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kal Forum Administrator
Joined: 12 Dec 2010 Posts: 11123 Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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Todd
Joined: 25 Nov 2012 Posts: 3 Location: Erie, CO
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Link Posted: Sun May 05, 2013 3:44 pm Post subject: Question about GFCI with 240v from a 14-30R |
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Question about GFCI with 240v from a 14-30R:
First, I'm no electrician, so I reserve the right to be wrong about any and all of this. I read a lot and scour forums, but I'm no expert...
In a US household 240v setup where I'm using the two out of phase hots to make 240, the neutral isn't being used. I thought GFCIs measure the difference between hot and neutral and trip if it exceed parameters. Neutral isn't being used in this, right, each out of phase hot acts as the others neutral/return path. If the dedicated neutral isn't used, only the two hots and ground, will the GFCI still work? [I'm not certain how a GFCI is wired internally - hopefully they also monitor the difference between out of phase hots.]
Note - my electric brewery setup is a little different, I don't use 120v in mine. I'm still using a 14-30P four-prong dryer plug, but I'm only tapping the two hots and the ground, and then distributing it through a three-prong NEMA 6-20R. My brewery plugs in with a 6-20P, pulling 240v and ground. It's a Speidel Braumeister designed for European 230v and many people have simply put a four-prong 14-30P dryer plug on it, skipping the plugs neutral and wiring the European hot and neutral to the two hots on the dryer plug. Ground is still used. Nobody has any issues with it, but I'd like to add the safety of GFCI if possible.
Cheers,
Todd
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Kevin59
Joined: 03 Aug 2012 Posts: 1047 Location: Fort Collins, CO
Drinking: Imperial Brown Ale
Working on: Oatmeal Stout, IPA
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Link Posted: Mon May 06, 2013 9:46 pm Post subject: Re: Question about GFCI with 240v from a 14-30R |
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Todd wrote: | In a US household 240v setup where I'm using the two out of phase hots to make 240, the neutral isn't being used. I thought GFCIs measure the difference between hot and neutral and trip if it exceed parameters. Neutral isn't being used in this, right, each out of phase hot acts as the others neutral/return path. If the dedicated neutral isn't used, only the two hots and ground, will the GFCI still work? [I'm not certain how a GFCI is wired internally - hopefully they also monitor the difference between out of phase hots. |
Todd - I remember doing a bunch of Googling and reading back when I started building my setup. Unfortunately I didn't save any of the links from then, but as best I can recall a 240V GFCI breaker that's tied to both hots and neutral in the panel monitors current between all 3 "poles", hot X, hot Y and neutral. With only a 240V connection without neutral it will look for differences between just the two hot legs, expecting a balanced load (sum of currents in each leg equals zero). If you threw 120V circuits in the mix then it's looking at the sum of currents. So if hot X is only connected to a 240V heating element, and hot Y is connected to the same element plus a 2 amp pump with neutral on the other side, the GFCI still expects the sum of all currents to be zero. Or something along those lines...
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Todd
Joined: 25 Nov 2012 Posts: 3 Location: Erie, CO
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Link Posted: Mon May 06, 2013 11:34 pm Post subject: |
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I'm coming to the same conclusion after an extensive Google search, it looks like GFCI works in our 240v setups whether we use neutral or not.
Thanks for the response.
Cheers,
Todd
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