NEC tap rule
NEC tap rule
(OP)
Does anyone know the emgineering/technical reasons for or historical evolution of the NEC 10ft, 25ft, and unlimited outdoor tap rule as applied to branch circuits, and the tranformer tap rule for 10ft commercial and 25ft industrial. i.e why the specific differences in tap conductor length?






RE: NEC tap rule
Also, there's practical considerations. For example, on the secondary of a transformer, you need to have some conductor length between the transformer and the downstream overcurrent protection, but the OC protection should be relatively close. Similarly, if you have an overhead line and you want to tap power off it, the base of the pole is a reasonable location to provide OC protection rather than at the top of the pole.
The tap rules address all of these issues.
RE: NEC tap rule
RE: NEC tap rule
Obviously, though, if you are changing from a really big wire to a really small wire (say, from 500MCM to #14, perhaps to power a pole-mounted light from overhead conductors), you'd need some kind of tap; you couldn't get a 500MCM to fit into a 15-amp overcurrent device. But there would also be a motivation to limit the length of such taps. Such practical considerations drove the adoption of the tap rule.
RE: NEC tap rule
RE: NEC tap rule
RE: NEC tap rule
RE: NEC tap rule
RE: NEC tap rule