I need to put in about 10 feet of 3wire to install 3way switches. I have a
huge roll of 2wire, but no 3wire, and I doubt I will need it in the future
to justify buying a roll.
Can I run two lengths of 2wire (using only one conductor in the second
length)? They would be right next to each other, going through holes
together, so it seems to me that it should be as safe as 3wire.
Well, the SMART thing to do is just buy the wire you need (as another poster
The DUMB thing to do is what your propose (using only one wire of the pair
in one cable.)
If you insist upon using twice as much 2 conductor cable as 3 conductor
cable) then ensure that the WHITE wire of each cable are connected at both
ends. This is true whether you used a "switch loop" or you run the power
through both switch boxes and then to the controlled fixture.
John Smith ( email@example.com) said...
I once had a conversation with someone I worked with who actaully believed
this was a preferred method by electrical contractors so that they could
reduce costs by buying and stocking more 2-wire cable instead of a smaller
amount of 2-wire plus 3-wire. It must have been the contractor he was
Anyhow, here in Canada it is not allowed, and I suspect the NEC has a
similar rule as we have:
12-106 Multi- and Single-Conductor Cables
(1) Where multi-conductor cable is used, all conductors of a circuit shall
be contained in the same multi-conductor cable except that, where it
is necessary to run conductors in parallel due to the capacity of an
alternating current circuit, additional cables shall be permitted to
be used provided any one such cable includes an equal number of
conductors from each phase and the neutral and shall be in accordance
with rule 12-108.
Rule 12-108 starts off: "Conductors of similar conductivity in sizes
No. 1/0 AWG copper or aluminum and larger shall be permitted in parallel
In other words, this is not allowed for 14/2 or 12/2 situations!!!
"Never ascribe to malice what can equally be explained by incompetence."
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