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tb001

Wiring For Kiln

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Finally getting close to getting my studio back up and running after a long break.I had an electrician come out and put in the wiring and check everything out, and he said I should have no problem with the wiring handling the kiln, but I'm nervous about it and would love a second opinion.

 

I have my kiln located in a garage about 10 ft from a subpanel, which is around 70-100ft from the main panel. The kiln draws 48amps and is on a 60 amp breaker. The catch is that I know there is a splice somewhere under the house in that 100ft run, I thick about 30ft from the subpanel, and even though I asked him to, I'm pretty sure the electrician didn't double check the splice.

 

So a few Qs:

Is a splice alone a cause for concern or if it's well done is it ok? If there's a problem with the splice, will it trip one of the breakers, or potentially cause a fire?

 

Assuming the splice is done correctly, should I be worried if it's not all #4 wire? I think they may have run #4 the first 70 ft and spliced to #6 for the last 30ft.

 

Any thoughts would be appreciated. I plan to have someone come take a look at the splice regardless, since the thought of a fire starting under the house completely freaks me out, and I know you can't always rely on breakers to do their job, but trying to understand why the original electrician wasn't worried about it and if I have cause for concern or I'm just being paranoid. Also want to know if I'm possibly looking at having to install 100ft of #4 wire...

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#1 (00)is rated for 100 amp, and #6 is rated for 60 amps. It should be 6/3 with ground to be exact. Electricity is like water in some respects: undersized wire restricts electrical flow just like an undersized hose will restrict water flow. Simple analogy- but you get the point. Whoever ran the original 70' of #4 knew enough about electricity to know that the longer the run, the more power loss due to resistance (ohms). >IF< the wire sizes you stated are correct: then it is more than enough to handle the load. The problem will be the junction box: how did they splice the wires? Did they use simple wire nuts? Did they solder them, and then use wire nuts?

Did they just twist them together < bad news! Did they use a wire compression nut? >best way< for that load.  If you have no idea what you are looking at- then hire a different electrician.

Nerd

--- doubt seriously if it is a #4 wire.  #3 (00) is a 200 amp wire. Wire rating changes after 6/3 into (00) numbers.

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Thanks Neil!

 

Unless I missed something more subtle in the gauges, pretty sure the initial run is #4--it was originally run to power a subpanel in an outbuilding where they had some big equipment and an AC unit hooked up. I'm not sure exactly what happened, but when we bought the house, the inspector said there was no power to the outbuilding and the next day when he came back, there was magically power...and a splice literally hanging under the house that wasn't there initially! No junction box at all...so you see why I'd be concerned!

 

Some of the wiring inside is really well done and some has me shaking my head--and of course I know just enough to know its wrong!

 

So if I understand you correctly, worst case is someone needs to double check the splice was done correctly, but 4 to 6 should be good enough, given a 30ft run after the 6?

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I would have your electrician double check everything for peace of mind. The wiring from the house to the subpanel should be large enough for whatever size the sub panel is. The wiring from the sub panel to the kiln should be large enough for the kiln breaker. The splice could definitely be an issue if it was not done properly. Get it checked out.

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Don't overlook the voltage drop associated with the 100+/- feet between the kiln and the main connection to the electric grid.  Bigger wire gives lower voltage drop; longer runs increases the drop.  If the voltage at the kiln is below the minimum voltage you may not be able to reach your target temperature.  You may need larger wire than the standard guidelines for the amperage rating of the breaker since the guidelines are calculated on an assumed relatively short run length. 
 

 

LT

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Some of the wiring inside is really well done and some has me shaking my head--and of course I know just enough to know its wrong!

 

So if I understand you correctly, worst case is someone needs to double check the splice was done correctly, but 4 to 6 should be good enough, given a 30ft run after the 6?

The really well done wiring was put in by a professional electrician when the house was built. The shaky head stuff was installed by the homeowner/s after market.

>IF< the wire gauge sizes you stated are correct, then the wire is not the problem. The conjunction box will be the weak link, (if) it was not properly done.

Nerd

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Thanks for all the input! Definitely going to have it checked out, but great to know that I'm not likely looking at putting in 100ft of expensive wire!

 

And nerd, wish I could blame the homeowner for the lousy wiring, but it was all done by two brother electricians our inspector nicknamed dumb and dumber.

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Several things concern me. As others have said, #6 is appropriate for 60amps of draw if the run is less than 50' from the main panel. Longer than that, you need to increase the wire gauge to #4 to eliminate voltage drop from the resistance of that long of a run. You say you have 70' of #4 with 30' of  #6 spliced on. Seems dicey to me, but theoretically it might work. The only way to be sure is with a voltmeter and an ampmeter at the other end.

 

One of the things that really concerns me is what you describe as an open hanging splice. Code requires any splice to be inside a box.

 

Second, I would be concerned with the wire size change. I am guessing that the circuit shows in the main panel as #4 wire. You are underfusing it with the 60A breaker, which is ok. Overfusing a wire is not ok. If the next owner of the house sees a #4 wire in the box and replaces your 60A breaker with an 80A breaker to plug in his new welder out there is what used to be your kiln shed, that would seem to be ok for the #4 wire apparent in the panel but it would overfuse the last 30' of #6 wire in that circuit.

 

So, if it were me, I would get 30' (or 40-50' just to have some extra) of #4 for the rest of the run, and properly splice it inside a properly rated box properly mounted under the house. No need to replace the whole 100' run.

 

JMO, others may disagree.

dw

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Just have it checked out

The run to the sub panel should all be the same size but any good electrician will know this and check out any splice as that's the trouble spot on high amp loads.

Again just get a qualified electrician to make the crawl look see.

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Yeah, getting someone willing to do the crawl under the house has been the hurdle--I certainly don't want to do it! I think I'll just plan on replacing that last run of wire as suggested. I know the splice needs to be checked and likely redone. Might as well have it done properly instead of worrying about it every time I run the kiln!

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