MWBC Question

Zuper Dave

Member
Location
Cincinnati, OH
Warning, warning, Danger Will Robins...

Warning, warning, Danger Will Robins...

Back in the day, in Data Centers, (or even in predominately flourescent lighting panels) before we got a handle on neutral harmonics, we fried a lot of neutrals. Very bad. And God have mercy on your miserable soul if you ever actually LOST the neutral. In that case, you had 208 or 240VAC running through all affected circuits. But the circuits were in series, so you usually didn't hit all the circuit components with the full 208 or 240. :ashamed1:
 

kwired

Electron manager
Location
NE Nebraska
Actually a dryer or range circuit can be...



...but I don't see any advantage to calling a dryer or range circuit a MWBC.

In my experience, mwbc wiring was taken advantage of as much as possible. Generally, there had to be a compelling reason (whether real or theoretical :huh:) to not run mwbcs. I haven't been involved in that part of the industry since before the simultaneous disconnect rule was implemented, so I don't know what the norm is now.
MWBC's are not too big of a deal to have to use handle ties or double pole breakers, three pole breakers are quite a bit more expensive than three single poles in most cases, then came the AFCI problems so MWBC's are not so common in dwellings anymore.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
In my experience, mwbc wiring was taken advantage of as much as possible. Generally, there had to be a compelling reason (whether real or theoretical :huh:) to not run mwbcs. I haven't been involved in that part of the industry since before the simultaneous disconnect rule was implemented, so I don't know what the norm is now.
Exactly the same for me. I never knew a job where they were not utilized. Even in houses. Guy I broke into the trade with would have me set J-Boxes in the attic and crawl and pull 12-3's to them and branch out from there.
 
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