2 services 1 building GEC

[yired29]

Yes if the first service went from the water clamp the the steel you could just drop down from the steel to your new equip and you'd have your water ground but both connections to the steel would be required to be irreversible here.

The AHJ always has the final say so in most cases.

 

[augie47]

I'm sorry, but I'm having a real problem here. As yired29 states, the AHJ may, of course, have requirements above the NEC.
But in your case you are, IMHO, misapplying NEC Code sections.

Yes but when you go from the connection to your electrode (on the water pipe clamp) to the equipment or common point the conductor in between the 2 points have to be uncut or spliced by irreversible means which means the conductor connecting to the steel at each end has to be irreversible means.

when you are SPLICING, Yes {250.64(C)} When you are CONNECTING an exothermic weld, listed lug, etc {250.70)
Per 250.52(A(2) once it is bonded, your building steel becomes and electrode so when you CONNECT to it you may follow 250.70.

As for where i get the need for 2 electrodes unless the electrical contractor provides proof of 25ohms or less on his one electrode you'll need the additional electrode. (how many people have the equipment to show the resistance to ground?)

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
single electrode consisting of a rod, pipe, or plate that does
not have a resistance to ground of 25 ohms or less shall be
augmented by one additional electrode of any of the types
specified by 250.52(A)(4) through (A)(8). Where multiple
rod, pipe, or plate electrodes are installed to meet the requirements
of this section, they shall not be less than 1.8 m
(6 ft) apart.

Check the sections you quoted 250.56 (25 ohm rule) refers to Rod Pipe of Plate electrodes.
250.53(D) requires a supplemental electrode for water piping

There is no mention of 25 ohms or less or a second electrode for building steel, concrete encased, etc.
If I have a CCE and that is the only electrode at the premises, show me in the NEC where an additional electrode is needed.

 

[ibew501ed]

I'm sorry, but I'm having a real problem here. As yired29 states, the AHJ may, of course, have requirements above the NEC.
But in your case you are, IMHO, misapplying NEC Code sections.


when you are SPLICING, Yes {250.64(C)} When you are CONNECTING an exothermic weld, listed lug, etc {250.70)
Per 250.52(A(2) once it is bonded, your building steel becomes and electrode so when you CONNECT to it you may follow 250.70.



Check the sections you quoted 250.56 (25 ohm rule) refers to Rod Pipe of Plate electrodes.
250.53(D) requires a supplemental electrode for water piping

There is no mention of 25 ohms or less or a second electrode for building steel, concrete encased, etc.
If I have a CCE and that is the only electrode at the premises, show me in the NEC where an additional electrode is needed.

100% correct Also, perhaps some confusion arises in the fact that you could run a GEC from service equipment to the bldg steel and then connect the water or cee or rod to the building steel (thus using steel as a conductor.

and irreversible could mean exothermic weld or hypress.

 

[david]

Correct. If they had originally connected from one electrode to the other, then you could also just hit the one (assuming all interconnections are properly sized). Had thy gone from water to steel, to UFER, etc. you could use their loop.
Since they ran independent GEC, you will need to do also, or make your own loop.

Read carefully what is being assumed here. The designer of the 1200 amp service look at the building and interconnected (bonded) all of the grounding electrodes that where present included as one of the grounding electrodes was the building steel.

A properly built grounding electrode system for a 1200 amp service would be over sized for a 400 amp system. The addition of a new 400 amp system would not require re-interconnecting (re-bonding) all of the grounding electrodes based on the size of the smaller ungrounded conductors for the 400 amp service entrance.

I believe you where correct to evaluate the 1200 amp service grounding electrode system. I believe your concern of a single ground rod is valid. So add a second rod.

If this where in reverse the 400 amp service was the original and a 1200 amp service was being added. Then there would be a need to evaluate the grounding electrode system and re-bond the grounding electrodes based on the 1200 amp service.

 

[augie47]

My concern, in that regard, is that when you state they "interconnected" the electrodes on the original service, I contend, from the OP, that they did not. According to the OP, each electrode was "hit" with a conductor from the service and, unless I misread, there was no interconnection between the electrodes without the common connection in the gear.

Since every service is required to use every available electrode, my contention is that he must either bond the existing electrodes together or follow the original service path and attach to each.
Removal of the 1st gear should not disconnect any portion of the second service from the electrodes.

When you state "re-interconnect" my point is they were never "inter-connected" in the first place, just all connected (to the service).

You also mention a second ground rod. Since they have building steel, CEE, etc please show me where they need ANY ground rods, much less a second one.

 

[david]

My concern, in that regard, is that when you state they "interconnected" the electrodes on the original service, I contend, from the OP, that they did not. According to the OP, each electrode was "hit" with a conductor from the service and, unless I misread, there was no interconnection between the electrodes without the common connection in the gear.

Since every service is required to use every available electrode, my contention is that he must either bond the existing electrodes together or follow the original service path and attach to each.
Removal of the 1st gear should not disconnect any portion of the second service from the electrodes.

When you state "re-interconnect" my point is they were never "inter-connected" in the first place, just all connected (to the service).

You also mention a second ground rod. Since they have building steel, CEE, etc please show me where they need ANY ground rods, much less a second one.

?If they had originally connected from one electrode to the other, then you could also just hit the one (assuming all interconnections are properly sized).?[/QUOTE]

I simply said read the assumption closely you clearly state the interconnections would have to be properly sized in order to rely on the first services grounding electrode system. I do relize that is not he case in the OP. Thank you for pointing that out.

As for where i get the need for 2 electrodes unless the electrical contractor provides proof of 25ohms or less on his one electrode you'll need the additional electrode. (how many people have the equipment to show the resistance to ground?)

I didn?t mention the ground rod it was mention in this post. I went back and read the OP and in that post it is stated that there are two ground rods.

Now as far as the need for ground rods, when there is building steel. The whole discussion is based on the fact that the building steel can be established as a grounding electrode. Just because some one used it as one doesn?t make it one. The conductor at the 1200 amp service goes from the service neutral to building steel as you pointed out. That conductor is ether a bond from the neutral to building steel or a grounding electrode conductor. Since that fact cannot be determined by the information given in the original post, we cannot assume the purpose of the conductor.
However the OP did mention two ground rods and if the two ground rods are bonded to the building steel ether as interconnection of the grounding electrode system or a ground for the building steel. In my opinion that would establish the building steel to be in fact a grounding electrode

 

[augie47]

David, I think we are in agreement and I did speak with an assumption concerning the building steel. Although the CEE can "stand alone" as THE grounding electrode, the building steel can only be an electrode if it is "effectively ground" by one of the means listed in 250.52(A)(2).
So, in the OPs situation as long as he has the CEE or effectively grounded building steel no ground rods are needed. Is that the way you see it ?

 

[yired29]

David, I think we are in agreement and I did speak with an assumption concerning the building steel. Although the CEE can "stand alone" as THE grounding electrode, the building steel can only be an electrode if it is "effectively ground" by one of the means listed in 250.52(A)(2).
So, in the OPs situation as long as he has the CEE or effectively grounded building steel no ground rods are needed. Is that the way you see it ?

Later in the post I asked if we were to run a properly sized GEC based on largest service conductors from water to building steel then building steel would become a GE. This would eliminate using the first service as a common connection point for the GEC's.

 

[augie47]

If the water line is an electrode (and not just bonded) and that conductor was installed within the 1st 5 ft of the incoming line that would make the steel a GE.

 

[david]

David, I think we are in agreement and I did speak with an assumption concerning the building steel. Although the CEE can "stand alone" as THE grounding electrode, the building steel can only be an electrode if it is "effectively ground" by one of the means listed in 250.52(A)(2).
So, in the OPs situation as long as he has the CEE or effectively grounded building steel no ground rods are needed. Is that the way you see it ?

yes we are in agreement and that is the way i see it