Finally 250.66

[david]

With all that being said, I dont see where the wording of 250.64 allows us not to bring the GEC to each service disconnect if there were 2 instead of just 1. It indicates it has to be brought to both does it not?

Jap>

If we are going by what was posted in the picture and the grounding electrode conductor is based on the service conductors supplying the service disconnect 250.64 (D) 2008 seems to agree with you. Of course connection points can be changed around and multiple ways of grounding the service can become a discussion

 

[jap]

What wording makes you think the GEC bonding to the service neutral can only be made in a service disconnect?

Roger

250.64 D2 2011 CODE.
Although the additional 2 Ground rods in the new picture are unnecessary.

<Jap>

 

[jap]

not saying its the only place,, only that if there were 2 ,a connection inside each one to the GEC needs to be made.
If there were 2 there would more than likely be 2 seperate panels inside and boding would have to be applied in both locations.

<Jap

 

[roger]

250.64 D2 2011 CODE.
Although the additional 2 Ground rods in the new picture are unnecessary.

<Jap>

See 250.64(D)(3) and 250.24(A)(1). The GEC connection to the service entrance neutral could actually be made at the weather head.

The number of rods shown in the illustration was just showing multiple electrodes.

Even if the choice is made to make a connection in multiple service disconnects, it is best to extend a single GEC through all disconnects and maintain a single connection to the GES.



Roger

 

[jap]

See 250.64(D)(3) and 250.24(A)(1). The GEC connection to the service entrance neutral could actually be made at the weather head.

The number of rods shown in the illustration was just showing multiple electrodes.

Even if the choice is made to make a connection in multiple service disconnects, it is best to extend a single GEC through all disconnects and maintain a single connection to the GES.

Roger

We don't do a lot of "Daisy Chaining"
Mostly a single grounding electrode conductor from each, much like the picture above shows.
very uncommon for multiple service disconnects GEC to be looped through each just to be able to make a single connecttion to the GES at the end.
In my opinion the single GEC from each, down to the GES is a better scenario but that's just my opinion.
In the end it all boils down to having everything bonded properly.

 

[jap]

I may have worded that wrong,,, in a hurry, got to go.

Thanks,
Jap.

 

[david]

See 250.64(D)(3) and 250.24(A)(1). The GEC connection to the service entrance neutral could actually be made at the weather head.

Even if the choice is made to make a connection in multiple service disconnects, it is best to extend a single GEC through all disconnects and maintain a single connection to the GES.
Roger

Where does 250.64 (D) give you the option to extend a single GEC through all disconnects?

" A tap conductor shall extend to the inside of each service disconnecting means enclosure"

 

[roger]

Where does 250.64 (D) give you the option to extend a single GEC through all disconnects?

The better question is, where is it prohibited?


Roger

 

[roger]

very uncommon for multiple service disconnects GEC to be looped through each just to be able to make a single connecttion to the GES at the end.
In my opinion the single GEC from each, down to the GES is a better scenario but that's just my opinion

Why would you want to deliberately create circulating net currents?
I know what you are used to doing is allowed but, if we can minimize EMF issues with simple wiring why not do it?

Roger

 

[jxofaltrds]

Why would you want to deliberately create circulating net currents?
I know what you are used to doing is allowed but, if we can minimize EMF issues with simple wiring why not do it?

Roger

:thumbsup:

250.6 Objectionable Current.
(A) Arrangement to Prevent Objectionable Current. The
grounding of electrical systems, circuit conductors, surge arresters,
surge-protective devices, and conductive normally
non?current-carrying metal parts of equipment shall be installed
and arranged in a manner that will prevent objectionable
current.

 

[jap]

Why would you want to deliberately create circulating net currents?
I know what you are used to doing is allowed but, if we can minimize EMF issues with simple wiring why not do it?

Roger

So your saying if you have 6 separate service disconnects at a location that you loop 1 GEC from the neutral of the first one to the next then the next and so on, so you only make one termination to the GE at the end? I guess that's ok if you want to do it that way but why?
Your bonding everything together at the service point, your not creating an objectional path.
Everything at that point is a path if a fault occurs.

I can see the advantage of a minimizing multiple return paths on the Load side of the Service Disconnecting means but that's a little different than bonding the GEC to the Neutral Conductors at the Service Entrance.

I must be misunderstanding what advantage of "Daisy Chaining" the GEC to each Service Disconnect has over bringing one from each to the GES.
It all becomes one at that point.

<JAP>

 

[roger]

So your saying if you have 6 separate service disconnects at a location that you loop 1 GEC from the neutral of the first one to the next then the next and so on, so you only make one termination to the GE at the end? I guess that's ok if you want to do it that way but why?


<JAP>

Go back and look at the current flow in the illustration, now think EMF, that gives you a short and sweet why it's best to have a single connection to earth. If you can get ahold of a Gauss meter take some readings around a service that has the type of loop you say you install, then disconnect one end of the loop and take another reading.


You can also use a simple clamp ammeter to show the current division, take a reading on the GEC with a loop verses a reading on the GEC with a single connection to earth.


Roger

 

[jap]

Go back and look at the current flow in the illustration, now think EMF, that gives you a short and sweet why it's best to have a single connection to earth. If you can get ahold of a Gauss meter take some readings around a service that has the type of loop you say you install, then disconnect one end of the loop and take another reading.


You can also use a simple clamp ammeter to show the current division, take a reading on the GEC with a loop verses a reading on the GEC with a single connection to earth.


Roger

And how would you avoid that current, seeing as how most buildings are metal that the service entrances are installed on and connected to earth already, even without the GEC's we are instaling ?

<JAP>

 

[david]

The better question is, where is it prohibited?


Roger

(D) Service with Multiple Disconnecting Means Enclosures. Where a service consists of more than a single enclosure as permitted in 230.71(A), grounding electrode connections shall be made in accordance with (D)(1), (D)(2), or (D)(3).

Where In (D) (1), (2), 0r (3) does it give the option to daisy chain through the grouped service equipment enclosures. Doesn't the text say shall be made in accordance with (D)(1), (D)(2), or (D)(3)?

 

[david]

Say you have three panels grouped and the third panel in the daisy chain has a fault why would you want to bring the fault through the other two panels. Why involve the other two panels unrelated to the fault.

 

[MasterTheNEC]

Say you have three panels grouped and the third panel in the daisy chain has a fault why would you want to bring the fault through the other two panels. Why involve the other two panels unrelated to the fault.

Ummmm has this conversation morphed from GEC's and GE Taps to EGC's and faults?.......hold on now......lets remember the discussion is about 250.66:angel:

 

[roger]

And how would you avoid that current, seeing as how most buildings are metal that the service entrances are installed on and connected to earth already, even without the GEC's we are instaling ?

<JAP>

You don't avoid current on the GEC, but you can minimize it with good wiring methods and deliberately creating net currents anywhere is not good wiring methods.


Roger

 

[david]

Go back and look at the current flow in the illustration, now think EMF, that gives you a short and sweet why it's best to have a single connection to earth. If you can get ahold of a Gauss meter take some readings around a service that has the type of loop you say you install, then disconnect one end of the loop and take another reading.


You can also use a simple clamp ammeter to show the current division, take a reading on the GEC with a loop verses a reading on the GEC with a single connection to earth.


Roger

Rodger I agree with your premise, but I do not see how daisy chaining is allowed. You can achieve this in principle by making the one point connection in the meter enclosure or some other accessible location.

 

[roger]

Say you have three panels grouped and the third panel in the daisy chain has a fault why would you want to bring the fault through the other two panels. Why involve the other two panels unrelated to the fault.

You would do the same thing in any gutter service.

If "daisy chaining" is a problem just run a single GEC from one and install a tap from the other one to the GEC.

The point is, a single point connection to earth reduces EMF issues.

As far as the NEC is concerned you can create loops all day long, as far as grounding performance, net currents, common mode noise, and other issues there are better ways using some common sense.

Roger

 

[roger]

Ummmm has this conversation morphed from GEC's and GE Taps to EGC's and faults?.......hold on now......lets remember the discussion is about 250.66:angel:

Uhhh, yes it has and I'm guilty.


Roger