Electric Service to Metal Building, Grounding, Etc.

[whitedogone]

Thanks for your responses, things are a little more clear. Once more question though....why do some sub-panels have main breakers, while others don't?

The NEC requires you to have a disconnet " at a readily accessible location either outside of a building or inside nearest the piont of entry of the dservice conductors." A subpanel some where in the same structure does not.

 

[whitedogone]

I'm a dirt farmer so don't rely on me for electrical advice, but legally if there are more than 'x' number of breaker openings in a box, it needs to have a main breaker. I think 'x' is very low, like 4 or so, maybe only 2....

At one time the limit was 6.

--->Paul

Wrong answer

 

[whitedogone]

Look here at figure #2

Two Buildings – Common Service, Grounding Requirements | IAEI Magazine Online

 

[whitedogone]

As to the question on building steel. It must be BONDED. If livestock are to be housed that means a equipotential plane with is covered in Art. 547

 

[Ken45101]

As to the question on building steel. It must be BONDED. If livestock are to be housed that means a equipotential plane with is covered in Art. 547

For those of us who are not electricians, can you please explain "bonded" and "equipotential plane"?

Thanks

 

[Ken45101]

Neutral and Ground are bonded only at the main panel, do not bond at the sub panel. Seperate neutral and ground are run from main panel to sub fed panel. Neutral to neutral, ground to ground.

All the breaker boxes I've bought for barn installation only have a common strip for neutral and ground. Am I missing something here?

Make sure main panel has proper breaker for the sub feed panel, minus the derating for the wire (if direct burial vs metallic conduit, or non metallic conduit).

Can you say more about "derating". I've buried 10/3 w/ground (UF) for a 30 amp circuit and 12/3 with ground for a 20 amp circuit (stupid Lowes was out of 10/3). Am I expecting too much capability?

If the neutral were to fail, the return path would be through the ground lead.

You never want ground to be carrying current, anywhere...

While I agree 100%, four times the neutral supplying our farm has broken and was discovered laying in the tree tops. It runs from hilltop to hill top, about 200' above the road. We never noticed it. I was amazed that there was no noticeable effect. Now I tend to watch that line.

Ken

 

[Eagle Dude]

NEC Code may have changed but it doesn't mean you can't go beyond the code. Remember the Codes are a minimum requirement. If I have a breaker box away from the main service panel then I provide a ground rod for that box. I would not rely on a netural wire to provide ground on a building over 50 feet away from the main service panel. After having worked in the electrical field over 40 years I still don't like getting shocked in any way. I've had many inspectors tell me I have gone too far past the requirement, but I have never failed an inspection. You can not err on the side of safety.

 

[whitedogone]

For those of us who are not electricians, can you please explain "bonded" and "equipotential plane"?

Thanks

bonded = Connected to establish electrical continuity and conductivity

http://www.lni.wa.gov/tradeslicensing/electrical/files/currents/elc9906.pdf

http://as.doa.go.th/aedweb/lecture slides/mr viboon/grain drying/aeae-1998/pdfs/section4/409.pdf

 

[Eric_Phillips]

I have had similar discussions on a woodworking forum about this subject. There is a max number of switches that can be used before needing a main disconnect and as of about 2 years ago that number was 5. I still opted for a main disconnect because most people are used to throwing one switch not 5.

You do need separate grounding rods for a detached building. You need 2 10' rods 6' apart. Check the length of the rods but I think 10' is correct. You can also use the rebar in the foundation if you have that and I think is prefered but not mandatory.

Ken you are missing something, a second bar for the ground. You can buy boxes with one or two grounding/neutral bars. Like stated earlier the singles are for the first box where you have the neutral and ground bonded. You need two and the neutral needs to be isolated. You can buy an additional bar for most boxes.

Be careful of using waterlines as some maybe plastic. My hose has copper inside but is fed by plastic. The barn also has a plastic line.

Best thing I did was call the inspector first and talked to him about what he wanted to see. He wanted UF cable anywhere the horses would be due to the ammonia. I could run regular indoor romex on the equipment side. That had nothing to do with code but what he wanted to see and was much cheaper than rewiring.

 

[whitedogone]

I have had similar discussions on a woodworking forum about this subject. There is a max number of switches that can be used before needing a main disconnect and as of about 2 years ago that number was 5. I still opted for a main disconnect because most people are used to throwing one switch not 5.

You do need separate grounding rods for a detached building. You need 2 10' rods 6' apart. Check the length of the rods but I think 10' is correct. You can also use the rebar in the foundation if you have that and I think is prefered but not mandatory.

Ken you are missing something, a second bar for the ground. You can buy boxes with one or two grounding/neutral bars. Like stated earlier the singles are for the first box where you have the neutral and ground bonded. You need two and the neutral needs to be isolated. You can buy an additional bar for most boxes.

Be careful of using waterlines as some maybe plastic. My hose has copper inside but is fed by plastic. The barn also has a plastic line.

Best thing I did was call the inspector first and talked to him about what he wanted to see. He wanted UF cable anywhere the horses would be due to the ammonia. I could run regular indoor romex on the equipment side. That had nothing to do with code but what he wanted to see and was much cheaper than rewiring.

Best advice so far in this thread. I might be a bit bias....being a electrical inspector and all