My father put up a pole building last fall and is now running electric lines
to it from the house. (150ft. away) He went out and bought the heavy cable
to do the job. (heavy enough for a welder) But he got three conductor
wire instead of four. (red,white,black,ground) Am I correct in telling him
that he could run the ground cable from the pole buildings box, outside, to
a grounding stake? If so what are the rules for doing so? I am pretty
electrical savy but have never installed a grounding stake. Assuming it has
to be copper? How long? what gauge?
Both he and I are hopeing this is possible since a single line of the same
gauge wire is $150.
| right now just 120, but the wire we are putting in is big enough for
| three-phase if we so choose in the future.
The wire size is not the issue for three-phase. The number of conductors
is the issue. For WYE, you need an additional conductor (blue). I think
you can do a corner grounded delta with just 3 wires (the gounded corner
would be white), but you have to be sure your equipment is rated for the
higher line to ground voltage (an ordinary 240/120 panel is not).
Where would you be getting three phase power, anyway? Utility? Generator?
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
If this is just regular 120/240 you can run a 3 wire feeder to a sub panel in a
separate building if there are no other metal paths present. In either case you
will still be driving a ground rod or some other grounding electrode.
You will ground the neutral in the pole barn, just like you would in a service
from the utility.
right now all we will be using is 120/240 and we have run the red,black and
white lines. My question concerns the bare grounding line, should it be run
back to the house with the other lines or can it just go to a grounding
stake right outside the barn.
On Sat, 8 May 2004 17:51:38 -0400, SBFan2000 put forth the notion
Local codes vary, so you should check with your local building inspector
to get the definitive answer. Having said that, there's no reason why
you can't safely ground the panel in the garage separately with a bond
to underground water pipes and/or a suitable ground rod. You will need
to make sure that the grounding source is adequate for the service. If
you end up going this route, do NOT bond the ground to the neutral bus
bar in the subpanel. Use a separate grounding bar, and do not bond any
neutral to any ground conductor. The only place the neutral and ground
are to be bonded together, is at your main service entrance.
| On Sat, 8 May 2004 17:51:38 -0400, SBFan2000 put forth the notion
|> right now all we will be using is 120/240 and we have run the red,black and|> white lines. My question concerns the bare grounding line, should it be run|> back to the house with the other lines or can it just go to a grounding|> stake right outside the barn.
| Local codes vary, so you should check with your local building inspector
| to get the definitive answer. Having said that, there's no reason why
| you can't safely ground the panel in the garage separately with a bond
| to underground water pipes and/or a suitable ground rod. You will need
| to make sure that the grounding source is adequate for the service. If
| you end up going this route, do NOT bond the ground to the neutral bus
| bar in the subpanel. Use a separate grounding bar, and do not bond any
| neutral to any ground conductor. The only place the neutral and ground
| are to be bonded together, is at your main service entrance.
The grounding in the separate building is not an option; it is required.
Further, when there is no separate grounding wire in the feed between the
builings, the neutral must also be bonded to the ground at that building
[NEC 250.32(B)(2)]. Had there been a separate grounding wire in the feed,
then there must be no such bonding [NEC 250.32(B)(1)].
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
If there are no metal paths between the house and the barn (and you never
plan any), then you only require the 3 wires you've already bought. If you
want metal paths (water pipe, phone line, CATV, etc), then running a 4th
wire would be a good idea now. The 4th wire, if you choose to run it,
doesn't have to be as large as the other three. You didn't say what size of
cable you bought (gauge), its material (cu or al), and how large of a
breaker will be protecting it. That is required in order to tell you what
size equipment grounding conductor is required.
If you run 3 wires, the barn neutral must be bonded (screwed with a green
screw) to the panel chassis. You then run a ground electrode conductor from
the neutral bus to the building ground rods. All of your circuit grounds and
circuit neutrals go to the same bus (but in separate holes).
If you run 4 wires, you must keep the barn neutral bus insulated from the
chassis (green screw not used). You also must install a separate grounding
bus if the panel doesn't already have it, and that bus must be screwed to
the chassis. The 4th green/bare ground wire from the house terminates into
this ground bus. Your ground electrode conductor to the building ground rods
also connects here. Circuit neutrals go to the neutral bus and circuit
grounds go to the separate ground bus.
the box we have has separate bus bars for everything. What I was going to
do was connect red to red, black to black, white to white, and the bare or
green bar outside to a grounding rod. The grounding bar would then be
bonded to the panel chassis and all other outlets in the barn, via the bare
Is this the right way to do it?? Just asked dad if he was going to install
3-phase and he said no, just a 240V welder.
If the above is correct, how much grounding rod should be drilled into the
If you only ran 3 wires, then it is very important that you bond the neutral
to the panel chassis with the green screw. A 4 wire feeder is better if you
can swing it, in which case you do not install the green neutral bonding
Ground rod must go into the ground 8 feet, and you probably need two of them
at least 6 feet apart. If your soil won't allow driving rods this deep,
consider a buried wire electrode (#2 copper, 20+ feet long, at least 30
inches down. It is supposed to encircle the building, but the inspector may
allow the minimum length of 20 feet.
Umm, the OP has four wires "(red,white,black,ground)". He's in
fine shape, given that the wire is large enough for the run (not
specified) and load/breaker (also not specified).
The question at hand was what to do with the ground-neutral at
the out-lying building. It's my understanding (I'm sure I'll be
corrected ;-), that if it is a *separate* building, each must
have their own ground-rods, and the ground and neutral bus get
tied together at the load end. If it's in one building, the sub-
panel (it's not a sub-panel in another structure) has the ground-
I just had an issue selling my MIL's place with a semi-attached
garage (no common wall, but sorta common roof-line). The
purchaser's inspector said they ground-neutral should be
separated, so I did it as the buyer demanded. No biggie, other
than the 2500 mile trip (this wasn't the only issue).
Your last sentence is the key, me thinks. When the trench is
open, ask the inspector what he wants to see. A loop of #2 wire
is fairly cheap. Make him happy and life gets wonderful, well at
least not *horrid*, later. I believe there are tests for such
things, but likely aren't required.
<not an electrician>
If there are 4 separate wires, then at the detached structure the panel
neutral bus and grounding bus must be isolated from each other. A separate
building is the only exception to reconnecting neutral and ground. But this
is not allowed if there is a conductive path, and the 4th wire is that
I couldn't tell from the OPs message whether he really had 4 conductors or
not. Hopefully, its SER with 3 insulated conductors and a 4th braided
actually, just to clearify, I said that I had installed a red, black, and
white, and was questioning if a ground wire needed to be run. After
thinking about it I happened to think that a ground would not be needed
since the neutral and ground are bonded. Asked a electrician friend and
sure enough, no ground needed.
| actually, just to clearify, I said that I had installed a red, black, and
| white, and was questioning if a ground wire needed to be run. After
| thinking about it I happened to think that a ground would not be needed
| since the neutral and ground are bonded. Asked a electrician friend and
| sure enough, no ground needed.
Whether a ground is needed depends on the equipment. If it has nothing
for the ground wire to be connected to, then it doesn't need it. But if
any wire is connected to the metallic chassis of the equipment, then it
needs a ground wire that is separate from the neutral wire, unless it is
not using the neutral wire for anything else and it is on a dedicated
circuit (e.g. no other equipment on the same circuit that might have
anything connected to the neutral wire). The point is so that if any
power is introduced into the neutral wire by either that equipment or
any other equipment anywhere, that power must first go to the point of
bonding before coming back along the ground wire. If that is done, then
any potential between neutral and earth ground will leak over to earth
ground at the bonding point, and not introduce a potential between any
chassis (properly connected to the ground wire) and earth ground on any
circuit. If your electrician friend based what he said solely on there
being a bond between neutral and ground, then I would say he does not
understand why there is a separate ground wire system. But if he is
aware of how the circuit and equipment is wired, he could be correct.
But that statement should never be blanketly applied to other things.
Equipment that uses 240 volts only, and does not have any 120 volt parts,
would not use the neutral wire. A typical clothes dryer does use 120 volts
for the motor. A typical stove uses 120 volts for at least some things
(and I have seen models that 120 volt elements, half on one side of the
circuit, and half on the other side). But a typical air conditioner that
is designed for 240 volts doesn't need 120 volts (and typically can't even
getit because it is usually wired on a NEMA 6-15 or 6-20 receptacle/plug
which doesn't have a neutral connection).
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
A barn is an agriculture building. You did say barn and not shop. There
were a number of changes made in the 2002 NEC for agriculture buildings that
you should be aware of.
Here they are:
547.9 Electrical Supply to Building or Structures from a Distribution Point.
(A) Site-Isolating Device. A disconnecting means shall be installed at the
distribution point where two or more agricultural buildings, structures,
associated farm dwelling(s), or other buildings are supplied from the
distribution point. For the purposes of applying the requirements of this
section, this disconnecting means shall be classified as a site-isolating
device and shall have provisions for bonding the grounding electrode
conductor to the grounded conductor.
(1) Purpose. The disconnecting means shall simultaneously interrupt all
ungrounded conductors for the purposes of isolation, system maintenance,
emergency disconnection, or connection of optional standby systems.
(2) Series Disconnects. An additional disconnecting means shall not be
required where the serving utility provides a disconnecting means as part of
their service requirements and this disconnecting means is accessible to the
user and meets the requirements of this section.
(3) Rating. The disconnecting means shall be rated for the calculated load
as determined by Part IV of Article 220.
(4) Overcurrent. The disconnecting means shall not be required to contain
(5) Accessibility. Where not readily accessible, the disconnecting means
shall be capable of operation from a readily accessible point.
(6) Grounding. The grounded conductor of the system shall be connected to a
grounding electrode through a grounding electrode conductor at the
(B) Electrical Supply. The buildings or structures shall be permitted to be
supplied by either 547.9(B)(1) or (B)(2).
(1) Building(s) or Structure(s). Where the disconnecting means and
overcurrent protection are located at the buildings or structures, the
supply conductors shall be sized in accordance with Part IV of Article 220
and installed in accordance with the requirements of Part II of Article 225.
For each building or structure, the conditions in either (a) or (b) shall be
(a) The grounded circuit conductor shall be permitted to be connected to the
building disconnecting means and to the grounding electrode system of that
building or structure where all the requirements of 250.32(B)(2) are met.
(b) A separate equipment grounding conductor shall be run with the supply
conductors to the building(s) or structure(s) and the following conditions
shall be met:
(1) The equipment grounding conductor is the same size as the largest supply
conductor, if of the same material, or is adjusted in size in accordance
with the equivalent size columns of Table 250.122 if of different materials.
(2) The equipment grounding conductor is bonded to the grounded circuit
conductor at the disconnecting means enclosure at the distribution point or
at the source of a separately derived system.
(3) A grounding electrode system is provided in accordance with Part III of
Article 250 and connected to the equipment grounding conductor at the
building(s) or structure(s) disconnecting means.
(4) The grounded circuit conductor is not connected to a grounding electrode
or to any equipment grounding conductor on the load side of the distribution
(2) Disconnecting Means and Overcurrent Protection at the Distribution
Point. Where the disconnecting means and overcurrent protection for each set
of feeder conductors are located at the distribution point, feeders to
building(s) or structure(s) shall meet the requirements of 250.32 and
Article 225, Parts I and II.
FPN: Methods to reduce neutral-to-earth voltages in livestock facilities
include supplying buildings or structures with 4-wire, single-phase
services, sizing of 3-wire service conductors to limit voltage drop to 2
percent, and connecting loads line-to-line.
(C) Underground Equipment Grounding Conductors. Where livestock is housed,
any portion of the equipment grounding conductor run underground to the
building or structure shall be insulated or covered copper.
547.10 Equipotential Planes and Bonding of Equipotential Planes.
For the purposes of this section, the term livestock shall not include
(A) Areas Requiring Equipotential Planes. Equipotential planes shall be
installed in all concrete floor confinement areas of livestock buildings
that contain metallic equipment that is accessible to animals and likely to
become energized. Outdoor confinement areas, such as feedlots, shall have
equipotential planes installed around metallic equipment that is accessible
to animals and likely to become energized. The equipotential plane shall
encompass the area around the equipment where the animal stands while
accessing the equipment.
(B) Areas Not Requiring Equipotential Planes. Equipotential planes shall not
be required in dirt confinement areas containing metallic equipment that is
accessible to animals and likely to become energized. All circuits providing
electric power to equipment that is accessible to animals in dirt
confinement areas shall have GFCI protection.
(C) Bonding. Equipotential planes shall be bonded to the electrical
grounding system. The bonding conductor shall be copper, insulated, covered
or bare, and not smaller and 8 AWG. The means of bonding to wire mesh or
conductive elements shall be by pressure connectors or clamps of brass,
copper, copper alloy, or an equally substantial approved means. Slatted
floors that are supported by structures that are a part of an equipotential
plane shall not require bonding.
FPN No. 1: Methods to establish equipotential planes are described in
American Society of Agricultural Engineers (ASAE) EP473-2001, Equipotential
Planes in Animal Containment Areas.
FPN No. 2: Low grounding electrode system resistances may reduce potential
differences in livestock facilities.
This gets more crazy every time we look at it.
The only "justification" for NOT bonding the neutral and ground at a
sub-panel is that SOME of the return current might end up flowing through
the GROUND (both real dirt and pipes as well as bare or green covered copper
I would hope that "everyone" knows that MOST of the current will "want" to
return via the metallic path closest to the supply wire. SO: most of the
current will either return via the WHITE wire or the GREEN (bare) wire which
is connected to the WHITE wire at BOTH ENDS. At worse there would be a few
volts drop between the out-building and the main house. SO WHAT? Similar
drops occur between two utility customers along the line.
"If I ruled the world," I would say that the WHITE and GREEN (bare) can be
bonded at any point where there is a connection to a permitted grounding
system (e.g.: two 8' rods, etc).
Obviously, if you leave out the GREEN (bare) wire between house and
outhouse, you definitely bond between "local" (two rods in ground) and the
Of course, I live in an area which it just isn't a problem to get ground
rods into the ground.
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