K8MHZ
Senior Member
- Occupation
- Electrician
IMHO, the difference is that the wire is not accessible, but the switch is. If the switch fails, it can be replaced without tearing the walls apart.
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- Thread starter mbrooke
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IMHO, the difference is that the wire is not accessible, but the switch is. If the switch fails, it can be replaced without tearing the walls apart.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
- Location
- Connecticut
- Occupation
- Engineer
You can, as long as you meet the branch circuit tap requirements in 210.19(A)(4) Ex. No. 1.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Did not know you could not.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Well I think you all know what the OP means. You cannot if you leave it on a 209 amp overcurrent protective device.
I agree that the reason the switch is allowed to be on a 20 amp circuit mostly because the load on the circuit is generally never that high and if it is then a 20 amp switch can be employed. However if the wire is 14 awg then that may not be able to be changed and the equipment grounding conductor would be smaller than required which could , in some situations , create a large impedance that may not trip a breaker in a ground fault or short circuit situation.
- Location
- Massachusetts
But we can do that
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
- Location
- Connecticut
- Occupation
- Engineer
You can, as long as you meet the branch circuit tap requirements in 210.19(A)(4) Ex. No. 1.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
I disagree, the trip curves of a 20 amp breaker do not go up to the point that the impedance of a 14 gauge wire causes the EGC to melt but not on a 12 gauge wire.
In fact 4 scenarios exist where an undersized EGC still provides ground fault protection:
1. In older NECs the EGCs were permitted to be substantially smaller for 15,20 and 30amp circuits.
2. In Canada a smaller EGC is permitted where a 12 gauge 20amp circuit can have a 14 guage ground.
3. Circuits over 30amps can have reduced size EGCs like a 60amp #6 subpanel with #10 ground.
4. Breakers for motors and AC units can be severally oversized in relation to the wire to allow for inrush. I could have an AC with an MCA of 12 amps mx breaker size 40amps and put #14 on a 40amp double pole breaker which usually have higher magnetic trip curves that single pole breakers.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
Missed that, always assumed you couldn't. That's why I come here!
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
That exception does not allow 14 wire run from the switch to the light fixture-- does it? I thought that was what we were talking about
- Location
- Connecticut
- Occupation
- Engineer
I didn't see any mention of a switch in the question about supplying a single light fixture with #14 from a 20A circuit, so I didn't consider it...but I don't see why the tap couldn't be considered as starting at the switch terminals.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
My understanding of the question was basically that you had a 20 amp cir feeding lights and then there 14 gauge wire being run from the switch to the lights. It would be a very unusual occurence for this to fit the exception, IMO
- Location
- Connecticut
- Occupation
- Engineer
I agree. The tap rule would only apply to a single luminaire.
david
Senior Member
- Location
- Pennsylvania
Just for clarification:
Are suggesting for example a 14-2 / Ground NM-B on a 20 amp branch circuit can extend from a bedroom light switch to a single bedroom ceiling light fixture outlet.
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