Grounding and bonding at the service
At the service, the neutral connects to the grounding electrode system, and each service disconnect enclosure needs a main bonding jumper. No neutral-to-ground connection is made on the load side, except where Article 250 specifically allows it.
What the code requires
The grounding electrode conductor (GEC) connects to the service neutral at an accessible point between the load end of the service drop, lateral or service conductors and the neutral terminal at the service disconnect. The meter socket or the disconnect both comply; check the utility's rules. An outdoor transformer needs at least one more neutral-to-electrode connection.
In the 2023 lettering, 250.24(B) prohibits any neutral-to-ground connection on the load side of the service disconnect, 250.24(C) requires a main bonding jumper in each service disconnect enclosure, and 250.24(E) sizes the GEC under 250.66.
Under 250.24(D), the neutral must be run with the phase conductors to each service disconnect, even if there are no line-to-neutral loads. It must be at least the size in Table 250.102(C)(1). Having enough ampacity for the calculated neutral load (220.61) is a separate check under the service conductor rules in 230.42. In parallel runs, the neutral in each raceway must be at least 1/0 AWG. On a 3-wire delta service, its ampacity must be at least that of the phase conductors.
On the job
- Bonding neutral to ground again in a downstream subpanel, for example by leaving the panel's bonding screw installed, violates the load-side rule in 250.24(B).
- A missing main bonding jumper in a service disconnect enclosure.
- An undersized neutral on a parallel service.
- Plans or checklists using 2020 letters, (B) for the main bonding jumper or (C) for the neutral, are outdated. The 2023 letters are (C) and (D).
Exceptions that matter
- A neutral-to-ground connection on the load side is allowed only where Article 250 specifically permits it elsewhere.
What changed in 2023
The 2023 code moved the load-side bonding ban from 250.24(A)(5) to a new 250.24(B), shifting the main bonding jumper to (C), the neutral to (D), the GEC to (E) and ungrounded-system connections to (F).
Related sections
- NEC 230.42: Sizing service-entrance conductors
- NEC 250.6(A)
- NEC 250.28
- NEC 250.32: Grounding at detached garages, ADUs and outbuildings
- NEC 250.66: Sizing the grounding electrode conductor
- NEC 250.102(C)(1)
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