Clay Times Back Issues Vol. 2 Issue 4 • May/June 1996 - Page 22

How to Keep Your Electric Kiln Purring BY STEVE BRANFMAN Part 3: Simple Repair Procedures In the previous two installments we discussed basic kiln preventative maintenance and the diagnosing of common ailments. But what do you do when you find a broken element, dysfunctional switch, or melted receptacle? Call Kiln Busters? I don’t think so.... While many potters accept the responsibility and have confidence in their ability to diagnose what may be causing their kiln to misfire, not quite as many are willing to tackle the actual repair. Well, let’s get over that intimidating hump and do what we can to feel enough confidence to finish the job. Before we tackle actual repair mechanisms, we must establish some benchmarks regarding the configuration of your kiln. The first of these is to draw a wiring diagram. No, I don’t mean one of those cryptic-looking, complicated, “full of electrical symbols that only an electrical engineer would understand”-type diagrams. I mean a simple drawing that you can understand, showing from where, and to where, each wire goes. Do not, under any circumstances, disconnect a wire without making a note of where it goes! The second benchmark is the length of the coils. Although some kiln manufacturers supply coils pre-stretched to their proper length, most coils will come to you unstretched. To determine the length, simply lay a string in the element’s groove, marking the beginning and the end on the 22 ▼ 22 string. (For your records, make a note of the length.) Now, stretching the coil to this length is a bit more complicated. Most important is that the coil be stretched evenly, without sections of “tight” or “loose” winds of the material. The easiest way to ensure an even stretch is to place the element end (the unwound part of the coil) in a vise. Measure the necessary distance from the end of the vise to a mark on the floor, wall, benchtop, or some other physical point. Holding the loose end of the coil, pull it evenly away from the vise in the direction of the distance mark. Pull it about 10% longer than your mark. Make a new mark at this point. Slowly release the tension, and you will see that the coil has not yet been stretched long enough. Repeat the procedure, each time pulling a bit farther than the time before, until you have stretched the coil to its proper length. You now will have marked the point to which your coil must be stretched to achieve the correct length. Avoid stretching the coil too far. (Compressing the length of a coil that has been stretched too far is a pain.) Realize that although coils from different kilns may be the same length, unless they are made of the same gauge material, they will have to be stretched different distances to arrive at the same length! Element replacement is without a doubt the most common “repair” procedure known to anyone who operates an electric kiln. Every potter who uses an electric kiln should know how to replace the elements. A common question regarding element replacement is whether or not to replace the entire set of coils when one coil fails. To answer this, you must have a good sense of: 1) how long your elements last before they wear out from age and use; and 2) how old and used the present set of elements in the kiln are. If you determine that the set of elements are near the end of their usefulness, then replace the whole set. If, on the other hand, the remaining coils still have considerable life and energy left, then replace only the damaged one. What you are trying to avoid here is the creation of a “hot” spot in your kiln by the introduction of a new, “fullstrength” coil to a set of marginally active ones. Proceeding with the replacement, remove the old coil by clipping the ends inside the kiln where they exit the kiln chamber. Remove the coil and carefully clean the groove in the brick of any debris, glaze melts, etc. Open the electrical box exposing the element connections and make careful note of where each end of the coil attaches. Disconnect the old element ends (tails), feed one end of the new coil