Design calls for the existing primary underground feeders in existing underground vault, directly near existing customer owned transformer primary connection, to be T-body tapped with new conductors that run underground for a portion of the run, then up the side of a building, along the parapet roof, then down the other side of the building near the new OCPD in RGS conduit. The tapped existing feeder has existing overcurrent protection upstream on the opposite end of existing transformer, and the new conductors that are tapping off the existing feeder also has OCPD at the opposite end, and everything is rated properly per NEC. The new and existing conductors are the same size. To utilize outside taps of unlimited length, the conductors must be located outside of a building. Do you consider these new conductors outside of a building being routed on exterior of building as described above in RGS?
Outside taps of Unlimited Length - Conductors/conduit on exterior roof parapet considered outside?
- Thread starter ChargedUp
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If they're the same size you do not have a tap so no tap rules are applicable. As to your other question yes any tap condcutors run outside on the building would fall under the unlimited length tap rule.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I would give this a definite "maybe."
A smaller sized (i.e., tapped) conductor does not get overcurrent protection at the point it gets its power. That runs the risk of overheating and a fire if something bad happens along the tap conductor, since the upstream breaker is rated too high to protect the tap conductor. The NEC allows us to take that risk by mitigating the risk with distance limits and the requirement for physical protection. I believe that the "unlimited length" allowance for outside conductors, clearly a greater risk, is acceptable because if the tap conductors start a fire, it won't set the building on fire.
If the tap conductors are run along the exterior of the building, then yes they are "outside." But could they set the building on fire? Thus, my "maybe."