Fuse blows at top temp

[FlorianFranken]

I'm hoping someone can help me with this issue.

My kiln is self built, it has been running for a few months now in the basement. Two days ago, for the first time, blew the fuse when it was at the top temperature (740 C/1360 F) for its firing. I replaced the fuse (an old screw type fuse), thinking it was just at the end of its life. Yesterday the fuse blew again on a similar firing. The kiln has gone up all the way to 960 C (1760 F) before without any problems. The fuse is rated for 20 amps and the kiln should only be drawing 14 amps. The elements are cycled on/off in 10 second windows, so its either drawing full capacity or nothing at all. The fuse was blown while on a holding phase, the elements are on for a shorter amount of time than while ramping up, so I think it couldn't be a continuous load problem.

Does anyone have a suggestion for what could be the problem here? I am stumped.

[Arnold Howard]

I would use a multimeter to be sure the kiln is drawing only 14 amps.

The fuse holder may be overheating. This would be due to a loose connection somewhere near the fuse box.

Sincerely,

Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com

[DonMcClennen]

Is there something else plugged into the same circuit? Maybe a lamp or coffee maker or something somewhere else in the building you haven't considered??

[Kevin Midgley]

The first clue would be if when you assembled the kiln wiring you made the connections tight, left and did something else for an hour perhaps, then went back and tightened the connections again and then repeated that process one more time.
You have a probable slightly loose connection as Howard suggested.
If you don't know what you are doing get an electrician in.

[jim simmons]

First til\me connections WILL loosen after awhile.
Re-tighten 2 more times.
Jim