Two circuits in one box?


I want to put in 2) 20A curcuits in my shop area. I would like to have them both go to a string of twin duplex boxes, with the left-hand duplex recepticle in all boxes on one curcuit, and the right-hand on the other circuit. My calculations show a 32 c.i. box is required for 12ga. wire. Questions: 1) I assume the grounds for both circuits can/should be tied together, correct? They are uninsulated, so I can't see how that could be avoided. 2) If the first box in line gets two GFCI outlets (one for each circuit), does that change the calculation for box size? Does the yoke count of 2 for each device change because of the depth of a GFCI receptacle?
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There's no particular reason why they need to be tied together, and if you use non-metallic boxes, it's avoidable.

I don't see anything in the Code that indicates that it does.
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Doug Miller (alphageek at milmac dot com)
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wrote:

them
use
for
When I read your reply and the original post, I starting thinking (always a dangerous thing to do.)
Would it be "legal" to just run a single 120/240 circuit and at the first J box put in a pair of GFCI's with the other circuits fed by the load side of that first pair? The advantage is there would be two less current carrying wires in each box (except the last), only one pair of GFCI's would be needed. The neutral and ground would have to be pigtailed of course.
Along that line, it is "legal" to have a 240 volt outlet share a 120/240 circuit with the 120 volt duplex outlets? I understand that the 15/20 amp duplex outlets are treated differently that the 120/240 or 240 outlets although it doesn't make much sense from a safety view point.
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On Fri, 08 Dec 2006 16:29:18 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Since we've recently, after a mere thousand messages, convinced me that you can put GFCI outlets on an edison circut, why not pull one 4-wire cable off a double-pole 20-Amp breaker?
That will reduce the # of wires in each box.
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Goedjn wrote:

You'd only need a 3-wire cable, actually. they can share a neutral if they are on opposite phases.
nate
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Yes, he can do that. However, if he does that he'll need to use a 2-pole GFCI breaker instead of two GFCI outlets. Have you seen the price of a 2-pole GFCI breaker recently?
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John Cochran wrote:

Depending on the breaker panel, they may actually have them at Home Depot - I know I've seen them and I don't remember what they went for but I don't recall being shocked by the price.
nate
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For safety of anyone working on these outlets in the future, I would suggest using a tiebar breaker (like for 240 volt circuits) for the circuits in these boxes and placing a note in the breaker panel that these outlets are on two circuits.
The tiebar will force them to turn off both circuits at the same time.
This would keep someone from turning off the circuit to say the left outlet and still having live power on the right side and zapping themselves...
"Al Tsiemers" wrote in message

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That's a good idea ... but IMO it's even more important to put that note at the *outlet* box.
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Doug Miller (alphageek at milmac dot com)
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Bill wrote:

I'm sorry, but IMHO, anyone who doesn't check all wires in a box for voltage deserves what they get......as they don't have any business doing electrical work in the first place.
Here's the preferred tool to use: http://www.emsco-usa.com/fluke/flvolt.htm
IMO, using a tied breaker just sets up an unqualified person who has a very bad habit of not testing for a presence of voltage on all wires for a wake up call. It doesn't happen a lot but sometimes circuits are accidently backfed. If the backfeed is on the same leg, the miswiring often goes unnoticed. I saw this on a circuit just two months ago on a service call. A tied breaker won't protect against it, as the circuit will still be fed from another circuit. Bottom line, the first rule to doing electrical work is to TEST ALL WIRES, even equipment grounding wires, for voltage with a known to be good tester. If one doesn't want to invest the $25(US) for the Fluke Volt Alert, or similar device, the old standby $3 neon tester will do, although more time consuming. And, yes, both can sometimes give a false positive from induced voltages, in which case one should investigate further with an analog meter or a test lamp.
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The most important part of this sentence is the last five words: "known to be good tester".
Before using the tester to verify that a wire is dead, test it on something that's supposed to be *live* to make sure it lights up / reads voltage / whatever. EVERY TIME.
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On Sat, 09 Dec 2006 12:51:53 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Yes. How about testing THAT CIRCUIT both before and after turning it off. I do that. Plug an outlet tester into that outlet, make sure it works, and leave it there while turning it off (and make sure it goes off).
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volts500 wrote:

What a load
The tie bar is a damn good idea.
Read this as "anyone who doesn't pay me to do the work is an idiot"
Why did they invent lock out tag out rules? Shouldn't they always check to see if its live?
Anything that is safer and not more complex/expensive is the way to go
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I test everything with a test lamp then intentially short stuff just to be safe.
getting hit doesnt scare me but I would prefer top avoid it.
very careful though in my jammed breaker box or on wet floor, stuff like that can be lethal.
having been a copier technician and fixing office equitment getting hit occasionally is part of the job:(
electronics school was a shocking experience at times..........
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yourname wrote:

For people who need laws to protect themselves from themselves?

Read it as "how to protect yourself from idiots."

To keep people like you from energizing circuits that other people are working on? To absolve employers and insurance companies from responsibility? LO/TO is one of the biggest screw jobs running for employees. I once worked for a large, top 50 in the US, electrical contracting company who went out of their way to bring a safety officer to the jobsite just to tell 60 electricians that they would be fired on the spot if they did not use LO/TO. By chance, later that day I had to LO/TO a 200 amp feeder to work on it. The jobsite LO/TO kit did not have a 200 amp breaker LO, so I told my supervisor that I needed one. What do you suppose I was told? That's right, just get r done.
I'd tell you how to _really_ protect oneself in such cases, but since you seem to think that I'm in it for the money, make a deposit in my PayPal account and I'll be glad to tell you.

If they did that then they wouldn't need to have breakers tied now would they?
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On Fri, 08 Dec 2006 16:14:22 GMT, Al Tsiemers

YES on the grounds.

I never get this technical. If the device fits in the box, plus the wires (without overcrowding or pinching a wire), it will work. GFIs take up quite a bit of space compared to a common outlet. Either get a large box, or just use 2 boxes. Dont evn think of trying to put a GFI in a standard handy box. It wont easily fit. I tried it once, that was a major headache. I just use a 4 inch quare box now for each GFI, and get the special cover plates for the larger box,
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