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Posted By: Redsy Conserving wire? - 02/13/05 11:01 PM
It seems that when wiring a new residence, if you feed the homeruns to the device boxes closest to the panel, less cable could be used.
However, the more I think about it, I don't think it is true.
What do you guys think?
Posted By: Dave55 Re: Conserving wire? - 02/14/05 12:34 AM
I wouldn't expect to save any cable by running to the farthest device!

Dave
Posted By: Redsy Re: Conserving wire? - 02/14/05 03:16 AM
Obviously, homerunning the farthest device would waste wire if you then had to back track to feed devices that you passed over on the way.
I'm just not convinced that, say, starting several different branch runs from the room closest to the panel will result in less wire used overall.
Posted By: e57 Re: Conserving wire? - 02/14/05 04:43 AM
I know this is a point of contention with those who feel strongly about the use of 2-wire circuits, but 3 and 4-wire ciruits are a savings in wire in themselves.

I try to maximize the use of them, and shed conductors of the circuit at nearest opprotunity, or best suitable location. Like some circuits are just stanard in method now. GB/DW is a 3-wire to a box under the sink. Kitchen Counters = another 3-wire, GFI the start of each. Baths are the same.... 3-wire for vanity recept GFI, and another appropriate 20A on the other.
Posted By: proguy Re: Conserving wire? - 02/14/05 07:23 AM
I also run a ton of three wire. My panel looks verrry pretty. It has alternating colors red-black-red-black. The only sitiuation is for GFI breakers and arc faults. Which brings up a ? I heard from a fellow electrician that you could share a nuetral with arc's. I told him that I never heard that before and went on my way.

What do you guys think about multiple sub panels? Are they cost effective? What size subs do you run for $4k sq/ft homes?
Posted By: Redsy Re: Conserving wire? - 02/14/05 12:51 PM
I also use multi-wire ckts. as needed.
But I am trying to reason through whether or not wire is saved by by the method described above. At first thought, it appears so. But the more I think about I don't believe so.
Posted By: frankft Re: Conserving wire? - 02/14/05 02:02 PM
210.4 says that when a multiwire circuit supplies the same yoke that it needs to be on a 2 pole breaker. My question is say with the 2 SA branch circuits do you put them on a 2 pole breaker just to be safe? It also seems that if somebody else at a later time goes to work on the panel, that they may notice quicker that the are mulitwire circuits in the panel and know not to start rearanging the circuits without thinking about the phasing first.
Posted By: detubbs Re: Conserving wire? - 02/14/05 02:11 PM
if i remember right our inspector allows us to put them on single pole breakers as long as the breakers are on the same phase, so there's no possibility of 240v through a short to a device
Posted By: iwire Re: Conserving wire? - 02/14/05 02:27 PM
Quote
if i remember right our inspector allows us to put them on single pole breakers as long as the breakers are on the same phase, so there's no possibility of 240v through a short to a device

I hope you are not remembering correctly.

Each leg of a multiwire branch circuit must be connected to different buses in the panel.

Any other way can result in overloading the neutral.

Quote
Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.


In order for the ungrounded conductors to have a 'voltage between them' they must be on opposite panel busses.



[This message has been edited by iwire (edited 02-14-2005).]
Posted By: Electricmanscott Re: Conserving wire? - 02/14/05 02:35 PM
detubbs, dude you are scaring me. [Linked Image] First off Bob pointed out the danger. Second your inspector should go back to school or give up inspecting. Third do you always let the inspector instruct you (incorrectly) on how to do your work? Now for the original question. I din't see a meaningfull savings of wire in the average home. One way or another all the outlets on the circuit have to get wired together. I don't see how starting here vs there makes a difference.
Posted By: Bert66 Re: Conserving wire? - 02/14/05 07:27 PM
My question is to the guy's who use 3 conductor wire for a home run to say a bathroom or a kitchen. Are you putting say a receptical circuit on one hot (red) and lighting circuit on the other hot (black) and then sharing the neutral. Did I understand you to use this as a homerun. I only ask because I have not done it like that. But I've never checked the per/ft cost of 50' of 14/3 vs 100' of 14/2. MMMMMMMMMMM might be a cost savings hiding there.
Posted By: Electricmanscott Re: Conserving wire? - 02/14/05 07:33 PM
Bert, you could run a 12/3 for a dishwasher and disposal, two ct circuits, ref and micro etc. I don't know if there is a noticeble cost savings in wire but I do know you would only run half the cables back to the panel. That could add up to a labor savings.
Posted By: Redsy Re: Conserving wire? - 02/14/05 10:07 PM
Thanks, Scott for getting back on track [Linked Image]
As far as multi-wire ckts saving wire, around here, 3-conductor NM cable typically costs about twice as much as 2 conductor(go figure!), so the savings realized are mostly labor costs.
As far as the original question, I believe that there is an illusion of less wire used by that method but I believe that is all it is.
Posted By: Sandro Re: Conserving wire? - 02/15/05 01:13 AM
PROGUY.....to answer your question, they DO make 2 pole Arc Faults for 3 wire and shared neutral circuits. I use em all the time!
Posted By: cvelectric Re: Conserving wire? - 02/16/05 02:49 PM
IMHO you do save wire and labor by going to the closest outlet with the HR. Also I like to try and wire in a way that I think would make the most sense to most electricians when troubleshooting. I do use multi-wire branch circuits when it makes sense to me but I am not real keen on using alot of them since I have seen too many that were not balanced on seperate legs. Breakers can get switched in the panel (to the same leg), after I'm done, by someone who does not know better. Also it seems like there is less possibility of power quality issues when running 2 wire home runs.
Any thoughts/comments on PQ with multi-wire branch circuits?
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