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...)
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...)
woops forgot the pic
An externally hosted image should be here but it was not working when we last tested it.
I'd check the voltage going to the coil, if that's ok I'd guess the replacement switch was underrated or installed wrong.
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.
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.
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.
Obviously the coil has over-heated. A bit of series resistance in the circuit feeding the coil might provide some future protection against failure.
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...
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...
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....
are there any numbers on the switch/coil? that contactor is sold separate from the switch
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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
IEC Mini Contactor, NonRev, 120VAC, 12A, 3P - Magnetic Contactors - Starters and Contactors - 6KYP4 : Grainger Industrial Supply
sorry, I was looking at GE industrial supply #MC1A400AT. Those two parts put together have a separate model no. #MC2A310ATJ
If the control circuit is putting out 120v 60hz it should be fine. is the contactor near any other heat source that might melt the insulation on the coil?
If the control circuit is putting out 120v 60hz it should be fine. is the contactor near any other heat source that might melt the insulation on the coil?
Well its Inside the oven housing, but the heating area is pretty well insulated from where the circuit board is....
I don't think a 4 pole Contactor is necessary here...I think it was probably used because that's all he had to repair it. Notice the jumper wires, which are basically sending the power through the Contactor twice. That serves no purpose, correct? Aka I can just get a Contactor with two poles to use it for each hot wire, and to send the 240V to the heating element...
I don't think a 4 pole Contactor is necessary here...I think it was probably used because that's all he had to repair it. Notice the jumper wires, which are basically sending the power through the Contactor twice. That serves no purpose, correct? Aka I can just get a Contactor with two poles to use it for each hot wire, and to send the 240V to the heating element...
We had some light contactors burn out their coils at work during a brownout. I think the 3 phase supply for the machine shop lost a phase and somehow toasted the 120v coils.
Actually....now that I think of it. The fan blade is bent and does cause a decent amount of vibration when operating. Hmmm you might be on to something!
Sorry for all the updates, but i just checked voltage across the two leads that go to each side of the coil on the contactor. 236 volts when the oven is turned on (which would send power to the heating element) and no power when turned off....soo is it safe to assume that the "technician" that replaced the contactor didn't verify voltage and used the wrong one (120 V instead of 240 V) or should i assume that there is something wrong with the circuit board and it is sending double the voltage that it should be?
I'm guessing the first option, the "technician" just used an under rated contactor.....
and as i stated earlier, since there are only two wires that need to be "switched" i can just use this 3 pole contactor, correct? with a 240V coil...
http://www.grainger.com/Grainger/SCHNEIDER-ELECTRIC-Contactor-3DY22?Pid=search
I'm guessing the first option, the "technician" just used an under rated contactor.....
and as i stated earlier, since there are only two wires that need to be "switched" i can just use this 3 pole contactor, correct? with a 240V coil...
http://www.grainger.com/Grainger/SCHNEIDER-ELECTRIC-Contactor-3DY22?Pid=search
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Normally contactors and switches will burn up eventually due to arcing. This happens because when switching an inductive load like a transformer or motor, current cannot change instantaneously. Therefore when the circuit is opened while operating, voltage will increase to maintain current flow and it will draw an arc which eventually causes the contact surfaces to burn. The charring causes increased contact resistance which causes further arcing. Also inrush current each time the appliance is turned on causes the contacts to momentarily get hot. However because you are using this for a resistive heating element that might not be the cause. The likely cause is that thermal conductivity from the heating element itself or heat radiated from the heating element and contained within the enclosure in which it is mounted caused the temperature to increase. As it does, the switch rating in amps goes down. Your switch is rated at 1.2 KW for 230 volts or about 5 amps. Anything in excess of that will cause the switch to fail prematurely at 75 degrees C or below. At higher temperature it will fail even sooner.
Don't feel too badly, I just had to replace the GE momentary contact starter switch on my gas dryer. I wanted it right away. A local store luckily had one in stock. $64 with tax. When I bought the dryer about 27 years ago, the whole thing was probably around $400 or $500. This is the second replacement I installed.
Don't feel too badly, I just had to replace the GE momentary contact starter switch on my gas dryer. I wanted it right away. A local store luckily had one in stock. $64 with tax. When I bought the dryer about 27 years ago, the whole thing was probably around $400 or $500. This is the second replacement I installed.
^thank you for the explanation! But if you read my last post, i'm almost certain that the problem was too much voltage going through the coil that caused it to burn....
I recommend you find a contactor to 220 v. and you feed him for that voltage. it is possible that the control is receiving more than 120 v. and causing overheating. have a neutral or not very reliable. make sure that the control has the appropriate protections.
If you look carefully at the nameplate you'll see it is rated to handle much higher voltages, 575 and more. Heat from the heating element itself breaking down insulation or some other part of it was the most likely cause of failure. Trust me on this, I do it every day for a living.
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