Chattering electrical contactor

M

moonlight machine

Diamond

Joined

Nov 19, 2007

Location

marysville ohio

• Nov 6, 2019

• #1

I have a Fostoria electric salamander. 240V 36A It has a internal thermostat that controls a contactor that controls the heat coils. It used to make and break the connection with one click. Now it sometimes chatters for 10 - 15 seconds. What is going on?

 

M

MattiJ

Titanium

Joined

May 31, 2017

• Nov 6, 2019

• #2

Quite typical for contactors to start buzz or chatter when they age.
Dust, rust or some other crap between the core halves.

They can also buzz if the coil voltage is lower than intended.

 

M

moonlight machine

Diamond

Joined

Nov 19, 2007

Location

marysville ohio

• Nov 6, 2019

• #3

MattiJ said:

Quite typical for contactors to start buzz or chatter when they age.
Dust, rust or some other crap between the core halves.

They can also buzz if the coil voltage is lower than intended.

Click to expand...

This thing is not buzzing, it is contacting and releasing, contacts arcing like crazy. It stops on its own.

 

D

DDoug

Diamond

Joined

Oct 18, 2005

Location

NW Pa

• Nov 6, 2019

• #4

'Cause it's cold outside....

You'd chatter too with the first snow of the year...

Seriously, open it up, and give it a dust off with some air, and look at the contacts as well.

Does it have the aux. contacts to latch it on ?

 

J

Jim Williams

Stainless

Joined

Oct 3, 2002

Location

Grant, Florida

• Nov 6, 2019

• #5

I had a relay in a lawn sprinkler system that chattered until it failed. A new unit was installed under warranty. The replacement worked OK for a while and then started chattering. On my own, I replaced that one and put in a larger gauge wire supplying the relay coil voltage. I have had no problems since then.

 

B

BoxcarPete

Stainless

Joined

Nov 30, 2018

Location

Michigan, USA

• Nov 6, 2019

• #6

Take a look for any potential short circuits. I had a relay in my truck get all clicky when my trailer wires decided to contact each other for a minute. Got it all sorted out with a new trailer connector.

Usually pull-in voltage is about 75% of the rated coil voltage, and once it's pulled in, won't release until voltage drops off to 25-30% or so. That means there's something swinging the voltage by at least 50% of the coil voltage.

 

9100

Diamond

Joined

Nov 1, 2004

Location

Webster Groves, MO

• Nov 6, 2019

• #7

The usual mechanism for a chattering contactor is-

It closes, connecting the heater

The load of the heater makes the voltage drop

The lower voltage releases the contactor

The voltage rises back high enough to pull the contactor in

Repeat until failure

The resistance of a heater is lower when cold, meaning that it will draw more current until it heats up. While chattering, the heater is probably getting enough current to eventually increase its resistance, lightening the load, until the contactor will stay in.

First look for poor connections. See if the plug gets warm or if any of the terminals in the unit get hot (after running with the unit unplugged, of course). Anything on the magnet poles can aggravate the problem, but that will also usually make the contactor buzz.

Bill

 

Cole2534

Diamond

Joined

Sep 10, 2010

Location

Oklahoma City, OK

• Nov 6, 2019

• #8

Jim Williams said:

I had a relay in a lawn sprinkler system that chattered until it failed. A new unit was installed under warranty. The replacement worked OK for a while and then started chattering. On my own, I replaced that one and put in a larger gauge wire supplying the relay coil voltage. I have had no problems since then.

Click to expand...

Voltage drop has always been the reason for chattering contacts in my experience.

Moonlight, do you have a thermal camera? If so, fire up the salamander and run it for while and look for hot connections.

 

J

Joe Gwinn

Stainless

Joined

Nov 22, 2009

Location

Boston, MA area

• Nov 6, 2019

• #9

I'd look for a loose power wire that is making and breaking in response the the contactor closing and opening.

 

P

Pathogen

Hot Rolled

Joined

Oct 18, 2016

• Nov 6, 2019

• #10

Thermostat signal to contactor may be the problem, check the voltage to the contactor coil and check for a steady voltage when heat is needed.

If you want to update, Solid State Relays (SSR) are the bomb for replacing mechanical contacts, they are dirt cheap and have many ways to control them. The biggest drawback is they leak a very small amount of current (output) when turned off by the controlling input

 

B

Bill D

Diamond

Joined

Apr 1, 2004

Location

Modesto, CA USA

• Nov 6, 2019

• #11

On my lathe I had to remove the armature and wire brush it off. Especially the end where it contacted the fixed pole pieces. it just did not close enough to make good contact and hold the point closed. It only happened once in a while. The sliding surfaces were a bit rusty and rough with dust jamming things as well.
Bill D

 

tomjelly

Stainless

Joined

Aug 26, 2007

Location

GA

• Nov 7, 2019

• #12

take apart the contactor if you can and check out the contacts. If they are pitted you may be able to dress them with a file to get by for a while, but you will probably need a new contactor.