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Dual switch light

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Posted by: from Edmonton
4/17/2017 at 12:48:41 PM

I have a light at the bottom of a staircase. It has a dual switch, One at the top and one at the bottom of the staircase. It seems to be on breaker #11 at the panel as when this breaker is off the light does not work.

Problem is I traced the wiring from the light and it seems to feed from a different line running back to breaker #27. After further investigation it seems there is two separate devices fed from the same box, each fed from a separate breaker.

I do not think this is legal???

REPLIES (8)
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Robert from Electrilight Ltd. in Oakville
Date/Time4/17/2017 at 4:08:10 PM

3-WAY switches are not wired the same as other switches. Not sure why you think this is a problem. But there are no rules regulating wiring boxes from 2 breakers... we do it everyday. Honestly there are so many DIY people and handymen who think they know how to wire things safely and properly, until someone gets electrocuted. We see the problem everyday in the service world. Luckily you tested and retested to ensure all wires were dead. Also the neutral can act like a live wire under a few conditions. If you are unsure what to do, call a licensed electrician to help.

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Date/Time4/17/2017 at 5:38:32 PM

Hi Ronald,

It just seems that someone has junctioned a device unnecessarily in the junction of the light. Not uncommon. There is a code that states that all circuits in that box should have an interlocked breaker so no power is left energized after a circuit is shut off but there is a few that sneak by and it is done the way you've found. Good you caught it.

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Robert from Electrilight Ltd. in Oakville
Date/Time4/17/2017 at 8:54:02 PM

What CEC rule would that be? I am curious to read that. I believe you would be confusing it with counter top outlets that require a tie handle on the breaker for 2 circuits controlling one device. We have been wiring homes since 1986 having 2 circuits in a 14/3 cable feeding lighting to 2 circuits, but never had tie handles on those.

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Date/Time4/17/2017 at 11:47:35 PM

Hello Ronald,

There is no issue with having more than one power supply in a junction, light or switch box. It is called a multiwire branch circuit (MWBC) and is very common.

John Kuehnl-Cadwell

Master Electrician

Datawise Solutions Inc

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Date/Time4/17/2017 at 11:50:02 PM

Further to my previous post, it is also permitted to have two separate circuits in a junction, light or switch box. This is not exactly the same as a MWBC, but is still permitted.

John Kuehnl-Cadwell

Master Electrician

Datawise Solutions Inc

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Date/Time4/18/2017 at 9:32:56 AM

Yes it's legal to bring two circuits into a junction box for a switch, once the tab is broken on the switch between both feeds the dual switches should work fine. The two switches should feed two separate light fixtures etc.

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Date/Time4/21/2017 at 8:33:22 AM

Thank you for posting!

I have brought this question up with the electrical safety authority in the past and in residential because lighting loads aren't as heavy unlike commercial and industrial, a shared neutral is commonly found. As for the breaker, if light is de-energized when only one breaker is off then you are only feeding from one. Some times multiple feeders are terminated in same switch gangs.

Hope this helps.

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Date/Time4/23/2017 at 2:34:15 PM

Get it looked at by a proper electrician and "fix"...to save money if running a new circuit is to expensive there are now wireless switches available for reno work.

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