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cracked pot

Wiring For Kiln

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I have to tell you how  much I appreciate this forum.  I bought my first kiln about four years ago, no experience at all with firing on my own.  My electrician ran the 220 line and put a plug on the end in case I ever needed to move the kiln. 

Soon after that I read here on the forums that hard wiring was better since oxidation in the plug could lead to overheating,  Electrician thought this was not likely.

Well, just to be safe, I always fire when I'm around and check each time to see if the wire or plug is hot.  In my last two firings the plug has been uncomfortably warm so I called the electrician.  He checked and everything looked OK but after his vacation he would return to install a box to wire the kiln. 

I fired one load before he returned since things looked OK.  When he came back to rewire and unplugged the kiln from the socket,  the socket had melted on one side and showed some burn marks.

I was incredibly lucky and would not have kept such a close eye on things if not for all your generous advise.  Should probably have followed it in the first place.

Thank You.

Joseph F likes this

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Cracked pot.......

 

Thanks for sharing this instructive posting.  A "service to the field".

 

A great example of why maybe the average electrician who is used to doing mainly (or exclusively) home wiring jobs.... like electric stoves, baseboard electric heating, and so on, is often not a great choice to listen to when installing KILNS.  They often do not really understand the continuous LOAD that kilns operate at when set to the high end on the last parts of firings.

 

When a kiln is on high (or at the top end of a programmed firing via computer control) the draw is basically whatever the full amperage rating the kiln is listed at...... for hours and hours straight.  Most home-type electrical appliances do NOT exhibit this behavior.

 

When recommending electricians to do kiln installations for clients, I tell them to find an electrician who has industrial experience, or to find an electrician who will willingly follow the kiln specific manufacturer's specifications for the install 100%.

 

If an electrician says something like "I know a way to do this that will save you as lot of money" or "this is not necessary" when looking at the kiln mfgr's specs............my advice..........  RUN AWAY!

 

I've said this before in threads on here...... years and years ago I did some research into what I called "kiln disasters" when I was preparing for acting as an expert witness in kiln legal matter for a client..... and what you are describing here was reported to me a LOT!  A statistically surprising amount.

 

Check those plugs folks.

 

best,

 

......................john

terraforma likes this

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Thanks for this post.

 

I check my plug nearly every firing. So far no real hot plugs, but before I go to bed my kiln is usually on the final temp climbs around the 1900-2000's and I feel the plug every time. 

 

I also unplug it about every 5-10 firings to check for any types of buildup.

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Ok, I'm new to pottery....don't have a kiln yet, but will eventually. So what is the proper way to wire for a kiln? I was planning on putting one in my garage in the future. Thanks.

 

The proper way is in the manual for the kiln, each kiln is different. Only hire someone like John spoke of above. No corners cut, no savings tricks, do it right and have someone who is willing to do everything by the book. 

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Ideally it should be hooked up to a fused disconnect box, either hard wired or with the pug directly below the disconnect. Beyond that, all local codes and manufacturer's recommendations should be followed.

 

My smaller kiln (E18T-3) is hooked up to a fused disconnect with an outlet below. I've fired it over 1,000 times in the 7 years that I've owned it, and it still has the original plug, even though my shop is not air conditioned so corrosion is always and issue. You just never know.

 

My big kiln, which pulls something around 70 amps on 3 phase power, has 3 levels of fusing. The first is in the control box itself, where each section of the kiln is on its own 40 amp branch- 6 fuses total. The second is the fused disconnect box that carries the full load of the kiln- 90 amp fuses, and the third is the breaker box across the room, a 90 amp breaker. Nothing has ever gotten past the 40 amp fuses in the box.

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