Required Ohms per grounding system

[dereckbc]

I mentioned nothing (Nor did the IEEE reference) about commercial appliactions. Or course we are talking MV/HV applications here.

Your printed words say differently.

IEEE 142 requires 5 ohms or less for large commercial or industrial systems and 1 ohm or less for generating or transmission stations.

 

[zog]

Ok, Large commerical, what is that to you?? What is your hang up on grounding requirements?? You know more than the IEEE Engineerers who wrote this requirement?? What is your point??

 

[don_resqcapt19]

zog,

A ground rod at a house or Taco Bell should not be discussed in the same post as a ground grid at a power plant switchyard.

I agree and that is why my question only asked for the technical justification for 5 ohm grounding system at for a " large commercial or industrial systems".

I mentioned nothing (Nor did the IEEE reference) about commercial appliactions.

You did in post #12.

IEEE 142 requires 5 ohms or less for large commercial or industrial systems ...

 

[dereckbc]

Ok, Large commerical, what is that to you?? What is your hang up on grounding requirements?? You know more than the IEEE Engineerers who wrote this requirement?? What is your point??

I am one of the many engineers that wrote the Emerald book.

 

[zog]

OK, OK it said commercial, Derek already pointed that out, what is it with you moderators and this grounding requirement?

The point is the OP asked about any requirements and I gave him one, "IEEE 142 requires 5 ohms or less for large commercial or industrial systems and 1 ohm or less for generating or transmission stations" I answered his question, you guys just have a hard time with anything that isnt in your precious NEC.

 

[bob]

you guys just have a hard time with anything that isnt in your precious NEC.

Wow !!!!!!. I did not know the NEC was mine. All you guys send $5.00 to me for using my code book. :grin: :grin: :grin:

 

[don_resqcapt19]

Zog,

OK, OK it said commercial, Derek already pointed that out

Sorry...I didn't refresh and did not see Derek's post before I made mine.

what is it with you moderators and this grounding requirement?

Maybe we just understand that it (grounding) really doesn't do what most in the industry from electricians to engineers think it does.
Don

 

[Jim W in Tampa]

5 ohms is what the customer wanted, Following the IEEE.
This is a build/design; I mean Design build project.

Long story short, the EC got caught putting in #1 awg instead of 2/0 for the ground loop. Now he wants me to write letter approving his VE from the orginal design.

I'm sticking with the orginal design.
Thanks for the help.

You can burn him on this one but very few buildings go up without changes and extras.He will get the money back on a change order.Might be wise to keep him as a friend.Also if he catches any mistakes on your part he can get even.But do what you think is best for the customer.

 

[zog]

I am one of the many engineers that wrote the Emerald book.

OK, let me get this right, you (With others) wrote that requirement and now you are saying it is worthless?? Or are you saying (Like I have been) that this only matters for MV/HV systems?

 

[dereckbc]

OK, let me get this right, you (With others) wrote that requirement and now you are saying it is worthless?? Or are you saying (Like I have been) that this only matters for MV/HV systems?

No I am not saying it is worthless, nor is there any NEC requirementt as this is a NEC forum. The only place where it is a requirement is NESC applications. The only way to make it a requirement in NEC applications is by job specifications in which case the engineer did as we found out later. As we discovered the EC used a #1 rather than a 2/0, which I say will not make one bit of difference in earth impedance.

With that said when you cross the line to HV/MV or special NEC applications, then low impedance becomes an important safety and/or operation factor.

Oh FWIW I took no part in writing any of the Green Book, just the Emerald Book. However there were many engineers that worked both projects, and info was shared

 

[brian john]

But, But, But, IF THE SPECs SAY 5 ohms 1/0, and the EC knows this going in then 5 ohms and 1/0 is required, be this a Johnny On the Spot, Data Center, Hospital or HV switch yard.

 

[dereckbc]

But, But, But, IF THE SPECs SAY 5 ohms 1/0, and the EC knows this going in then 5 ohms and 1/0 is required, be this a Johnny On the Spot, Data Center, Hospital or HV switch yard.

I agree, however if the engineer detailed the design spec?s like how many rods, where, how deep, connection method, etc and the EC used #1 rather than 1/0, and the impedance came out to say 6-ohms, then changing out the #1 to 1/0, 2/0 or even 750 is not going to change that.

So if it were my job, I would look at the overall performance of the EC. If he is doing a good job and I wanted to use him again, I would just let it slide, change the as-built prints, and let him know he owes me something providing it doesn?t effect performance and/or safety. That?s just me as I am getting more flexible with age.