Kiln receptacle burnt

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steve_p

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Hi,

went to look at a customers kiln setup yesterday. House is 1.5 years old. She asked for a kiln cuicuit to a small garage. The builders electrician ran 6/3 aluminum ser breakered at 50A, I thought ser behind drywall used the 60 degree column which i read at 40 amps
the kiln is rated at 240V 39.4 amps.
trying to figure if the failure was a loose termination, undersized conductor, or both.
 
I have fixed a few of those.

No fancy math. REAL hot environment, continuous load, ceramic dust everywhere and the receptacle is usually about 3 or 4 feet from a 2900 degree kiln. Lots of thermal cycling and they often get plugged and unplugged in order to clean the floor.
 
Like others have said, probably loose termination, aluminum got it’s bad name from terminations not staying tight. It expands and contracts greater than copper, so doesn’t take much to get a loose connection if the load is heavy.
 
As long as the receptacle and breaker are listed to 75C terminations the #6 is ok. There was a short period of time all SE cable was restricted to 60C but someone realized how stupid that was and now only #10 and smaller in thermal insulation is restricted to 60C.
 
K8MHZ said:
I have fixed a few of those.

No fancy math. REAL hot environment, continuous load, ceramic dust everywhere and the receptacle is usually about 3 or 4 feet from a 2900 degree kiln. Lots of thermal cycling and they often get plugged and unplugged in order to clean the floor.
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Yeah same here. AL wiring does not hold up well with kilns, I personally specify copper for kiln circuits.
lots of dust.
The elements are like a dead short for a moment while they warm up.
Much like old tungsten lighting they are hard on contactors.
 
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