bonding lightning protection systems

[electrofelon]

250.106 states that these systems shall be bonded to the grounding electrode system, but does not specify how to size the bonding jumper? 250.66?

 

[George Stolz]

Electrofelon, whenever you start a thread I can't help but remember some of the humdinger-threads your seemingly innocent questions spark.

I would say given the lack of text, it would be up to the AHJ, but Table 250.66 does seem like a likely candidate.

Perhaps one of the members with access to NFPA 780 could see if that standard says anything about it.

 

[bphgravity]

To comply with the NFPA 780, follow the requirements in section 4.14 for "Common Grounding". For both Class I and Class II materials, a 26,240 cir. mil conductor (#6 AWG) would be sufficient.

 

[George Stolz]

For both Class I and Class II materials...

Can you explain what that means?

 

[bphgravity]

Sure...

Class I materials are required for structures not exceeding 75' in height.

Class II materials are required for structures over 75' in height.

The height of a structure in relation to surrounding structures is one of the more significant considerations when considering lightning risk analysis.

 

[electrofelon]

Interesting, thanks guys. We are doing a service upgrade and I looked up to the roof and noticed the air terminals - guess its time to keep an eye out for them. This will be the first lightning protection system I have bonded. I am interested in how the actual connection will be made between the bonding jumper and the loose-braid cable of the LPS. I suppose I will just split bolt it. Contrary to the way it sometimes seems George, my goal isnt to just stump you guys or try to break the longest thread record

 

[NoVA Comms Power]

... I am interested in how the actual connection will be made between the bonding jumper and the loose-braid cable of the LPS. I suppose I will just split bolt it. ...

Is a #6 jumper between a LPS elecrode and an electrical grounding electode (or GEC, buss bar, or grounding electrode jumper) a possible option?

 

[George Stolz]

Thanks, Bryan, learn something new every day.

Contrary to the way it sometimes seems George, my goal isnt to just stump you guys or try to break the longest thread record

Well, if you're secretly harboring such desires, you'll have to get back into Article 210 to try again.

 

[electrofelon]

Is a #6 jumper between a LPS elecrode and an electrical grounding electode (or GEC, buss bar, or grounding electrode jumper) a possible option?

Yes I could see if the electrode is easily accessible, and attach my jumper to that rather than the loose braid cable, that would be a more desirable connection in my book

 

[ibew441dc]

250.106 states that these systems shall be bonded to the grounding electrode system, but does not specify how to size the bonding jumper? 250.66?

I do not have much experience with LPS but I have wandered the answer to that question.

The answer that I came up with (and it doesn't mean its right) is found in 250.94(1)(2)and(3). (2005 NEC)

There is no code language leading me to 250.66 or 250.122.

ibew441dc

LONG LIVE THE FORUM!

 

[ibew441dc]

It is obvious to me why we bond the LPS to our electrical systems, but misleading on how to size the jumper correctly.



ibew441dc

 

[cripple]

bonding lightning protection systems

NFPA 780 requires the lightning protection systems to be bonded to the electrical system, and the bonding conductor is to the same size of the main lightning conductor.

4.14 Common Grounding.
4.14.1 General. All grounding media in or on a structure shall be interconnected to provide a common ground potential.
4.14.1.1 This interconnection shall include lightning protection, electric service, telephone, and antenna system grounds, as well as underground metallic piping systems.
4.14.1.2 Underground metallic piping systems shall include water service, well casings located within 7.6 m (25 ft) of the structure, gas piping, underground conduits, underground liquefied petroleum gas piping systems, and so on.
4.14.1.3 Interconnection to a gas line shall be made on the customer?s side of the meter.
4.14.1.4 Main-size lightning conductors shall be used for interconnecting these grounding systems to the lightning protection system.

The definition of main conductor is as follows:
3.3.5.3* Main Conductor. A conductor intended to be used to carry lightning currents between strike termination devices and ground terminals.

when installing this bonding jumper you will to check on the size of main lightning conductor.