Odd intriguing and perhaps dangerous multi unit grounding question/problem: JUMPER??

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docj67 said:
I reread some of my postings and I see how they could have been misinterpreted!- thx

I like that this forum IS hardcore about terminology--I will be more precise going forward.

In the meantime, I'm mostly curious about :

1) what is an OCPD?

2) How specifically does running an EGC to a subpanel ground bar violate 250.24(A)(1). I read 250.24(A)(1 several times. My training and experience ( lol ) tells me its wrong irregardless of
250.24(A)(1) but the verbiage is so damn dense I was unable to make the intellectual link.

I'm not too concerned about solving the issue but I would like to better understand from an practical POV what the possible issues are from such a whacked build out. If those 4 GEC's aren't bonded to metal framing that is hidden then the whole issue is sorta moot and only worthwhile as intellectual fodder;) The solution is to snip those 4 GEC's and drop in two new ground rods according to NEC rules.

I began this dialogue in an attempt to learn what sort of problems could be created by landing service GEC's on a subpanel not part of the services per se. The fix is straightforward: Correct buidling GES and unit GEC's to code. Boom!

I hope this is clear sir:) My tele can be given by PM if u have any further curiosity about the install's topology. In gratitude, js
Click to expand...

First, I removed your phone number. This is an open forum and your privacy is important.

OCPD is Over Current Protection Device=circuit breaker or fuse.

Not sure how I got you caught up in tieing EGCs to 250.24 together. I was trying to say where GECs could be landed. Prolly my bad.

Correct me if I am wrong. The service comes into the building and there is no main disconnect or breaker, but a trough or box where the conductors split up and go to each occupancy.

Therefore, each occupancy has a main panel and breaker.

Correct so far?

If yes, there should be a three wire feed from service trough to each occupancy.

There is not a GEC, connected to the service neutral, in this trough/box that goes to a GES for the building.

I will continue after you answer and correct me if needed.
 
yes!

yes!

sorry about phone post

have not opened trough ( NEC calls this " gutter " or "wireway"? ) nor more than my customers's can.
there are 3 wires from coming into his can, 2 phases plus neutral.
customer's service is open one on far right.

again, I've only opened my customer's main and it contains 2 50 two pole amp breakers for each of his two subs, one of which I'm slated to replace.....

thx so much bro!

here is the picture confirming your statements about service and splitting:)4unitservices.jpg
 
I made a MISTAKE but I'm feelin pretty grounded-thx

I made a MISTAKE but I'm feelin pretty grounded-thx

2) How specifically does running an EGC to a subpanel ground bar violate 250.24(A)(1). I read 250.24(A)(1 several times. My training and experience ( lol ) tells me its wrong irregardless of
250.24(A)(1) but the verbiage is so damn dense I was unable to make the intellectual link.

I meant GEC not EGC!!!
 
docj67 said:
2) How specifically does running an EGC to a subpanel ground bar violate 250.24(A)(1). I read 250.24(A)(1 several times. My training and experience ( lol ) tells me its wrong irregardless of
250.24(A)(1) but the verbiage is so damn dense I was unable to make the intellectual link.

I meant GEC not EGC!!!
Click to expand...

Freaking NEC drives all of us bonkers at times.
 
docj67 said:
sorry about phone post

have not opened trough ( NEC calls this " gutter " or "wireway"? ) nor more than my customers's can.
there are 3 wires from coming into his can, 2 phases plus neutral.
customer's service is open one on far right.

again, I've only opened my customer's main and it contains 2 50 two pole amp breakers for each of his two subs, one of which I'm slated to replace.....

thx so much bro!

here is the picture confirming your statements about service and splitting:)View attachment 19287
Click to expand...

Okay, I see a service raceway/conduit/mast coming down into a trough/gutter/wireway, this has 4 meters. The meters are fed by splitting the service conductors to feed each meter and then continue on to enclosures with main OCPD/breakers. All conductors before breakers are service conductors and all ones after the breakers are feeders.

Each enclosure contains OCPDs/breakers that feed to panels in each occupancy. We are going to call these sub panels. Wires between breakers and sub panels are feeders.

Correct so far?
 
docj67 said:
nailed!
Click to expand...

Cool.

Minor FYI: although we are going to say sub panel for clarity since we all understand the meaning, it is a made up term. The NEC does not use the term anywhere.

Onward:

This is where 250.24(A)comes into play. These enclosures are the service disconnecting means and service OCPDs. At this or these points the connection of GECs to the building GES must occur.

There a couple of ways to accomplish this, we will come back to this in a few minutes.

First let’s travel to the sub panels in the occupancies.

Since we have established where the service conductors end and feeders begin. We need to discuss these feeders. They should be 4 wires, 2 hots + 1 neutral + 1 EGC, between the service enclosures and the sub panels. In the sub panels, the EGCs and neutrals should be separated and the neutral bus isolated from the ground bus and sub panel enclosure/cabinet. Enclosure should be bonded to EGC bus.

Is this done like I just described? This is all 250.24 also. part C I think.

Do not concern yourself with any GECs that may be in these sub panels at this moment.
 
not to be arrogant but

not to be arrogant but

a) I knew all this before I posted first post, ie your posted spec for how stuff should be configured as described in your most recent post

b) I've yet to see anything past my customer( 1 of the 4)'s layout.

c) I'm most interested in theoretical exploration of possible issues based on hypothetical lack of correction to current config

d) suggest thread close and continue private

In gratitude,

newBie Nick
 
docj67 said:
a) I knew all this before I posted first post, ie your posted spec for how stuff should be configured as described in your most recent post

b) I've yet to see anything past my customer( 1 of the 4)'s layout.

c) I'm most interested in theoretical exploration of possible issues based on hypothetical lack of correction to current config

d) suggest thread close and continue private

In gratitude,

newBie Nick
Click to expand...

A. Cool, we need not continue those steps then

B. That is fine, we can now focus there now.

C. I was trying to understand current customers layout, I needed to see and understand service connection first. I will go back and reread earlier posts of yours and post what I think.

D. Why? The benefit of this place is the sum knowledge of all the members. Others are reading this and can chime in with ideas or point out any mistakes I may make. Best to continue here.

So, there is a four wire feed to the occupancy and connections are correct, but GECs are landed in these subs. Correct?
 
not quite

not quite

so much for a day off, but I love this stuff

customer's occupancy has two 50 amp 240 feeds to two subs

a) panel A is panel in question w 2 #8's -surmise EMT/RMC?IMC ground

b) panel B is fed pacfic whcih I've been hired to rebuild out of closet

siging off, tx
 
not quite

not quite

so much for a day off, but I love this stuff

customer's occupancy has two 50 amp 240 feeds to two subs

a) panel A is panel in question w 2 #8's -surmise EMT/RMC/IMC ground as no EGC feed from EITHER sub present at his service

b) panel B is fed pacific which I've been hired to rebuild out of closet

siging off, tx
 
Okay, post 7 had the clues, but I missed them in the confusion.

Sub are fed with 3 wires, but in a metallic raceway, Rigid or a EMT, which is prolly the EGC. Good so far.

Service Enclosures do not have GECs landed there but rather subs do. Bad.

Electrodes of the GES are unknown. Bad.

GECs from other occupancies are landed in customers subs. Bad, but not necessarily dangerous if corrections at service enclosures are done. Prolly just disconnect them and be done with them.

Am I getting this correct?
 
mostly correct sir! one minor correction tomorrow! thx!

mostly correct sir! one minor correction tomorrow! thx!

mostly correct sir! one minor correction tomorrow! thx!
 
docj67 said:
so much for a day off, but I love this stuff

customer's occupancy has two 50 amp 240 feeds to two subs

a) panel A is panel in question w 2 #8's -surmise EMT/RMC/IMC ground as no EGC feed from EITHER sub present at his service

b) panel B is fed pacific which I've been hired to rebuild out of closet

siging off, tx
Click to expand...

I was typing when you posted, but I get it now.

Have a good night.

Sorry it got dragged out, but the mixed terminology got us confused at first.

Hope project works out.

Derek
 
all good no apology needed enjoyed thorougly

all good no apology needed enjoyed thorougly

Title:
clear.gif
all good no apology needed enjoyed thorougly
 
jumper said:
If I/we seem to be a bit hardcore about correct terminology, it is because if we all do not use the same terms and definitions then confusion results.

Remember, we are spread out in all the states and also a few countries, so keeping an established common language of terms, definitions, and such is essential for effective communication.
Click to expand...

:thumbsup::thumbsup::thumbsup::thumbsup:

Not only does a shared common understanding of the Article 100 Definitions of Terms help in this limited text / picture medium of the Forum, but, I have personally found, it returns me to the roots that I build my working-in-the-field knowledge on.

Dereck and Doc, I just read the thread and I greatly appreciate what is unfolding in it.

In my experience, being willing to return to the Article 100 Definitions NEVER stops yielding new insights for me, as I strive to make useful mechanical assemblies that provide Power, Light and Communications from the printed word.

That being said, Doc, may I ask. . . the second 50 Amp feeder to your client's non-FPE panel. . . how does it connect at the Service Entrance gutter with the four meters and four Service Disconnects?

The reason I ask goes to the size of the conductors inside the Service Entrance conduit leading down from the Power Company to the gutter. Those conductors will have been sized based upon the "calculated load" (Article 220) at the original time of installation. Your client has added an additional subpanel and feeder, and, presumably, additional load. The question becomes: What is today's connected load carried by the Service Entrance Conductors, as calculated by, probably, Part IV of Article 220, and 220.84? Is the service entrance still adequate for the connected load?
 
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