Electrical Question

[Moonbeam]

I have one conduit running to my basement and attached garage with a 14 ga / 15 amp circuit. I want to beef it up a bit and run two 12 ga / 20 amp wires / circuits to the basement and garage and make one circuit strictly for outlets at the work bench. Now I don't think you can run two neutral wires in the same conduit, so do I use one of the those circuit breakers with the switches tied to each other? Make sure that the hot wires are on the different legs in the main box?
The reason I ask this is because looking at the current wiring in my main box, I have a two wires running to the kitchen that share a neutral but the circuit breakers are not tied together. Now the house is not new and other home owners have changed stuff around with the electrical and someone could have done something wrong.

 

[Flatmotor]

You can share a neutral on 2 seperate 1-pole 20A circuits as long as they are on different phases. If you don't have seperate phases available you need a seperate neutral for each circuit. There is no problem with more than one neutral in the same conduit. Also don't forget the ground conductor. Hope this helps, Bill

 

[Charles (in GA)]

Don't forget to calculate conduit fill limits based on conduit and wire sizes, and to derate the wires if necessary, when more than three current carrying conductors are put in the same conduit.

Charles

 

[trovato]

I think the way your kitchen is wired is wrong. The breakers should be tied together. I'm not a big fan of sharing the neutral like this. I think it adds complexity and confusion, usually just to save the cost of one wire.

 

[bochnak]

Here is a conduit fill chart:

http://www.westernextralite.com/resources.asp?key=47

If you are running EMT, it acts as the ground.

 

[Aceman]

I think the way your kitchen is wired is wrong. The breakers should be tied together. I'm not a big fan of sharing the neutral like this. I think it adds complexity and confusion, usually just to save the cost of one wire.

I'm sorry but you're wrong! If understanding a typical multiwire branch circuit is over your head, you shouldn't be working on it. When I wire I house, I'm not going to waste time and resources pulling extra wires just to make it easier for future diy'ers.

 

[MAD]

The type of circuit where more than one 120v circuit share the same neutral wire is called a Multiwire branch circuit. I believe it was once permissible in some situations to use individual single pole breakers for each line as long as the circuits did not terminate in the same device (such as like a duplex receptacle where the circuits are split). I believe the 2008 code now stipulates that a common trip two pole breaker must be used in all multiwire branch circuits.

Edit- This assumes a two circuit multiwire like the OP described. I guess you could have a three circuit multiwire branch circuit with a three pole breaker if the electrical service was three phase. In any case I believe all of the ungrounded (hot) wires must be disconnected at the same time under the new code.

 

[kbs2244]

Mad:
I have always wired garages with 2 hots and a single netural going to 4x4 boxs with one duplex outlet per hot. Each hot on it's own breaker.
The logic is that if you are working at the far corner of the garage and pop a breaker you can just plug into the other duplex and finish up your job before having to go reset the breaker.
Are you saying the 2008 code will not allow this.
That I have to tie the breakers together so they both pop at once?
Or I have to use 2 neturals?

 

[trovato]

I'm sorry but you're wrong! If understanding a typical multiwire branch circuit is over your head, you shouldn't be working on it. When I wire I house, I'm not going to waste time and resources pulling extra wires just to make it easier for future diy'ers.

Like MAD, I was under the impression that a common trip two pole breaker must be used in all multiwire branch circuits. That's how I always see them done. I don't particularly like them because of the complexity/confusion and because I can't just pop in a GFI breaker to get protection on one whole circuit. Also, when tied together, a trip means losing two circuits instead of one.

Now, if I was doing this for a living, wire = money might be my greatest interest as well. For my own projects, the cost saving is small.

 

[trovato]

I found this article:

http://www.necplus.org/Articles/Multiwire Branch Circuits.aspx

It states:

Safe Disconnection of Ungrounded (Phase) Conductors

The 2008 edition of the NEC requires that all multiwire branch circuits “be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.” This can be accomplished with a double-pole breaker or two single-pole breakers with an identified handle tie. Prior to 2008, only multiwire branch circuits that supplied more than one device or equipment on the same yoke required a means of simultaneous disconnection.

So Moonbeam's kitchen is OK by the code from when it was wired, but would not be allowed by the latest code.

 

[Moonbeam]

If you run two neutral wires in a conduit, which I assume always have to be white, how would you be able to keep track of balancing the load between the two phases? For a new install I guess it would be easy, but anyone changing something or adding something later on would seem to cause confusion.

 

[MAD]

Like MAD, I was under the impression that a common trip two pole breaker must be used in all multiwire branch circuits. .

I think that if read my post again you will see that I said that single pole breakers had been allowed for multiwire branch circuits in some instances but under the latest code you must use a multipole common trip breaker for all multiwire branch circuits.

 

[MAD]

Mad:
I have always wired garages with 2 hots and a single netural going to 4x4 boxs with one duplex outlet per hot. Each hot on it's own breaker.
The logic is that if you are working at the far corner of the garage and pop a breaker you can just plug into the other duplex and finish up your job before having to go reset the breaker.
Are you saying the 2008 code will not allow this.
That I have to tie the breakers together so they both pop at once?
Or I have to use 2 neturals?

Yes that is what I am saying.

If the work was inspected then you shouldn't have to change anything just because the code changed. If you make changes to the your electrical system the inspector may make you bring those circuits op to the latest code. In that case all you would need to do is put some handle ties on the breakers.

 

[MAD]

If you run two neutral wires in a conduit, which I assume always have to be white, how would you be able to keep track of balancing the load between the two phases? For a new install I guess it would be easy, but anyone changing something or adding something later on would seem to cause confusion.

The bus bars in the panel alternate vertically one hot leg of service then the other.

Extreme example:
If for some odd reason you were to install single pole breakers and leave a space between each breaker installing only in every other space then you would be drawing current through only one of the hot legs of your single phase service.

I hope this answers your question.

Please be careful and get some experienced help if you need it.

 

[trovato]

I think that if read my post again you will see that I said that single pole breakers had been allowed for multiwire branch circuits in some instances but under the latest code you must use a multipole common trip breaker for all multiwire branch circuits.

I followed you. I meant "under the latest code". Sorry if I wasn't clear.

 

[MAD]

I followed you. I meant "under the latest code". Sorry if I wasn't clear.

No problem-that makes sense.

 

[trovato]

If you run two neutral wires in a conduit, which I assume always have to be white, how would you be able to keep track of balancing the load between the two phases? For a new install I guess it would be easy, but anyone changing something or adding something later on would seem to cause confusion.

NEC 200.6 (D) says that where grounded conductors of different systems are installed together, each has to be identifiable. One should be white/gray. Others can be white with a readily distinguishable colored stripe other than green. I'm paraphrasing here, as the code has more detail, and allows other means of identification as well. Some means of identification, though, is required.

 

[Aceman]

NEC 200.6 (D) says that where grounded conductors of different systems are installed together, each has to be identifiable. One should be white/gray. Others can be white with a readily distinguishable colored stripe other than green. I'm paraphrasing here, as the code has more detail, and allows other means of identification as well. Some means of identification, though, is required.

That doesn't apply here since he's coming from one panel. Different systems means different voltages, panelboards, etc. All he needs are two plain white wires. If he wants to put a little tape on each one to keep track of them that's fine and a good practice to get into. The important part is keeping track of which neutral goes with which hot if both circuits are going to be passing through the same boxes.

 

[trovato]

That doesn't apply here since he's coming from one panel. Different systems means different voltages, panelboards, etc. All he needs are two plain white wires. If he wants to put a little tape on each one to keep track of them that's fine and a good practice to get into. The important part is keeping track of which neutral goes with which hot if both circuits are going to be passing through the same boxes.

Aceman, you may have a point there, but it sure sounds like a good idea. Personally, I can't imagine installing two neutrals without having a way to tell which is which.