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Old 12-16-2011, 07:07 PM   #1
El_Cabrito
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I'm sure this has been posted to death, but i can't seem to find it doing a search. looking to setup an electric brewery of some kind, and i have an unused drier outlet in the basement. it has 3 prongs, so does that mean 1 hot (A), 1 hot (B), and 1 neutral (with ground tied to it)? if i want to use this outlet, do i have to add a ground somehow? i have seen spa panel additions after the outlet, but that appears to be for GFCI (which i would also need). Does this provide grounding? what is the way that is commonly used to get a ground on the current outlet? i own the house and am not looking to make a portable system. thinking 240V/30A with two 5kW element(s) switched.

Thanks!
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Old 12-16-2011, 07:19 PM   #2
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That outlet does not have a safety ground. The neutral might seem connected to ground, but neutrals are meant to carry current, and that means the voltage on it at your rig will rise (and your entire rig will be at some elevated potential).

You need to add a safety ground, regardless of the GFCI setup you use.

By far, the easiest thing to do is to replace that outlet with a 4-prong. I can't tell you where to get the earth ground, but you could pull another piece of wire to that outlet from a ground somewhere else.

I know you might be tempted to run a separate ground to your rig, and continue to use the plug as it is, but that isn't any easier than doing it the right way, probably violates code, and isn't as reliable as doing it the right way.
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Old 12-16-2011, 07:21 PM   #3
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already answered

 
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Old 12-16-2011, 07:23 PM   #4
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A NEMA 10-30 receptacle (3-wire, 30A, commonly used for a dryer) looks like this:


and is defined as a non-grounded 240V receptacle. It contains the two 120V hot lines and the neutral. The dryer has 120V items in it (buzzers, lights, etc) and those things use the neutral to carry current. The dryer's body is also 'grounded' via this neutral.

When you add the GFCI spa panel and plug that into the dryer outlet, what you are basically doing is splitting the neutral line into two lines. One of those lines is allowed to carry current (the one that passes through the breaker) and the other is not. The one that is not allowed to carry current is passed on from the spa-panel to your brewery to be used as a ground.
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Old 12-16-2011, 07:26 PM   #5
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Quote:
Originally Posted by passedpawn View Post
You need to add a safety ground, regardless of the GFCI setup you use.
Ultimately, the ground and neutral are tied together in the main panel, so the two wires really are the same thing. But, by using the GFCI spa panel to clone the neutral into one that is OK and one that is not OK to carry current, you create a wire that will sink current to ground and trip the GFCI if anything ever passes through it.
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Old 12-16-2011, 08:08 PM   #6
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Walker,

Very well said and right on the money. Due to the fact that the line is terminated in a dedicated outlet, it IS according to code.

To the OP,

The GE Spa Panel from HomeDepot can be wired this way:



And it will fit the need very well.

Also: If wanted, a 4 prong dryer outlet can be installed directly in the Spa panel for the brewery panel if you want - like this:



Hope this helps.

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Old 12-16-2011, 08:32 PM   #7
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Thank you so much for this post, p-j!
It prompted me to get off my butt & buy the spa panel.
With that diagram, it is so well simplified!

 
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Old 12-16-2011, 09:57 PM   #8
El_Cabrito
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That's fantastic. thanks. i was hoping to not have to run a separate grnd line to the outlet from the breaker + this means no GFCI install in the main breaker either.
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Old 12-16-2011, 10:49 PM   #9
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Quote:
Originally Posted by Walker View Post
But, by using the GFCI spa panel to clone the neutral into one that is OK and one that is not OK to carry current, you create a wire that will sink current to ground and trip the GFCI if anything ever passes through it.
Clone the neutral? If there is no earth ground going to the spa panel, how do you "create" one? There needs to be an earth ground somewhere.
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Old 12-16-2011, 10:55 PM   #10
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Quote:
Originally Posted by passedpawn

Clone the neutral? If there is no earth ground going to the spa panel, how do you "create" one? There needs to be an earth ground somewhere.
Look in your main panel. Neutral and ground are bonded together. Any where were you had connected something to neutral you have also connected to ground.
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