Pulling wire through existing conduit

Discussion in 'Electrical Forum discussion & Blog' started by nelsonba, Nov 20, 2008.

  1. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    I need to install a 3-way switch for a stairway. I want to avoid tearing out the wall. Right now there is a switch at the top of the stairs that operates a light at the bottom, but that's it. I'd like to replace that switch with a 3-way switch and add a 3-way switch at the bottom. I should be able to get the bottom one in with little demolition. Is it possible to pull new 3-way wiring through existing conduit for the switch at the top? House was built in 1931. Wiring is metal conduit with two wires inside. I haven't looked at this run yet, but I'm guessing it's the smaller size conduit. Just wondering if this was a common solution for this problem?

    Thanks
  2. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    If you can get from the switch of the light to the new switch location it should be easy enough.

    The wiring details depend on the existing wiring and if you come from the light ot the switch.

    Must have been a high end house to be conduit in 1931.
  3. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    I think the wiring is referred to as "BX". Basically two wires that are inside a metal flexible tube.
  4. Billy_Bob

    Billy_Bob In the Trades

    Messages:
    422
    If there is enough room in the conduit, yes.

    Note is is much much easier to use the old wires as pull wires and pull all new wires.
  5. maintenanceguy

    maintenanceguy In the Trades

    Messages:
    107
    Location:
    Pennsylvania
    It's probably type MC, which is very similar to the older BX.

    MC (and BX) comes with the wires already inside the metal cladding. There is not room for any more wires and you don't pull your own wires through MC (or BX). You run the factory assembled cable (wires and cladding together) from box to box and the wires that come with it are all you get.

    There is a flexible aluminum conduit, often called "greenfield", that looks just like MC. This comes empty and you do pull wires through it. It's not usually used between switch boxes to light fixtures though.
  6. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689

    House was built in 1931 :)



    BX is cable, not conduit, so no.

    You can still do it but you will use a new and improved version of the BX.

    You will need to get a path from the existing switch or light to the new switch location...possibly both
    Last edited by a moderator: Nov 20, 2008
  7. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    Can you do it without opening up walls?
  8. Old Coot

    Old Coot New Member

    Messages:
    15
    What Billy_Bob said. The two existing wires inside of the MC/BX likely are likely really "fat" with old-style insulation. Try this: kill the circuit, carefully disconnect old wires at both ends and see if you can move the old wires back/forth just a little. If you can, I don't understand why you couldn't use the old wires to pull as many new wires as you need using modern THHN whose insulation is relatively thin and slippery. The O.D. of modern #12 THHN is substantially smaller than the antique #14 you probably have.
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    Don't you just love the Do-It-Yourself help given on some of these web sites?

    Rolling on the floor laughing at some of these answers. :D :D

    Why not just install a pull chain keyless with a string at the top and bottom of the stairwell? We call this a hillbilly three way and you don't even have to change anything. :p :p
    Last edited by a moderator: Nov 22, 2008
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    switches

    I think you would have to be VERY lucky to pull new wires through a BX sheath, given the turns it usually took to get from point A to point B. And even luckier if the BX actually went between the two boxes you need for the switch.
  11. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    988
    Location:
    NY State, USA
    I am laughing at the suggestion of pulling the conductors out of old BX and pulling new ones in.

    It is hard enough to pull off an 8" section of sheathing off that old crap. :rolleyes:
  12. brownizs

    brownizs In the Trades

    Messages:
    196
    Location:
    Springfield, IL
    Short answer no. You will have to open up some walls, or pull the moulding that runs along the top edge of the risers to run wire, then will have to use a Pull Lead to bring it up the wall. From there, will have to figure how to get to the lighting to pull the new up to date wire. It can be done, but there is some work involved.

    We still have not pulled new wire for the ceiling lights in the 2 bedrooms, and split the bathroom off to its own circuit, due to the amount of work needed to pull the wiring, and update it. Same for the other lights through out the house. All the outlets have been done to get rid of the old Greenield.
  13. Old Coot

    Old Coot New Member

    Messages:
    15
    I am laughing at the suggestion of pulling the conductors out of old BX and pulling new ones in.

    My suggestion was merely to try that approach as a last resort. The attempt will cost nothing but a little time and (with a lot of luck) it just might work. Interesting that someone would laugh at that, but hey, it's a free country. :cool:
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    laugh

    We can laugh at it, because we KNOW it will not work and the suggestion is laughable to even try. It will not even take any lost time, because it will be apparent as soon as he grabs hold of it and pulls. The fish may keep bumping the dam, but we can laugh at his attempt to knock it down, regardless of what the song says.
  15. WV Hillbilly

    WV Hillbilly New Member

    Messages:
    178
    Location:
    WV
    If I'm not mistaken there is a wireless kit available to make a single switch light into a 3 way . If you don't want to tear up walls and/or spend a lot of time & money this might be an option for you . I think the kit has a piece that screws into the existing light socket & a switch with a couple batteries in it that you just mount wherever you want . Works kind of like a remote control .
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    x-10

    X-10 makes a "stick on" switch, that works with one of their regular switches, and the controller, to make any light work from as many switch locations as you desire.
  17. ccandreva

    ccandreva New Member

    Messages:
    4
    Location:
    Port Chester, NY
    I realize this thread is 2 years old, but given everyone saying it won't work, I wanted to add that it can indeed work, because I have done it.

    Now, the trick is to not expect to be able to pull between any two random points. If you can, say, access the BX where it comes out in the basement directly below a switch or outlet, you can pull wire through the old BX and avoid breaking up old plaster. I did this with an outlet, and was able to run #12 3 conductor ROMEX®, with the ROMEX® sheath, through the old #14 2 conductor BX metal 'conduit'.

    I would be interested to know what the original poster did.
    Last edited by a moderator: Dec 7, 2011
  18. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    The X-10 system uses a electronic switch module in place of the existing switch and a "wireless" switch screwed to the wall where you need it to provide 3-way operation.
  19. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    I would bet a dozen donuts that what you thought was "BX" was in reality "Greenfield" flexible metallic conduit.
    Last edited by a moderator: Dec 7, 2011
  20. ccandreva

    ccandreva New Member

    Messages:
    4
    Location:
    Port Chester, NY
    I've since sold that house so I have no way to check. But I'm about to try it again, so in the interest of getting my donuts :) How would I confirm it is BX as opposed to Greenfield ?
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