burnt, disintegrated (blocking the switch from pulling in), replaced it, checked voltage all around 219v, put unit on defrost, all the same all around, nothing crazy, turned unit on and off, checked voltage and amps, all good. Next day, back to square 1. WTF is going on? All connections are tight, no short, this is a walk in freezer remote condenser, about 10 years old. Has this ever ever happen to any of you? Right now is Saturday night here and just got a call back for it (this will be the 4th), I suggested to call the electric company to check the 3 phase, I'm lost on this one. Thanks for any suggestions, anything pointing towards a different angle would be welcome, thanks guys

loose connection can cause chattering , then the coil will burn out

Try looking elsewhere on your control circuit. You might have a faulty pressure switch or thermistor block which is making and breaking rapidly,this will cause the coil to overheat and possibly fail. If it is a defrost contractor look at your defrost termination control this can also cause chattering and eventually coil failure. Also you may want to check your neutral path as sometimes panel manufacturers link some of the neutrals together and just because your contactor neutral may look ok it might be further down the line where your fault is.

Check the coil voltage when the contractor is de-energised, obviously it should be zero, but any residual voltage (even a couple of volts) would produce heat in the coil without pulling the armature in & consequently burn it out.

i take it this has a neutral,not sure of your voltages over there between any two phases what voltage do you get and is it the same L1-L2,L2-L3,LI-L3,also L1-N etc,and when you say 30 amp contactor are you certain its up to the job in the amperage it can take is it the same as the original.

I would look for voltage surge from electronic card, maybe some small capacitors?

Hi
contactor coil burnout is usually due to either wrong voltage , or a missing neutral!!!
if the coil is totaly burnt and expanded, i would connect a neutral wire directly to the coil from the neutral bus.
if this is the only contactor with a problem in this board , i recommend you check the control circuit from output to coil input and make sure you arent feeding 400v by mistake or disconnecting neutral by mistake.
good luck

If electrical side checks out concentrate on lp/hp oil pressure switch if its short cycling at all it will cause strain on your contactor.

I had this same problem 3 times, the third time I realised that when I asked for the coil I asked for 400V when it should have been 230V. Strangely enough it worked when I first tested it, it was when I went back the third time I saw it didn't pull in it's self but when I pushed it in with screw driver it held and then chattered in and out rapidly.

I found a loose wire nut in a switch box a little away from the unit, thanks for suggestions, this was a mess to play with from the start

Loose wires can be a right pain to find as well.

just going blowing me trumpet!!

21-04-2013, 08:21 AM

#2

http://www.refrigeration-engineer.co...tar14239_3.gifinstall monkey

Join DateOct 2007LocationmanchesterAge39Posts3,594Rep Power18

Re: Contactor Coil Burning

loose connection can cause chattering , then the coil will burn out

Good call install monkey. :-)