GEC for pole building

[JoeNorm]

If a building has a concrete slab but no footing it will either need rods or plates, correct? I need at least 100 characters so i'm still typing.

 

[tom baker]

Yes. Rods are much easier to install than a plate

 

[letgomywago]

On pole buildings with just a slab LNI Is all for the 2 rods. On a new house you have a footing with uffer or ground ring.

 

[infinity]

I agree two rods and call it a day. Although its code compliant to do so I'm not sure why anyone would ever install a ground ring for a building.

 

[ptonsparky]

I agree two rods and call it a day. Although its code compliant to do so I'm not sure why anyone would ever install a ground ring for a building.

I put one around a small building containing a standby generator and the service for a feedlot. Plus a rod at each corner.

No lightening damage. No polar bears either.
So it must have done some good.

 

[augie47]

I put one around a small building containing a standby generator and the service for a feedlot. Plus a rod at each corner.

No lightening damage. No polar bears either.
So it must have done some good.

Finally, a valid reason for ground rods... polar bear protection !

 

[Tulsa Electrician]

I put one around a small building containing a standby generator and the service for a feedlot. Plus a rod at each corner.

No lightening damage. No polar bears either.
So it must have done some good.

I take it you mean a ground ring?
I would like to here more about your thought on this.

When it comes to pole barns I do a few items other than rods. So it interest me.
That of course if you don't mind.
On lighter side. If no polar bears may be did not follow 547.10
Instead provided an anti 547.10.

 

[ptonsparky]

I take it you mean a ground ring?
I would like to here more about your thought on this.

When it comes to pole barns I do a few items other than rods. So it interest me.
That of course if you don't mind.
On lighter side. If no polar bears may be did not follow 547.10
Instead provided an anti 547.10.

It was directly below pole top transformer bank and brand new service for the lot

 

[infinity]

When it comes to pole barns I do a few items other than rods. So it interest me.

I'm curious what other things do you do besides rods?

 

[Tulsa Electrician]

It was directly below pole top transformer bank and brand new service for the lot

Thank you

I'm curious what other things do you do besides rods?

With pole barns there are many conditions of use.
Livestock was mentioned above.
I'll get back to that.
The condition of use is one item I pay close attention to.
I start with the permit issues for the structure. A lot of owner pull an agg permit to save in taxes. Then our permit is pull on top of there's. This changes wiring methods.
As far as one item I do no matter the permit is add bonding for an equipotential plane as well as metal skin bonding back to a single point.
The four cornor ground rod to form a ring peeked my interest.

I do the concrete bonding no matter what residential or agg.
A lot of people walk bear foot in the pole barn. Most pole barns are feed from feeders. So there is no isolation from the two GEC's and a risk of potential when electrical equipment is installed in the building. Another good reason for GFCI protection.

Almost everyone I do has wire mess or bars in slab. So I take a 20' of #4 bare CU, lay in the concrete slab and attach to the mess which is all tied toghter or the reinforcing bars ( re- bar). I'm not trying to create a electrode just bonding.

This conductor is attach in the panle on the EGC buss.
Along the way it goes thru an communication bond bar attached to the metal skin of the structure. The #6 to rods also run thru this comm bar.
What I have observed is that when they pour the slab it is poured up against the bottom wood at grade. This provided a isolation to the skin.
Even if it did I find it an issue of potential.

The majority of the time these end up have HVAC, water etc. Some have propane,gas etc.
Some times these slabs are poured in dirt and sometimes with a vapor barrier. The last thing I want to see is any stay voltage from an equipment ground fault to earth ( remote water pump, etc) getting into that concrete slab. Then when a person bare foot steps onto the slab and contacts any part of the metal structure there's a risk of receive a shock.
I look at it a pool install just change a few things.
With a pool the ring attaches to equipment and relies on the EGC. What is important is that it reduces the potential for shock from an equipment failure or out side source of shock potential.

For me 20' of #4 bare and fifteen minutes of my time is worth every penny.

Now if your wondering if I tie this to the drive or any other concrete attached to this slab the ansawer is yes. I insist or I install a jumper ( lack of better term) from one slab to the other. To do this I use a couple different methods depending on what's available.
I prefer #4 bar tie just like a uffer.
Again not a uffer or using as an electrode. If mess I use another 20' piece #4 cu to tie the wire mesh toghter.

When most concrete guys pour a drive they pin it to the slab with short pieces of #4 bar. I attach the #4 cu across these and have them tie mess to this or I do it my self.
the #4 re-bar if used is already tied to these and the extension from other slab. I work closely with the concrete contractor. The workers only do what there told. A box of donuts on pour morning don't hurt either. It's like an inspection. Other then the insp is buying donuts.

I do each there own way depending on application and condition of use.

Now why not a wood framed basic garage.
Simple, footing. The slab is tied to the footing. The drive is tied to slab.
The permit is taken out as a garage.

Even if a detached garage I make sure there is some tie to all poured concrete sections.

There is one exception and have found a good solution. That is a small pad for an a/c condinsor.
Code helped out there with the GFCI rule.
Now if the equipment had an issue this would resolve any potential shock to personal.
What it does not do is protect from others voltage sources from earth.
With the installation of snow feet there is no contact from grounded metal frame to slab and provided isolation. I don't feel that's it as big of an issue versus any one bare foot,wet etc. opening a big metal door on steel rollers attached to bonded metal building.

With the size of the slab that the ac unit set on does not concern me as much. I usually ask them to provide a Polly pad in line of concrete.
They find it a strange request. I respond is that not cheaper and easy to install. The GC I work for just says do it.

 

[kwired]

There is a difference though between a CEE and equipotential plane in 547 and equipotential bonding in 680.

At swimming pools the equipotential bonding is stringent in and within first 6 or 10 feet from the inside walls of the pool, where the voltage gradient would be the most severe if the bonding ended right at the wall of the pool.

In agriculture buildings we generally make a voltage gradient ramp at building openings, particularly openings intended for livestock use. Without those there potentially can be a bigger gradient at the edge of the pavement if we just suddenly stopped our equipotential bonding right there. Many these livestock have larger span between contact points than humans do and therefore are more subject to ending up across a larger voltage gradient than a human would be.

 

[mbednarik]

Just rods are sufficient. If you want something better get 10ft rods and the coupling style, with the long rods they are more effective when they are further apart (greater sphere of influence).

 

[electrofelon]

Just rods are sufficient. If you want something better get 10ft rods and the coupling style, with the long rods they are more effective when they are further apart (greater sphere of influence).

And let's just be clear that by better and more effective we mean a lower resistance to Earth. Except for perhaps some specialized applications, the resistance figure just doesn't matter and lower doesn't really even accomplish anything. A high ground resistance is just fine.

 

[JoeNorm]

Thanks for the replies. There was a comment about rods being easier but not necessarily where I am. I probably install 90% plates because any deeper than 30" and we often find solid rock.

 

[ptonsparky]

Thanks for the replies. There was a comment about rods being easier but not necessarily where I am. I probably install 90% plates because any deeper than 30" and we often find solid rock.

You just need a healthier apprentice!

 

[infinity]

Thanks for the replies. There was a comment about rods being easier but not necessarily where I am. I probably install 90% plates because any deeper than 30" and we often find solid rock.

That's a good solution.

 

[tom baker]

Thanks for the replies. There was a comment about rods being easier but not necessarily where I am. I probably install 90% plates because any deeper than 30" and we often find solid rock.

Interesting. What is the cost of copper plate?

 

[infinity]

What is the cost of copper plate?

I'm guessing that the plates are steel.

 

[tom baker]

I have never seen or installed a plate electrode. I need to look and see if you can use just one. Or is it bury two and go home?

 

[kwired]

I have never seen or installed a plate electrode. I need to look and see if you can use just one. Or is it bury two and go home?

rods, pipes or plates all require a supplemental electrode from any those mentioned in 250.52(A)(2)through (A)(8), which could include a second plate type electrode, unless you can prove the first electrode is 25 ohms or less.