Electronics > Power & Renewable Energy

Field Mounted Switch Enclosure and Grounding/Bonding

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Ground_Loop:
Unfortunately, this is completely a letter-of-the-law compliance issue.  Technical arguments will not win at this level. I'll be headed up the chain for this one. Thanks for the support of my confirmation bias. :)

bdunham7:

--- Quote from: Brumby on September 17, 2021, 12:15:17 am ---bdunham7 seems to have some experience on the subject.   :D

--- End quote ---

Unfortunately just enough to understand the difficulty of the problem, not to offer much of a solution.  My ears perk up when I hear the term 'equipotential' because it seems to acquire some mystical meaning and the actual practicalities are sometimes lost.  At some level everyone seems to understand that 'equipotential' grounds serve a different purpose than 'fault protection' grounds, but some people seem to think that just because you call it one or the other it magically acquires some metaphysical property that distinguishes it from the other.  First, "equipotential" is a local concept and trying to extend it over any distance runs into some serious issues.  Then there is the practical issue that even though some might imagine that the two are somehow separate, they always end up connected and not always in a way that prevents the possibility of fault currents in the nominally equipotential branch.  But I'm pretty sure Ground_Loop already knows all of that and is just... |O

Sometimes if you have level-headed, common-sense people having a good faith argument you can point out that the regulation isn't completely clear in some way (subject to interpretation) and that it would be really bad to interpret it in one of those ways.  Other times you run into folks that only seem to know one thing and they have that pretty much wrong as well, but they won't let go. 

Ground_Loop:

--- Quote from: bdunham7 on September 16, 2021, 08:28:02 pm ---Is the "server room central equipotential ground bus" itself bonded directly to the grounding system of its  own power service entrance?

It seems that situations like this come down to winning an argument.  And they effectively want to bridge the air-gaps you deliberately put in the conduit for the fiber.  :palm: 

You may have already thought of this, but perhaps argue like this:  If the service panel for the servers and the one that you get your power from are fed from separate transformers that get their 4160V 3PH--but not ground-- from the substation, and the initial grounding point for each is separate and they are not bonded together, then you might propose simply adding whatever grounding is needed to complete the connection between your service panel and wherever the "server room central equipotential ground bus" point is.  If that seems unacceptable, then point out that the ground wire they are proposing will do the exact same thing.

Now in reality, those points may already be connected.  I don't know anything about this facility, but a lot of times connections end up being made whether they are intended or not...so maybe it would be interesting to test that.

--- End quote ---
Bridging the air gap aint gonna get it. They are insisting on me running a green #6 ground wire in conduit from my cabinet bus bar to their common ground point.  In some cases this is nearly 2000 feet.  Completely Efing insane.  And no I haven't done anything to piss them off.  Most of those involved share my opinion at least to some extent, but they also need to support their 'inspector'.  I'm sure many of you have run into intransigent inspectors. They don't have a grasp of the intent, but by God they know that code inside and out.  Unfortunately for me this is buried in second level doc references in my contract.  The most vexing part is that this is not a code issue, it's a local facility standard.

bdunham7:

--- Quote from: Ground_Loop on September 17, 2021, 10:51:32 am ---Bridging the air gap aint gonna get it. They are insisting on me running a green #6 ground wire in conduit from my cabinet bus bar to their common ground point.

--- End quote ---

I don't have the whole standard to look at, but you may find that they cite the phrase "is or may become" or something similar.  The remote panel may not be connected, but it may become so.


--- Quote ---I'm sure many of you have run into intransigent inspectors. They don't have a grasp of the intent, but by God they know that code inside and out.  Unfortunately for me this is buried in second level doc references in my contract.  The most vexing part is that this is not a code issue, it's a local facility standard.

--- End quote ---

Yes, but in most cases the cost of compliance was small enough that it was the easiest way out.  Only once did a moron zoning inspector threaten to cause me some serious harm, and that only resulted in a lot paperwork and sleepless nights.  In your case it is worse--since it is their standard, they interpret it.  Unless you get lawyers involved, which I can't recommend.  You have my sympathy.  :(

Ground_Loop:
Yea, no lawyers.  Been there.  I once spent more than 7 months arguing the order of precedence of conjunctions, stated as (1 and 2 or 3) interpreted as ((1 and 2) or 3) or (1 and (2 or 3)), with legal teams of both sides.

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