Bonding Jumper

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Dennis Alwon

Dennis Alwon

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I have service conductors that are larger than 1100kcm copper so the grounding electrode conductor is 3/0. However if I run 3/0 to my building steel and then use a bonding jumper to water pipes I have to size the bonding jumper per T.250.102(C)(1). That could potentially be larger than the grounding electrode conductor which would not make sense.

Is there an exception for this that I haven't found?
 
I think your conductor to the building steel would have to be as large as the jumper to the water. Under the '17 CVode it would need to be sized by 250.102 just like the water bond plus you can't interject a "weak link" in the chain.
I'll work on Code references.
 
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Is your conductor any of these?

Table 250.102(C)(1) Grounded Conductor, Main Bonding Jumper, System Bonding Jumper, and Supply-Side Bonding Jumper for Alternating-Current Systems
Click to expand...
 
Dennis Alwon said:
I have service conductors that are larger than 1100kcm copper so the grounding electrode conductor is 3/0. However if I run 3/0 to my building steel and then use a bonding jumper to water pipes I have to size the bonding jumper per T.250.102(C)(1). That could potentially be larger than the grounding electrode conductor which would not make sense.

Is there an exception for this that I haven't found?
Click to expand...


You had me work on this one,

In the context of the bonding jumper you describe see 250.53 specifically 250.53(C) which tells you to size per 250.66

otherwise you had me scratching my head too.
 
mopowr steve said:
You had me work on this one,

In the context of the bonding jumper you describe see 250.53 specifically 250.53(C) which tells you to size per 250.66

otherwise you had me scratching my head too.
Click to expand...

I agree that's why I asked if it was one of the ones in that table, this type of bonding jumper is not in T250.102(C)(1).
 
The steel is the grounding electrode so a 3/0 is run to that based on 250.66. If I continue to a water pipe with a bonding jumper- say the water is not an electrode ( I don't think it matters) would I have to size my jumper based on 250.102 if that is larger than 3/0
 
Is the “non grounding electrode waterline” you call it subject to being energized by the service entrance conductors? I would think NOT. So needing to bond sized by 250.102 seems mute.

Now the bonding jumper within the service cabinet.....YES
 
Under '17 would your building steel be a grounding electrode ??
At first thought in reading 250.104 in '17 it does appear you could jump to building steel since 250.68(C) states building steel can be used as an interconnection but I still think your jumper from service to steel would need to be sized by 250.102 also per 250.102(C).
 
augie47 said:
Under '17 would your building steel be a grounding electrode ??
At first thought in reading 250.104 in '17 it does appear you could jump to building steel since 250.68(C) states building steel can be used as an interconnection but I still think your jumper from service to steel would need to be sized by 250.102 also per 250.102(C).
Click to expand...


If the building steel meets the conditions it can be an electrode. This is just a hypothetical.

If you don't like that then suppose I had a grounding electrode conductor to a water line based on 250.66-- water line is an electrode. Now I have to bond the building steel If I use a bonding jumper based on 250.102(C)(1) to the steel from the water pipe it appears it could be larger than the 3/0 grounding electrode conductor.
 
I have to admit that I’m only looking in the ‘14 NEC, that’s what’s setting next to me right now.
 
I still go back to 250.104(C) in that the structural metal frame can be connected to one or more grounding electrodes if the grounding electrode or bonding jumper is of sufficient size. To me, if the jumper from the water to the steel has to be sized per 250.102, so would the jumper to the water from the service for the path to be of sufficient size.
 
Gus, you are saying even though the the code states the grounding electrode conductor can be sized to 250.66 you are saying by installing the bonding jumper, which may be larger, would make me have to upsize my grounding electrode conductor. I don't see that... Seems crazy that the bonding jumper needs to be larger when it is part of the grounding electrode system. I can see it with a bonding jumper for the conduit but not for the grounding electrode system.
 
Maybe be a bad analogy, but look at 250.66(A).
Note the GEC to the ground rod can be a #6 UNLESS it extends to other electrodes that require a larger conductor.
To me, it's the same principle.. if the water or steel reqquire a certain size bonding conductor you have to assure there is not a smaller conductor in that path.
 
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