How did you ground your detached garage/barn?

[V-10 Killer]

I'm trying to figure out how much coppper I gotta buy for this project.
For 220v 100A service with a 150' run from meter to main panel, I was told by a local electrician to use #3 copper.
But do I need 3 runs or 4. I know I need 2 hots, one neutral, but do I need to run a ground back to the pole, or ground locally?
What did you guys/gals do?

Thanks

 

[brownbagg]

you got to run four wires and if the bldg is not attached you have to install a ground rod too.

 

[V-10 Killer]

Damn. That's what I was expecting to hear, but it never hurts to ask
I'd better start saving my pennies (to melt down)

 

[PAToyota]

Detached buildings need their own ground. So you only need the two hots and neutral between the buildings. No need to have a ground linking the two buildings - just grounding rods at each building.

 

[fefarms]

Providing 4 wires, including an equipment grounding conductor, is almost always the superior solution.

You MUST provide such a grounding conductor when there is a continuous metallic path between the two buildings, such as a metal water pipe, compressed air piping, network or telephone cable. The grounding conductor can be sized smaller than the branch circuit conductors; for a feeder protected by a 100 amp circuit breaker you can go as small as #8 copper. You MUST provide such a grounding conductor if either building is considered an agricultural building.

With one exception (for a single 20 amp circuit_, you MUST provide a grounding electrode system at EACH detached building without regard to whether you run three or 4 wires between buildings.

IF and only IF there are no continuous metallic paths between the buildings AND neither is agricultural (but you did say "barn" not "shop" or "garage") AND you CHOOSE to only run three wires between buildings, then the neutral conductor must be bonded to the grounding electrode system at the remote building. This practice may give rise to undesirable effects such as elevated voltages on exposed metal parts and discomfort to livestock.

Ground rods are vasty overrated by those who have not tested them. It can be very difficult to get a ground resistance of less than 25 ohms from a single ground rod. The code allows you to drive two ground rods 8 feet apart and assume they will be adequate, but often the resistance of the two in parallel is still more than 25 ohms. A "Ufer Ground" (rebar within a concrete slab or footer) works much better than any driven ground rod but an 8 AWG grounding conductor is still better than that.

Depending on the detached building load you have the option to save a little money by downsizing the neutral conductor relative to the "hot" conductors. One typical choice is 4 AWG hots with a 6 AWG neutral.

 

[Stuart in MN]

We need more information...

Is this a totally separate service from the house, or is the house and the new building fed from the same service? Is this a subpanel, connected to a main panel somewhere else? Since you're talking about running wire from a meter on a pole it sounds like a whole new thing.

Where is the main service disconnect? Is it a separate switch at the pole, or is it going to be the main breaker in the panel at the new building? The ground wire (technically it's called the EGC, or equipment grounding conductor) is connected at the main service disconnect, wherever that is.

For a 100 amp service, typically a #6 wire is adequate for the EGC. Is the building built yet, or is it still just a bare patch of ground? Depending on the codes in your area, you may be required to use what's called an Ufer ground instead of ground rods - basically, it's a piece of rebar 20 feet long, laid horizontally inside the concrete footing or slab. This method is called out in the 2005 edition of the National Electric Code; some parts of the country still use earlier versions that may not include the Ufer ground as a requirement, and then they probably want you to have two ground rods in the earth next to the building, five or ten feet apart (I don't have my code book in front of me so I can't be sure on the exact details.)

My guess (and this is just a guess so don't take it as gospel) you have a new service from a new meter on a pole that's separate from your house or any other existing buildings, and you're bringing the service conductors from the pole into the new building. Inside the building there will be a new panelboard, where the main circuit breaker is. If this is the case, the EGC wire is connected inside this new panelboard, and then is connected to either an Ufer ground connection in the building's footing or to a couple ground rods.

If you're already working with a local electrician, ask him about the grounding requirements to make sure you do the right thing. There are lots of variables here and it's difficult to give an absolute answer over the Internet. He can see just what your situation is in person, and will know what the local codes are.

 

[V-10 Killer]

Basically whats happening is I'm having my house wiring down my mast, thru the utility meter, and into the exterior disconnect for the house upgraded to handle 200A service (including the disconnect panel). I'm powering the detached garage from this external disconnect, running 150 feet from that disconnect to the breaker panel in the garage.

 

[wilbilt]

Detached buildings need their own ground. So you only need the two hots and neutral between the buildings. No need to have a ground linking the two buildings - just grounding rods at each building.

But my favorite NEC bathroom reader states that any such multiple ground rods (assuming all subs are fed from the same service panel) must be bonded together with minimum #6 copper. It looks like 4 wire to me.

 

[Stuart in MN]

In that case, yes you do need to run the ground conductor from the disconnect out to the new garage, along with installing ground rods or an Ufer ground at the new garage as required. The ground and neutral busses in the new panel in the garage must be kept separate from each other, and the neutral bus must be isolated from the breaker panel enclosure.

 

[wilbilt]

IF and only IF there are no continuous metallic paths between the buildings AND neither is agricultural (but you did say "barn" not "shop" or "garage") AND you CHOOSE to only run three wires between buildings, then the neutral conductor must be bonded to the grounding electrode system at the remote building. This practice may give rise to undesirable effects such as elevated voltages on exposed metal parts and discomfort to livestock.

...and people....

 

[Charles (in GA)]

The new garage ground rods must be connected together, and then to the new garage's panel, using a single, continous, un-interrupted solid gound wire of the size specified in the code (I'm too lazy to look tonite, but I think its #6). You cannot use stranded wire for the ground rods.

Much cheaper than copper for the connection to the meter/disconnect, would be to use 2-2-2-4 twisted direct burial aluminum wire. Given proper connections on each end, anti-corrosive paste on the wire and connections, you can expect years of trouble free use out of it.

Charles

 

[Aceman]

The new garage ground rods must be connected together, and then to the new garage's panel, using a single, continous, un-interrupted solid gound wire of the size specified in the code (I'm too lazy to look tonite, but I think its #6). You cannot use stranded wire for the ground rods.

You CAN use stranded #6 to ground rods. There is no requirement for solid wire.

Much cheaper than copper for the connection to the meter/disconnect, would be to use 2-2-2-4 twisted direct burial aluminum wire. Given proper connections on each end, anti-corrosive paste on the wire and connections, you can expect years of trouble free use out of it.
Charles

This is one method but it must be protected by no more than a 90 amp breaker. You cannot go to a 100 amp breaker when a 90 amp breaker is available.

I agree with Fefarms. Personally, I'd spend the extra money and bury 1 1/2-2" pvc conduit and pull 3-3awg phase/neutral conductors(#2 wire may be cheaper as #3 isn't commonly used) with a #8 grounding wire. Direct burial wire is fine but it's obviously not as protected from ground hogs/rocks cutting into it as wires sleeved in conduit. Space your ground rods a minimum of 6' apart.

 

[V-10 Killer]

I fully intend to bury this inside the proper plastic conduit from building to building, as I will be using the same trench to bury water, phone and 3/4" black iron for natural gas. I checked locally, and there doesn't seem to be any restrictions on using the same trench. I'm guessing the trench will be 100' long. I'm throwing in a rough guess of 50' for entry into the new garage, and to go up the wall and over the ceiling of my existing garage to reach the disconnect on the other side.
I did see #2 copper (single line) at Lowes the other day for around $3 per foot if I remember. The electrician I'm having do the main service work recommended #3. I'll have to see if it's readily available around here. If not, I'll go with the #2.

 

[Junkman]

Putting them all into the same trench might be OK if they are spaced apart from each other. I know that when I did this in CT, the inspector wanted each conduit to be a foot away from the other conduits. Since my trench was dug with an excavator it wasn't any problem doing this. You might want to consider one extra tube for future expansion for some presently unknown. I also installed weather heads at the tops of all my conduits, even though they weren't required. The local electrical utility uses clay packed around the wires to seal the top of the conduit. I gave them a weather head to install instead. The guys on the truck thought that was the better method, but clay is cheaper, so they don't supply weather heads. Same for telephone and cable. Cost skimping on something that you only want to do once in a lifetime doesn't make sense to me. Spend a little extra and do it as best that it can be done, and you will never regret it later on.

 

[twostory]

This web site should answer most of your questions. Just scroll down the very long page, until you see a picture of your building setup.

http://www.selfhelpandmore.com/homewiringusa/2002/accessory/detgarage/index.htm

I covers many different ways to connect power to a detached building. Note, you have to use schedule 80 PVC when the pipe is exposed. i.e. above the ground and on your building wall.

 

[FarmerSid]

I agree with what eveyone is saying but what you should do is contact your local electrical inspector and see what says. He is the person you have to please in the end so let him tell you what you need. I just recently finished a shop about the same distance away as you. In 5 minutes he told me what to use and how to do it. Also, look into using aluminum wire as your frreder wire. Alot cheaper. Here in Ontario, Canada alot of houses have their services feeding the house wired with aluminum. Using #2 for 100A and #6 for ground. Ask your inspector. He will tell you anything you need to know.

Cheers!

Sid

 

[JMURiz]

The local inspector will say what he's expecting to see. I went with #2 wire for my 100 amp sub and #4 for the ground (4 wires from the main to sub panel)...then ran solid copper from the sub panel to 2 8' grounding rods. I had to wait till the inspector failed me before I knew I had to have a dedicated ground for it.

 

[kbs2244]

Amen on seeing what the local inspector wants.
Personal experience says use both a local ground rod and a run back to the meter. I tried skimping and had to redig the trench to run a ground back.
It sure made the lights brighter. The drill ran better too.

 

[V-10 Killer]

I just stopped in Lowes today to check this out a little more. I see that they had 4/0 4/0 4/0 aluminum for $3.26/linear foot versus single 2/0 copper at 2.97/linear foot. I can certainly see the cost advantage, even if I need to run the aluminum line plus a seperate ground wire. But MAN was that cable thick LOL. I think it was all of 1 1/2" diameter. I just want to make sure whatever I buy and bury will someday power a 2 post lift, mig/tig welder, and any other 220V stuff I decide to buy. As people have mentioned, I don't want to go cheap just to go cheap and regret it later.

 

[Charles (in GA)]

You CAN use stranded #6 to ground rods. There is no requirement for solid wire. .

I agree, my bad, NEC 250.62 says either stranded or solid. My county insists on solid, guess I got that stuck in my mind.

This is one method but it must be protected by no more than a 90 amp breaker. You cannot go to a 100 amp breaker when a 90 amp breaker is available. .

I'll disagree on this. 310.15(B)(6) says for service or feeder #2 AL is OK for 100 amps. In addition, 310.16 says for AL wire #2 is OK for 100 amps if a 90C rated wire, which is very common today. Matter of fact, I have 150 ft of this coiled up out in the shop. I intended to use it for a run from a neighbors panel to her outbuilding, so she can do away with the second meter. Its a " 'round-to-it" that hasn't happened yet. It is 2-2-2-4 twisted direct burial (commonly called "mobile home service" here in the south). Its rated USE-2, RHH, RHW-2, SIS, which is a 90C cable.

If you have rocky soil, by all means, protect the cable. If the soil is clay or sand with few rocks, why bother. We've got rocks and it took about 20 years but I did have my service to the house fail due to a rock eating thru the insulation and letting moisture in causing corrosion, hot spot, etc. Three different places.

Charles

 

[Aceman]

I'll disagree on this. 310.15(B)(6) says for service or feeder #2 AL is OK for 100 amps. In addition, 310.16 says for AL wire #2 is OK for 100 amps if a 90C rated wire, which is very common today. Matter of fact, I have 150 ft of this coiled up out in the shop. I intended to use it for a run from a neighbors panel to her outbuilding, so she can do away with the second meter. Its a " 'round-to-it" that hasn't happened yet. It is 2-2-2-4 twisted direct burial (commonly called "mobile home service" here in the south). Its rated USE-2, RHH, RHW-2, SIS, which is a 90C cable.
Charles

Charles, Table 310.15(B)(6) is for feeders to dwelling units only. Not a shop, garage, or barn. Table 310.16 states #2 aluminum 75C wire is good for 90 amps. You cannot use the 90C rating because the terminations are not 90C rated. 110.14(C)(1) Breakers are only rated at 75C.

V10killer, I'd suggest finding an electrical parts house to buy your material from. Having to make do with what a Lowes or HD has on hand will only cost you more money. Copper or aluminum, either is fine, as long as you terminate it correctly.

 

[Steve in Mi]

V10killer, I'd suggest finding an electrical parts house to buy your material from. Having to make do with what a Lowes or HD has on hand will only cost you more money. Copper or aluminum, either is fine, as long as you terminate it correctly.

You have both Standard Electric and Medler Electric in Midland for electrical supplies. I'd suggest you have your electrician get pricing for you if he gets a good (?) discount.

 

[PanelDeland]

Just a quick suggestion.Run at least one extra conduit and run one seperate from what you already have for electric.In it run a cable and phone lines.If you're going to the trouble of building a doghouse then it might as well be a nice one.

 

[toolman]

When I built my pole barn five years ago I didn’t need a permit from the county. I am zoned AR. All I needed was a land use permit from my township. However I did have to stop by the county office and fill out a few questions (maybe 5) as to what I was using it for. It took about 5 min to fill out. I just told them it was being used as a storage building. It stores all of my workshop tools When I ran power to mine (30 amp service) I ran two #8 hots, and one #8 neutral thhn/thwn. Then I drove two ground rods at the pole barn and ran #6 stranded wire to the rods. I also bonded my neutral inside the sub panel with the provided strap and also ran #6 solid from the neutral to ground bar.

 

[V-10 Killer]

Edit: found it.