Proper wiring of furnace 'Emergency' switch

onawhimFebruary 5, 2008

I live in New Brunswick, Canada; have P.S. Knight's 'Electrical Code Simplified' for 2006-2010, and have tried to study it well. But I've run up against a situation that isn't covered in his book, and that no-one can seem to answer.

We have a fuel-oil furnace in the basement with what I'll call a Master On-Off Switch close to it. I want to add a 'Remote' Emergency On-Off Switch at the head of the basement stairs so the furnace can be shut off from there.

This is not only because it's required by the Code, but because it will give some peace of mind to my aging parents who are finding it difficult to get down the basement stairs when 'there's a strange noise in the furnace'.

(The furnace is about 14' from the Service Entrance, but the shortest distance from the furnace to the head of the stairs is 45'.)

I (briefly) considered moving the Master Switch to a position at the bottom of the basement stairs, which would satisfy Code requirements. However, the 'ageing parents & stairs' problem would remain, and I wondered about what the furnace man would say to it.

He said - and I see his point - that repairmen want the main furnace On-Off switch as close to the furnace as is practical.

He agreed that a 'remote' emergency switch should be installed at the head of the stairs, and said just "wire it off the Master switch."

But that brings up a grey area. Mr. Knight says junctions are 'usually' made in light, switch or plug outlet boxes.

He does not specifically say junctions cannot be made in a Master On-Off switch housing/box, but the 'feeling' I get is that you shouldn't do it.

So, the plan is install a junction box close to the Master Switch and run 12-2 cable to the Remote Switch...which leads to the question...before or after?

Should the Remote Switch control the Master Switch, or the Master control the Remote?

My philosophy is that the Master On-Off Switch at the furnace should do just that - shut off the furnace and everything connected to it, including a Remote Switch.

But what does the Code say?

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I'm not expert in all details of the NEC much less the CEC, but I can't think of any reason it matters which order the power goes through the switches.

You probably have figured out that you just want to add a simple single-pole (two-terminal) switch in series with the original one. If you run NM (Romex) cable, to the top of the stairs mark the white wire with black tape or marker to indicate that it may sometimes be hot.

I also think it should be ok to make the wire junction in the switch box if it has room for more wires and one wire nut.

    Bookmark   February 5, 2008 at 5:51PM
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I would have two single pole switches in series, ie either switch being off kills the circuit. I'd avoid a switch loop for the top of the stairs, wire is cheap enough that you can rewire the whole mess. If you go to the electrical supply shop, you can get an emergency shut-off switch, it is red and looks a lot like a fire alarm.

    Bookmark   February 5, 2008 at 5:54PM
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Thanks for the answers...but I dunno about 'cheap' cable. One hundred feet of Romex 14/2, NMD-90, FT-1 cable runs around $43.00-$45.00 + 14% tax...that's as much as a tank of gas!
And you don't want to know what 4-wire cable for a dryer runs a foot...

    Bookmark   February 5, 2008 at 10:03PM
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I also like the idea of two SP switches in series. I wouldn't use 3 way switches as you can't label them "ON" and "OFF". Make sure and use 14/2 AC90 where the cable runs from the closest switch to the furnace itself. That's a code requirement. And yes, any device box can also function as a junction box.

    Bookmark   February 5, 2008 at 11:14PM
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You want two single pole switches in series so that either one can shut off the furnace and not have it turn on by the other switch. You don't want the furnace to be turned on from the top of the stairs when you are working on it.
There is no problem making connections in switch boxes to extend to a second switch. I think it is a good idea and don't any code issues with this setup.

    Bookmark   February 6, 2008 at 8:16AM
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onawhim, with all the talk about 14-2, make sure to check what the demant of the furnace is. My furnace at home requires 20AMPS, which means no 14AWG wire. The habitat for humanity house I am helping on right now has a furnace that only rewuires 15AMP.

In both cases, they are wired the same. From panel to a j-box directly above the furnace, then 1 cable down to the master switch and then on to the power supply. from the jbox the other cable goes to another shutoff switch at the top of the stairs (basic switch loop). in the jbox, the incoming power from the panel gets sent up the switch loop and returns via the white wire (wrapped with black tape) and connects to the black for to the furnace. the neutral from the panel gets wire nutted to the neutral from the furnace and all the grounds get wire nutted togehter and bonded to the jbox.

    Bookmark   February 6, 2008 at 8:20AM
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Thanks again for the responses - you folks have described what I'd already planned to do.

As for the mention of 14/2 cable - that was merely an example of 'cheap' wire. I knew the price because I'd bought a roll earlier in the week.
12/2 is required by the 2006-2010 Code for fuel-oil furnaces, and a 20A breaker.

As for 'AC90', if you mean Armored Cable, it isn't required(at least in New Brunswick) for furnace wiring.
Unless the cable runs below 60" above the floor, or is 'subject to mechanical damage'(Rule 12-518), unprotected Loomex can be used.
If it's low enough or gonna get whacked, it has to be run inside 7/16" flexible conduit.

    Bookmark   February 6, 2008 at 9:30PM
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"Unless the cable runs below 60" above the floor, or is 'subject to mechanical damage'(Rule 12-518), unprotected Loomex can be used. "

Never seen electrical cable entering a residential furnace blower motor that was higher than 5' off the floor. I'm not talking about Highboys used in heated garages. I'm talking a home gas furnace. Must be a New Brunswick thing, because it sure isn't a Manitoba thing.

    Bookmark   February 6, 2008 at 10:09PM
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