Quick Hits

EPISODE 5 — Grounding Service-Supplied Systems (270.24, 270.25, 270.26)

Slide 1 — Hook "How do you actually ground a system at the service point? Today we break down the two main scenarios."

Slide 2 — 270.24(A) & (B) — the fork in the road

• (A) IF the utility provides a grounded conductor at the service point: you run that grounded conductor to each service disconnect, connect it to the grounded terminal/bus, and install a main bonding jumper connecting it to each disconnect's enclosure.

• (B) IF the utility does NOT provide a grounded conductor at the service point (but the system is grounded somewhere): you install a supply-side bonding jumper instead, routed with the ungrounded conductors to each disconnect and connected to the equipment grounding terminal/bus.

• Both scenarios need a grounding electrode conductor (sized per 270.66) connecting everything to the grounding electrode system.

Slide 3 — 270.25 & 270.26

• 270.25: If equipment is connected on the SUPPLY side of the service disconnect (per 268.82) in a separate enclosure, it still has to follow the same 270.24 grounding rules — grounded or ungrounded utility supply determines which path applies.

• 270.26: Which conductor gets grounded on an AC system — single-phase 2-wire: one conductor; single-phase 3-wire: the neutral; multiphase with a common wire: the neutral; multiphase with one phase grounded: that phase conductor.

Slide 4 — Quiz + CTA Q: "If the utility does NOT provide a grounded conductor at the service point, what has to be installed instead?" A) A grounding electrode conductor only B) A supply-side bonding jumper C) Nothing — ungrounded is assumed D) A system bonding jumper

✅ Answer: B — 270.24(B): a supply-side bonding jumper routed with the ungrounded conductors.

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