coil resistance

[Terry Rothwell]

I've been having troubles with my kiln not completing cycles I've used successfully for years. It appears that the kiln will not reach temps. on ramp up in the timeframe programed. I have changed the relays and thermocouple to no avail. So I am now thinking that the coils may be the cause. This kiln is 13 years old with 4 coils (1 lid and three in the body) and the coils are the originals. I've checked for continuity and that checks out ok. I've checked resistance and found that the lid reads 14.7 and top coil reads 15.9 ohms. The lower two coils read 9.6 ohms each. Does anyone know what the resistance range should be? It's an Olympic kiln but I can't imagine that makes much difference.

[suds]

Heating element resistance is very much dependent on the model and wattage of your kiln.

What model # is it?

[Terry Rothwell]

It is a 3014GFE 208v 11,280 watts

[Bert Weiss]

I would look at the coils at the point when it is not reaching temperature. Are they all glowing red? Is the red remarkably different colors?

I have to admit, I have never had much luck reading ohms from element wires. If you have an ammeter, that is a lot easier. When the element is full on, the ammeter will tell you how many amps are being drawn on that circuit. A volt meter will tell you how many volts you have. Amps X volts = watts. Watts translate in to heating power.

My kiln has 3 separate zones. When one zone is not heating, there is not enough heat to make top temperature (above 1400ºF).

Typically, element wires corrode right away, and that layer of corrosion makes them relatively stable. They do get brittle though, and can break.

[Terry Rothwell]

I don't see glowing from the lowest coils, however they do get hot enough to scorch paper when first heating. I usually don't try the paper check at temps over 250.

[Bert Weiss]

I don't see glowing from the lowest coils, however they do get hot enough to scorch paper when first heating. I usually don't try the paper check at temps over 250.

Then chances are there is a bad connection or a break in the wire for the lowest coil. Sometimes you can overlap coils with a broken wire. This is a quick short fix, until you can order a new element.

I'll bet the wire picks up enough heat from other elements to scorch paper. That is a pretty low temp.