Outbuilding wiring

[nate379]

I need a little help on how to connect a wire to an outbuilding.

I am going from the main panel in my garage to a subpanel about 100ft from garage to a shed.

Just a 30 amp 240v feed, I already ran the 10-3 UF wire last year. Going to be for an air compressor (15 amp) and a few lights/outlets.

I'm a little confused with what bonding neutral means and what I need to do for this setup. I know hot and hot off the breaker but someone want to explain what I do with ground and neutral?

Do I hook either from the main to the sub panel?

 

[sammm]

I am fairly handy, but have a lot of respect for electricity...especially around the main service panel. This might be a good time to call in a pro. Just my .02

 

[Charles (in GA)]

You need a bar to attach neutral wires to, and that bar should not be screwed directly to the box. Rather it should be insulated from the box. This is where the neutral would attach, and from this bar, any neutrals you would need for lights, receptacles, etc would come from.

In addition, you would need another bar that is screwed directly to the box. This would be the ground bar. You would connect the bare ground wire from the UF cable to it, and would run grounds for receptacles and light fixtures from this.

Charles

 

[sberry]

Also ground rods attach to the aux ground bar, at the main, assuming its a main service entrance panel both can be connected to the neutral bar or the bare can be attached to an aux ground bar if it has one.

 

[nate379]

I'm not spending $500-1000 for something I can do myself.

I am fairly handy, but have a lot of respect for electricity...especially around the main service panel. This might be a good time to call in a pro. Just my .02

 

[nate379]

Ok apparently I have confused everyone.


I run hot and hot from the main to the sub panel of course.

I'm going to guess same applies to the neutral.

Now ground, do I run ground from main to sub and ground rod out there? No ground rod out there? or no ground from main to sub but ground rod for sub?


I have run a few sub panels before, but I'm just trying to find out what the "correct NEC" way is. The ones I have run I just ran everything off the main and didn't put a ground rod at the sub panel.

 

[oleguy]

I need a little help on how to connect a wire to an outbuilding.

I am going from the main panel in my garage to a subpanel about 100ft from garage to a shed.

Just a 30 amp 240v feed, I already ran the 10-3 UF wire last year. Going to be for an air compressor (15 amp) and a few lights/outlets.

I'm a little confused with what bonding neutral means and what I need to do for this setup. I know hot and hot off the breaker but someone want to explain what I do with ground and neutral?

Do I hook either from the main to the sub panel?

.as said befor you need an isolated from the box neutral buss,and a bonded to the box ground bar at the sub panel in shed.the neutral is bonded at the main panel only.that is neutral and ground together.seperate in all sub panels.

 

[Nostraquedeo]

Charles has addressed your questions, with the exception of installing a ground rod at the shed.

 

[nate379]

Ok, but in my main box ground and neutral are not bonded though.

.as said befor you need an isolated from the box neutral buss,and a bonded to the box ground bar at the sub panel in shed.the neutral is bonded at the main panel only.that is neutral and ground together.seperate in all sub panels.

 

[6768rogues]

We do it one of two ways.
We can run separate ground and neutral wires from the source and not put a ground rod at the destination.
Or we can run a neutral from the source and ground the destination panel to ground rods.
Having a ground wire to the destination panel and having a ground rod can cause problems. If the ground potential at the two locations is different, it will turn the ground wire connecting the two panels into a current carrying conductor.

 

[Nostraquedeo]

^ This "main box" is where the underground or overhead service comes in? All of the neutrals and grounds are isolated in your "main box"? Do you have a picture of the "main box"?

 

[Nostraquedeo]

See link for additional clarification.

http://www.garagejournal.com/forum/showthread.php?t=63670

 

[Charles (in GA)]

Ok, but in my main box ground and neutral are not bonded though.

If you have an outside disconnect, they are bonded at that point, and then continue separately inside to the panel. If you do not have an outside disconnect, and the first disconnect after the meter is the one in your main panel, then they should be bonded at that point.

In any case, you want to carry the neutral and ground separately to the outbuilding. Yes, install a ground rod at the outbuilding and also connect it to the ground bar that is screwed or bonded directly to the metal of the subpanel box.

Charles

 

[nate379]

Yup, I do have an outside disconnect.

Thanks for the help.

Also didn't know about needing 2 rods. Guess I will have to go buy another one.

 

[akdiesel]

Sorry to add a l little bit more of confusion.

6768rogues said "If the ground potential at the two locations is different, it will turn the ground wire connecting the two panels into a current carrying conductor."

Charles said "Yes, install a ground rod at the outbuilding and also connect it to the ground bar that is screwed or bonded directly to the metal of the subpanel box."

This sounds like conflicting info. I respect those that know this field and offer suggestions for us less experienced. It seems that the answer should be one or the other with comments as mentioned.
Is the potential to send current through a second ground rod is possible? Or am I miss under standing the comment?
Nate sorry to jack your thread but I am confused on this.

 

[walrus]

We do it one of two ways.
We can run separate ground and neutral wires from the source and not put a ground rod at the destination.
Or we can run a neutral from the source and ground the destination panel to ground rods.
Having a ground wire to the destination panel and having a ground rod can cause problems. If the ground potential at the two locations is different, it will turn the ground wire connecting the two panels into a current carrying conductor.

Not under 2008 code, seperate ground and neutral, 2 rods for a detached structure

 

[nate379]

2 rods, how deep do they need to go?

I have an 8ft rod, can I cut it in 1/2? I honestly think there will be no way I can pound in something 8ft without digging a hole and filling it (so much rock around here it's nuts)

 

[Rudeboy 1]

2 rods, how deep do they need to go?

I have an 8ft rod, can I cut it in 1/2? I honestly think there will be no way I can pound in something 8ft without digging a hole and filling it (so much rock around here it's nuts)

No, you can't cut them in half. That would defeat the purpose. I drive ground rods all the time and I use a bosch hammer drill with rod attachment bit.

 

[nate379]

Defeat the purpose of what? You can't tell me that 2 rods 4ft in the ground aren't acting as a "ground" vs 2 rods that are 8ft in the ground.

 

[Norcal]

Defeat the purpose of what? You can't tell me that 2 rods 4ft in the ground aren't acting as a "ground" vs 2 rods that are 8ft in the ground.

"Code" requires a 2nd rod if you cannot prove 25 Ohms of resistance or less, the testing equipment is expensive so it's cheaper to drive 2 rods, if you encounter rocks it is permitted to drive them at a angle, cutting a rod in half is hack work, & if not willing to do the job right may I suggest battery powered lighting......


NEC art 250.56 2008 Ed.

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
single electrode consisting of a rod, pipe, or plate that does
not have a resistance to ground of 25 ohms or less shall be
augmented by one additional electrode of any of the types
specified by 250.52(A)(4) through (A)(8). Where multiple
rod, pipe, or plate electrodes are installed to meet the requirements
of this section, they shall not be less than 1.8 m
(6 ft) apart.
FPN: The paralleling efficiency of rods longer than 2.5 m
(8 ft) is improved by spacing greater than 1.8 m (6 ft).

 

[nate379]

Do you have the paragraph that says the rod needs to be 8ft?

I spent a whole weekend getting a 1.25" pipe 6ft in the ground for something else and that amounted to me digging a hole about 3.5ft of it too. I don't think without digging down or something other than a big sledge I will be able to get it 8ft down.

 

[Norcal]

Do you have the paragraph that says the rod needs to be 8ft?

I spent a whole weekend getting a 1.25" pipe 6ft in the ground for something else and that amounted to me digging a hole about 3.5ft of it too. I don't think without digging down or something other than a big sledge I will be able to get it 8ft down.

(G) Rod and Pipe Electrodes. The electrode shall be installed
such that at least 2.44 m (8 ft) of length is in contact
with the soil. It shall be driven to a depth of not less than
2.44 m (8 ft) except that, where rock bottom is encountered,
the electrode shall be driven at an oblique angle not
to exceed 45 degrees from the vertical or, where rock bottom
is encountered at an angle up to 45 degrees, the electrode
shall be permitted to be buried in a trench that is at
least 750 mm (30 in.) deep. The upper end of the electrode
shall be flush with or below ground level unless the aboveground
end and the grounding electrode conductor attachment
are protected against physical damage as specified in
250.10.

 

[sdowney717]

Not under 2008 code, seperate ground and neutral, 2 rods for a detached structure

In 2006, we ran 100 amp 240v to a subpanel in a separate building with 4 copper wires, 2 hots, 1 neutral, 1 ground in conduit.
I also asked the inspector st the time and he said we did not need the ground rod at the new panel, since we had run a ground from the main panel. I had already driven on and did hook it up anyway since it was easy.

So has the code changed? And if he does not put in the ground rod, what difference would it make seeing likely hundreds of thousands of buildings dont have them at these subpanels?

ALSO, just recently like 2009, we added 400 amp service and split off 200 amp to what used to be a main panel. We added a ground bar in the box and ran 4 wire service entrance cable to the old box from the 200 amp fused disconnect next to the new box at the new service entrance. So the house has 2 large circuit boxes. The old box you can shut power off at the new box location 75 feet away with the disconnect switch. It is a nice switch with huge fuses. (had 3 fuses so I suppose it could have been for 3 phase power)

The inspector told use to not hook up the old ground rod at the old original box that was served by the new 4 wire feeder SEC. Just use the new SEC ground feeder wire.
Was he wrong?

 

[Rudeboy 1]

Do you have the paragraph that says the rod needs to be 8ft?

I spent a whole weekend getting a 1.25" pipe 6ft in the ground for something else and that amounted to me digging a hole about 3.5ft of it too. I don't think without digging down or something other than a big sledge I will be able to get it 8ft down.

Hammer drill. You'll get them down there.

 

[Rudeboy 1]

So has the code changed?

Yes, the code changed for detached buildings in the 2008.

 

[Falcon67]

Yes, the code changed for detached buildings in the 2008.

Yes, mine is wired to older code - 3 wires, box in detached bldg treated as a service entrance, single 8' rod.

I think it should be a "right of passage" requirement for nubie home electricians to drive at least one 8' rod into the earth with a 2 lb hammer!

 

[Rudeboy 1]

Yes, mine is wired to older code - 3 wires, box in detached bldg treated as a service entrance, single 8' rod.

I think it should be a "right of passage" requirement for nubie home electricians to drive at least one 8' rod into the earth with a 2 lb hammer!

Haha! I agree, only they should only be able to pound it in with an old pair of linesman pliers.

Really though, I've sledged in more ground rods than I care to remember.

 

[nate379]

Would be at it next year!

I used a 25lb sledge to drive the 1.25" pipe and that fought me the whole way.

 

[Rudeboy 1]

Would be at it next year!

I used a 25lb sledge to drive the 1.25" pipe and that fought me the whole way.

My humble opinion is that you need to rent a hammer drill. It'll make quick work of those pesky electrodes.