705.12(B)(2) Taps.
Code Change Summary: New code language clarifies the existing rules on taps in relation to interconnected power source connections.
In the 2020 NEC®, the existing language on load side feeder taps was relocated and slightly reworded to provide clarity.
Section 705.12(B)(2) provides the rules on utility interactive power sources such as wind, batteries, or a PV system inverter output circuit connecting to the premises wiring system through a feeder on the load side of the service disconnect.
In the 2017 NEC®, the code language addressed “any” taps but in the 2020 NEC®, “any” was changed to “all” to make sure the code reader understands that this section applies to either existing taps with a new utility interactive power source being added, or to new taps where an existing utility interactive power source was already connected. In either case, the size of the tap conductors is affected by the current added by the additional utility interactive power source.
The size of feeder tap conductors in the above scenario is directly related to determining the amount of potential current from all sources, both utility, and the interconnected power production source.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
705.15(B)(2)(2)Taps. In systems where power source output connections are made at feeders, any taps shall be sized based on the sum of 125 percent of the power source(s) output circuit current and the rating of the overcurrent device protecting the feeder conductors as calculated in 240.21(B).
2020 Code Language:
N 705.12(B)(2) Taps. Where power source output connections are made at feeders, all taps shall be sized based on the sum of 125 percent of all power source(s) output circuit current(s) and the rating of the overcurrent device protecting the feeder conductors for sizing tap conductors using the calculations in 240.21(B).