Electrical Kiln Installation -- Anybody done one of these?

Question

I have some experience wiring in new circuits, but this is a new one for me. My wife recently purchased an 8000 watt electrical ceramic kiln, 240V 1 phase power, 33.6 amps.

I am installing in the basement of my home (owner occupant, not in a municipality that requires an electrician's license):

1. 50 amp dedicated breaker in the panel, per kiln manufacturer's recommendation. I have space for it in the existing panel.

2. 8/2 NM wire, per kin manufacturer's recommendation (60 ft run)

3. 6-50 NEMA outlet

Given the power amount we're talking about here and the price of the kiln I'm putting in, I'm trying to make sure I cross all the i's and dot all the t's. Does anybody in the community immediately see anything I should look out for that might be unusual about this job? If you're going to warn me not to fry myself, thanks, but I already knew that.

David Cruice · Answer

@Jim K. ignore my previous post, I missed the part where you said, "I have space for it in the existing panel".  Could have saved myself a lot of typing!  :-)  No harm though if you want to run 6g wire for that extra peace of mind.

@Mike McCarthy   You are correct in everything you are stating, but I believe the manufacturer is recommending only 8g wire because the kiln only draws a maximum of 33.6 amps.  The difference is subtle in that one is load amps (for the wire gauge) and the other is capacity (the size of the breaker) x 80% rule.  That's why the manufacturer is recommending a 50 amp breaker.  A 45 amp breaker (x 80% = 34 amps) would just be sufficient, but it would be cutting it close.  Plus, most stores prefer to carry 40 and 50 amp breakers; not so much the 45 amp ones.

Jim K. · Answer

Follow-up -- everything went off fine with the 6/2 and 50-amp breaker. Kiln is running smoothly.

David Cruice · Answer

@Jim K. , if you're following the manufacturer's instructions as outlined above, then your installation will be ok.  However, the only thing you have left out of your post is if you are sure you have the extra capacity (with respect to amps) in your panel to run an additional 33+ amps.  If you have a new panel in a moderately sized house, you're most probably have a 150 amp panel.  Most breaker boxes are 100, 150, or 200 amps.  If your panel is a 150 or 200 amp version and has lots of unused slots for breakers, you've most probably got enough capacity for the new kiln.  The quickest way to confirm though is to use an amp meter to measure the amps being drawn through each of the phases (120v lines entering the panel, usually at the top or bottom of the panel) when running the typical amount of appliances all at the same time, i.e. stove, washer, dryer, water heater, and AC should do it.  Add the amount of amp draw on each line together, then subtract that from the size of the panel and that will give you your spare capacity to accommodate the kiln.  Let me know if you have any questions.

Jim K. · Answer

@David Cruice

Thanks again, David. Your post just reinforces it, really. The choice is to to save myself some grief bending the thicker cable, $30 for the difference in price, and explaining a simple return to HD (when I shell out as much as I do with my local store every year), or cutting it close with an 8000-watt appliance in a basement.Going with the 6/2. I'm not winning a Darwin award this week. There are a million risks in this business I have to take. I'll skip an avoidable one like this.

Jim K. · Answer

@Mike McCarthy

That is exactly my main concern right now. I called and verified. Skutt, the most reputable ceramics kiln manufacturer in the USA, told me to go for it with 8/2 and a 50-amp breaker. I'm still wondering if I should just rewire with 6/2 after we leave because God only knows who's going to stick what in the 6-50 receptacle after I leave, but until then, it's dedicated to this one and only appliance. If it gets even close to being hot to the touch, I'll pull the 8/2 and run 6/2. I've never worked with either 8 or 6-gauge cable before and I'm a bit worried about working in the panel with both.

Actually, this is stupid, amateur hour. The price difference is $30. I'll take back the 8/2 and get 6/2 tomorrow. Trust a kiln manufacturer to give me the safest specs on electricity? These people focus on pots, not wires.

Thanks, Mike.

Jim K. · Answer

@David Cruice

It's 150-amp service, David. Thanks for pointing that out. I have four slots free in the panel and the 50-amp breaker will take 2 slots. Right now the dwelling is nowhere near what it would be with full power draw, and I'm confident we have enough free amperage to run this thing. I will do the amp test when we start drawing closer to anything like our full power amount, and if we don't have enough, we'll upgrade to 200 amp service.

Electrical Kiln Installation -- Anybody done one of these?

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