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.
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 that...
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.
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 wire.
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 ground?
"SBFan2000" wrote in message news: snipped-for-privacy@corp.supernews.com...
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 overload protection. (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 disconnecting means. (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 permitted. (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 point. (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 poultry. (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.
On Sat, 8 May 2004 16:27:38 -0400 SBFan2000 wrote: | 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? Converter?
| On Sat, 8 May 2004 17:51:38 -0400, SBFan2000 put forth the notion | that... | |> 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)].
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 screw.
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- neutral separated.
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.
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 conductive path.
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 ground.
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 wires) conductors.
BIG DEAL.
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 neutral.
Of course, I live in an area which it just isn't a problem to get ground rods into the ground.
On Mon, 10 May 2004 07:25:26 -0400 John Gilmer wrote: | Gad! | | 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 | wires) conductors. | | BIG DEAL. | | 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).
Then the green/bare grounding wire in the feeder is redundant (except for cases involving 3 phase power with a lot of harmonic load). The problem with this is that now you also introduce ground currents onto the neutral (white) wire, which the grounding (green) wire should separately handle. These are generally insignificant except during very close lightning strikes. Double bonding like that will put more surges on your electrical system in both buildings.
On Mon, 10 May 2004 07:25:26 -0400, John Gilmer put forth the notion that...
It can be a big deal. When part of the current is being carried to ground in places other than the neutral as intended, your plumbing and appliances can become energized to the point that you can get a shock if you become between a grounded object that is carrying part of a load to ground, and a better source of ground, which is only too happy to take its share through you. Another problem which I've seen first hand, is a brand new garbage disposal with bad bearings in less than a year, because the plumbing was carrying current, which apparently was also passing through the bearings.
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