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I live in a 90 yr old house. The basement lights are all on 1 switch at the top of the stairs. I would like to change this to a 3 way switch and add a switch at the bottom of the stairs. Am I right that all I need to do is run 14/3 from the new box/3 way switch to the current box and add a 3 way switch?

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    If the circuit is on a 15A breaker, then basically yes. If it is on a 20A breaker then you need to use 12/3. May 9, 2021 at 15:38
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    It is a 15A breaker. Thanks! Now to have fun fishing cable behind plaster and lath.
    – Jhadur
    May 9, 2021 at 16:03
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    Check with your electrical inspector about what the applicable code requires if you want to use a pair of 3-way switches to control by toggling because there are two different ways to wire this, 2-wire control and 3-wire control.* You might be able to avoid this altogether by using a smart switch at the top and a wireless switch at the bottom so no fishing of wire would be required.*electronicshub.org/2-way-switch-wiring May 9, 2021 at 16:39
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    Can you post photos of the inside of the existing switch box please? May 9, 2021 at 17:00

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Current code requires neutrals at switch locations, but provides exceptions. If the existing switch doesn't have a neutral you aren't required to remove building finish. But if the neutral is at the top of the stairs and it isn't visible to the entire floor space then you will need to extend the neutral to the new switch, which may mean 4 conductor cable or a raceway.

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  • Is it demand for new installation only or for renovation too?
    – user263983
    May 9, 2021 at 17:51
  • Exception regarding existing locations reads "shall not apply to replacement or retrofit switches installed in locations prior to local adoption of 404.2(C) and where the grounded conductor cannot be extended without removing finish materials.". So if the neutral is accessible (I.e. already at switch at top of stairs or a two wire switch loop with raceway capacity for neutral) then the exception doesn't apply. May 10, 2021 at 1:03

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