replacing 3-way switches -- non standard installation


Old 01-04-13, 01:45 PM
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replacing 3-way switches -- non standard installation


I am helping my son replace decrepit wiring in a 1916-vintage house. We are now in one situation that has got me stumped.

There are two pairs of 3-way switches, one pair upstairs, one pair downstairs. At each end one controls an upstairs hall light, the other controls a downstairs light.

From downstairs there were two 2-conductor armored cables of 1930s or 40s vintage to the upstairs switchbox. (The insulation is crumbling off.)

One of the cables goes through the upstairs switchbox and powers a circuit in the attic. (There are two cables exiting the upstairs switchbox, one to the attic, the other is the switched circuit to the upstairs light.) That clearly has both a hot and a neutral. It was also wired into the upstairs 3-way switches, but we are not sure how. The other must have carried the switched circuits.

Unfortunately my son dismantled the wiring without documenting the circuits at either end. This is a mistake we have made before but don't seem to learn from!

Since it originally had been wired with two 2-conductor cables we went ahead and pulled 2 new 2-conductor cables, assuming we would be able to figure it out later. That was a big mistake!

Any suggestions on how we can avoid pulling new 3-conductor cables in addition to the supply cable to the upstairs switches and the attic?

Thanks a lot!
Bill Fletcher
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Old 01-04-13, 02:44 PM
ray2047's Avatar
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Join Date: Mar 2006
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There is no way to wire 3-way switches to meet modern code with out running some 3-conductor cables. Pre 2011 code at least one between the switches. This is because modern code requires all current carrying conductors of a circuit be in the same raceway (sheath, conduit).

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