ECN Forum
Posted By: sparky66wv Equipotential Plane - 05/22/01 10:52 AM
My Buddy Joe M. (EC) has a job to wire a dairy barn. The concrete slab was poured before they even called him for the job, so needless to say, the equipotential plane was left out.

Having grown up on a dairy, I know first hand the importance of an EP.

Is there a fix for "retrofitting" an EP to an existing slab? Jackhammer down to the rebar? What does Joe (and I) do?
Posted By: sparky Re: Equipotential Plane - 05/22/01 11:35 AM
i suppose that there should be one, as not many builders are calling for an electrician before the pour.
[Linked Image]

has he built/poured an entrance ramp yet?

[This message has been edited by sparky (edited 05-22-2001).]
Posted By: sparky Re: Equipotential Plane - 05/22/01 11:57 PM
maybe 250-50(d) would do?

[Linked Image]
Posted By: sparky66wv Re: Equipotential Plane - 05/23/01 02:54 AM
Yeah, a Ground Ring...and bond *somewhere* to the rebar as well?

Steve, IAEI has a similar thread and I posed the same question there...

Posted By: sparky66wv Re: Equipotential Plane - 05/23/01 02:03 PM
Seems I'm getting completely ignored at the IAEI BB... Musta made an as* out of myself the last time...

Screw it... It's too much effort to do things right when no one else cares...

... OK I'm a little calmer now... I've posted it as its own thread... maybe that'll help...

[This message has been edited by sparky66wv (edited 05-23-2001).]
Posted By: sparky Re: Equipotential Plane - 05/23/01 03:31 PM
those guys make me wonder how i ever made master!
but now that you've thrown a grounding issue into the mix, i've gotta at least lurk there
[Linked Image]
(obsessive compulsive, yeah!)

on the subject, look at 250-32 (e)
Posted By: sparky Re: Equipotential Plane - 05/23/01 04:14 PM
well Virgil, no soap yet!

As a point of discussion,this is a good example of the NEC basically pushing it's wishes on other trades.
Once the code is made, it is somehow thought to be accepted practice by those trades.
However,the word usually gets out via us tradesmen in the trenches, myself i'm pro-ufer,etc..and try to convince who i can of being needed before the pour.
I have found no other mode of communication, and as yet have not seen any AHJ site 547-9 as a violation to the point of tearing up a pour ( now that would be something!) [Linked Image]

I also must add, that 547-9 is somewhat biased to chickens here. I'm sure there's a chicken association or something that could chime in!
My hens should write an ROP!

[Linked Image]

[This message has been edited by sparky (edited 05-23-2001).]
Posted By: Mike Re: Equipotential Plane - 05/23/01 05:14 PM
Don't feel bad. I posted the "sizing feeder conductors" thread on the IAEI. Get many opinions, but still don't know what the consensus is. [Linked Image]
Posted By: sparky Re: Equipotential Plane - 05/23/01 06:41 PM
man , i think you've come close to some of Ben's posts there! I am Chicken Steve there,take it from me, be careful where you stick your neck out

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Posted By: Glenn Re: Equipotential Plane - 05/23/01 11:32 PM
Sparky, and others,

I am guessing that the IAEI BB is only for people like us that have been on these other BB's.

It is my opinion that the "Big Guns at the IAEI BB", mentioned by someone on these other BB's, are some-what muffled by their home office.

In the IAEI NEWS magazine, usually only CMP members answer specific questions with "their own" opinions.

If someone reading a post on the IAEI BB posted by a CMP member, everyone would take that as being the opinion of the NFPA 70 ( NEC )and be gospel. The NFPA ( not a CMP member) must make all rulings.

I'm feel quite sure those CMP members would very much like to make comments, But I don't blame them for not making comments.

There has been some very good, and some very bad, opinions on these BB sites.

I've made bad comments also.

I wish everyone would use NEC Sections to back-up their opinions and mention which NEC Year they are using.

Sort-out the BAD opinions and read the NEC for a understanding of the GOOD opinions.

Posted By: sparky Re: Equipotential Plane - 05/24/01 02:43 AM
i can sense the point you pose in the posts there , but short of the ROP's , that BB has the ear of Batterymarch Park.
Posted By: sparky66wv Re: Equipotential Plane - 05/24/01 03:00 AM
In their defense, with the new thread I received some useful answers.

I'm with Mike on the 100A Feeder thing though! Guess I'll use #2 SER Al on 'em until I tick off an AHJ!
Posted By: rmiell Re: Equipotential Plane - 05/24/01 03:46 AM
You guys must remember, the IAEI forum is hosted by the Michigan Chapter, not the International Office. I e-mailed Phil Cox a question about the IAEI membership bonus point program, and he replied back to me. He had not heard of that forum. So, it's up to us to make sure that our replies are factual, and give article & section numbers when required.

Rick Miell
Posted By: sparky66wv Re: Equipotential Plane - 05/24/01 04:14 AM
Uhhh..2 out of 3 posters are ECN members...
They already knew me... (Thanks Steve and Don... Rick too) JD Dewitt the only non-ECN poster, that I know of...

Steve, you're the Bonding and Grounding guru anyway; may as well have the thread here amongst buddies as to talk between us over there... I'll suggest the Ufer in the entrance ramp idea,... What is a voltage gradient ramp? I kinda know what it is for, but no idea otherwise... Details...I need details! [Linked Image]

Posted By: sparky Re: Equipotential Plane - 05/24/01 11:08 AM
If anything else, the depth and detail of the responses are worth reading in the IAEI BB. Many lead me to investigate the current ROP's , where said issues may be in the process of being addressed. This is testimonial to the 'chat level' there, so i understand why it's a 'take no prisoners' room. [Linked Image]

So Virgil,
I've been struggling with 250 for some time, ask a lot of Q's, that's all. what's 'voltage gradient', i suppose the term implies that stray voltage could not exist in different readings given the amount of bonding.
note the same term is applied to pools in 680-22 and the intent of it being an isolated entity.
Consider also the theory, in that only energized equipment can constitute a return path, the point being that the bonding of such items, and/or it's direct line of sight back to the power source would be what is most pertinent to bond. Note rop # 3720 mentions Mich State U as having done studies on the topic, that would be good info if we could access it.

The pad being poured, i would simply make the best of the situation here. There is no harm in running a #2cu around the pad, loop it thru as many G-rods as you can, maybe a bag or 2 of bentonite, and hit at least all 4 corners of the pad's rebar via J-hammer at points where the sill plate will hide the damage. Note the article does not go into detail on HOW this bonding is done....

Note 250-32(e) is for a reason, probably to exclude any opportunity for parrallel paths.

hope this helps, maybe others will comment on the fix for this, i call this the NEC's "field of dreams" mentality, assuming other trades ( or manufacturers)will acknowledge their wishes.
It would seem this requirement would be just as easy as requiring cows to sing the national anthem on sunrise.. [Linked Image]

have you ever said "equpotential plane" to a farmer? most would probably tell you to land it elsewhere....

[Linked Image]

[This message has been edited by sparky (edited 05-24-2001).]
Posted By: resqcapt19 Re: Equipotential Plane - 05/24/01 02:44 PM
The connection to ground is not what is important here. The bonding of everyting together to make sure there is no voltage between anything that the cows can contact is what needs to be done. That means the concrete must be bonded to the electrical system. Cows are very sensitive to small amounts of voltage and it will cause loss of milk output.

The voltage gradient ramp is a system to reduce any stray earth voltage between the inside and outside of the barn to a level that the coew can't detect. It is often accomplished by installing conductive rods bonded to the building bonding system on a 30° to 45° angle into the earth at the entrances to the building. The deep end is away from the building. This should reduce any voltage gradient to a level that the cows won't feel. Remember that the step potentional for a cow is between front and back feet.
Posted By: Bill Addiss Re: Equipotential Plane - 05/24/01 06:31 PM

Remember that the step potentional for a cow is between front and back feet
That's a good point to bring up as We 2 legged creatures might not think of that. The whole 'Bird on a Wire' question (as discussed many moons ago) may have a completely different answer if it was 'Cow on a Wire' [Linked Image]


I'll take a look around and see what I come up with. I think I remember a short Article on it in EC Magazine a ways back and it was a topic of prolonged (sometimes Humorous) discussion in one of the Safety Listserves I subscribe to.

[Linked Image]
Posted By: sparky Re: Equipotential Plane - 05/24/01 07:56 PM
that might be useful
I stand corrected, thank you.
perhaps some of the 'fixes' that would accomodate an existing dairy farm would apply here?

[Linked Image]
Posted By: Bill Addiss Re: Equipotential Plane - 05/24/01 10:56 PM

Here's some links to info that I was able to find. I'll keep looking for the EC Article.
Too bad you don't live in Wisconsin Virgil

Posted By: sparky Re: Equipotential Plane - 05/25/01 12:36 AM
Good links Bill!
Note the peak load readings on one link were all N to G, water bowl to flr, feed bin to flr, etc.
There seems to be much focus on N to G , and metal objects. So would the effect be lessened by substituting composites for conductables , and running all on 220V ?

[Linked Image]

[This message has been edited by sparky (edited 05-24-2001).]
Posted By: Anonymous Re: Equipotential Plane - 05/25/01 02:02 AM
>would the effect be lessened by substituting conductables for composites,
No. Composites are better as they do not contribute to the problem.

For example, you will not find stray voltage from a plastic water cup to the floor or from a dry wooden gate to a concrete wall.

>and running all on 220V?
If the stray voltage is coming from something bad like cracked, wet insulation on a wire, then 220 V won't help.

But if the problem is from neutral current, then obviously using 220 greatly reduces the neutral current.
Posted By: sparky66wv Re: Equipotential Plane - 05/25/01 03:23 AM
I spent a year+ in word...BRRRRRRR! (My wife is a cheesehead, from Sheboygan...)

Great info and links guys... I'll pass this info along, and remember it for any future reference...

Posted By: sparky Re: Equipotential Plane - 05/26/01 01:23 PM
we in VT also make a lot of cheese, but i suspect that there are more NY cows employed than VT cows.
maybe VT cows could compete given rubber boots?

[Linked Image]
Posted By: sparky Re: Equipotential Plane - 05/28/01 12:31 AM
Of interest , and out of concern for the cows well being, i did notice a 110V fencer at a farm today. They have a rod on one leg, and the fence on the other. I did wonder about it having the rod in the barn's milk room.
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