An electrician installs a 100A subpanel in a detached garage using a 3-wire feeder (two hots, one neutral) and bonds the neutral to the ground bus at the subpanel. What is the primary safety risk here?
Answers
AThe subpanel will not have 240V available
BObjectionable current will flow on the neutral and metal enclosures back to the main panel
CThe breakers in the subpanel will trip instantly
DThe ground rod at the garage will overheat
Correct answer: B — Objectionable current will flow on the neutral and metal enclosures back to the main panel
NEC requires a 4-wire feeder (separated neutral and ground) to detached buildings to prevent the neutral current from traveling on the equipment grounding path.
MIFOTRA exam practicealigned to NFPA 70 / IEC 60364·4 marks·Hard