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Not So Obvious Problem


Marko

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This is an element plug that had melted. Just one. What ever happened, it wasn't so obvious. I fired a 3/4 full to ^6 kiln. But it never reached ^6. And it run 20 hours on my timer.  So I checked my elements for continuity. I opened the control panel and proceeded to measure past the plugs and they were good. I thought they would be since they were brand new and only fired about 4x before. So I put the control cover back on and did a refire. Once again after 10 hours it was still at ^05, so I shut it down. Waited for it to cool and completely removed the control panel, so I could see if any switches, relays, wire or power relay were burnt. But every thing was fine. Not even a smell. So I decided to see if I had a loose connections. Started tightening screws on the wire and busbar connectors. And sure enough the parts broke off as I began to tighten. It was just holding on because of the fusion. It was in a series of 4 elements. The other 3 elements were fine. As where all the rest. 

 

So how did this one brand new element melt and fuse with the ceramic plug?  Anyone?  :huh:

 

It's working fine now that I put a new element in. But I will continue to monitor. 

post-64410-0-19540700-1490318254_thumb.jpg

post-64410-0-19540700-1490318254_thumb.jpg

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The ends of an element are doubled twisted wire. That doubled wire needs to be part of the connection to the power input wire. If you cut the pigtail short and connect directly to the element where it has become single wire, you will be connecting to the part that heats up. Can't tell from the picture if you were on the doubled pigtail or the single area. Also, corrosion inside the bolt connector can cause a bad connection that will overheat.

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Had the exact same thing happen to me. I had replaced the elements in my test kiln for the third time and inspected the connectors. They "looked" useable; but I happen to be in the studio when I started hearing the "hiss" of electrical arcing. I loosened the screws on the cover enough to slip an inspection mirror in to look: sure enough it was arcing on the connector. The temp rise was lagging just as in your case.  I looked on the inside of the old connectors; where the screw would hit the element, and a blue coating of oxidation was very evident. Might look all perty on the outside, but the inside connection areas are not so nice.

 

Nerd

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Make sure you make this element connection as Dick says back a bit so it runs cooler.Also any loose connections as well as any with corrosion or scale on them will heat up so cleaning them down to bare metal is always good idea and get them as tight as you can.The high amp draws of an electric will kill any dirty or loose connections fast.Clean it all before assembling-

I use  a copper coating as well on most electrical screw  connections that may heat up but its hard to find and costly.It prevents corrosion and handles heat well and is mostly ground copper.

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