# Chattering contactors?



## gnuuser (Jan 13, 2013)

your key switch may have burn scarred contacts this can cause them to overheat and separate momentarily
this can often cause chattering of a contactor
weak coil is another cause
and lets not forget hysteresis resonance in the laminates.


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## bill39 (Sep 4, 2009)

Are the contactors old or new (does "plain old" mean new, or old)?

Anyway, just a couple of things:
Are the coils the correct voltage?
Maybe try swapping one of the coils to a different contactor and see if that helps.
Are the connections all tight? If they are all chattering it could be a loose neutral?

Hope this helps & fun.


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## MDShunk (Jan 7, 2007)

Coils powered through a control power transformer? I've seen control power transformers (and DC power supplies) sized such that they don't really take into account inrush and, as such, they can't provide the necessary current to seal the coil in nice. Some contactors are even marked with a separate "sealing current".


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## Wirenuting (Sep 12, 2010)

If all the contactors are using the same single key switch to lock them out, your single control transformer might be undersized. (Assuming your using just one)
Like Gnuuser also said, worm contacts on keyed switch.


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## quarky2001 (May 29, 2014)

MDShunk said:


> Coils powered through a control power transformer? I've seen control power transformers (and DC power supplies) sized such that they don't really take into account inrush and, as such, they can't provide the necessary current to seal the coil in nice. Some contactors are even marked with a separate "sealing current".


The coils are fed off straight AC power from the panel they're tied to, so I don't think that's it. My only other suspicion is something funny happening with the wiring setup - the two key switches operate a little Omron relay each - one for 3 contactors, another for the other one. The relay then fires the coils. Tried switching out the smaller relays without success, though I'm curious if they might somehow be the culprit.


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## MotoGP1199 (Aug 11, 2014)

I’ve had this same issuse when they undersized the control transformer as well. Disconnect one or two contactors and see if that fixes the issue. If so, up size the control transformer. Also try bypassing the key switch.

EDIT: You beet me to the punch with the supply power response. In that case bypass the relays if possible and have straight power from the breaker to them for testing. If that fixes it, you know its the relays.


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## MDShunk (Jan 7, 2007)

Were these contractors in storage in an unheated job trailer or similar for a while? Surface rust on the E lamination faces will make them hum, buzz, and chatter like mad. You can scrub that off with a little Emory or a stiff cloth.


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## MDShunk (Jan 7, 2007)

Agreed. I'd put a jumper wire from one of the poles to A1 and see if the chatter goes away as a first step.


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## Helmut (May 7, 2014)

Are they chattering, or just buzzing loudly?

If it's the latter, put in mechanically held ones.


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## mitch65 (Mar 26, 2015)

Does the contactor stop chattering only when you manually hold it in? Or start again when you remove your hand? I've run into a few SqD definite purpose contactors that buzz terribly out of the box. it seems like the tolerances on the moving parts are so loose that the armature gets cocked and can't close properly.


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## JRaef (Mar 23, 2009)

When you checked the voltage, did you do so with the coils attempting to energize? Another common issue is that when the contactor closes and starts the motor, the added motor starting current causes a voltage drop, which chatters the contactor. If you have a loose neutral somewhere, this could make it worse.


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## Helmut (May 7, 2014)

JRaef said:


> When you checked the voltage, did you do so with the coils attempting to energize? .


????


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## Helmut (May 7, 2014)

If the contactor is chaterring, you would see the load coming on and off.

Is this really happening?

What do these contactors feed? Panels within the shop, where machines are being fed from?


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## John Valdes (May 17, 2007)

Try a new contactor and see if its the contactors themselves.
You say Square D but tell us nothing about the contactors. Are they motor rated? Are they NEMA? Are they correct choice for the application? Are they brand new?

If the coil voltage is good with the contactor pulled in, its a contactor issue.
I have seen cheap lighting contactors installed for motors. Not a good idea.


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## Wiresmith (Feb 9, 2013)

quarky2001 said:


> This has me stumped, so I'm hoping someone has another idea for me.
> Besides the voltage and the shading coils, I can't think of anything that would cause chattering.




make sure coils are correct ac or dc, sounds like they may be dc coils and your using ac


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## MDShunk (Jan 7, 2007)

hd13 said:


> make sure coils are correct ac or dc, sounds like they may be dc coils and your using ac


Don't know if I've ever seen a 120 or 240 volt DC coil.


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## Wiresmith (Feb 9, 2013)

MDShunk said:


> Don't know if I've ever seen a 120 or 240 volt DC coil.


might not be 120 or 240 coil either


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## MDShunk (Jan 7, 2007)

hd13 said:


> might not be 120 or 240 coil either


You're right. It could be 208. He already said it was powered from the panel that it's switching circuits from, and in the very first post he said they were 120.


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## Wiresmith (Feb 9, 2013)

MDShunk said:


> You're right. It could be 208. He already said it was powered from the panel that it's switching circuits from, and in the very first post he said they were 120.




square d

115/125VDC V62 (Coil PN 31071-412-44)
230/250VDC V66 (Coil PN 31071-412-53)

just throwing it out there, he may have looked at it quickly,


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## Wiresmith (Feb 9, 2013)

what is contactor and coil part numbers your using, some of those square d's are from china they could have different coil in them than the label


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## John Valdes (May 17, 2007)

Wiresmith said:


> what is contactor and coil part numbers your using, some of those square d's are from china they could have different coil in them than the label


And he is listing them using DC power at AC power levels?


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## MDShunk (Jan 7, 2007)

I think this is one of those instances where troubleshooters need to keep Occam's Razor in mind. "When you hear hoofbeats, think horses, not zebras". The possibility of a new coil being a 120vdc coil is a zebra, and would be at the very bottom of my list of considerations, but, admittedly, it is quick and easy to check.


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## JRaef (Mar 23, 2009)

Helmut said:


> ????





Helmut said:


> If the contactor is chaterring, you would see the load coming on and off.
> 
> Is this really happening?
> 
> What do these contactors feed? Panels within the shop, where machines are being fed from?


Concept is this:

When he is checking the control voltage while nothing is running, he is just checking voltage AT the switches and everything looks good. But when the controls are energized, all of the LOADS on those starters come on line and cause a general voltage drop because they are overloading the supply transformer. That then causes the control voltage to drop too, which then makes the contactors chatter. then with the contactors chattering, the machinery motors are constantly going through inrush current and making the situation worse, or keeping it the same. 

So if you put your meter on the COIL terminals, not the SWITCH, and then close the switch withe the meter connected, you are seeing the actual COIL voltage that it is getting WHEN the loads come on line. It's often a very revealing exercise.


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## Helmut (May 7, 2014)

JRaef said:


> Concept is this:
> 
> When he is checking the control voltage while nothing is running, he is just checking voltage AT the switches and everything looks good. But when the controls are energized, all of the LOADS on those starters come on line and cause a general voltage drop because they are overloading the supply transformer. That then causes the control voltage to drop too, which then makes the contactors chatter. then with the contactors chattering, the machinery motors are constantly going through inrush current and making the situation worse, or keeping it the same.
> 
> So if you put your meter on the COIL terminals, not the SWITCH, and then close the switch withe the meter connected, you are seeing the actual COIL voltage that it is getting WHEN the loads come on line. It's often a very revealing exercise.


I was just questioning how you could check the voltage at the coil, and the coil not be energizing at the same time, that's all.

He said he checked the voltage at the coil and it read 110v, 
He might just have a batch of shorted coils, if it is in fact chattering and not buzzing.


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## 220/221 (Sep 25, 2007)

I don't know what "chattering" means here so I will toss out an experience from 20 years ago.....probably unrelated.

I came across a large contactor...probably 100 amp, controlling a lighting panel.

This thing would *bang *on/off/on/off continually about 4 or 5 times a second.

I'd never seen this system in play but apparently there was some DC involved because there was an ac to dc component in the box. It was a long round piece, kind of like a 10" long fuse.

I believe the DC voltage somehow held the contactor closed. Sorry. That's all I remember because I pawned it off on someone smarter than myself.


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## Helmut (May 7, 2014)

220/221 said:


> I don't know what "chattering" means here so I will toss out an experience from 20 years ago.....probably unrelated.
> 
> I came across a large contactor...probably 100 amp, controlling a lighting panel.
> 
> ...


It's the effort that went behind the post, that's important.


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## Wiresmith (Feb 9, 2013)

220/221 said:


> I don't know what "chattering" means here so I will toss out an experience from 20 years ago.....probably unrelated.
> 
> I came across a large contactor...probably 100 amp, controlling a lighting panel.
> 
> ...



was this when it was initially installed?


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## 220/221 (Sep 25, 2007)

No. Stock installation....parking lot lights at a car dealer. 

The service call was probably 30 years after it was built.


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## Wiresmith (Feb 9, 2013)

quarky2001 said:


> This has me stumped, so I'm hoping someone has another idea for me.


what was it?


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## catsparky1 (Sep 24, 2013)

I got a guy who uses self tapers to secure the contactor to the can . He holds the contactor with one hand and screws it on . The metal shavings fall in and cause it to chatter . I have had to take apart zillions of them and clean them to get the metal out . 

No matter how I ask , tell or threaten him he still does it . Maybe monday I will make him a shovel operator . Poor guy will have no idea he is being punished because I read this .


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## Jlarson (Jun 28, 2009)

You have to better define "chattering"

Could just be that they are vibrating the back plate of the can or transmitting noise through the conduits.

Typically here we use mechanically held contactors or more commonly we will put an ASCO switch on the feed to a dedicated equipment panel in HS shops.


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## 99cents (Aug 20, 2012)

I know this is a zombie thread but I brought it up for a reason.

A year ago, I had the same problem with Square D contactors. They buzzed like crazy, brand new out of the box. I replaced them with ABB, exact same terminations, and they worked, no problem, and have been working ever since.

I have a new job to do and bought Square D again, simply because it was Monday and I had to buy something before the suppliers shut down. Can I expect trouble again? I need to do this job off hours and time is tight.


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## samgregger (Jan 23, 2013)

I guess I would grab a trusty cut off lamp cord and test fire them first.


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## Wirenuting (Sep 12, 2010)

99cents said:


> I know this is a zombie thread but I brought it up for a reason.
> 
> A year ago, I had the same problem with Square D contactors. They buzzed like crazy, brand new out of the box. I replaced them with ABB, exact same terminations, and they worked, no problem, and have been working ever since.
> 
> I have a new job to do and bought Square D again, simply because it was Monday and I had to buy something before the suppliers shut down. Can I expect trouble again? I need to do this job off hours and time is tight.


I use Square D a lot and rarely get a bad one out of the box. 
But about a year or so a go I got a couple of chatty ones. 
Been fine ever since.


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## Cow (Jan 16, 2008)

samgregger said:


> I guess I would grab a trusty cut off lamp cord and test fire them first.


I agree, if there was any concern, this is what I would do.

In our shop we bench test the crap out fixtures, controls, anything questionable with an appliance whip all the time.


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## Mobius87 (May 20, 2019)

99cents said:


> I know this is a zombie thread but I brought it up for a reason.
> 
> 
> 
> ...


I have nothing but trouble with those. It was to the point that 75% of them would chatter like crazy right out of the box.

At this point that I take them apart and clean them as soon as they arrive from the wholesaler.

Sent from my SM-G960W using Tapatalk


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## Liteitup (Jun 15, 2011)

Had same problem. Would really like to know why it happens. Ended up replacing with RIB relays. Never had a problem after that. Just check your current requirements to make sure the relay can handle it.


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