A master electrician is installing a new 120/240V, single-phase service for a modular home. The home is supplied by a feeder from a remote service equipment location. Which of the following statements regarding the grounding and bonding of this modular home is correct?
- AThe main bonding jumper must be installed at the modular home's main panelboard.
- BThe neutral conductor must be bonded to the modular home's metallic enclosure at the modular home's service entrance.
- CAn independent grounding electrode system is not permitted at the modular home location.
- DThe equipment grounding conductor must be run with the feeder conductors and terminate at the modular home's panelboard.
Show answer & explanationAnswer & explanation
Correct answer: D. The equipment grounding conductor must be run with the feeder conductors and terminate at the modular home's panelboard.
For a modular home supplied by a feeder from a remote service, it is considered a separately derived structure. NEC 550.33(B) and 250.32(B) require that an equipment grounding conductor be run with the feeder conductors to the modular home and be connected to the modular home's panelboard and non-current-carrying metal parts. The neutral conductor is kept isolated from ground at the modular home's panelboard.
Why the other options are wrong
- A. Incorrect. The main bonding jumper is installed at the service equipment, which is at the remote location, not at the modular home's panelboard when supplied by a feeder.
- B. Incorrect. The neutral must be isolated from ground at the modular home's panelboard when supplied by a feeder from a remote service.
- C. Incorrect. An independent grounding electrode system is permitted and often required at the modular home location (NEC 250.32(A)).
Modular Home Feeder Grounding
When a modular home is supplied by a feeder from remote service equipment, an equipment grounding conductor must be run with the feeder, and the neutral isolated at the modular home's panelboard.
- Feeder-supplied structure.
- EGC required with feeder.
- Neutral isolated at modular home.
- Independent GES permitted/required.
Memory trick: Feeder to structure, grounding's the key, neutral's apart, for safety you see.