MWBC to garage

[tom baker]

I am running a 20 amp 12-3 MWBC to a garage. I know I need a disconnecting means (snap switch). Is there a snap switche that can be used on a 120/240 volt circuit, or do I need to use two snap switches? I just remember from years ago there was not one that was listed for this use.

 

[AC\DC]

Leviton 1222-2W :: Toggle Switch, 2-Pole, 20A, 120/277V, Industrial Grade, White :: PLATT ELECTRIC SUPPLY

20 Amp, 120/277 Volt, 1HP at 120V or 2HP at 240V-277V, Toggle Double-Pole AC Quiet Switch, Industrial Grade, Self Grounding, Back & Side Wired - White, Cat #: 1222-2W, Mfr: Leviton

www.platt.com

These are what I use

 

[electrofelon]

I am running a 20 amp 12-3 MWBC to a garage. I know I need a disconnecting means (snap switch). Is there a snap switche that can be used on a 120/240 volt circuit, or do I need to use two snap switches? I just remember from years ago there was not one that was listed for this use.

A double pole switch will work Tom. I think you have the issue backwards, where most double pole switched say "single circuit only"?

 

[tom baker]

A double pole switch will work Tom. I think you have the issue backwards, where most double pole switched say "single circuit only"?

Probably backwards, Now I do recall discussion about single circuit only. But it’s way at the back of the brain.

 

[AC\DC]

A double pole switch will work Tom. I think you have the issue backwards, where most double pole switched say "single circuit only"?

Can you elaborate on the "Single Circuit only" got me paranoid now I don't see that in the one I use.

 

[goldstar]

Isn't one MWBC fed from a 2-P 20A breaker considered ONE circuit ?

 

[Dennis Alwon]

Isn't one MWBC fed from a 2-P 20A breaker considered ONE circuit ?

Yes for the purpose of that section anyway

 

[Dennis Alwon]

Here is the section

225.30 Number of Supplies. A building or other structure
that is served by a branch circuit or feeder on the load side of a
service disconnecting means shall be supplied by only one
feeder or branch circuit unless permitted in 225.30(A)
through (E). For the purpose of this section, a multiwire
branch circuit shall be considered a single circuit.
Where a branch circuit or feeder originates in these additional
buildings or other structures, only one feeder or branch
circuit shall be permitted to supply power back to the original
building or structure, unless permitted in 225.30(A)
through (E).

 

[roger]

225.30 doesn't really need to make mention of it although it is nice that it does. Technically a MWBC is a single circuit and the article 100 definition along with 210.4 covers it.

Roger

 

[electrofelon]

Can you elaborate on the "Single Circuit only" got me paranoid now I don't see that in the one I use.

If I remember correctly, most / all 15 and 20 amp double pole switches say single circuit only. A multi-wire circuit would be okay though. Probably quite rare to actually have two separate circuits on a double pole switch.

 

[wwhitney]

If I remember correctly, most / all 15 and 20 amp double pole switches say single circuit only. A multi-wire circuit would be okay though. Probably quite rare to actually have two separate circuits on a double pole switch.

So, how do the electrons at the switch know the difference of whether the loads on the ungrounded conductors going through the switch are sharing a neutral or not?

Seems to me that electrically all that matters is the voltage between various parts of the switching mechanism. 210.7 requires a common disconnect (handle-tie) whether the two circuits have separate neutrals or are a single MWBC.

Cheers, Wayne

 

[electrofelon]

So, how do the electrons at the switch know the difference of whether the loads on the ungrounded conductors going through the switch are sharing a neutral or not?

Seems to me that electrically all that matters is the voltage between various parts of the switching mechanism. 210.7 requires a common disconnect (handle-tie) whether the two circuits have separate neutrals or are a single MWBC.

Cheers, Wayne

Maybe electrons are smarter than we think?

Seriously though, I fully agree. I would be curious how that came to be such a common requirement in the switch destructions.