Electric Service to Metal Building, Grounding, Etc.

[Zinno87]

I'm in the process of running water and electric to a 30' x 60' metal building. It's all steel, shell and structural. The foundation is comprised of 12 concrete columns. They're all loaded with rebar. I'm going to run a 100 amp service to the building via aluminum feeds. Do I need to do anything to ground the building? Maybe a grounding rod driven into the ground and bonded to the structural steel? Also, if I ground the panel to the building, would this take case of all my grounding requirements?

Thanks

 

[sld]

I am not an expert, but my wood framed, wood sided detached building simply runs the copper grounds from the fuse panel out the side and into a steel rod driven into the ground.

 

[Old Paths]

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. Because you are in a seperate bulding, you are required to have ground rod(s) installed, some say it is ok to use water lines, I feel water lines carry water, ground rods carry electric.
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). Also make sure you are using 4 conductor wire to feed the sub fed panel, assuming 120/208 service.

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

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

This is a change that came about in the 2008 revision of the NEC (National Electrical Code).
Jerry

 

[bota7800]

We built a barn, 36 x 42 metal on concrete foundation, a couple years ago. I also had an existing pole building wired at the same time. Each barn had its own breakerbox . The electrical ran from the main line in (tapped before the house circuits) The electrical ran to the polebarn then to the new barn.

The electrician (a young journeyman) drove a conventional grounding rod by each building. The inspector failed it requiring the metal building grounded to the foundation rebar. Luckily, one section had not been poured yet so it was doable.

 

[Cat_Driver]

Side note always add more power than you think you need. 100 Amp goes quickly.

 

[cycle_gator]

Depending on your intended use you might want to consult with an electrician on the grounding. For example, livestock are very sensitive to stray electircal currents and may require special grounding techniques to protect them.

What "Old Paths" said is exactly correct, but isolation may not be all that easy. For example, is there a metallic water pipe connecting the new building and a current building also served by power? The pipe makes a great ground connection and may well be bonded to the neutral at the existing building.

I am studying the new code now for use in developing my own property and had not thought all that much about how things are grounded and return faults if the neutral is compromised. I will do the design myself then consult with an electrician as an insurance policy.

Anyway, best of luck

 

[SpringHollow]

i usually do not recommend bonding a ground to a water pipe (it might even be against code now) and replaced it on homes I have owned. Every so often someone runs into trouble because someone spliced plastic pipe in the water line between the electrical ground and where the water line enters the dirt. Lots of new city water lines are plastic when they replace them as well.

Ken

 

[Zinno87]

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?

 

[hr3]

A "sub panel" that has no main switch goes in the same building that it gets power from.. The "sub panel" with a main switch goes in a seperate building... "I-E" Every building with have it's own means of disconection..

Hope that helps..

 

[rambler]

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?

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