Bonding subpanel to electrode

[don_resqcapt19]

How do you justify, or interpet article 250.104(A)(1)?? The only time u allowed to bond the metal piping at another panel(sub panel) is a building with multiple occupancy and multiple buildings or structures etc..

So as far as physics/ mehcanically maybe there is no difference (i think there is) , but its definitely a code violation.

I see nothing in 250.104(A)(1) that prohibits additional water pipe bonding. The rule only specifies the required bonding and does not prohibit additional bonding once the required bonding is installed. In fact I will say that this additional bonding is directly permitted by 250.54.

On second though, 250.54 does not apply as the water pipe is not a grounding electrode at this point in the system.

 

[shepelec]

If in fact the subpanel has a seperate ground from the service main, as he stated. And the main service was properly grounded, then this would be a bonding jumper. You can bond anything. Too many times people get confused between bonding and grounding.:-?

 

[Dexie123]

Ok this thing (topic) was mislabled and/or misunderstood this entire dialogue.

It is a jumper for sure. The fact that it goes to the water main is, IMO, odd and adding to the confusion. It's certainly not necessary to do this and it borders on ponderous really but it is what it is.

So this thread should be changed to "Bonding Jumper to subpanel to water main" to make it more clearly understood.

Oh, and Baba booey to ya'll

 

[brother]

I see nothing in 250.104(A)(1) that prohibits additional water pipe bonding. The rule only specifies the required bonding and does not prohibit additional bonding once the required bonding is installed. In fact I will say that this additional bonding is directly permitted by 250.54.

I respectfully disagree with you don_resqcapt19 . NEC 2005 250.54 deals with SUPPLEMENTARY grounding electrodes!! this water pipe is not a supplementary electrode. In fact 250.53 (D)(2) says the water pipe will be SUPPLEMENTED by an aditional electrode. So it clearly makes a distinction in the electrodes, supplementary wise.

when i read 250.104(A)(1) I also read those additional ones as well (2), (3) etc.. Why would they go on and say where the additional bonding is ALLOWED to take place if they did not intend to limit it in (A)(1) ????If they did not intend to limit it, then there was no need for the additional writings of 2, and 3.

Also remember that gec appears to be acting as 2 functions when bonded to water pipe. Thats why i believe they make the statement in 250.104.

 

[don_resqcapt19]

Bother,
You are correct about 250.54 and I made an edit to my post just before you posted this one.

I don't agree about the rest. There is no statement in the code that prohibits multiple connections from the EGC to the water pipe. Without such a direct statement there is no code violation, there is no increase in hazard, and as others have stated there is a reduction in the impedance of the fault clearing path. The provisions of (A)(2) and (3) only act as exceptions permitting the required water pipe bonding connection to be made at other than the service equipment. These sections are to make it easier to comply with the bonding requirement, and do not act in any way to limit any additional bonding connection.

 

[brother]

Bother,
You are correct about 250.54 and I made an edit to my post just before you posted this one.

lol figures, as i was typing you put that edited version up.

I don't agree about the rest. There is no statement in the code that prohibits multiple connections from the EGC to the water pipe. Without such a direct statement there is no code violation, there is no increase in hazard, and as others have stated there is a reduction in the impedance of the fault clearing path. .

there is a DIRECT statement in 250.104(A)(1) that says "metal water piping system installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductore where of sufficient size, or to the one or more grounding electrodes used.

Why would you want to create a 'parrallel path' for the fault current to flow on the water pipe?? Lets say, just for sake of argument, that the section of water pipe that is jumpered to the subpanel going back to the service panel has a lower resistance than the actual egc from the service to the subpanel, then most of the fault current will take that path on that water pipe. This is an unnecessary hazard i see here (i wish i could post pics as good as pierre). It would be different if there was a 'plastic' section of pipe that was replaced and you were bonding that metal inbetween.

If they did not add the other 2 sections #2 and #3,(that are exceptions to #1 like you said) then i could see your point, but they felt the need to give the exceptions. You only give an exception when you have required something to done a certain way.

The provisions of (A)(2) and (3) only act as exceptions permitting the required water pipe bonding connection to be made at other than the service equipment. These sections are to make it easier to comply with the bonding requirement, and do not act in any way to limit any additional bonding connection.

I was not stating that those additional sections 2, 3 limited the extra bonding, I was stating that if they (CMP) DID not intend to limit it in the 1st section then there would be NO need for the EXCEPTIONS. Thats just basic reasoning and reading it in context. Thats how they do all the code sections, if they did not intend to limit something then there would be no need for an exception, would you not agree ??

 

[don_resqcapt19]

there is a DIRECT statement in 250.104(A)(1) that says "metal water piping system installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductore where of sufficient size, or to the one or more grounding electrodes used.

Why would you want to create a 'parrallel path' for the fault current to flow on the water pipe?? Lets say, just for sake of argument, that the section of water pipe that is jumpered to the subpanel going back to the service panel has a lower resistance than the actual egc from the service to the subpanel, then most of the fault current will take that path on that water pipe. This is an unnecessary hazard i see here (i wish i could post pics as good as pierre). It would be different if there was a 'plastic' section of pipe that was replaced and you were bonding that metal inbetween.

So you are telling me that the direct statement that requires raceways to be supported every 10' prohibits installing supports at less than 10'? The code is a permissive document and if it does not say you can't, then you can.
As far as the parallel path, I have no problem with multiple parallel paths for the EGC. There is no hazard and infact it actually decreases the impedance of the fault clearing path, not as much as you may think based on the resistance becuase the impedance of a "remote" path goes up significantly as a result of inductive recatance. Most of the fault current will not flow on the pipe, it will flow on the EGC that is run with the feeder conductors, but I don't see fault current flowing on the EGC as any type of issue and the local bonding also acts to limit the touch potential between the water pipe and everything connected to the electrical grounding system during the fault. With out the bond at the sub panel everything connected to the electrical grounding system is has a voltage to the water pipe that is equal to the voltage drop on the EGC between the point of the fault and the main bonding jumper. This voltage should only exist for a very short time, but it is very possible to have a 40+ volt drop on the EGC under fault conditions creating a touch potential. With a local bond this voltage does not exist as the water pipe and the electrical grounding system are at the same potential. I just see neither a code nor a technical reason to say you can't make this bond between the EGC and the water pipe.
This same type of installation is very common in industrial installations where a lot of the equipment will have both an EGC and a bonding conductor to the building steel and or the grounding grid.

I was not stating that those additional sections 2, 3 limited the extra bonding, I was stating that if they (CMP) DID not intend to limit it in the 1st section then there would be NO need for the EXCEPTIONS. Thats just basic reasoning and reading it in context. Thats how they do all the code sections, if they did not intend to limit something then there would be no need for an exception, would you not agree ??

No, I don't agree. The "exceptions" permit the pipe to be connected to the electrical system at a point other than the service equipment only because under the conditions given in those sections it would be difficult to make the bonding connection at the service equipment.

 

[brother]

So you are telling me that the direct statement that requires raceways to be supported every 10' prohibits installing supports at less than 10'? The code is a permissive document and if it does not say you can't, then you can. .

No im not saying that.
It actually says at 'least' (sp?) every 10ft. so if you go less then its ok because of the word 'least'. but not more.
I believe as you do its generally a permissive document when taken everything in context. That just supports my previous statements, there would be no need to add sections 2 and 3 since it wouldve already been permissable to do those actions stated in 2 and 3, cause there wasnt anything saying you can not, if we follow your logic. But apparently it was their intent to make it not permissible, cause they did add 2 and 3.

 

[M. D.]

Brother , there is no prohibition in the NEC against re-grounding non- current carrying metal piping , duct work, waste pipes, air lines ,.or any other metal equipment ,..whether it is part of a wiring system or not... It may not serve much of a purpose as it does not relieve any of the required grounding/ bonding ,..but it is perfectly acceptable .

I just don't understand why you think this is a problem,... If I wire a water heater with a # eight equipment ground from the sub panel what is the difference?? Same sub panel I wire the boiler with a # 10 run in EMT ,.. water pipe is bonded again. and it can be re bonded over and over again ... and many times is.

 

[don_resqcapt19]

I believe as you do its generally a permissive document when taken everything in context. That just supports my previous statements, there would be no need to add sections 2 and 3 since it wouldve already been permissable to do those actions stated in 2 and 3, cause there wasnt anything saying you can not, if we follow your logic. But apparently it was their intent to make it not permissible, cause they did add 2 and 3.

There is no intent to prohibit additional bonds. There is no rule that prohibits additional bonds. The two "exceptions" just make it easier to comply with the main bonding rule in specific cases. In those cases, with out the "exceptions" you would have to run the bonding conductor back to the service disconnect. These "exceptions" just let you make the required bond at a point other than the service disconnect and have no effect on any non-required bonds. There is no hazard and there is no code violation with an additional bond and there is some safety benefit as I pointed out in my previous post.