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Old 23rd October 2011, 07:16 PM   #1
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Default What causes a Contactor to burn like this?

I know this isn't the right forum, but i figured this place gets a lot of views. So...I'm trying to fix a Cadco bread oven, the heating element never gets hot. I tested the element, it works when connected to a power source.

This contactor was supplying power to the element, and obviously burnt up, hence the element never getting hot...
The thing is, this is a General Electric Contactor, and its an Italian made oven, so that leads me to believe this was already replaced once. (The oven is 3 years old, out of warranty, been serviced once)

So what would cause this to happen? Too much voltage going to the magnetic coil? That would be a circuit board problem then, correct? anyway, the contactor needs to be replaced, should I upgrade that now? (it's already a 230 NOT a 24 volt contactor...)
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Old 23rd October 2011, 07:18 PM   #2
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woops forgot the pic
Click the image to open in full size.
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Old 23rd October 2011, 07:50 PM   #3
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I'd check the voltage going to the coil, if that's ok I'd guess the replacement switch was underrated or installed wrong.
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Old 23rd October 2011, 08:10 PM   #4
DaveG is offline DaveG  United States
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could just be mechanical vibration that over time causes the coil wires to rub together, eventually getting through the insulation- and then it's over quick-
but I'd also check the supply voltage.

And I would not be too surprised at a GE part inside.

It could have been repaired before with the identical problem, and had the original part replaced with an original part, and had it fail the same way...again.
A comment on the general decline of parts quality is withheld....

But, since you probably don't know what the 1st repair was, myself...I would just replace it with an exact part and see how long it holds, but do check the supply voltage. If the coil shorted it may have caused some more damage.
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Old 23rd October 2011, 08:16 PM   #5
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Are your certain that the coil is rated at 230 volts and not 120 volts?
Obviously the coil has over-heated. A bit of series resistance in the circuit feeding the coil might provide some future protection against failure.
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Old 23rd October 2011, 08:46 PM   #6
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What sometimes happens is that a bad screw or other connection causes overheating of that connection, plastic and wire insulation can melt then, in some cases the plastic and insulation carbonizes becoming a conductor leading to even more heat... If the wire insulation of the coil melted then several windings could have been shorted causing a "chain reaction" and resulting in a total burn out...
Here in Belgium we also have a 3 phase system where there is a higher voltage between the phases (for example 380V) and a lower voltage between each phase and the neutral wire (230V) there are also other voltages possible with a 3 phase system, so when we buy a second hand machine the first thing we do is check if the connection is suited for our 3 phase system, but it did happen already that we missed and a motor or heating element burned...
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Old 23rd October 2011, 09:28 PM   #7
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Quote:
Originally Posted by Frank Berry View Post
Are your certain that the coil is rated at 230 volts and not 120 volts?
Obviously the coil has over-heated. A bit of series resistance in the circuit feeding the coil might provide some future protection against failure.
Well the voltage going to the coil on the contactor is 120V...and thats what i saw with my multimeter when i tested it.

The other two hots feed the heating element, which makes it 240V. I'm pretty sure the contactor is rated for 240V, but the coil itself is only 120V....
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Old 23rd October 2011, 09:37 PM   #8
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here is whats written on the contactor...
Click the image to open in full size.

Last edited by m R g S r; 23rd October 2011 at 09:39 PM.
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Old 23rd October 2011, 09:47 PM   #9
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are there any numbers on the switch/coil? that contactor is sold separate from the switch
Attached Images
File Type: jpg contactor.jpg (71.8 KB, 160 views)

Last edited by revboden; 23rd October 2011 at 09:50 PM.
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Old 23rd October 2011, 09:52 PM   #10
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really? i thought it was all one unit when purchased new...here...

IEC Mini Contactor, NonRev, 120VAC, 12A, 3P - Magnetic Contactors - Starters and Contactors - 6KYP4 : Grainger Industrial Supply
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