splattered points on contactor

[joe magee]

I have a Liebert 30 ton unit. Two of the three poles on the contactor points get splattered and I need to replace the contactor every two months.

I tightened ALL electrical connections, I checked amp draw and voltage. The compressor does not short cycle. The voltage is 460. The one set of points is fine. Any clues?

[icecube51]

what is contracting the contractor??

Ice

[nike123]

What is voltage and current balance?

[icecube51]

i think more in de way of a faulty helpcontractor,who has not enough currert to contract the maincontractor so its going on/of a few times before doing the job correcly. see if its fed by 24V or 220V. its taking current from the same line as where the points are burnt.

Ice

[Yuri B.]

All contact points get splattered - some more some less. How you are making your mind for opening the contactor (then changing it)? Contacts are hot? Voltage drop? A pictrure would be better here.

[joe magee]

Actually pitting is normal on contactors, splattering isn't. Usually it's due to high starting amp draw which this o6d compressor does not have. No voltage or amperage imbalance. I need to change the contactor every couple of months. And remember it's only on two points.

[Yuri B.]

Then nothing left as to put a larger contactor, only remember, as Icecube hints, feed its coil through a larger help-relay.

[Yuri B.]

I would swapped the leads to see whether the disposition of damaged and undamaged poles had changed.

[nike123]

What is compressor FLA and what is contactor make and model #?

[Yuri B.]

I suspect either a drawback in design or faulty production methods for the particular type of contactors you use.

Springs may have different release times, in the first place (in terms of milliseconds).

If all three poles go off simultaneously - no splatters.

If two poles switch off earlier than the left third one - no circuit , no arc.

But if one pole swithes off slightly earlier than the other two, greater arc will be produced in the circuit formed by the left two poles during releasing.

That is why you have always damaged just two poles - neither one nor all three.

Try to find contactors of other manufactures.

[joe magee]

Running load amps is 12 to 20. Contactor is a 30 amp Furnas. Where is Riga?

[nike123]

Running load amps is 12 to 20. Contactor is a 30 amp Furnas. Where is Riga?

Model number please!

[Yuri B.]

Hello Joe. But indeed, only two possibilities -
a/ current disbalance (I have, for instance, one motor running with 120/90/140 A)
b/ flaw in the contactor itself - one pole releses milliseconds earlier, the left two receiving increased switching off load
(Maybe I am incorrect in the latter saying about switching off. On the contrary, possibly, one pole is lagging behind the other two on switching ON thus leaving them with increased starting current.)

[Yuri B.]

To add about the possibility a/
That disbalanced current motor that I mentioned, is starting through a soft-start, otherwise, I am afraid, we would too have been regularly changing its contactor.

[icecube51]

is the compressor starting on the full load of 100% ??? because when starting at 50% and then straight away going to 100% gives you the same effect of a compressor that is underloaded.
check the capacity relais.

Ice