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Following are excerpts from the National electrical code on grounding
etc of your RV:
Any question should be referred to the code.
Table 250-122. Minimum Size Equipment Grounding Conductors for Grounding Raceway and
Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit,
etc., Not Exceeding (Amperes)
||Copper Size (AWG or kcmil)
c) Equipment Grounding Conductors Smaller than No. 6.
Equipment grounding conductors smaller than No. 6 shall be protected from physical damage
by a raceway or cable armor except where run in hollow spaces of walls or partitions,
where not subject to physical damage, or where protected from physical damage.
250-124. Equipment Grounding Conductor Continuity
(a) Separable Connections. Separable connections such as those provided
in drawout equipment or attachment plugs and mating connectors and receptacles shall
provide for first-make, last-break of the equipment grounding conductor. First-make,
last-break shall not be required where interlocked equipment, plugs, receptacles, and
connectors preclude energization without grounding continuity.
(b) Switches. No automatic cutout or switch shall be placed in the
equipment grounding conductor of a premises wiring system unless the opening of the cutout
or switch disconnects all sources of energy.
250-126. Identification of Wiring Device Terminals
The terminal for the connection of the equipment grounding conductor
shall be identified by one of the following.
1. A green, not readily removable terminal screw with a hexagonal head.
2. A green, hexagonal, not readily removable terminal nut.
3. A green pressure wire connector. If the terminal for the grounding conductor is not
visible, the conductor entrance hole shall be marked with the word green or ground, the
letters G or GR or the grounding symbol shown in Figure 250-126, or otherwise identified
by a distinctive green color. If the terminal for the equipment grounding conductor is
readily removable, the area adjacent to the terminal shall be similarly marked.
Figure 250-126 Grounding symbol.
G. Methods of Equipment Grounding
250-130. Equipment Grounding Conductor Connections
Equipment grounding conductor connections at the source of separately
derived systems shall be made in accordance with Section 250-30(a)(1). Equipment grounding
conductor connections at service equipment shall be made as indicated in (a) or (b). For
replacement of nongrounding-type receptacles with grounding type receptacles and for
branch-circuit extensions only in existing installations that do not have an equipment
grounding conductor in the branch circuit, connections shall be permitted as indicated in
- For Grounded Systems. The connection shall be made by bonding the
equipment grounding conductor to the grounded service conductor and the grounding
250-104. Bonding of Piping Systems and Exposed Structural Steel
(a) Metal Water Piping. The interior metal water piping system shall be
bonded as required in (1), (2), (3), or (4) of this section. The bonding jumper shall be
installed in accordance with Section 250-64(a), (b), and (e). The points of attachment of
the bonding jumper(s) shall be accessible.
- General. The interior metal water piping system shall be bonded to the
service equipment enclosure, the grounded conductor at the service, the grounding
electrode conductor where of sufficient size, or to the one or more grounding electrodes
used. The bonding jumper shall be sized in accordance with Table 250-66 except as
permitted in (2) and (3).
551-30. Generator Installations
(a) Mounting. Generators shall be mounted in such a manner as to be
effectively bonded to the recreational vehicle chassis.
(b) Generator Protection. Equipment shall be installed to ensure that the current-carrying
conductors from the engine generator and from an outside source are not connected to a
vehicle circuit at the same time. Receptacles used as disconnecting means shall be
accessible (as applied to wiring methods) and capable of interrupting their rated current
without hazard to the operator.
(c) Installation of Storage Batteries and Generators. Storage batteries
and internal-combustion-driven generator units (subject to the provisions of this Code)
shall be secured in place to avoid displacement from vibration and road shock.
(d) Ventilation of Generator Compartments. Compartments accommodating
internal-combustion-driven generator units shall be provided with ventilation in
accordance with instructions provided by the manufacturer of the generator unit.
FPN: For generator compartment construction requirements, see Standard
on Recreational Vehicles, NFPA 501C-1996.
(e) Supply Conductors. The supply conductors from the engine generator
to the first termination on the vehicle shall be of the stranded type and be installed in
listed flexible conduit or listed liquidtight flexible conduit. The point of first
termination shall be in a:
2. Junction box with a blank cover,
3. Junction box with a receptacle,
4. Enclosed transfer switch, or
5. Receptacle assembly listed in conjunction with the generator.
The panelboard or junction box with a receptacle shall be installed
within the vehicles interior and within 18 in. (457 mm) of the compartment wall but
not inside the compartment. If the generator is below the floor level and not in a
compartment, the panelboard or junction box with receptacle shall be installed within the
vehicle interior within 18 in. (457 mm) of the point of entry into the vehicle. A junction
box with a blank cover shall be mounted on the compartment wall and shall be permitted
inside or outside the compartment. A receptacle assembly listed in conjunction with the
generator shall be mounted in accordance with its listing. If the generator is below floor
level and not in a compartment, the junction box with blank cover shall be mounted either
to any part of the generator supporting structure (but not to the generator) or to the
vehicle floor within 18 in. (457 mm) of any point directly above the generator on either
the inside or outside of the floor surface. Overcurrent protection in accordance with
Section 240-3 shall be provided for supply conductors as an integral part of a listed
generator or shall be located within 18 in. (457 mm) of their point of entry into the
e) Power-Supply Assembly Not Less than 30 Amperes. The external
power-supply assembly shall be permitted to be less than the calculated load but not less
than 30 amperes and shall have overcurrent protection not greater than the capacity of the
external power-supply assembly.
551-32. Other Sources
Other sources of ac power, such as inverters or motor generators, shall
be listed for use in recreational vehicles and shall be installed in accordance with the
terms of the listing. Other sources of ac power shall be wired in full conformity with the
requirements in Parts A, C, D, E, and F of this article covering 120-volt electrical
551-33. Alternate Source Restriction
Transfer equipment, if not integral with the listed power source, shall
be installed to ensure that the current-carrying conductors from other sources of ac power
and from an outside source are not connected to the vehicle circuit at the same time.
Low-Voltage Wiring Methods.
1. Conductors shall be protected against physical damage and shall be
secured. Where insulated conductors are clamped to the structure, the conductor insulation
shall be supplemented by an additional wrap or layer of equivalent material, except that
jacketed cables shall not be required to be so protected. Wiring shall be routed away from
sharp edges, moving parts, or heat sources.
2. Conductors shall be spliced or joined with splicing devices that
provide a secure connection or by brazing, welding, or soldering with a fusible metal or
alloy. Soldered splices shall first be spliced or joined so as to be mechanically and
electrically secure without solder and then soldered. All splices, joints, and free ends
of conductors shall be covered with an insulation equivalent to that on the conductors.
3. Battery and dc circuits shall be physically separated by at least a
½-in. (12.7-mm) gap or other approved means from circuits of a different power source.
Acceptable methods shall be by clamping, routing, or equivalent means that ensure
permanent total separation. Where circuits of different power sources cross, the external
jacket of the nonmetallic-sheathed cables shall be deemed adequate separation.
4. Ground connections to the chassis or frame shall be made in an
accessible location and shall be mechanically secure. Ground connections shall be by means
of copper conductors and copper or copper-alloy terminals of the solderless type
identified for the size of wire used. The surface on which ground terminals make contact
shall be cleaned and be free from oxide or paint or shall be electrically connected
through the use of a cadmium, tin, or zinc-plated internal/external-toothed lockwasher or
locking terminals. Ground terminal attaching screws, rivets or bolts, nuts, and
lockwashers shall be cadmium, tin, or zinc-plated except rivets shall be permitted to be
unanodized aluminum where attaching to aluminum structures.
5. The chassis-grounding terminal of the battery shall be bonded to the
vehicle chassis with a minimum No. 8 copper conductor. In the event the power lead from
the battery exceeds No. 8, then the bonding conductor shall be of an equal size.
(d) Battery Installations. Storage batteries subject to the provisions
of this Code shall be securely attached to the vehicle and installed in an area vaportight
to the interior and ventilated directly to the exterior of the vehicle. Where batteries
are installed in a compartment, the compartment shall be ventilated with openings having a
minimum area of 1.7 in.2 (1100 mm2) at both the top and at the bottom. Where compartment
doors are equipped for ventilation, the openings shall be within 2 in. (50.8 mm) of the
top and bottom. Batteries shall not be installed in a compartment containing spark- or
flame-producing equipment, except that they shall be permitted to be installed in the
engine generator compartment if the only charging source is from the engine generator.
(e) Overcurrent Protection.
1. Low-voltage circuit wiring shall be protected by overcurrent
protective devices rated not in excess of the ampacity of copper conductors, as follows.
Table 551-10(e)(1). Low-Voltage Overcurrent Protection
Wire Size (AWG) Ampacity Wire Type
18 6 Stranded only
16 8 Stranded only
14 15 Stranded or solid
12 20 Stranded or solid
10 30 Stranded or solid
2. Circuit breakers or fuses shall be of an approved type, including
automotive types. Fuseholders shall be clearly marked with maximum fuse size, and both
circuit breakers and fuses shall be protected against shorting and physical damage by a
cover or equivalent means.
FPN: For further information, see Standard for Electric Fuses (Cartridge
Type), ANSI/SAE J554-1987; Standard for Blade Type Electric Fuses, SAE J1284-1988; and
Standard for Automotive Glass Tube Fuses, UL 275-1993.
3. Higher current-consuming, dc appliances, such as pumps, compressors,
heater blowers, and similar motor-driven appliances, shall be installed in accordance with
the manufacturers instructions. Motors that are controlled by automatic switching or
by latching-type manual switches shall be protected in accordance with Section 430-32(c).
4. The overcurrent protective device shall be installed in an accessible
location on the vehicle within 18 in. (457 mm) of the point where the power supply
connects to the vehicle circuits. If located outside the recreational vehicle, the device
shall be protected against weather and physical damage.
Exception: External low-voltage supply shall be permitted to have the
overcurrent protective device within 18 in. (457 mm) after entering the vehicle or after
leaving a metal raceway.
(f) Switches. Switches shall have a dc rating not less than the
Voltage Converters (120-Volt Alternating Current to Low-Voltage Direct
Current). The 120-volt ac side of the voltage converter shall be wired in full conformity
with Parts A, C, D, E, and F requirements of this article for 120-volt electrical systems.
Exception: Converters supplied as an integral part of a listed appliance
shall not be subject to the above.
All converters and transformers shall be listed for use in recreation
vehicles and designed or equipped to provide over-temperature protection. To determine the
converter rating, the following formula shall be applied to the total connected load,
including average battery charging rate, of all 12-volt equipment:
The first 20 amperes of load at 100 percent, plus
The second 20 amperes of load at 50 percent, plus
All load above 40 amperes at 25 percent
Exception: A low-voltage appliance that is controlled by a momentary
switch (normally open) that has no means for holding in the closed position shall not be
considered as a connected load when determining the required converter rating. Momentarily
energized appliances shall be limited to those used to prepare the vehicle for occupancy
(c) Bonding Voltage Converter Enclosures. The noncurrent-carrying metal
enclosure of the voltage converter shall be bonded to the frame of the vehicle with a
minimum No. 8 copper conductor. The grounding conductor for the battery and the metal
enclosure shall be permitted to be the same conductor.
In my article on RV batteries, I tell you to
hook the "battery negative" to the ground, if you have a positive ground system
then change that wording to be "battery positive", I intended to say to hook the
normally grounded terminal of the battery to ground along with the equipment ground. (this
equipment grounding conductor should conduct current only when there is a fault in the
system unlike the neutral which conducts the unbalanced current between the two phase
legs). Since you do not want the metal skin of your coach to act as a return path for 120v
loads, you must Isolate Neutral (Always white on 120/240v wiring) from the skin or frame
of the coach-hence an isolated buss or connection for the neutral and a grounded or bonded
connection (always green or a green stripe)to the panel and coach frame.
I recommend this bond be made at 2 or three
places on the frame with a #6 copper wire equidistant spacing as the steel frame is not a
good conductor and could give you electronic noise and possibly a little grief with some
of the heavier battery powered equipment. a good ground buss for this purpose could be
some scrap copper pipe hammered flat and bolted to the frame with a good oxide inhibitor
(never seize for instance)I will be using a stainless bolt setup but will not use the bolt
as a conductor as SS is a poor conductor.
Pigtails will probably always have red or black
for phase leg or 120v connection, but will ALWAYS have white for neutral and green for