Kiln Circuit

[mbrooke]

I wired pair of kiln circuits for an artist last year, one 30a on #10 and one 50a on #6. Breakers can be replaced easier than wire.

Technically speaking because the elements are resting within insulating material the circuit breaker could be up-sized but not the wire like done with heaters in the CEC.

 

[roger]

Haven't read the whole thread but my wife's kiln is continuous and even runs for slow cool down that can take as long as 12 hours.

Roger

 

[electrofelon]

I don't know how warm "alarmingly" is. But TM breakers can get very warm before they trip. It can be uncomfortable to the touch kind of warm.

Yes, I fully agree just going by touch is certainly not an accurate way to analyze temperature. What a person might feel as "too hot" may well be fine and within spec for the electrical equipment. That said, A fully loaded panelboard running with everything at 100% very likely will result in breakers tripping on thermal. I have seen it. I have even seen tripping at less than 100% on the branches when the ambient temp is rather high. So the fact is, there either needs to be some sort of derating, such as the continuous load thing, or panelboards designed to allow more space, cooling, and airflow.

 

[Buck Parrish]

The op's must be a small kiln. All the ones I've done require a 50 Amp breaker on a #6 cu. (That's according to the manufactures specs.)

 

[tom baker]

I don't see how it will ever be over 20 Amps. The silliness over continuous and non-continuous loads ought to go away.

What is the point of making the wire bigger because the load is "continuous"?

The larger wire acts as a heat sink to keep the breaker from tripping on thermal . It reflects the way UL tests the breakers.

 

[mbrooke]

The larger wire acts as a heat sink to keep the breaker from tripping on thermal . It reflects the way UL tests the breakers.

I disagree, see section 62 of the Canadian Electrical Code.





This is yet again where theoretical knowledge of standards (cough 60364 cough) comes in.

 

[electrofelon]

I am also skeptical of the heat sink theory for 125% conductor sizing. I hear it stated frequently, but have never seen that in any "offical" literature. Doesn't sizing the conductor at 125% just follow from the OCPD being sized at 125%? A 100% breaker will have smaller conductors than the 80% breaker so it just doesnt hold water to me.

 

[mbrooke]

I am also skeptical of the heat sink theory for 125% conductor sizing. I hear it stated frequently, but have never seen that in any "offical" literature. Doesn't sizing the conductor at 125% just follow from the OCPD being sized at 125%? A 100% breaker will have smaller conductors than the 80% breaker so it just doesnt hold water to me.

I'm guessing in part the hold over from cloth/rubber insulation days, and before it was known it was terminations, not the wire itself overheating: