Updated: Aug 29
A 21-year-old kiln needed some love and attention and new parts.
When I began using my kiln in 2016, I began keeping a log of the hours that each firing took at a certain cone or temperature. For a few years, the number of hours really didn't change too much unless the kiln was really loaded but about six months ago I began to notice the number of firing hours started getting longer. A bisque firing that should have taken only 13 hours started taking 15, then 18, then 20... I'd get an error code when the kiln couldn't ramp up past Cone 3 to get to Cone 6 (2160 deg F). Wtf???
My log was showing me that something was wrong. Really wrong.
To test it, I fired up an empty kiln to 800 deg F to see if the coils were getting cherry red and found that of the 6 coils, only the two in the middle were firing! Bits of paper placed on all the coils were charred which told me that electricity was getting to the coils-- but why weren't they all getting hot? (And -- holy crap-- let's just take a moment here to appreciate how amazing it is that a kiln can still get as hot as 1800 deg F with only two freaking coils!!) My Guild mentor, Bill Thompson, advised me that perhaps the thermocouples which act as the thermometers of the kiln were probably bad and needed to be replaced. This would be the first and most logical step to solving the problem.
However, only a few test firings later, it was apparent that the kiln was still having issues maintaining the proper temperatures. In fact it got worse; the temperature would reach only Cone 04 (1840 deg F) and then fluctuate and eventually start to fall slowly. I called L & L Kilns and the expert there, Rob Battey, suggested that with the age of the kiln, it was likely that the relay switches were worn. A photograph of the kiln's interior confirmed for him that the coils were also quite bad and should be replaced.
So now I was looking at a complete rebuild of my kiln's guts-- which meant that I'd practically have a new kiln!
While I waited for the parts to be shipped to me, I set about disassembling the kiln, disconnecting the wiring, and removing the aged coils with a needle nosed pliers. This was a royal pain in the butt, and took the most time in this whole re-building process. So, kids, if you perform proper maintenance on your kiln and replace the coils when you're supposed to, you can remove the old one in one piece. Who knew? Now you do.
The kiln is a modular device- the computer control panel (the "head") is one piece and the body of the kiln has three ring sections or regions which can be separated.
Each section has its own set of coils
that heat up and must be disconnected from the contacts in order to be de-installed.
When my parts arrived, I first installed the three new relay switches in the control panel using a fool-proof method of moving one wire at a time from each prong of the old switch to each new prong of the new switch. Then I secured the new relay switch to the inside of the control panel box. Snap, snap.
The new coils had to be stretched a little bit to the proper length, but installation was a heck of lot easier than removal!
I took a photo of the wiring beforehand as my guide which made re-wiring with some new hardware fairly straightforward.
Once the wiring was finished, I re-stacked the kiln segments, reattached the sensor wires to the thermocouples, re-mounted the computer head unit, plugged it all in and turned the power supply back on. In all, I'd say it took about three hours to complete (minus having the run to the hardware store for stainless steel washers).
Test firing the empty kiln at 800 deg F showed all coils glowing cherry red-- yay!-- proof that the wiring and the coils were properly installed. An empty-kiln test firing to Cone 5 properly seated the coils in the channels and now the kiln is ready for use. Big thanks to Rob Battey at L&L Kilns for his amazing customer service and help, and for Bill Thompson's patience and ready advice, my kiln is now repaired and my pottery studio will be back in full swing. Good thing, since I have lots of new work waiting to be fired!