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Old 09-20-2011, 11:32 PM   #1
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Default 3-Wire Vs. 4-Wire GFCI

I’ve been using a Brutus 20 clone for awhile & decided that I would like to add an Electric HLT to the brewery to save on propane costs & simplify the brewday.

I had planned to run the element @ 240V, convert my control panel from 120V and power the whole thing with a single 240V 4-Wire Plug. So I bought a 30A 4-Wire GFCI for it… I then got around to moving the dryer & discovered that I only have a 3-Wire 240V Outlet to work with.

Now comes my question: Would the GFCI still function properly if I rewired it using a 240V 3-wire plug and simply ignored the neutral wire?

I would add a separate 120V input to the control panel to power pumps, valves…

Thanks,
Theo


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Old 09-21-2011, 01:56 AM   #2
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You would not ignore the neutral (white wire). That is the main return current circuit. If anything, the ground wire (green wire) would be ignored. Actually its not ignored, its just wired to ground all the equipment that might get energized.


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Old 09-21-2011, 02:21 AM   #3
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Since you have a 3 wire plug why not just use the ground from that plug as your neutral and ground. I mean yeah you aren't supposed to do it. But ground and neutral are actually the same thing in the breaker box. It wouldn't pass codes inspection but shoot ask any electrician it will work just fine.
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Old 09-21-2011, 02:23 AM   #4
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Have you turned your breaker off and removed the dryer plug? I bet you have a forth wire in there.
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Old 09-21-2011, 02:24 AM   #5
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I don't consider myself an expert but here's what I think.

On older dryer plugs (3 wire) the ground prong was missing. Somewhere around 2000, the NEC or NFPA required new installations to be 4 wire (two hots, neutral and ground).

Your GFCI should still work. It doesn't measure current on the ground wire... it compares the current leaving the breaker to current returning to the breaker. So the wiring at the panel will be the same. Your two pole GFCI breaker will have two hot lines and a neutral to hook up. The white coil (pigtail) will be tied to the panel's neutral bus.

You don't need to add a separate input for 120Vac... you'll still have 120Vac between either hot and neutral. The breaker will still operate properly if you have the pigtail hooked up to the neutral bus and the outlet's neutral to the breaker.
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Old 09-21-2011, 02:32 AM   #6
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I actually had problems running my 120 v march pumps and my 240 elements on the same circuit. It created enough current imbalance(notsurenthe right term) that it would throw the breaker. I had an electrician confirm this for me.
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Old 09-21-2011, 03:44 AM   #7
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Quote:
Originally Posted by mabrungard View Post
You would not ignore the neutral (white wire). That is the main return current circuit. If anything, the ground wire (green wire) would be ignored. Actually its not ignored, its just wired to ground all the equipment that might get energized.
I'm no expert, but I believe its the voltage difference between the 2 hot lines that creates 240V. I know its 120V between either hot line & neutral. So I reasoned that since this circuit is just for the 240V element the neutral line could be ignored.
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Old 09-21-2011, 03:45 AM   #8
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Quote:
Originally Posted by milldoggy View Post
Have you turned your breaker off and removed the dryer plug? I bet you have a forth wire in there.
I'll have to take a look at that tomorrow.
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Old 09-21-2011, 03:54 AM   #9
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Quote:
Originally Posted by SeattleMatt View Post
I don't consider myself an expert but here's what I think.

On older dryer plugs (3 wire) the ground prong was missing. Somewhere around 2000, the NEC or NFPA required new installations to be 4 wire (two hots, neutral and ground).

My understanding is that the 3 wires are 2 hots & ground with the neutral wire missing
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Old 09-21-2011, 02:11 PM   #10
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I bought one of these on ebay too, I took it apart and re wired it to a 4 wire pigtail, the two hots go through the GFI the the ground and neutral go under the circuit board. In these pictures you can see the black and white wires are the original to hot leads, I connected them to the black and red of the dryer pigtail, and routed the white and green wires of the dryer pigtail around the gfi.

I have not tested it yet, so don't take my word for it yet, but I can't see any reason it wont work.

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DON'T DO THIS...IT DOES NOT WORK...I figured this out the hard way, these are monitoring both wires at the same time so when pulling of one leg to run your 120V equipment the GCFI will trip. just get a $50 spa panel...



Reason: Missleading info.
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