Excessive contactor Chatter

[W.ma.RefrigTech]

I have a Carrier RTU 48TJE012-521 208/230 3ph that I can't seem to find the reason why one of the comp. contactors chatter so bad it will eventually brake apart like the other one did when I arrived on the first call to this unit. but when I remove the 3ph comp. wiring from the comp. and power the rtu back up, that contactor pulls in and is fine (no more excessive chatting). I have the same ohms across the three terminal and nothing to ground and when it does run shortly before the contactor chatters badly I'm pulling about the same amp as the other comp. What would make that contactor chatter so excessive that it will eventually brake apart. Any ideas?

J

[nike123]

High drop of power supply voltage caused by insufficient cross section of supply cable or/and high load of local power supply transformer.

[cadwaladr]

what is the coil voltage of the contactor

[monkey spanners]

Faulty hp switch pulsing on and off with the discharge from the comp, have seen it a couple of times on refrigeration systems.

[glenn1340]

Maybe a faulty auxillary contactor if fitted. I`ve come across this before on compressors especially if the control voltage is low, eg 24v, and the enviroment dusty.

[Magoo]

Have you had a multi meter across the contactor coil terminals while the chattering is happening. Generally the chattering is because the supply votage is too low to hold the contactor coil in position. It would seem the control circuit supply transformer is dropping output voltage due to system loads, no compressor load the transformer is fine. As Nike said earlier voltage drop in system. You will probably find the control circuit transformer is 2or 3 phase primary and low voltage output/secondary. No compressor load and the transformer is fine. Try replacing the transformer.

[sachin230]

The most common cause is foreign contaminates between the magnet and armature. You can remove the coil and clean these contaminates using air or alcohol. Be sure all power is off before attempting this.

[Pauly.]

Gauges on? Check LP HP switch as above mentioned if auto reset

[goshen]

The most common cause is foreign contaminates between the magnet and armature. You can remove the coil and clean these contaminates using air or alcohol. Be sure all power is off before attempting this.
HI I have to agree if there is no evident control problem,this problem is usualy due to dirt or shavings or even bugs inside the contactor,if the contactor is just buzzing all said regarding is true,if the contactor is actully chattering ,you should check control sys excpecially a loose neutral,or bad relay contact.:)
good luck