Grounding Electrodes Question

[ksmith846]

We just started a new 20,000 sq ft 2 story bank.

The Engineer has a detail showing how they want the ground rods to be installed.

They are requiring to install 3/4" ground rods at three locations 30 feet apart with 30 feet of rod at each location. They also want the system tested using a fall of potential test to prove 5 ohms of resistance.

We sent an RFI to them asking why they have detailed this installation this way. Answer was this is the only way to acheive 5 ohms.

I have never come across this before......I am pretty sure 5 ohms can be reached without the overkill......?????

Is this really necessary?

 

[Dennis Alwon]

The 5 ohms is very difficult to achieve. Wetness and solid chemicals can change those numbers. So I am guessing they have done a 3 point fall of potential test and have been successful with the system. One ground rod will get 98 ohms here.

 

[cdslotz]

Does the spec call for that to tested by a third party independent agency?
That can be expensive.

 

[Cavie]

Do the testing in the rainy season or hire a water truck.

 

[ksmith846]

Does the spec call for that to tested by a third party independent agency?
That can be expensive.

Yes it does, but I excluded those costs in my quote.

 

[cdslotz]

How can you exclude it when it's in your spec? Usually if it's in the grounding spec, it's in other sections as well.
I bid a job last week where the independent testing was $67,000.

 

[mcclary's electrical]

Be glad it's not a cell site or sub station. Some of them are 1.0-2.5 ohms. Very hard to acheive. Hundereds of 30 ft. rods.

 

[ibew501ed]

what the heck is a 30' ground rod??:-?

 

[mcclary's electrical]

what the heck is a 30' ground rod??:-?

I've seen 60' rods




http://www.cpccorp.com/deep.htm

 

[infinity]

Sounds like a big waste of someone's money. Even after all of that you'll still have to use a CEE if there's 1/2" or larger rebar in the footing.

 

[ksmith846]

How can you exclude it when it's in your spec? Usually if it's in the grounding spec, it's in other sections as well.
I bid a job last week where the independent testing was $67,000.

Easy......"Pricing excludes all costs for any third party testing required per plans and specs. All required testing will be billed directly to the owner upon invoicing from third party."

This particular set of plans is actually very vague on most items. For example there is no spec on devices, but they had time to draw up excessive requirements for the electrode system.

 

[ksmith846]

Sounds like a big waste of someone's money. Even after all of that you'll still have to use a CEE if there's 1/2" or larger rebar in the footing.

I agree on the waste of time comment.......and we do have a CEE and water pipe as well.

 

[ksmith846]

It's just a bank......why would they need such a requirement anyhow???

 

[mcclary's electrical]

It's just a bank......why would they need such a requirement anyhow???

Some engineers belive it helps protect electronics during lightning strikes. I bid a TV & electronics rent to own store, they wanted (3) 20' 3/4" rods, 25 feet apart in a delta configuration, cadwelded with bare 4/0 copper. All this for a 400 amp service

 

[ksmith846]

Some engineers belive it helps protect electronics during lightning strikes. I bid a TV & electronics rent to own store, they wanted (3) 20' 3/4" rods, 25 feet apart in a delta configuration, cadwelded with bare 4/0 copper. All this for a 400 amp service

I think I could get on board if I were building that type of store, but not A Bank.

 

[Cavie]

what the heck is a 30' ground rod??:-?

3- 10' copper ground rods screwed together with a threaded coupling.

 

[ksmith846]

3- 10' copper ground rods screwed together with a threaded coupling.

That's what I will be using

 

[rich000]

It's just a bank......why would they need such a requirement anyhow???

It could be that they have a data center in there with sensitive equipment. Maybe they have electronic transactions going through there (credit card, online banking, etc.). Plus, all their security and surveillance.

Also, if this is what the customer wants, and it was in the specs when you bid it, then give it to them.

 

[iwire]

It's just a bank......why would they need such a requirement anyhow???

I can't help but ask ..... why do you care what they want, you bid it so install it.

I think it is a waste as well but I earn a living installing electrical equipment so extra work is not a bad thing.

 

[ksmith846]

I can't help but ask ..... why do you care what they want, you bid it so install it.

I think it is a waste as well but I earn a living installing electrical equipment so extra work is not a bad thing.

We are going to install them. I was never trying to get out of installing them. I was just trying to utilize this medium to gain a better understanding of why it is required. That is why I RFI'd the Engineer in the first place. I asked why they wanted it and they answered back with "it is the best way to acheive 5 ohms". I wanted a little more insight therefore my query on this site.