upgrading service

[iwire]

Here is another illustration from the 2008 NECH.

Another from an earlier handbook.

This second one points out the difference between a GEC and a bonding jumper. :smile:

 

[steelersman]

#3 The UFER (CEE) must be a continuous GEC with no splices from the Main Disconnect panel terminal bar

After reading these sections you listed it doesn't say that it must be continuous to the main panel bar.

#(Service grounded and Equipment grounding). This requirement is very subtle in that the water pipe electrode can be a continuous #6 [250.52(A)(1)]

It doesn't say anything about it being #6 in this section although it does in 250.53 (E)

#while the UFER must have a continuous #4 GEC [250.52(A)(3)] in order to be compliant to [250.58] Common GEC's and [250.64(C)] Continuous GEC's.

The ufer doesn't have to be a #4. It is saying if you are using copper wire as the actual concrete encased electrode (instead of a rebar)then it must be #4. I don't see anything in 250.58 that wouldn't be met by this installation.

 

[steelersman]

That is one of the most persistent myths in the electrical trade, and there is still widespread ignorance about how the GES conductors are to be connected. Thankfully both of those graphics clear up the confusion quite well.

I must admit it is one of the myths that I beleived. For example in homes whenever I've driven 2 ground rods I've always thought that they had to be continuous. Something I've just realized is the following: In the past, there have been homes that we've wired (standard 200amp service, 4/O AL which should require the GEC to be #2 AL or #4 CU), that didn't have a metal underground water pipe, so in that case we always have just driven 2 ground rods with #6 CU and that's it. So technically in this case that was wrong, because nowhere did we install the properly sized GEC (#2 AL).

And in some cases where the water pipe was plastic coming in but changed to copper once insisde we still pulled #2 AL to the copper and bonded it, but that doesn't count as the GEC. I guess when using 2 ground rods one for the primary and the other for the secondary we should've used a #4 CU GEC to the first rod and then we could've used #6 CU to the second rod.

 

[infinity]

In the past, there have been homes that we've wired (standard 200amp service, 4/O AL which should require the GEC to be #2 AL or #4 CU), that didn't have a metal underground water pipe, so in that case we always have just driven 2 ground rods with #6 CU and that's it. So technically in this case that was wrong, because nowhere did we install the properly sized GEC (#2 AL).

Actually it was right, because in that case nothing larger than #6 is required. A ground rod never needs a GEC larger than #6 regardless of the service entrance conductor size.

 

[peter d]

Something I've just realized is the following: In the past, there have been homes that we've wired (standard 200amp service, 4/O AL which should require the GEC to be #2 AL or #4 CU), that didn't have a metal underground water pipe, so in that case we always have just driven 2 ground rods with #6 CU and that's it. So technically in this case that was wrong, because nowhere did we install the properly sized GEC (#2 AL).

That wasn't wrong at all. No matter what size the service is, the sole connection to ground rods is never required to be larger than #6, nor does it need to be.

 

[steelersman]

Actually it was right, because in that case nothing larger than #6 is required. A ground rod never needs a GEC larger than #6 regardless of the service entrance conductor size.

right but in that case what was my GEC? My GEC is suppossed to be a #2 AL or #4 CU

 

[steelersman]

That wasn't wrong at all. No matter what size the service is, the sole connection to ground rods is never required to be larger than #6, nor does it need to be.

Yes but where was my GEC? Doesn't there need to be a #2CU or #4 AL sized per 250.66 for the GEC (to something, not necessarily the ground rod) since I had a 4/O AL service entrance conductor?

 

[peter d]

right but in that case what was my GEC

The connection to your ground rods is your GEC. Finished, done. If you have no other electrodes your #6 is fine.

Remember the purpose of the GEC is for lightning protection and accidental contact with high voltages. It is not for fault clearing on typical household voltage, or anything up to 600 volt systems covered by the NEC for that matter

 

[roger]

I must admit it is one of the myths that I beleived. For example in homes whenever I've driven 2 ground rods I've always thought that they had to be continuous.

Actually doing it continuous will save the expense of one connector.

so in that case we always have just driven 2 ground rods with #6 CU and that's it. So technically in this case that was wrong, because nowhere did we install the properly sized GEC (#2 AL).

No, the connection to the rod(s) only had to be #6 CU so you were correct

I guess when using 2 ground rods one for the primary and the other for the secondary we should've used a #4 CU GEC to the first rod and then we could've used #6 CU to the second rod.

No again, a #6 is all that is required.

Roger

 

[iwire]

Yes but where was my GEC? Doesn't there need to be a #2CU or #4 AL sized per 250.66 for the GEC (to something, not necessarily the ground rod) since I had a 4/O AL service entrance conductor?

No matter how large your service conductors the largest required conductor to a ground rod is 6 CU or 4 AL.

If the service has only one or two ground rods as electrodes your GEC would never be required to be larger then 6 or 4.

 

[steelersman]

Okay. I got it now. This has been a good refresher for me. I was thinking that somewhere I had to have a primary GEC sized per 250.66, b ut since nothing was available except for 2 rods then #6 CU to the rods covers it. Thanks for clearing that up guys.

 

[steelersman]

Remember the purpose of the GEC is for lightning protection and accidental contact with high voltages.

So let's say lightning strikes the home wouldn't most of the current from the lightning travel back to the POCO transformer via the neutral vs. going right into the ground via the ground rods?

 

[peter d]

I was thinking that somewhere I had to have a primary GEC sized per 250.66, b ut since nothing was available except for 2 rods then #6 CU to the rods covers it.

What helps is to remember that there really is no such thing as a "primary GEC." As the illustrations show there are multiple GEC's to consider, particularly in an industrial or commercial establishment

 

[peter d]

So let's say lightning strikes the home wouldn't most of the current from the lightning travel back to the POCO transformer via the neutral vs. going right into the ground via the ground rods?

Hopefully someone with some lightning protection experience (Bryan?) can answer that, but I'd say lightning does what it pleases and there isn't much we can do to control where it goes.

 

[roger]

So let's say lightning strikes the home wouldn't most of the current from the lightning travel back to the POCO transformer via the neutral vs. going right into the ground via the ground rods?

Probably not, the POCO source is not directly related to the discharge path of lighting, in a surge from the POCO source it may or may not.

Roger

 

[steelersman]

What helps is to remember that there really is no such thing as a "primary GEC." As the illustrations show there are multiple GEC's to consider, particularly in an industrial or commercial establishment

So in my example before where the water pipe was plastic and the only GEC is my #6 CU to the rods, would just 1 rod be sufficient or do I need 2?

 

[roger]

So in my example before where the water pipe was plastic and the only GEC is my #6 CU to the rods, would just 1 rod be sufficient or do I need 2?

If you can show that the rod is 25 ohms or less one is sufficient, but even if you own the test equipment it is usually cheaper to just drive two rods and go home.

Roger

 

[steelersman]

If you can show that the rod is 25 ohms or less one is sufficient, but even if you own the test equipment it is usually cheaper to just drive two rods and go home.

Roger

Got it thanks....

 

[infinity]

Okay. I got it now. This has been a good refresher for me. I was thinking that somewhere I had to have a primary GEC sized per 250.66, b ut since nothing was available except for 2 rods then #6 CU to the rods covers it. Thanks for clearing that up guys.

Same thing holds true for the CEE. #4 Cu is the largest GEC required to the CEE even if table 250.66 calls for a larger conductor.

 

[gndrod]

Same thing holds true for the CEE. #4 Cu is the largest GEC required to the CEE even if table 250.66 calls for a larger conductor.

Rob,
Your statement is in agreement of what I have posted earlier. The illustration may be a "generic" representation as is the opinion mentioned earlier, but the detail is still incorrect. Please refer to [250.52(A)(3)] and the CEE minimum conductor is not smaller than a #4 AWG x 20ft. conductor.

The CEE must exist in new construction per 2008. (Note the 2005 copyright on the illustration that is out of date in 2008) Please also note that the "Bonding jumper" detail connects to the H20 pipe that does not show a permanent exothermic or irreversible bond connecting device.

The detail is non-compliant to [250.64(C)] that stipulates one continuous length without a splice or JOINT except as permitted in (1) and (2) of the same paragraph.

Sure the generic illustration does not mention GEC sizes, but the illustration presents the non-continuous conductor detail that will mislead many readers into thinking that residential Grounding Electrode Systems can be wired in this configuration.

I hope you can see what I have stated earlier as the detail is not per per the 2008 NEC 250 Articles mentioned. rbj