Originally Posted by
John Steinke
Feeders get a separate ground wire ... an insulated one ... period. (Well, not quite .... the ground wire need not be insulated if a cable, like SER, is used as the wiring method). Whether you need a bushing is determined by the wire size alone - not what it's used for. You don't get to use the pipe as your ground wire for feeders - only branch circuits.
John,
You need to go read: (from the 2008 NEC - underlining and bold are mine)
215.6 Feeder Equipment Grounding Conductor.
Where a feeder supplies branch circuits in which equipment grounding conductors are required, the feeder
shall include or provide an equipment grounding conductor
in accordance with the provisions of 250.134, to which the equipment grounding conductors of the branch circuits shall be connected. Where the feeder supplies a separate building or structure, the requirements of 250.32(B) shall apply.
Now you need to go to:
250.134 Equipment Fastened in Place or Connected by Permanent Wiring Methods (Fixed) — Grounding.
Unless grounded by connection to the grounded circuit conductor as permitted by 250.32, 250.140, and 250.142, non–current-carrying metal parts of equipment, raceways, and other enclosures, if grounded, shall be connected to an equipment grounding conductor
by one of the methods specified in 250.134(A) or (B).
(A) Equipment Grounding Conductor Types. By connecting to
any of the equipment grounding conductors
permitted by 250.118.
(B) With Circuit Conductors. By connecting to an equipment grounding conductor contained within the same raceway, cable, or otherwise run with the circuit conductors.
Exception No. 1: As provided in 250.130(C), the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.
Exception No. 2: For dc circuits, the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.
FPN No. 1: See 250.102 and 250.168 for equipment bonding jumper requirements.
FPN No. 2: See 400.7 for use of cords for fixed equipment.
Now you need to go to:
250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor
run with or enclosing the circuit conductors
shall be one or more or a combination of the following:
FPN: For effective ground-fault current path, see 250.2 Definition.
(1) A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded;
insulated, covered, or bare; and in the form of a wire or a busbar of any shape.
(2) Rigid metal conduit.
(3) Intermediate metal conduit.
(4) Electrical metallic tubing.
(5) Listed flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).
d. Where used to connect equipment where flexibility is necessary after installation, an equipment grounding conductor shall be installed.
(6) Listed liquidtight flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. For metric designators 12 through 16 (trade sizes through ½), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. For metric designators 21 through 35 (trade sizes ¾ through 1¼), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in trade sizes metric designators 12 through 16 (trade sizes through ½) in the grounding path.
d. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).
e. Where used to connect equipment where flexibility is necessary after installation, an equipment grounding conductor shall be installed.
(7) Flexible metallic tubing where the tubing is terminated in listed fittings and meeting the following conditions:
a. The circuit conductors contained in the tubing are protected by overcurrent devices rated at 20 amperes or less.
b. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).
(8)
Armor of Type AC cable as provided in 320.108.
(9)
The copper sheath of mineral-insulated, metal-sheathed cable.
(10)
Type MC cable where listed and identified for grounding in accordance with the following:
a. The combined metallic sheath and grounding conductor of interlocked metal tape–type MC cable
b. The metallic sheath or the combined metallic sheath and grounding conductors of the smooth or corrugated tube-type MC cable
(11)
Cable trays as permitted in 392.3 and 392.7.
(12)
Cablebus framework as permitted in 370.3.
(13)
Other listed electrically continuous metal raceways and listed auxiliary gutters.
(14)
Surface metal raceways listed for grounding.
There are *A LOT* of choices *OTHER THAN* ...
Feeders get a separate ground wire ... an insulated one ... period.
