why i HATE shared NEUTRALS!!

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brother

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"I have learned, in whatsoever STATE I am, therewi
:shock: OK OK, I know this has been discussed a few times. Ive been reading some of the posts. And yes i understand about lowering costs (not having to pull as many wires) and reducing conduit fill. :wink:

But i just dont LIKE, or should i say i HATE :evil: sharing neutrals on circuits!!
Beside the fact that only qualified people should be adding circuits and working on them.

Ive been on a few jobs and especially in old apartment houses and some single family homes, and when i hear about some complaining that their tv or computer was 'fried' and i find out its because there is 240 volts on that circuit cause the neutral got 'lost' going home, It just IRRATES me :evil:

Other jobs i seen that poor neutral :x turning black because of the new circuits added and seems like 'joe handyman' wanted to just add a another load to that neutral. Theres already 5 circuits on one neutral and he adds another 5! :!: :evil:

As for me, i would go head and add extra neutrals, and yes , :roll: kick me out for running up costs on building single family homes. But i would not allow shared neutrals. Dont care if its just 2 circuits!!

Ok im done. Im sure im gonna catch flack, and i probably wont work for some of you contractors. But thats my beef!! :wink: have a good day.
 
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bphgravity

Senior Member
Location
Florida
Nearly every service installed utilizes a shared neutral. The problem isn't with multiwire branch circuits, it's with poorly trained and uneducated electricians.
 
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dnem

Senior Member
Location
Ohio
The biggest problem with shared neutrals is the improper installation of mini breakers. Electricans are so used to loading the black next to the red that many times I find installations were they land the black next to the red but on the same mini breaker.

It's a mistake that I find on about 50% of panels with mini breakers.

David
 
roger

roger

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Location
Fl
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Retired Electrician
So far the only argument against MWBC's in this thread is non electricians (David, I think you used the word loosely) having their hands where they don't belong, and if they are apprentices their work should be supervised and checked anyways.

Brother,
And yes i understand about lowering costs (not having to pull as many wires) and reducing conduit fill
Click to expand...
tell us how else they save money and resources, it is not just at initial installation of the conductors.

Hint; Fuel to produce electricity, reducing voltage drop, and I?xR losses.

Roger
 
DGrant041

DGrant041

Senior Member
Location
Peoria, Illinois
roger said:
So far the only argument against MWBC's in this thread is non electricians (David, I think you used the word loosely) having their hands where they don't belong, and if they are apprentices their work should be supervised and checked anyways.
Click to expand...

Well, let me elaborate. It doesn't necessarily take "non-electrical hands" to fry equipment when the neutral breaks. (I was going to mention this on an earlier thread but it morphed into a discussion on motor shaft currents and third order harmonics--how can I compete with that?!) I live in a 1930's house with a 125A breaker box installed in the 70's. A couple years ago, I found that a pull chain light in the laundry area had burned out. . .so I changed it. When I turned it on, the light bulb started out very dim and in a couple seconds went very bright--poof! Light burned out again. Now I'd never run into ANYTHING like this before but somehow I KNEW the shared neutrals were involved. What else could possibly cause something like that?!

Sure enough: When I removed the porcelain light fixture, I found the wire nut had come off the neutral. So what else was on this circuit? The cordless telephone (not to hard to replace the power supply) and the outside garage. . .which had the garage door opener plugged into it! :evil: Well, there went a Saturday!

On other circuits like the dishwasher and garbage disposal, if they are on a shared neutral, you will probably have to run an extra circuit to put it on a ground fault, depending on what else is daisy chained to it.

Roger, you proved me wrong when I thought that you HAD to put MWBC on a two- or three-pole breaker. I'll eat that slice of humble pie. But I will never accept that this is a good practice to anyone except to the Electrical Contractor who installs it.

Thanks Brother. Now I'm ready to take my licks, too. :wink:
 
infinity

infinity

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New Jersey
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Journeyman Electrician
I love MWBC's. I will always use them. They save materials and labor. I don't really care about the untrained guy working on them after I'm gone. Personally I love it when a homeowner hires a handyman or does his own electrical work and blows up his $3000 plasma TV. You get what you pay for. If a cheapskate doesn't want to hire a professional to do the job than he gets what he deserves.
 
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macmikeman

Senior Member
Location
Planet macmikeman
Untrained "handymen" should not so much as remove the cover plate of a receptacle outlet, much less add loads to an existing multiwire circuit. That is the problem pure and simple. There is no more a problem with a properly installed mwbc than any other wiring. Would open heart surgery done by doctors be a " lousy" method just because when hospital orderly's try performing it on "side jobs at home on people" botch it up and kill the patient?
 
DGrant041

DGrant041

Senior Member
Location
Peoria, Illinois
hockeyoligist2 said:
MWBC...... Multi wire branch circuit? sometimes I think I need a list for all the acronym's here! :D
Click to expand...

Ain't that the truth! I don't know how long I read "IMO" before I looked it up on the internet. I found this site, I hope it helps someone else. The best part is that SpellCheck always has strange suggestions for several abbreviations that most in the electrical field would know.

L8r

edit to add: OR you could visit charlie's thread as it is much more relevant than my link. And he hit "send" before I did. :lol:
 
D

dnem

Senior Member
Location
Ohio
roger said:
So far the only argument against MWBC's in this thread is non electricians (David, I think you used the word loosely) having their hands where they don't belong, and if they are apprentices their work should be supervised and checked anyways.
Click to expand...

I don't find that genuine reputable electricians screw up multis on common breakers. But I do find good electricians far too often follow a trained pattern of landing the black and red side by side. It's a pattern that works great for regular breakers but can be a disaster on minis.

One of the biggest potential dangers from electrical fire is the overloaded neutral. With no OC it sits there and burns.

As far as the toasted plasma TV goes, I agree with another poster that said that open home run neutrals that energize loads in series is the cost of DIY or getting the neighbor handyman to do electrical work for cheap in your house. It's not so cheap when the plasma gets fried.

But if the plasma gets toasted, it gets toasted. That's not a big deal from a safety/shock/fire point of view.

But if the neutral gets overloaded, that's getting really serious. We're talking realistic possibility of a fire.

So for you guys doing multis on minis. Don't let yourself go thru the motions on autopilot while you're landing the panel. I've found even good electricians that have made that mistake. Hopefully when that mistake is made, the inspector is paying attention and catches it.

David
 
iwire

iwire

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Location
Massachusetts
dnem said:
I don't find that genuine reputable electricians screw up multis on common breakers. But I do find good electricians far too often follow a trained pattern of landing the black and red side by side. It's a pattern that works great for regular breakers but can be a disaster on minis.

One of the biggest potential dangers from electrical fire is the overloaded neutral. With no OC it sits there and burns.
Click to expand...

David in a home panel with both legs of a MWBC on the same leg as you describe what is the actual chance of a neutral 'burning'?

Look at the 310.16 rating of 12 and 14 AWG.

Not that I am saying it is a good thing when a MWBC is landed improperly just that I do not think it is the disaster you make it sound like. :wink:
 
electricman2

electricman2

Senior Member
Location
North Carolina
Occupation
Retired Electrical Contractor
infinity said:
I love MWBC's. I will always use them. They save materials and labor. I don't really care about the untrained guy working on them after I'm gone. Personally I love it when a homeowner hires a handyman or does his own electrical work and blows up his $3000 plasma TV. You get what you pay for. If a cheapskate doesn't want to hire a professional to do the job than he gets what he deserves.
Click to expand...

Well put, couldn't agree more. :)
 
paul

paul

Senior Member
Location
Snohomish, WA
I've never seen the tandems phased incorrectly. That's the first think I look for when trying to free up space in a full panel. That red wire hooked to the breaker your moving to a tandem should be sending up red flags and letting you know to watch your phasing.

As for shared neutrals, I run them all the time. No reason, whatsoever, to run three hots with three neuts for your homerun. Well, except when I wired up a security room with all the CCTV monitors and they needed to be on the same phase or else the screens would roll.
 
Jim W in Tampa

Jim W in Tampa

Senior Member
Location
Tampa Florida
On my own home i dont want or have any.Just makes me sleep a bit better.And if a customer is willing to pay the cost i will do same for him.Most jobs do not spec it so they get mwbc.
 
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brother

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"I have learned, in whatsoever STATE I am, therewi
Just check out these links AGAINST using shared neutrals. especially in lighting (277volts) :wink:
I know it wont change all of you, but it will open some eyes. :)

Experts About Shared Neutrals


AFCI's against shared neutrals

Shared neutrals pose danger if not properly identified on safety checks
http://www.eh.doe.gov/paa/oesummary/oesummary2005/oes2005-15-
1.pdf#search='shared%20neutrals%20circuits'


IAEI against shared neutrals

[size=18]


Question 1. Is there NEC code that prohibits shared neutrals in lighting and duplex branch circuits? This is one of the most dangerous things for electricians working on 277-volt lighting circuits. "No shared neutrals" was a standard in the facility I was working in. Please let me know if this is covered somewhere the NEC code. ? T.V. a [/size]

Moderators Note. I worked on the links to clean them up, one seems to be dead.

Bob
 
iwire

iwire

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Staff member
Location
Massachusetts
Use em all the time and always will unless job specs say otherwise. 8)

http://experts.about.com/

If thats all you got bring it on. :lol:

I hardly think that anything you find there is going to change peoples mind here. :lol:

By the way 'line voltage' is inherently dangerous we better switch to 24/12 VAC systems. :wink:

Copper org would get behind that change. :p

You did say you knew you where gonna get beat up. :p
 
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