Does anyone out there own a Duncan LT-4K, 45 amp kiln?
I’m going to put it in my detached garage. What size breaker did you use, and what size wire?
Does anyone out there own a Duncan LT-4K, 45 amp kiln?
I’m going to put it in my detached garage. What size breaker did you use, and what size wire?
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Replies
Wire
You need #6 copper wire and a 50 amp breaker.
Of course, presumably this is a 240V unit, so that's a double-pole breaker. And it never hurts (except the pocketbook) to go ahead and pull a neutral (ie, 3 wires + ground), even if code doesn't require it.
And I'm remembering that if this is a detached garage there are some special grounding rules, though I'm fuzzy on the details.
Grounding rules
Neutral and ground pulled from the main service panel to the garage, and tied to the appropriate buss in the subpanel. At the sub panel the bonding jumper between the neutral and ground buss is removed. A seperate grounding wire from the ground buss in the sub is then taken to driven ground rods at the garage.
The neutral and ground must be isolated at the garage sub panel, the neutral wire and ground must be connected together at the main panel neutral bus, and the garage requires an additional ground rod (or two). Basically speaking, but codes vary somewhat. A disconnect switch may also be required at the garage.
Isolated?
The neutral and ground bus bars are seperate at the subpanel. This means removing the bonding jumber between the two busses.
The main in the subpanel serves as the disconnect for the panel.
Yes, that is what isolates them, otherwise it is possible to carry current in the ground wire. Codes are strange, an outside disconnect may be required in some locations.
Isolated.
Isolated is not used in the NEC for this type of situation.
Isolated grounds are totally seperated from any neutral buss. In this case the ground at the main panel and the neutral are still tied together. To become an isolated ground that jumper must also be removed. It is only the jumper at the subpanel that is required to be removed and additional ground rods installed in this instance.
Grounds are not current carrying conductors. Neutrals are. Grounds are fault current paths. There are a few places where isolated grounds are spected, but this isn't one of them.
As is the case with many terms, the argument is more over the meaning of words rather than the intent. "Isolated" has a specific formal meaning in the code, but it's a term that people are apt to use in a generic sense, with a slightly different meaning.
Terms
That is why the NEC devotes a whole section to definitions of terms. Loosely interpreting terms when answering an electrical question can get someone hurt. You are an EE and know that. It is also why, sometimes it is best if they hire a professional (licensed electrician) to do the work. at least we are all suppose to be on the same page.
You're repeating everything I said, except for the terminology which you haven't defined yet.
What if there were a sub panel with no main breaker in the garage? Would a separate disconnect normally be required?
Yes
It's nearly certain that you need to do a LOT more than just run some wire. Let's start at the kiln and work back ....
First off, the wires need to be a higher-temperature rating near the kiln, and in a metal raceway "such as "flex"). While the box store have 90-degree rated THHN, I'd prefer the wire closest to the kiln to be at least 105- check appliance repair places and real electrical supply houses for that. Maybe a range cord will work.
The flex -with proper support along the way- needs to terminate at a rated disconect, located where you can easily reach it. A range receptacle instead? I don't really like the idea- especially since rated disconects cost about $12.
Now ... where does the power come from? If your garage doesn't already have its' own panel, an outside disconnect, and ground rod, now is the time to add them. Any existing garage circuits will need to go to this panel as well.
There are a number of details in this plan that have been directly affected by recent code changes. Most of what you've seen done in the past is now 'wrong.' Plus, you need a permit. It's time to call in a pro.
Kilms
Most of the newer kilms are cord and plug connections untill you get to the 3 phase stage. Even many of the older hobbie kilms were cord and plug configuration. Plug configuration change depending on amperage and age of the kilms.
However, you are still right. Might be best for him to hire a local pro, if for no other reason than to evaluate what he ahs and what he is wanting to do.