Grounding Electrodes Question

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ksmith846

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Port St Lucie, Florida
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?
 
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.
 
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.
 
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.
 
cdslotz said:
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.
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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 said:
It's just a bank......why would they need such a requirement anyhow???
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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 said:
It's just a bank......why would they need such a requirement anyhow???
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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.
 
ksmith846 said:
It's just a bank......why would they need such a requirement anyhow???
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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.
 
iwire said:
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.
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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.;)
 
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