Lightning Protection (Structural Steel + Grounding Rods?)

[mbk.2k3]

I am using the CSA-B72-M87 Installation code for lightning protection systems.
It is closely related to NFPA 780.


My building is a standard industrial facility, with the framework comprising of structural steel that is connected to the ground grid via bolted/welded connections.


According to the CSA standard:
8.6 Use of Reinforcing Steel

Reinforcing steel in an exterior wall, in a column, or in a reinforced concrete post that complies with CSA Standard CAN3-A23.3, may be used as a down conductor or ring conductor if the electrical continuity of the bars equivalent to No. 2 AWG is ensured.

According to NFPA 780:

4.16 Structural Steel Systems.
4.16.1 General. The structural steel framework of a structure shall be permitted to be utilized as the main conductor of a lightning protection system if it is electrically continuous or is made electrically continuous.

So my question is this:
If I have air terminals and copper down conductors, do they need to be connected to a grounding rod directly? Or can i simply connect them to the structural steel closest to grade level (at the bottom of the building?)

 

[mkgrady]

I am using the CSA-B72-M87 Installation code for lightning protection systems.
It is closely related to NFPA 780.

So my question is this:
If I have air terminals and copper down conductors, do they need to be connected to a grounding rod directly? Or can i simply connect them to the structural steel closest to grade level (at the bottom of the building?)

I believe when the steel is acceptable as the down conductor it just replaces the conductor. You still have to extend the down conductor to ground rods from the steel at the lower level

 

[mgookin]

I am using the CSA-B72-M87 Installation code for lightning protection systems.
It is closely related to NFPA 780.

My building is a standard industrial facility, with the framework comprising of structural steel that is connected to the ground grid via bolted/welded connections.

According to the CSA standard:

8.6 Use of Reinforcing Steel
Reinforcing steel in an exterior wall, in a column, or in a reinforced concrete post that complies with CSA Standard CAN3-A23.3, may be used as a down conductor or ring conductor if the electrical continuity of the bars equivalent to No. 2 AWG is ensured.

According to NFPA 780:

4.16.1 General. The structural steel framework of a structure shall be permitted to be utilized as the main conductor of a lightning protection system if it is electrically continuous or is made electrically continuous.

So my question is this:
If I have air terminals and copper down conductors, do they need to be connected to a grounding rod directly? Or can i simply connect them to the structural steel closest to grade level (at the bottom of the building?)

The way I read that, one deals with reinforcing steel (rebar) and the other deals with structural steel (steel columns, beams, etc.). Reinforcing steel is lapped when it is placed. IIRC correctly it's about 30 bar diameters. While the laps are typically tied together with tie wire, I don't see how you could depend on electrical continuity in those laps.

If it were my job I'd run the down conductor all the way down and not mess with steel other than bonding as required.
.

 

[mbk.2k3]

The way I read that, one deals with reinforcing steel (rebar) and the other deals with structural steel (steel columns, beams, etc.). Reinforcing steel is lapped when it is placed. IIRC correctly it's about 30 bar diameters. While the laps are typically tied together with tie wire, I don't see how you could depend on electrical continuity in those laps.

If it were my job I'd run the down conductor all the way down and not mess with steel other than bonding as required.
.

once you run the down conductor all the way down, you would connect it to its own grounding rod? and not touch the existing rods/grounds for structural steel?

 

[mgookin]

For a job in Canada I'd defer to the CSA standard.
Do you have access to a copy of it?
Getting it wrong could be expensive.

 

[LightningProtectionDesign]

I am using the CSA-B72-M87 Installation code for lightning protection systems.
It is closely related to NFPA 780.


My building is a standard industrial facility, with the framework comprising of structural steel that is connected to the ground grid via bolted/welded connections.


According to the CSA standard:
8.6 Use of Reinforcing Steel



According to NFPA 780:



So my question is this:
If I have air terminals and copper down conductors, do they need to be connected to a grounding rod directly? Or can i simply connect them to the structural steel closest to grade level (at the bottom of the building?)

I don't know about the CSA standards, but per the NFPA 780 you can use the structural steel as a down conductor, but would still have to attach the steel to ground rods. If using the steel as a down conductor you would have to have a ground rod for every 60' of perimeter (instead of one for every 100' of perimeter if using full cable down conductors.

As as I said, I don't know about the CSA standard in terms of the number of down conductors relative to the perimeter, but from what you posted if using the steel as a down conductor you would still need to go from the steel to a ground rod at the base.

 

[north star]

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mbk.2k3,

Is the building existing, or still in the design phase ?


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