in article 210.12 a3b it states cable lengths for afci devices. 14 ga. wire is limited to 50 ft. and 12 ga. limited to 70 feet between overcurrent device and the first outlet. is this to combat voltage drop or is there an issue with the afci device function and cable length? I ask because it goes on to say that dormitory units are also covered in this same length restrictions. it may be hard to have a 70 foot span between the panel and first outlet in a home but in a dormitory you could easily pass 100 feet before hitting your first outlet. if voltage drop is the issue then would we be able to run 10 gauge wires to make this acceptable correct? there is no clarification for this in the code so I have to ask.
arc fault cable length
- Thread starter billk554
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
The first issue with useing that section is that there are no listed "supplemental arc protection circuit breakers" on the market and I don't think they have even developed a standard for such a breaker.
If you had the required type of breaker, the code rule is to make sure that the conductor can flow enough current under ground fault or short circuit conditions to operate the OCPD in its instananeous trip range. The added impedance of additional lenght may reduce the current flow under ground fault or short circuit conditions to the point where the OCPD is not operating in the instantaneous range.
Inceasing the wire size for longer lengths should accomplish the same thing, but there is no provision in the NEC that lets you do that.
If you had the required type of breaker, the code rule is to make sure that the conductor can flow enough current under ground fault or short circuit conditions to operate the OCPD in its instananeous trip range. The added impedance of additional lenght may reduce the current flow under ground fault or short circuit conditions to the point where the OCPD is not operating in the instantaneous range.
Inceasing the wire size for longer lengths should accomplish the same thing, but there is no provision in the NEC that lets you do that.
- Status