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Electrical Wires Fried in Kiln

04/24/2012 3:37 PM

Hello,

We have burnt out electrical wires in our kiln. At the spot where the electrical wires connect to the elements all of the wires burned up, and all at the same time. The electrical wire is a #6 so it was heavy duty enough. The elements and their pigtails are all fine. We have three phase power and the wiring is in delta formation.

Any thoughts on what could have caused this?

Thanks in advance for any help!

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#1

Re: Electrical wires fried in kiln

04/24/2012 3:44 PM

You might start by giving the wattage total on the unit, voltage, etc. When you say

"burned out electrical wires' do you mean? You said the elements are fine.

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#2

Re: Electrical Wires Fried in Kiln

04/24/2012 3:53 PM

Can you send pictures?

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#3

Re: Electrical Wires Fried in Kiln

04/24/2012 4:18 PM

I'm not an electrical guru, but it sounds like the connections loosened, creating a high resistance, so the voltage drop (i.e. heating) occurred at the connection and wires instead of the elements.

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#4

Re: Electrical Wires Fried in Kiln

04/24/2012 4:50 PM

Sounds like a bad/loose connection...Proper connectors are important, and clean tight connections are as important as proper wire size...Periodic inspection for signs of overheating is regular maintenance procedure...

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#5

Re: Electrical Wires Fried in Kiln

04/24/2012 6:42 PM

How are (or were) the wires connected to the elements?

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#6

Re: Electrical Wires Fried in Kiln

04/24/2012 6:43 PM

expansion differentials between to dissimilar metals can cause corrosion, and bad conections, raising resistance and leading to more heat at the connections.

i'm having the same problem with an outdoor light.

i don't know the solution.

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#7
In reply to #6

Re: Electrical Wires Fried in Kiln

04/24/2012 7:00 PM

What is the age, wattage and type light? Have you tried cutting the ends of the wire at connections off and stripping wire for new connection?

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#8

Re: Electrical Wires Fried in Kiln

04/24/2012 8:09 PM

For stove, and kiln, connections I have special stainless steel crimp connectors. Other connectors just can't take the stress. Stainless is not a good heat conductor, so the wire has a better chance of survival.

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#9
In reply to #7

Re: Electrical Wires Fried in Kiln

04/24/2012 9:38 PM

it's a 500w quartz light. copper leads connected to nickle or stainless wires that lead to the bulb. the housing is to small and is very hot to the touch.

it's just a bad design.

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#10

Re: Electrical Wires Fried in Kiln

04/24/2012 10:44 PM

Welding, to carry the current without local temperature rise?

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#11
In reply to #4

Re: Electrical Wires Fried in Kiln

04/24/2012 10:44 PM

If you have an amp probe it would be a good idea to check amp draw on each leg to verify wire size is sufficient....

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#12

Re: Electrical Wires Fried in Kiln

04/24/2012 11:51 PM

I've not wired a kiln, but I have a lot of experience with muffle and tube furnaces where the same problem crops-up frequently. The heating element (probably nichrome or Kanthal) should never be connected directly to copper, regardless of its size. Most furnace suppliers sell nickel hardware and wire to transition from the heating element and the copper supplies. Nickel has low enough resistance to not heat on its own and sufficient heat resistance to mate with the element which is a nickel alloyed with chromium, and a few other trace metals in the case of Kanthal. Check with Google for furnace hardware.

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#13

Re: Electrical Wires Fried in Kiln

04/25/2012 12:04 AM

Did the copper wiring fail, or did just the insulation burn?

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#14
In reply to #3

Re: Electrical Wires Fried in Kiln

04/25/2012 12:21 AM

Nice, Right on the money. Don't down play your electrical experience.

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#15
In reply to #9

Re: Electrical Wires Fried in Kiln

04/25/2012 4:26 AM

LED matrix replacement units are now available that use a tiny fraction of the power to produce a similar light level. Heat dissipation is less, meaning nothing in the unit or its connections will get cooked.

These things can annoy neighbours; the lower the light level, the better in many cases.

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#16
In reply to #15

Re: Electrical Wires Fried in Kiln

04/25/2012 11:52 AM

It's a kiln...it's supposed to be hot.

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#17
In reply to #13

Re: Electrical Wires Fried in Kiln

04/25/2012 1:06 PM

The copper wire failed. And, of course the insulation burned too.

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#18
In reply to #2

Re: Electrical Wires Fried in Kiln

04/25/2012 1:22 PM

Hope this helps.

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#19
In reply to #3

Re: Electrical Wires Fried in Kiln

04/25/2012 1:28 PM

Thanks. It is a great thought, but unfortunately the connections were all still tight.

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#20
In reply to #5

Re: Electrical Wires Fried in Kiln

04/25/2012 1:31 PM

We used copper split nut connectors. There are some pictures above in the thread.

Thanks.

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#21
In reply to #8

Re: Electrical Wires Fried in Kiln

04/25/2012 1:34 PM

Thanks Mike. We had copper wire and copper split bolt connectors. I am wondering if there was a reaction between the different metals.

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#22
In reply to #11

Re: Electrical Wires Fried in Kiln

04/25/2012 1:37 PM

Thanks. We don't have an amp proble, but maybe we should.

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#23
In reply to #19

Re: Electrical Wires Fried in Kiln

04/25/2012 5:48 PM

They may well be tight, but all that oxidation (the green stuff) could mean poor connections regardless.

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#24

Re: Electrical Wires Fried in Kiln

04/26/2012 10:40 PM

We have had a similar problem (at a client, where we supplied the cables and lugs) of the wires burning out at the junction between the wires and the heating elements, not because of the voltage or wire guage or other problems but because of the lugs.

Our application involved a plastic coating paper machine, where a thin film of plastic is molten and dropped as a film onto a paper travelling perpendicular to the falling molten plastic film. The heating elements were used to melt the plastic pellets.

Yes, we solved the problem by replacing the normal lugs with nickel plated ones and touch wood, it has not repeated over the last 7 years.

Trust this helps and share the results with CR4.

Madhav / Hyderabad / (0) 98491 69056

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#25

Re: Electrical Wires Fried in Kiln

04/27/2012 8:19 AM

It looks to me like the copper conducted quite a bit of heat directly from the heating element. Copper is an excellent thermal conductor and therefore it should not be connected directly through a heating element.

A better approach would be to use an intermediate connection between the copper and the heating element. I have seen short bus bars of stainless steel used in the middle of the connection. Stainless steel is a poor thermal conductor but a good electrical conductor. That acts as a buffer. But the stainless steel is also going to get hot so it needs some air circulation so the absorbed heat can be dissipated.

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#26
In reply to #25

Re: Electrical Wires Fried in Kiln

04/28/2012 12:02 AM

"... Copper is an excellent thermal conductor and therefore it should not be connected directly through a heating element.

A better approach would be to use an intermediate connection between the copper and the heating element. I have seen short bus bars of stainless steel used in the middle of the connection. ..."

Now that is an interesting bit of knowledge I'm going to file away for future reference! It's one of those things that is so obvious in hind-sight, but not having experience with high output heating elements, I never considered it.

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#27

Re: Electrical Wires Fried in Kiln

05/13/2012 8:15 PM

sorry for the late response. it just came to me. consider tinning the copper wires with solder 'silver solder perhaps" before using crimps suggested from other posts.

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