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Using 2 Pole breakers to feed 2 120v circuits.


jcrack_corn
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I've searched and read, but I just need a quick clarification or Link that i can read!

Just moved into a house that the guy did everything "commercial" style (foundation/HVAC/Electrical)...I'm used to single circuits being fed from 1 pole breakers.

This house has all circuits being fed from 2 pole breakers (of course I'm not talking about the 240v circuits)....so example...bedroom #2 and #3 are fed from a single 2-pole CB, and I assume at some point (havent dug around the attic) the red branches off to bedroom 2 and black to bedroom 3, neutral shared).

All the CBs are also propery "physically" connected so that both poles are de-energized together.

To me the disadvantage of doing this is that I have to turn off 2 circuits together (instead of isolating one room/circuit)....i know this is necessary so that the shared neutral is always dead with this setup...

However, what is the ADVANTAGE to doing residential wiring this way, the only one I could come up with this that all of the wiring is VERY neat and clean....is there another that i'm missing?

THANKS!

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Crack,

It reduces the amount of cable and the labor to install it. Called a multiwire circuit. For instance, one 12/3 cable can be run for two circuits instead of installing two separate 12/2 cables. The handle tie actually is not required except when the two circuits are run to the same duplex outlet.

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Originally posted by jcrack_corn

I've searched and read, but I just need a quick clarification or Link that i can read!

Get "Electrical Inspection Of Existing Dwellings" by Douglas Hansen. Also, if you don't own one, get a copy of the latest edition of the National Electrical Code.

Just moved into a house that the guy did everything "commercial" style (foundation/HVAC/Electrical)...I'm used to single circuits being fed from 1 pole breakers.

This house has all circuits being fed from 2 pole breakers (of course I'm not talking about the 240v circuits)....so example...bedroom #2 and #3 are fed from a single 2-pole CB, and I assume at some point (havent dug around the attic) the red branches off to bedroom 2 and black to bedroom 3, neutral shared).

As Neal said, these are called multi-wire circuits. They're extremely common in commercial wiring where it's important to keep to a minimum the number of wires that you run through a conduit.

All the CBs are also propery "physically" connected so that both poles are de-energized together.

That's required when you have more than one device or equipment on the same yoke. The most common example is the dishwasher and disposal. Otherwise, there's no requirement for the connecting device at the breakers.

To me the disadvantage of doing this is that I have to turn off 2 circuits together (instead of isolating one room/circuit)

And that's precisely why multi-wire circuits aren't generally wired like this. In a home it isn't a big deal, but in a commercial installation, you most definitely don't want to have to shut off two circuits in order to work on one.

....i know this is necessary so that the shared neutral is always dead with this setup...

It's not "necessary" according to the NEC.

However, what is the ADVANTAGE to doing residential wiring this way, the only one I could come up with this that all of the wiring is VERY neat and clean....is there another that i'm missing?

THANKS!

It saves time and materials. If you're running wire in conduit, the advantages are even greater since you've got to contend with derating.

- Jim Katen, Oregon

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