DETACHED BUILDINGS
Single circuits run to a detached building which provide a proper and adequate equipment grounding method does not require a separate grounding electrode. 250.32(A), Exception.
A feeder ran to a separate building that DOES CONTAIN a proper and adequate equipment grounding method (e.g. conduit or separate EGC):
• DOES require a separate grounding electrode.
• The neutral bus bar in the subpanel is NOT bonded in this case. (To do so would provide multiple paths for neutral current to flow to ground.)
• The grounding electrode conductor is sized according to Table 250.66, but does not have to be larger than the largest ungrounded supply conductor. 250.32(E)
A feeder ran to a separate building that DOES NOT have a metal path between the two buildings, such as conduit or a water pipe, and no EGC is run with the feeder, then:
• A separate grounding electrode IS required.
• DO bond the neutral bus and grounding bus together.
• The grounded (neutral) conductor of the feeder must not be smaller than listed in Table 250.122, but doesn’t need to be larger than the largest ungrounded conductor. 230.32
Kevin
