Frogesan Posted October 2, 2023 Report Share Posted October 2, 2023 Hi, I'm buying a new kiln and having my garage wiring updated for it. I haven't picked out which model yet, but all the ones I'm looking at have the same electrical requirements (kiln needs to be on 60-amp circuit). My understanding is that because the kiln is a continuous load, one that draws 48 amps needs to be on a 60-amp circuit. My electrician agrees, although he's not a kiln expert. I've run into problems with the inspector, who INSISTS that I must use a 50-amp breaker in the garage subpanel because the kiln has a 50-amp plug. The current (ha) plan is to put in the 50-amp breaker to pass inspection, then swap it out for a 60-amp breaker so I don't burn down the garage. Just as a sanity check, can someone confirm that Skutt and L & L are right about what size breaker I need, and the inspector is wrong? Thanks! Roberta12 1 Quote Link to comment Share on other sites More sharing options...
Roberta12 Posted October 3, 2023 Report Share Posted October 3, 2023 skutt and L&L are correct. I ran into a similar situation when I got my kiln. And because the building it was going into was new construction and we had to upgrade our electrical, and the inspector didn't have experience with kilns.....we ended up hardwiring my kiln at the inspector's command. And we went with the 60 amp breaker. I talked to Steven Lewecki at L&L and he was proper upset with our inspector, but....there it was. The upside of hardwiring it was that my insurance company was very happy about the hardwiring. So I guess there is that. Would hardwiring it make a difference to your inspector? Roberta Hulk 1 Quote Link to comment Share on other sites More sharing options...
Hulk Posted October 3, 2023 Report Share Posted October 3, 2023 Hi Frogesan, Welcome to the Forum! Kiln wiring comes up quite often here. The experts (I'm not an expert...) point out the 125% rule, etc.; try using the built in search using "125%" to find a few, e.g. https://community.ceramicartsdaily.org/topic/31343-skutt-822-wire-gauge-size-vs-breaker-size As for burning down the garage, going with a too small breaker should just result in the breaker tripping, nuisance trips! Running too small a wire with too large a breaker could get hot, I believe (I'm not an expert!). For reasonable run lengths, #6 wire, correct? And for runs much over fifty feet, start looking at the next bigger wire? Any road, the kiln manufacturer's documentation looks correct to me, and it lines up with what the more expert regulars on this Forum say. The wiring for my new 48 amp kiln was recently completed, 60 amp breaker, per specification. I only needed the two hots and a ground, however I ran the neutral (and left it capped off on both ends), just in case someone comes along years from now and needs/wants the 120v, having recently ran into a similar situation with our son's wellhouse (wiring for 240v well pump), where we wanted 120v to run some water treatment equipment... Roberta12 1 Quote Link to comment Share on other sites More sharing options...
Mark C. Posted October 3, 2023 Report Share Posted October 3, 2023 My skutt 10 cubic foot kiln -48 amps wired with copper #6 wire is hooked to a 60 amp breaker-the 125 rule is in effect and youir inspector is not familiar with that for kilns. You can educate them of do the 50 and swap out later if they are hardheaded . Hulk and Roberta12 2 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 3, 2023 Report Share Posted October 3, 2023 (edited) 14 hours ago, Frogesan said: I've run into problems with the inspector, who INSISTS that I must use a 50-amp breaker in the garage subpanel because the kiln has a 50-amp plug. The current (ha) plan is to put in the 50-amp breaker to pass inspection, then swap it out for a 60-amp breaker so I don't burn down the garage. You have it right, the manufacture has it right, the inspector has it wrong. Interestingly a 60 amp breaker is the minimum allowed. Breakers that you buy for home are usually rated and thermally limited in load to no more than 80%. 80% of 60 amps is 48 amps. Lots of folks know the 80% rule so if it dawns on him he may suddenly change his mind. In the end your electrician has it right and can point him to the NEC and NFPA requirements for a continuous load - resistance heat. Basically not less than 125% nor greater than 150%. Edited October 3, 2023 by Bill Kielb Roberta12 1 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 3, 2023 Report Share Posted October 3, 2023 Typically the inspector will defer to the recommendations of the manufacturer, especially because your insurance will probably require that it's hooked up according to manufacturer's specs. If he has an issue with the 50 amp plug, he should know that the UL listing on the kiln was with that plug, so it's being done the way it's supposed to. Plus the 50 amp and 60 amp circuits use the same size wires. If he really won't budge, do it like you said and just swap the breaker after inspection. Quote Link to comment Share on other sites More sharing options...
davidh4976 Posted October 4, 2023 Report Share Posted October 4, 2023 Make sure you install wires that are suitable for 60 amp. If you want to argue with the inspector, and assuming you are in the US, here is the applicable section from the National Electrical code. 210.19(A)(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of 210.19(A)(1)(a) or (b). (a) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 25 percent of the continuous load. neilestrick 1 Quote Link to comment Share on other sites More sharing options...
Frogesan Posted October 4, 2023 Author Report Share Posted October 4, 2023 Thanks, everybody! The electrician actually broke out the code book during the inspection (and we had a kiln manual page explaining why the plug is 50 and the breaker is 60), but the inspector still wouldn't budge. So we're going to swap out the breaker. (The wire is sized appropriately, but thanks for the reminder.) Bill Kielb 1 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 4, 2023 Report Share Posted October 4, 2023 Terrible inspector, overloading the breaker and ignoring the manufacturer's instructions. Plus sometimes 48 amp kilns will trip a 50 amp breaker, especially if your voltage is running a little high, which is not at all uncommon. Pass inspection, swap the breaker, and fire it up! Piedmont Pottery 1 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 20, 2023 Report Share Posted October 20, 2023 (edited) Kiln Breaker Sizing, Code, Manufactures breaker recommendations - North America electrical practices Just thought I would post here, these things seem to come up often. Anyway ran across an inspection I did several months ago. The issue was breaker sizing for multiple commercial water heaters, which are very similar to a kiln load in many respects. Anyway long story short, in NorthAmerica breakers sizings are usually limited to 80% design load or for special continuous use resistance appliances a minimum of 125% of the continuous load but not more than 150%. This was created to keep the operation of the breaker in a typical panel reasonably cool and therefore extend the life and reliability of the breaker. My anNonimized picture and infrared photo below depicts the unexpected continuous run time of one of a bank of water heaters (over three hours). Anyway, the breaker was sized slightly under 125% of the water heater load but still at least 100%. The manufacture listed the maximum breaker size as 30 amps. The electrician used a 25 amp, stating it was enough. Anyway, I think my infrared picture in operation at over 133 degrees f and the fact that it tripped validates the reason for the code and manufactures generally conservatively follow that code. Additionally this code has true time tested proven merit so ignoring it or misunderstanding it can reduce breaker lifespan and elevate the hazard of fire. It is scary to think an inspector would not take the time to learn their craft. Codes are important, manufactures have insight into the engineering and operation of their equipment. Generally their minimum and maximum recommendations are well researched and compliant with code requirements. Sizing breakers for kilns seems to be a tricky thing. Sizing them smaller than the manufacture suggests is probably not a good idea as can be plainly seen below. Hopefully this post will be useful for someone searching in the future wondering. Edited October 20, 2023 by Bill Kielb PeterH and neilestrick 2 Quote Link to comment Share on other sites More sharing options...
Babs Posted October 20, 2023 Report Share Posted October 20, 2023 Ego got in the way of best practice, or lack of education couldbe tge go. go above inspector level and state your case but it may backfire and they will inspect your propert forever...how does this sit with insurance cover? Quote Link to comment Share on other sites More sharing options...
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