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

[docj67]

Oh mighty gurus: I have the following scenario:

A 4 unit condo has a 4 tapped gutter from one main service drop providing 4 services/disconnects. I have been hired and maybe soon to be fired, to replace a FED Pacific subpanel in a closet in one unit and replace the FP disconnect. This unit has another newer subpanel installed by the prior owner /contractor /builder. I discovered early on that the the ground bar of this newer panel has TWO #8 GEC"S attached to it.

It was brought to my attention early on in the project; I was originally hired for data work , that there were 4 ground wires going into my customer's unit--this came up when he mentioned the possible FP replacement project.

I discovered that the 4 ground wires into his unit were in fact the 4 ground wires from the 4 units disconnects--they go into his unit right under the prior mentioned newer subpanel

The customer's unit has two 50 amp 240 feeds for the two subpanels---one is FP and has no ground and is slated for replacement, the other is new. Today I stopped by the unit bc I suddenly realized there was no recollection on my part of whether I had seen a GEC for newer subpanel. BC this is my first permitted / to be inspected job, I have been sweating bullets. I looked in the FP disconnect and saw NO ground from the newer subpanel.

My assumption is that the the 1.25 inch feeder for the subpanel feed was used as ground, as all circuits on that newer subpanel have "valid" grounds.

If this is true then it means that likely the 2 #8's on that subpanel bar are main grounding connectors from other unit's services!!!

My sense is not to proceed w work until this is resolved.

I'd like to request feedback on hazard potential of such an odd grounding scenario, or maybe I'm losing my mind and it's legit.

If it is UNLEGIT, I'd like to know as much as possible, or if more info is needed, I may be interested in any experts in
grounding in Northern Calif who maybe avail for hire.

Then there's the main building ground: I don't have the test equipment to see if the apparent bond to a waterpipe of all 4 units meets 25ohms NOR whether there is the second Grounding Electrode present.

Thx so much!

Newbie_Nate

 

[petersonra]

First off I think we ought to get the right terminology so we know exactly what it is you are asking. The grounding electrode conductor is the wire that goes from the neutral bar (or wherever the grounded conductor is connected to Earth) to the grounding electrode system..

Equipment grounding conductors are the green wires that connect all the metal parts of the system together that are not electrically energized.

There are also bonding conductors that connect the various grounding electrodes together to form a grounding electrode system.

I don't believe there's any prohibition in a code that says you can't connect equipment grounding conductors from one unit to another.

I don't even recall that there is any prohibition on running grounding electrode conductors through one unit to get to another unit. I'm not entirely sure you're allowed to use a ground bar in a panel to connect multiple grounding electrodes together though but I think you could use the neutral bar for such a purpose.

 

[jumper]

What the heck! Don’t yell at me, I did not do it. I swear!

So, I am intriguing and dangerous, I thought I was just nuts.

 

[docj67]

reply to Bob

reply to Bob

Thx for the reply: What can I clarify in my use of terminology?

Multiple service grounds are possibly connected to a subpanel from another service

Please detail what I can clarify.

thx!

First off I think we ought to get the right terminology so we know exactly what it is you are asking. The grounding electrode conductor is the wire that goes from the neutral bar (or wherever the grounded conductor is connected to Earth) to the grounding electrode system..

Equipment grounding conductors are the green wires that connect all the metal parts of the system together that are not electrically energized.

There are also bonding conductors that connect the various grounding electrodes together to form a grounding electrode system.

I don't believe there's any prohibition in a code that says you can't connect equipment grounding conductors from one unit to another.

It seems to me that most likely the place where the grounding electrode conductor is terminated would be at the service Point outside.

 

[petersonra]

Thx for the reply: What can I clarify in my use of terminology?

Multiple service grounds are possibly connected to a subpanel from another service

Please detail what I can clarify.

thx!

What do you mean by Service ground? Is this the grounding electrode system, the grounding electrode conductor, or an equipment grounding conductor?

The term Service ground does not have a defined meaning

 

[tom baker]

"We have met the enemy and they are us" - Pogo. I use this in my grounding and bonding classes. We are confused on grounding and bonding as we tend to use "ground" for different functions.
Mike Holt once said (for grounding) what color is it and what does it do?

 

[docj67]

reivisted job site: here are some pics and hopefully this makes my q clearer.....

reivisted job site: here are some pics and hopefully this makes my q clearer.....

It's likely that at least ONE Grounding Electrode Conductor from one unit's main panel is bonded to ground bar in another unit'subpanel. All 4 units are tapped from one feed from Pacific Gas and Electric. Building ground electrode is most likely not up to code and I have recommended to client that we simply redo the building ground to code. This would involve removing that ( or those ) #8(s) from my customer's sub panel. The Subpanel ground appears to be done with the RMC or EMT used to run the subpanel feed from is service, as there is no discrete wire from that panel coming in to the main panel.

This all began when the customer showed me inspection report questioning why 4 #8's go into his unit. I traced them back and found they were the 4 service Grounding Electrode Conductors....

 

[jumper]

The whole set up is a little too muddled for me to understand what is going on.

I will just say the if these are (main) GECs, what I assume you were calling service grounds, and land in sub panels then you have violations of 250.24(A)(1).

If these GECs are going to auxiliary electrodes then it could be legal, this assumes building has a proper GES to start with.

 

[docj67]

Thx J

Thx J

If they do land on other subpanel bar in fact and i ve yet to prove that conclusively, that would be violating as you say

250.24(A)(1).

If that is the case is there a risk for unpredictable behavior in subpanel if say there's a ground fault incoming to the subpanel?

Also this scenario if true has a ground loop between customer service and subpanel.....

going to recon 250.24(A)(1).

THX !!

 

[docj67]

250.24(A)(1).

250.24(A)(1).

My interpretation is that it would be a violation BC it does not bond directly to building electrode.

Care to shed some wisdom from this scenario if true relative to 250.24(A)(1).?

thx!

 

[docj67]

Thx Jumper, your reply confirms my basic thinking My theory is

Thx Jumper, your reply confirms my basic thinking My theory is

that 2 of the 4 go to secondary GES and other two are on sub panel


WEIRD!!

 

[jumper]

If they do land on other subpanel bar in fact and i ve yet to prove that conclusively, that would be violating as you say

250.24(A)(1).

If that is the case is there a risk for unpredictable behavior in subpanel if say there's a ground fault incoming to the subpanel?

Also this scenario if true has a ground loop between customer service and subpanel.....

going to recon 250.24(A)(1).

THX !!

A GES has nothing to do with clearing ground faults. If the EGC system is correct, then whatever’s happening with these GECs/ wires will not effect operation of the OCPDs.

Might be some unwanted/illegal parallel paths for neutral current though.

My interpretation is that it would be a violation BC it does not bond directly to building electrode.

Care to shed some wisdom from this scenario if true relative to 250.24(A)(1).?

thx!

Does the main distribution panel have a correct connection to a proper GES?

that 2 of the 4 go to secondary GES and other two are on sub panel


WEIRD!!

I have no clue what you mean here, other than it seems that some wires are crossed up or landed incorrectly. Secondary GES???

 

[docj67]

A GES has nothing to do with clearing ground faults. If the EGC system is correct, then whatever’s happening with these GECs/ wires will not effect operation of the OCPDs.

Might be some unwanted/illegal parallel paths for neutral current though.



Does the main distribution panel have a correct connection to a proper GES?


--there's no main, there are 4 mains, one for each unit as per picture. I have yet to open gutter or other customers' service can.


I have no clue what you mean here, other than it seems that some wires are crossed up or landed incorrectly. Secondary GES???

That is the $64,000,000 question. We dont know. What we do know is that building GES likely is not to code, and it appears my customer's subpanel has 1-2 GEC's attched to it from other unit's services. I assume GES= Grounding Electrode System. My understanding regarding groundfaults is that a EGCis needed to bond to system GES vai GEC to clear them and if there's no GEC to GES they remain active until removed.

In anycase, it appears impossible for any of us to get clearer via this means of communication....... If you might please define OCPD and how whatever it is that does make sense to you here violates 250.24(A)(1).

Thanks so much for all efforts!!

 

[docj67]

GEC versus EGC versus GES defined

GEC versus EGC versus GES defined

Grounding Electrode conductor- runs from service to GES
Grounding Electrode system- 1 or more electrodes as defined by 250.52A
EGC-Equipment grounding conductor--per branch circuit bonded to all metal cans / devices on a given branch circuit

Sorry if my use of terms other than these is confusing.

Do these definitions match your usage/understanding?

Thx so much!

 

[jumper]

Grounding Electrode conductor- runs from service to GES
Grounding Electrode system- 1 or more electrodes as defined by 250.52A
EGC-Equipment grounding conductor--per branch circuit bonded to all metal cans / devices on a given branch circuit

Sorry if my use of terms other than these is confusing.

Do these definitions match your usage/understanding?

Thx so much!

Yes. Note that EGCs are not limited to branch circuits, feeders have one also. A feeder EGC would bond a sub panel, fused disco or such.

 

[jumper]

That is the $64,000,000 question. We dont know. What we do know is that building GES likely is not to code, and it appears my customer's subpanel has 1-2 GEC's attched to it from other unit's services. I assume GES= Grounding Electrode System. My understanding regarding groundfaults is that a EGCis needed to bond to system GES vai GEC to clear them and if there's no GEC to GES they remain active until removed.

In anycase, it appears impossible for any of us to get clearer via this means of communication....... If you might please define OCPD and how whatever it is that does make sense to you here violates 250.24(A)(1).

Thanks so much for all efforts!!

Your understanding of the GES is incorrect. Read below, nothing about clearing faults.

250.4
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

Informational Note: An important consideration for limit- ing the imposed voltage is the routing of bonding and grounding electrode conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided.

(2) Grounding of Electrical Equipment. Normally non– current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equip- ment, shall be connected to earth so as to limit the voltage to ground on these materials.

 

[docj67]

Thank you...

Thank you...

Perhaps as I am still getting used to matching NEC veribiage to field experience, I misspoke.
I'm afraid to comment further less more confusion results.

I did not mean imply whatever I did to suggest that 250.4 referenced clearing ground faults.

Thx again for all the feedback.

Your understanding of the GES is incorrect. Read below, nothing about clearing faults.

250.4
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

Informational Note: An important consideration for limit- ing the imposed voltage is the routing of bonding and grounding electrode conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided.

(2) Grounding of Electrical Equipment. Normally non– current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equip- ment, shall be connected to earth so as to limit the voltage to ground on these materials.

 

[jumper]

Perhaps as I am still getting used to matching NEC veribiage to field experience, I misspoke.
I'm afraid to comment further less more confusion results.

I did not mean imply whatever I did to suggest that 250.4 referenced clearing ground faults.

Thx again for all the feedback.

Okay maybe I was wrong and you understand the difference between grounding and bonding, but your following statement implies to me there was a bit of confusion:

I assume GES= Grounding Electrode System. My understanding regarding groundfaults is that a EGCis needed to bond to system GES vai GEC to clear them and if there's no GEC to GES they remain active until removed.

From that wording I had inferred that a little theory on the subject would be useful to you.

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.

Also writing out what you actually mean is quite difficult for most of us. What we write is not always what we mean or it is written in a way that can interpreted more than one way.

And some times one’s brain just goes haywire and the resulting post is a bit whacked. Trust me I know, posted more than one doozy myself. It happens. Most members here are a forgiving lot if one just says “Oops” or “ My bad”.

Now, as far as your installation is concerned - at this point I think I now have a pretty good idea what you are facing. Later I will post what I percieve and you can correct me as needed.

 

[docj67]

excellent

excellent

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

Okay maybe I was wrong and you understand the difference between grounding and bonding, but your following statement implies to me there was a bit of confusion:



From that wording I had inferred that a little theory on the subject would be useful to you.

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.

Also writing out what you actually mean is quite difficult for most of us. What we write is not always what we mean or it is written in a way that can interpreted more than one way.

And some times one’s brain just goes haywire and the resulting post is a bit whacked. Trust me I know, posted more than one doozy myself. It happens. Most members here are a forgiving lot if one just says “Oops” or “ My bad”.

Now, as far as your installation is concerned - at this point I think I now have a pretty good idea what you are facing. Later I will post what I percieve and you can correct me as needed.

 

[docj67]

solution clarified

solution clarified

I'm pitching to client cutting those 4 GEC's into his unit and re wiring the 4 disconnects/services with new GEC's run to new ground rods meeting NEC placement rules.

He's trying to contact building's builder in a last attempt to shed light on what he did.......

js

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 is xxxxxxxxxif u have any further curiosity about the install's topology. In gratitude, js