Residential Remodel

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OldSparks

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Vacaville CA USA
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Retired: Electrician, Submarine Electronics (21 years), Potable water system maintenance boss (21 years).
Existing residential structure where #12 copper is used for receptacle circuits with 20-amp breakers. Owner wants to convert an external light (which presently is tapped-off a receptacle circuit) from single switch to 3-way. Can I use 14/3 to run the new switch legs?
 
OldSparks said:
Existing residential structure where #12 copper is used for receptacle circuits with 20-amp breakers. Owner wants to convert an external light (which presently is tapped-off a receptacle circuit) from single switch to 3-way. Can I use 14/3 to run the new switch legs?
Click to expand...

No- see 240.4 D(3)

15 amp max brkr in this case if the 14/3 is used.
 
OldSparks said:
Existing residential structure where #12 copper is used for receptacle circuits with 20-amp breakers. Owner wants to convert an external light (which presently is tapped-off a receptacle circuit) from single switch to 3-way. Can I use 14/3 to run the new switch legs?
Click to expand...

No. For a 20-amp circuit, all conductors on the circuit must be #12 AWG -- even if a certain part of the circuit is a fixed load (such as lights) and can't possibly draw more than 15 amps. He would need to take the light off that circuit and find a 15A source to tap into (can't be the furnace, sump pump, or disposal). The can run the 14/3 cable from the existing switch to a new location for the second switch, to provide 3-way operation.
 
OldSparks said:
Existing residential structure where #12 copper is used for receptacle circuits with 20-amp breakers. Owner wants to convert an external light (which presently is tapped-off a receptacle circuit) from single switch to 3-way. Can I use 14/3 to run the new switch legs?
Click to expand...

You can as long as you change the breaker to a 15 amp. Depending on what code cycle you are currently on, you may need to install AFCI protection. Note, certain circumstances you may not be able to do what I described depending on what the 20 amp circuit serves.


*** Check with the AHJ. Your local codes may completely nullify what I just stated***
 
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