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I’m installing a circuit for my wife’s new pottery kiln and have received contradictory information about GFCI breakers. I’m hoping someone can shed light on two questions.
The situation: the kiln is located in an essentially dirt-floored outbuilding (we’ve got bricks on it, right over dirt). The kiln is pure 220 volt (no 110 volt, so no neutral returning to the panel), plus an equipment ground. Due to limited space on the panel, we’d like to use the same circuit for our son’s occasional use of an arc welder (not at same time as kiln). Because of the dirt floor, and because my wife is pretty valuable to me, I’ve been thinking to put in a GFCI breaker. As 50 amp, two-pole breakers are about $100 (as opposed to $9 for a conventional one), I want to be sure it’s the right move. I’ve been told:
1. By a Cutler-Hammer rep that, if there’s no neutral leg returning to the panel, the GFCI feature won’t work, so don’t waste my money. By others, including a contractor and the electrical supply house, that it sure as heck will work as a GFCI even with no neutral returning.
2. That, because of the power surges created by an arc welder, using the welder on the circuit will result in a very early death of the GFCI. Others say it should be ok.
I’m now completely confused and hope someone can help.
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If you understand how a GFCI works, the Cutler-Hammer rep is correct, but I don't know about #2, as far as power surges go. Arc welders transform AC into DC (AC doesn't arc), so there may not be the surges that would/could trip a GFCI, as with my washing machine's timer and motor. Contact the welder's manufacturer to be sure. You may wish to consider a secondary box that would allow you to have service to both devices, providing 240V to the kiln and 120v (with neutral and GFCI) to the welder, if that's its electrical rating.
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Bill:
I did a bit of research on the Square D website and I believe you can use a 2-pole GFCI breaker for your kiln. It has a white neutral wire in the panel that must be connected to the neutral bus, but it does not need to extend to the load (kiln). The breaker measures the balance across the lines versus the neutral and trips if there's an acceptable level of leakage. Square D part #QO250GFI. I don't know cost.
I suspect the Cutler-Hammer products have a similar item.
The addition of a welder for occasional use is a bit dicey because of the distinct possibility of connecting both appliances concurrently - a bad thing. If you're creating a single recepticle to service both - then it's OK. I don't know what type of behavior to expect from the welder on the GFI breaker.
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AC doesn't arc? Gee, Barry, maybe that's why my welding with my AC only Lincoln welder has been so poor...
Not that it is really germaine to this discussion, but there are both AC and DC welders that do, indeed, arc. Most of the inexpensive welders (often termed "buzz boxes") are AC welders (including my 225 amp Lincoln welder). Most larger, production welders for steel that I have seen are DC, but aluminum cannot be welded with DC (has to do with aluminum oxide formation). Most welders change whatever input voltage to around 30 volts for the output. My 250 amp TIG (Tungsten Inert Gas) machine requires about 30 amps at 230 volts and the output can be selected for either AC or DC depending upon the requirement of the metal to be welded (this machine allows me to weld up to around 3/8" material).
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I agree with what you said.......The breakers are about $70.00 at our local wholesalers. I have never seen a welder hooked to a GFCI so can't comment on that, but if it will work, your idea of using only one receptacle is a good one.
*Bill--A GCFI (I'm going to call it a GFI) works by comparing the current in the supply and return conductors. For a conventional GFI in the States, if the current is different by more than 6 mA, the GFI must open the circuit within a few seconds (5 to 6).For most of the 120V branch circuits on which GFIs are installed, the supply conductor is the "hot" or "phase", and the return conductor is the neutral (actually the 'i'groundedi'i') conductor. In a 240 V circuit, there is no neutral, but there is a return conductor--it's just the other phase conductor.So, a GFI breaker designed for it WILL work in a 240 V circuit.I suggest the question you ask yourself is, what is the potential for someone to come in contact with an energized part of the kiln? Is the frame made of metal and is it grounded? Are the electrical controls & splices in a grounded metal box? Is there any way (even failure of two levels of electrical insulation/isolation) for a person to provide a current path to ground? If the answer is an easy 'yes', then go for the GFI.Major appliances (washing machines, electric dryers & range/ovens, etc.) are NOT protected by GFIs. This is because they usually have some leakage current, more than 6 mA, that would trip a common GFI. (It's not because of the nature of the motor's current draw or the timer). When properly grounded, there's a low impedance path for the leakage to get to ground, so there's little chance of the current taking a path through someone.If you do want to install a GFI, look into one with a higher trip point; they are commercially available in the States. In fact, in Europe, GFIs are set to trip at a higher current and time than 6 mA & 6 seconds, which is an extremely protective standard. I believe it's between 12 and 15 mA and all I remember is it's more than 6 sec. One commercial GFI is settable--6, 12, or 30 mA trip. It's a 240V job, and it's not a breaker/GFI.On the arc welder issue--pick a GFI breaker (can't go wrong w/Square-D) and call the manufacturer. Get the technical people on the line. They'll be able to tell you. Also they'll confirm the fact the you can protect a 240V circuit with a GFI. But I bet that you'll be able to use the weldeer. The GFI is just a current comparator; I don't see how surges of current would kill it.Good luck with the pottery.
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I'm installing a circuit for my wife's new pottery kiln and have received contradictory information about GFCI breakers. I'm hoping someone can shed light on two questions.
The situation: the kiln is located in an essentially dirt-floored outbuilding (we've got bricks on it, right over dirt). The kiln is pure 220 volt (no 110 volt, so no neutral returning to the panel), plus an equipment ground. Due to limited space on the panel, we'd like to use the same circuit for our son's occasional use of an arc welder (not at same time as kiln). Because of the dirt floor, and because my wife is pretty valuable to me, I've been thinking to put in a GFCI breaker. As 50 amp, two-pole breakers are about $100 (as opposed to $9 for a conventional one), I want to be sure it's the right move. I've been told:
1. By a Cutler-Hammer rep that, if there's no neutral leg returning to the panel, the GFCI feature won't work, so don't waste my money. By others, including a contractor and the electrical supply house, that it sure as heck will work as a GFCI even with no neutral returning.
2. That, because of the power surges created by an arc welder, using the welder on the circuit will result in a very early death of the GFCI. Others say it should be ok.
I'm now completely confused and hope someone can help.
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Just installed a G.E. brand 240V GFCI and it had instructions for both applications. With or without a neutral. If there is a neutral then it is connected to the breaker where it is labled "load neutral". If there is no neutral involved and the application is strictly 240V then all that is required is to connect the white pigtail supplied and made into the breaker to the neutral bus. The point is that a load neutral is not "required" for it to work properly.
As far as the arc welder on a GFCI I do not know.
If a Cutler-Hammer is the panel you have and thats the breaker you need, I would call back and ask another rep.
glenn