Calling all electricians- Sharing neutral on split wired circuit ?

[David L Morse]

Could someone put this in a drawing. I can't see where no current is traveling back to the breaker box in the neutral when using a 120v circuit ...

These might help:

Improper Multiwire diagram.JPGMultiwire diagram.JPG

[Andrew Seemann]

The other thing to remember about split/multi wire circuits is that if you disconnect one of the hot wires, the neutral can still be carrying current from the other hot. In a correctly wired modern split/multi wire circuit, the breaker handles are tied together, so that both hots are de-energized at the same time.

However, in an old box before the breakers were required to be tied together (or just weren't tied together), or in an old screw-in-fuse box, or where some futz 1960's handyman just tied into a random neutral without tracing it, you can have a neutral carrying current when you might not expect it, especially where they used conduit or greenfield and the circuits wires aren't grouped like they are in romex. Very early, I learned the hard way never to assume that a neutral wire was not energized, unless I had dropped the main breaker.

[David Ruhland]

Davids images should help clarify why you need to use a DUAL POLE BREAKER as some one else had indicated.

[John Goodin]

Surprisingly, I see multi-wire circuits without a tied breaker all the time in new construction. It used to be in the disposal dishwasher circuits but now it is common when the house has two furnaces in the attic. 12/3 is run and the hots are separated in the attic. The building inspectors let it go but I have to write it up.

[Frank Pratt]

Don't know about the NEC, But CEC require a 2 pole breaker for a 3 wire circuit feeding a split receptacle, but if a 3 wire circuit is feeding discrete loads then they can be fed from separate breakers. They still have to be on different lines in the panel though.

[Jim Becker]

Don't know about the NEC, But CEC require a 2 pole breaker for a 3 wire circuit feeding a split receptacle, but if a 3 wire circuit is feeding discrete loads then they can be fed from separate breakers. They still have to be on different lines in the panel though.

That last part is important and without a tied breaker, someone could easily move one side to the same buss while rearranging things in the future and cause risk. Having them adjacent and tied makes sure that can't happen.

[Art Mann]

David Morse's first illustration is erroneous in my opinon because it appears to show that the two hot legs do not originate from the same place but are 180 degrees out of phase with respect to neutral. It should show that the two 120VAC legs are coming from the same place but through different breakers or fuses. One should be very careful to avoid confusion.

[Frank Pratt]

David Morse's first illustration is erroneous in my opinon because it appears to show that the two hot legs do not originate from the same place but are 180 degrees out of phase with respect to neutral. It should show that the two 120VAC legs are coming from the same place but through different breakers or fuses. One should be very careful to avoid confusion.

The look right to me. The 1st (labelled improper) shows both breakers connected to the same line, while the 2nd pretty clearly shows the correct connections. In the 1st, both lines are in phase & so the neutral load is additive. The 2nd shows them connected to the 2 lines that are 180* out of phase & so the neutral currents are subtractive.

[Frank Pratt]

That last part is important and without a tied breaker, someone could easily move one side to the same buss while rearranging things in the future and cause risk. Having them adjacent and tied makes sure that can't happen.

That's why it's important, for those who don't have a clear understanding of how to to it right, to keep their hands out of the box. Codes are written on the premise that those doing the work are properly trained & certified.

[Art Mann]

You are right! I don't know how I missed it.

The look right to me. The 1st (labelled improper) shows both breakers connected to the same line, while the 2nd pretty clearly shows the correct connections. In the 1st, both lines are in phase & so the neutral load is additive. The 2nd shows them connected to the 2 lines that are 180* out of phase & so the neutral currents are subtractive.

[Jim Becker]

That's why it's important, for those who don't have a clear understanding of how to to it right, to keep their hands out of the box. Codes are written on the premise that those doing the work are properly trained & certified.

That's very true, Frank, but the reality is that many folks do dive in...so if things are setup by the original professional with the breakers bonded, it helps insure someone later on doesn't mess things up. (easily)

[Frank Pratt]

That's very true, Frank, but the reality is that many folks do dive in...so if things are setup by the original professional with the breakers bonded, it helps insure someone later on doesn't mess things up. (easily)

And I should have phrased it a little differently to emphasize the importance of being sure to gain the required understanding. Because yes, people are going to DIY & that's a good thing. It's a bit of a touchy subject for me because of all the bad stuff I see at work. A lot of it presents an extreme & immediate danger.

[Jim Becker]

I hear you Frank. There were some darn scary things in this house when we first moved in...and some of them were installed by "pros". Sheesh!

[Matt Mattingley]

I hear you Frank. There were some darn scary things in this house when we first moved in...and some of them were installed by "pros". Sheesh!

So did you upgrade all your plug outlets to tamper resistant and all your bedroom plugs fed by arc fault and all wet locations by ground fault breaker‘s? Well you brought it up to code? Did you pull a city inspection for your new wiring situations?

Did you hire any pros with license certificates and have licensed certificate inspectors double checking any of the work performed by yourself or certified professionals??

Do you obtain a electrical certificate of qualification?

[Jim Becker]

Matt, the major remediation work we needed/wanted was done by a licensed electrician and yes it was inspected. We were not required to bring everything to code in the existing structure, such as with ARC-Fault, although I did that later for what became our adopted daughter's bedrooms. Our addition was also handled by a licensed electrician...although that dude installed every single outlet upside down like they were in commercial space. That wreaks havoc with wall warts! He also left some switches/feeds unmarked that are there for future use which I'm not happy about. The service to my shop and panel was installed by a licensed electrician and inspected. Yes, I install my own shop circuits and no I do not get them inspected.