I am starting this thread to expand on multiwire discussion which was brought up in another post. I use multiwire circuits all the time and I think they are a Godsend in making our jobs easier and neater. I too mark each set of hots by taping them to their corresponding neutral in the panel. Recently I have thought up the idea of having my printshop make me up a roll of adhesive labels saying something like: "Caution: This system utilizes shared neutral conductors. Re-arrangement of breakers by unqualified persons could result in a fire hazard"
Has anyone thought of or done this? Any opinions?
As far as Joe Homeowner screwing it up, I see far worse almost daily. Just today I found a bathroom receptacle wired with some single lengths of old #18 stranded, tapped from a 20 amp circuit. I wonder how hot they'd get from a 1500 watt heater?
We multi wire anythig we can. I call it networking though. We never had a complaint or problem. We allways tape them together in the panel and some boxes depending on whats going on. Some panels we put the stick on numbers on the nutrals with the corisponding breaker. Other times we put the nutral near the corisponding breaker or in order. We put the networked breakers next to each other. On our homes the 1st network is always black, red, white. Then we save blue & gray for the other.
Ortganisation is the key. Some inspectors here require grooping the networks together in all boxes. I do hate going into a old panel with a pipe packed with wires going to breakers all over and nothing is marked.
I like the warning. I should put it on the panel schedules I print out.
I would add something to it like "The system utilizes shared nutral conductors TO PROVIDE BETTER ELECTRICAL EFFICIENTY." Something to make it sound more positive. Otherwise to a homeowner it might make them think you cut corners and something is not as safe as it could be.
Or maybe "Your electrical system has been ballanced to provide you with the best service. To keep the system ballanced only have a qualified person make chanegs inside service panel or branch wiering. Failure to follow this could result in overloading and a fire hazard."
I'm with John Steinke on this one, however I think the notice is a great idea.
"I run shared-neutral circuits to save on material costs, it's not a code violation, so I save where I can."
Sarcasm aside, what benefit is there in running shared-neutrals other than saving a little wire? You can sugar-coat it any way you want.
The signs are actually a very good idea. If it were possible to say something, ANYTHING, that would keep non-electricians out of distribution panels, I'm all for it. Anyone with a screwdriver can electrocute themselves, or create a fire hazard.
My personal feelings on the matter are that someone could have a fair understanding of home wiring and still not understand the importance of having breakers in the correct positions for shared-neutral circuits.
John, how are Multi-Wire branch circuits served from a single winding affected by harmonic distortion?
The harmonics would be the same on both sides of zero and would cancel the same as current cancels in any equal current flow.
Power quality would be a concern other than a shared netral when talking about single phase services.
Dave, there are many reasons to use Multi-Wire circuits and yet the biggest reason not to is the "unqualified person" making a mistake.
A qualified individual will look at the conduit or cable entry before lifting a neutral, and if there is more than one ungrounded conducted present not tied to a common trip breaker, they would know this is the case.