Neutral

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fjdulzaides

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St. Petersburg Fl.
I'm a Maintenance tech and I have a question about to use one neutral for two diffrerents circuits from the same panel breakers but different phases. It is permitted? my partner says that he asked to others contractors with experience and they said yes, that we can do it, and I have a question what happen if the neutral is opened or loose.What's wrong with all those equipment in these circuits. :confused:
 
210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article shall be permitted as multiwire circuits. A multiwire circuit shall be permitted to be considered as multiple circuits. All conductors of a multiwire branch circuit shall originate from the same panelboard or similar distribution equipment.
(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
(C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads.
Exception No. 1: A multiwire branch circuit that supplies only one utilization equipment.
Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device.
(D) Grouping. The ungrounded and grounded conductors of each multiwire branch circuit shall be grouped by wire ties or similar means in at least one location within the panelboard or other point of origination.
Exception: The requirement for grouping shall not apply if the circuit enters from a cable or raceway unique to the circuit that makes the grouping obvious.

300.13(B) Device Removal. In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity.
 
what happen if the neutral is opened or loose. What's wrong with all those equipment in these circuits
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It lets the smoke out of the equipment.


Draw a simple diagram of a multi wire circuit including loads, and see what happens when you take out the neutral going back to the panel.

The electrons want to go somewhere. They are being pushed by the others in line behind them. If there is a path, they will take it.
 
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fjdulzaides said:
I'm a Maintenance tech and I have a question about to use one neutral for two diffrerents circuits from the same panel breakers but different phases. It is permitted? my partner says that he asked to others contractors with experience and they said yes, that we can do it, and I have a question what happen if the neutral is opened or loose.What's wrong with all those equipment in these circuits. :confused:
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It's a standard practice but it's important to make sure you don't lose the neutral because of just what you've said. The NEC pays a little extra attention to this for that reason.

300.13(B), for instance, says you can't rely on a neutral connection that's made through a device on a muliwire branch circuit in case that device is removed.
 
I will only use shared neutrals in my house when its a last resort. Usually if i am runing a new 120 circuit in my own house i will use 12-3 and cap the red. Then if i need an extra circuit that is too hard to get back to panel i will use it. Having seen the damage it causes thru the years makes me think twice before using them. Now if its wiring others houses or buildings for profit then yes i will.
Damage can easily be thousands to equipment. It's all about money.
 
I don't have the energy nor the impetus right now but 210.4 is so poorly written. I wish we could make proposals just based on poor language. But, then again, what would I do without CMP 2?
 
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charlie said:
You can and some do; the 2014 NEC is ripe for the picking as soon as the 2011 issue is distributed. :smile:
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C'mon Charlie, you know it's neerly impossible to get a proposal accepted unless people are getting hurt or you have something new.
 
Jim W in Tampa said:
I will only use shared neutrals in my house when its a last resort. . . Having seen the damage it causes thru the years makes me think twice before using them. . . Damage can easily be thousands to equipment.
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Services use shared neutrals, and an open there can damage half of the house.

I bet you've never asked the POCO to supply you with two 120v services. :grin:
 
steelersman said:
how about some 14-3? Or are you one of those commercial guys that thinks that #12 is the only way to go. :)
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I have nothing against 14 AWG but at the same time, I primarily use 12 AWG NM because I can buy larger quantities while spending less money than I would have to if I bought both gauges. The draw back is that 12 AWG isn't as easy to handle as the 14.
 
physis said:
C'mon Charlie, you know it's neerly impossible to get a proposal accepted unless people are getting hurt or you have something new.
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That is not true. The first thing I do is to find a good reason to reject. If I find none, then it must be accepted. There are several proposals each cycle to just add a comma or something similar that are accepted because the code language is incorrect.

Rewire said:
or a product you need to sell.
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I find it unfortunate that your statement has become true if the manufacturers have enough clout.
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I have to apologize Charlie. I was thinking your avitar was Charlie B.'s. I'm still having to get used to your presence here, as much as mine, none the less, you were the first guy here that was friendly toward me when I knew nobody. And you've always made me feel comfortabale here.
 
charlie said:
The first thing I do is to find a good reason to reject. If I find none, then it must be accepted.
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I know that you guys first look for something to reject. But the next step is not acceptance. I so much wish it were.

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I love you Charlie, I really do. But what I've quoted from you is simply not true. The CMP's do not accept symantic proposals.

If I'm wrong, could you point to a few examples?
 
physis said:
. . . If I'm wrong, could you point to a few examples?
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Not without combing through the 2008 ROP & ROC which I am not inclined to do. However, if you wish to look, search for proposals from Dan Leaf. Dan has submitted a lot of editorial proposals and there are a lot more for the 2011 cycle but the ballot recirculation has not been done yet; therefore, the 2011 ROP has yet to be published yet.

Keep in mind that the code making panel has to make a clear statement for the reason that they are rejecting any proposal. That also applies to the comment period that will produce the ROC. :smile:
 
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