ECN Forum Forums General Topics of the Trade General Discussion Area First Time I ever saw this!

Why are you folks who are against multiwire brach circuits against using them? Is it a liability issue for when the HO later on "upgrades" his electricial system and improperly reconnects the MWBC to the busbar?

I've become a big fan of this type of homerun simply because it saves me money on wire, and on time installing the circuit (s). Why would you not like to make more money? The whole single phase system in a single family dwelling is itself a MWBC!!

Now, the only situtation where I wouldn't use a MWBC is for a computer ckt or some other sensitive electronic circuit, like home theatre/ sourround sound set up where harmonics could be an issue.

Shockme, I can't speak for others, but I have a personal bias in favor of KISS ... keep it simple, stupid ... especially in situations where the wiring method comes 'pre-packed" (romex, MC, etc.), or the system is likely to be worked on by lesser qualified folks (homes, apartments).

I do, in fact, often use shared neutrals. in particular where I am running all the circuits new.

Unfortunately, I've had to sort out too many places where somebody had only heard that 'it was OK to share a neutral' ... then went about re-arranging white wires at random. Or combining several neutrals into one, for a single wire back to the panel.

I suppose my 'moment of truth' came the day I mis-connected some white wires in a ceiling junction box ... and then had the honor of smoking a change machine someone had cobbled onto the circuits; killing the three 'hots' associated with that neutral was not enough to prevent that appliance from getting a nice dose of over-voltage.

I guess the 'lesson' here is that 'all neutrals are not the same,' or, 'we really MUST identify our neutrals.'

Yet, I have seen far too many situations where someone added to a system by grabbing any hot, and any neutral. This works just fine ... until the next problem arises.

Actually, none of the newer ones do.

The manufacturers realized that the xenon lamp ignitors and house lighting dimmers cause too many noise and harmonics issues, with the modern electronic automation systems.

However, it was at one time common practice to have projection consoles with built-in subpanels to serve the projection loads.

As we've discussed before, my bias is against MW branch circuits, where as Reno and many others have related, trouble can easily arise.




[This message has been edited by mxslick (edited 01-03-2007).]

Found a fan motor for a furnace wired using the bare ground as a neutral! The origional neutral had a break in it so someone just used the bare ground.
I've also opened a neutral connection in a j-box not knowing that it is a shared neutral. You hear "Hey, what happened to my computer?" coming from the next office!