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Old 03-18-2013, 08:00 PM   #1
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Default 2/10 vs 3/10 EHERMS Wiring Setup

2/10 vs 3/10 EHERMS Wiring Setup

I have a 50 amp panel outlet in my garage, and I also came into possession of a 50 amp GFCI breaker for my box. The problem is that the outlet is a dryer outlet with 2 hots and 1 ground.

Before I call out an electrician to install the GFCI breaker that might not work for me, is there a way that I can run my single element pid controlled EHERMS rig on that 2/10 setup or do I need to have the 2 hots, 1 neutral, and 1 ground wiring in order to do that?

My original wiring setup was going to be this…



, but I’m curious if there is a way to do it without the neutral.

Will a 220 GFCI even work without a neutral?

I know the wire for the outlet was very recently installed, do they still run a lot of 2/10 or is it generally 3/10 these days?

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Old 03-18-2013, 08:07 PM   #2
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The three-pronged dryer outlets, if properly installed, are actually non-grounded receptacles. They are hot-hot-neutral.

The only time you need a neutral for your brewing rig is if you are going to power some 120v items from that 240v feed.

But, the fact that you have no ground is kind of ugly. I've seen people use the 3-wire dryer outlet for hot-hot-neutral and run a separate wire to another receptacle for ground, but it always feels kind of clunky and ugly to me.

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Old 03-18-2013, 08:19 PM   #3
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I've seen people use the 3-wire dryer outlet for hot-hot-neutral and run a separate wire to another receptacle for ground, but it always feels kind of clunky and ugly to me.
That does sound clunky.

I'm not an electrician, so I'm curious why you can't use neutral as a ground even if you’re running a 120V application like a pump?

In fact, the second cord for a ground seems like it would blow the GFI because there would be juice going out that was grounding through a different breaker.
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Old 03-18-2013, 08:37 PM   #4
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check the actual wire to see if there is an unused ground. sometimes the outlet gets changed to match an appliance and the extra wire is coiled in the box.

also, 10 awg => 30 amps; 6awg => 50 amps; 14awg => 15 amps for most wiring types.

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Old 03-18-2013, 08:37 PM   #5
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Neutral and ground are connected to the same point in your main panel (and should be only in your main panel). The main difference is code stipulates that ground is NOT to be used to carry current (except in fault conditions) for safety reasons.

GFCI's work by detecting current imbalances. Current that is flowing out but not coming back through the breaker (therefore likely through ground). You could use a ground from another breaker as current would only flow in fault conditions (tripping the GFCI) but you COULD NOT use a neutral from another plug (would trip the GFCI), Either way is against code. A 240V gfci will work without a neutral, as long as your not trying to supply any 120V loads.

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Old 03-18-2013, 08:43 PM   #6
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I'm not an electrician, so I'm curious why you can't use neutral as a ground even if you’re running a 120V application like a pump?
Because if you are using neutral as a ground, the GFCI breaker will consider it legal when you end up with a "ground fault".

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In fact, the second cord for a ground seems like it would blow the GFI because there would be juice going out that was grounding through a different breaker.
Ground should never carry current. The ground wire is there as a safety measure. In the event of a short, you have provided a way for the bad current to reach ground instead of waiting for your body or your cat or whatever to form that path to ground when they touch an errantly energized item.

GFCIs never see ground. As AlanMar mentioned, if any current goes AWOL and finds a way to ground, this shows up to the GFCI breaker as current going in on legal wires, but not coming back out on legal wires.
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Old 03-18-2013, 10:11 PM   #7
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Because if you are using neutral as a ground, the GFCI breaker will consider it legal when you end up with a "ground fault".
Wow, that sounds absolutely disastrous.

Thanks for all of the help guys, this answered my questions.
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Old 03-19-2013, 04:08 AM   #8
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I popped the cover on the outlet and there is a ground wire in there to go with the other three.

It looks like I just need to grab a four prong outlet and I'm in business.

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Old 03-19-2013, 07:17 AM   #9
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Good news

Maybe just maybe... check that it does connect to ground with 0 ohms resistance. Can you trace the groundwire, does it go to a ground rod?

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Old 03-19-2013, 03:38 PM   #10
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My electrician friend is coming over to replace the breaker with a GFCI breaker on Wednesday. I'll have him do all of the testing to make sure we're good to go.

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