Wiring for Kiln

[Dan Stuewe]

My wife is buying a kiln for her glass work. The specs are 240 V, 27.8 Amps single phase. The manufacture recommends 8 gauge wire with a 40 amp breaker. We haven't been able to get our electrician over to give our garage an overhaul (we want to put in a sub-panel and I'm going to have a few 220 circuits put in for future ww tools ). Anyway, since we don't have the wiring yet, and my wife will be very anxious to play with her new electron killer, I was hoping to use the clothes drier circuit. It is currently on a 30 Amp breaker, but I don't know what gauge the wire is. Could I expect the wiring to already be 8 gauge? Or is there an easy way to check (wiring is in the drywall)? Also, the current breaker for the dryer is actually one switch(?) of two adjacent breakers connected with a little bar. If the wiring is okay (8 gauge) could I just buy two new breakers with 40 amp switches and connect them?

Thanks,

[Kent Fitzgerald]

Most likely the existing 30A circuit is 10 gauge wire (which is smaller than 8 ga, if that's not obvious).

[Rob Russell]

What Ken said.

If you have a 4-wire circuit installed for an electric range, you could likely use that (they are typically 40 amps). Of course, that means dragging your range in and out ...

Rob

[Dan Stuewe]

Thanks for the replies. It looks like we'll have to wait for an electrician. I did notice that the breakers for the range and oven 40 and 50 amps, but the range looks to be hard wired and we have a double oven, so there's no way it is coming in and out for this!

As a follow up question (since we're still trying to get a hold of our electrician), the main breaker is 100 amps, will we be able to have a 100 amp subpanel? I'm starting to be concerned that this will be more expensive than I think.

Thanks,

[Rob Russell]

Dan,

What kind of hot water do you have - gas or electric? You may run into an issue where you have to be careful with what loads you try to run concurrently. If that's the case, you could be looking at a 100 to 200 amp service upgrade if you want to be able to run everything at the same time.

It all depends on what your loads are. I'm guessing that you've got an electric dryer, otherwise you wouldn't have a dryer receptacle. Based on that, I'm also going to guess electric hot water.

If you have kids taking showers or the wife doing laundry (yeah, I know - stereotype) with a load in the dryer, a roast in the oven for dinner later on and she wants to fire up the kiln while you're in the shop ... add up all those loads and possible poof! Well, poof isn't accurate, you'd just trip the main breaker if you overload it. You're not in any real danger of fires - that's the whole point of the breaker.

In terms of your 100 amp subpanel question - ask your local AHJ (Authority Having Jurisdiction, aka the electrical inspector) what their local enforcement is. From comments I've seen on some of the electrical forums, that appears to be one point where areas allow different things. I looked and could not find anything in the code specific to feeders or branch circuits that would limit you to below 100 amps, but I certainly could have missed something. After all - I ain't a licensed electrician.

Rob