Wriring questions

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Edison circuit (I didn't know how it is called though) is what I was asking about. Using one neutral wire for two circuits. My Siemens main panel can contian up to 60 breakers so I am not worried about this.
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One neutral for two circuits is fine. One neutral for *more* than two circuits is not fine, unless you increase the size of the neutral.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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wrote:

circuits
I believe an Edison circuit is as follows:
A 220 line with neutral (two 110 lines and a neutral) split into to separate 110 lines, both sharing the common neutral. If both 110 lines come from the same leg of the mains it is not safe for them to share a neutral. As long as the 110 lines are from opposite legs of the mains coming in then you're fine. (AKA splitting a 220 line down in to two 110 lines)
If you run two 110 lines from the same leg of the main incoming line you will overload the neutral.
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Entirely correct.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Why "almost a dozen"?

Yes.... but it probably won't save you much hassle, and may wind up costing more money.

You can share the neutral between *two* 20A 120V circuits, provided that all of the circuit conductors share the same cable or conduit, and you put the two hot conductors on opposite legs of your 240V service and use a two-pole breaker.

Please don't take offense, but I must point out that the fact that you even consider doing this suggests that you don't know anywhere nearly enough to be doing your own wiring safely. Now here's the answer to your question:
No, for several reasons.
First, the National Electrical Code flatly prohibits using the white wire as a hot circuit conductor. There are a few specific, narrow exceptions, but your proposed use is not one of them.
Second, what you propose is highly dangerous. In a properly installed shared neutral circuit, the neutral conductor carries the *difference* in current between two hot conductors, e.g. with 15A in one hot leg, and 12A in the other, the neutral carries only 3A. The neutral cannot be overloaded, because in the worst case (one hot leg fully loaded, the other hot leg carrying no load) the neutral carries the same current as the loaded hot leg. In your proposed situation, however, you have *five* hot conductors sharing a neutral. Even if you have these divided across the two hot legs of your service as closely as possible (three on one leg, two on the other), you could have, in the worst case, the full current of *three* hot conductors carried on the neutral wire. If your circuits are all 20A, you'd need at *minimum* a 6-gauge neutral in order to safely carry the 60A that it might be subjected to.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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When I bought my house three years ago I hired a licensed electrician to install 6 receptacles in my workshop. 1st, 3rd and 5th receptacle are on one 20 A circuit, 2nd, 4th and 6th on another. The electrician ran NM-3 cable from sub-panel though all 6 receptacles putting all of them on single white neutral wire, hot of 1st, 3rd and 5th on black wire and hot of 2nd, 4th and 6th on red wire. Doesn't this mean two circuits share the same neutral wire?
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Yup, and as Doug stated, this is kosher as long as the hots are on opposite legs of the 240, and a two-pole breaker is used.
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Sasha wrote:

Yes; this kind of wiring is ok and was alluded to in one of the prior posts, though I think it was called "split receptacle", which really means that in one duplex outlet, one plug is on the black wire and one is on the red. In either case it's also called an "Edison circuit".
It's ok if, and only if, the black and the red are connected to the two opposite legs (commonly called "phases", but purists retch at that) of power in your panel. The AC in the two legs is exactly out of phase and so cancels itself out rather than adding in the neutral. In the extreme case of you drawing exactly the same current - even the full 20 A - on both the black and red, the two cancel completely and the neutral carries no current at all.
In a true split recepatacle, code usually requires that the two breakers be linked so that both will trip if either shorts. In a case such as yours, from what I glean from this group, most jurisdictions do not require this.
If you put a voltmeter between the hot pins of two adjacent receptacles, you should find it reads 240 V. (But code generally prohibits you from installing a 240 V outlet or appliance on a circuit that also has 120 V loads.)
If you find that the black and red are on the *same* leg, you've got a problem.
Chip C Toronto
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Chip C wrote:

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Sorry to follow up on my own post, but I got some of your other postings only after I wrote this. I see that you've already mentioned Edison circuits. The key point is that in such a circuit the two hots (red and black) are on opposite legs and so can share a neutral. Thus you cannot extend it to more than two hot wires.
In your list of circuits (which I count as nine), any loads that are close together are good candidates for wiring this way. The DW and disposal, for example; and maybe the two appliance circuits.
Chip C
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Yes, so what? There's nothing wrong with that, as long as it's installed correctly. It's having *more* than two circuits sharing a single neutral, using the same size conductor, that's dangerous.
If you don't understand why two 20A circuits sharing a single 12-gauge neutral are safe when properly installed, but three 20A circuits sharing a single 12-gauge neutral *cannot* be installed so that they are safe, you shouldn't be doing your own wiring.
It's not like painting or wallpapering, where screwing up because you don't know what you're doing just makes your house look silly. Screwing up electrical wiring can make houses burn, and people die. If you don't know enough to do it safely - and it appears you don't - leave it to a pro.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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I do understand now. That's why I posted the question and didn't do anything before getting the answer. I wouldn't though scare people because they post a question. I see the advatange of this newsgroup is to gain knowledge befor doing something. As opposite to you I consider wriring the easiest of home improvement. Yes, it is dangeruous if done incorrectly. However, the number of rules is quite limitted and if followed combined with understanding wiring is not a rocket science. Finally, there is inspection that ensures safetly and adherence to code. After looking at electrician's work and reading a couple of books I rewired almost entire my house, installed sub-panel 16 120 V and 4 220 V circuits. Had electrical inspector checked all work twice (rough and final), passed from first time. Never had any problems since then. I myself never though combined even two circuits together.
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sasha, its time for you to own up to this project. if its not rocket science, why are you asking these questions? the answers are easy to find for one who is looking.
get off the newsgroups and go down to the library.
randy
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Nobody's trying to scare you. You've missed the point: it's your questions that are scary. They display a level of understanding that is insufficient to the task.
Next time you reply to a post, please quote the post you're replying to. It makes it much easier to figure out what you're talking about.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Looks like the technical questions are being answered already.
What I'd like to ask is "why a dozen new circuits"? Damn, I don't anywhere that many circuits in my *shop*, for Pete's Sake, and I can guarantee that the stuff in that shop draws w-a-a-a-a-y more power than anything you'll find in a kitchen.
Sure you don't just want to have a dozen or so new *outlets*? That's a heck of a lot easier job -- just daisy chain the outlets. In general, a couple of 20A circuits for all the kitchen outlets is plenty.
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Run a conduit with individual conductors and share the ground wire (the green one). I personally would not share any neutral wires, even if it's permitted.
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