Lightning protection & rooftop solar

Status
Not open for further replies.
B

BandGap1.1eV

Member
Location
East Coast
Good morning all -

As PV design professionals, I think it's widely understood that PV and lightning protection systems should be kept separate. They are governed by different codes/requirements, and are designed to handle wildly different environmental situations.

A lightning protection "guy" on a current project is INSISTING he needs to bond his rooftop conductors to my EGC/racking whenever he gets within 6' and is threatening to withhold the UL Master Certification Label if he's not allowed to.

I've searched what I could in NFPA780 (UL96A and LPI175 I would have to pay for) and can't find any reference to this. Any citations from the gourp would be appreciated. I've already pointed out the earthing requirements for lightning protection (NFPA780 4.13.1) is very different that PV.

Why would we take an engineered lighting protection system that uses massive conductors to direct 30,000A to ground, and bond it to a #6 copper?
 
BandGap1.1eV said:
Why would we take an engineered lighting protection system that uses massive conductors to direct 30,000A to ground, and bond it to a #6 copper?
Click to expand...
so you don't get lightning jumping between the two conductors. it is safer if they are bonded together.

if you do not want him to bond to your stuff just don't put your stuff within 6 feet of his down conductors.

NFPA 780 has a whole section on solar arrays.

1634744392957.png
 
Have the owner sign a waiver that any damage to the PV system will not be borne by you or the manufacturer?

Maybe also tell the 'guy' that you can extend a copper EGC to the points he wants but that he may not bond directly to the solar modules?
 
jaggedben said:
Have the owner sign a waiver that any damage to the PV system will not be borne by you or the manufacturer?

Maybe also tell the 'guy' that you can extend a copper EGC to the points he wants but that he may not bond directly to the solar modules?
Click to expand...
Yeah. I'd want any bonding to happen between the modules and the grounding electrode system, not upstream of the modules..
 
ggunn said:
Yeah. I'd want any bonding to happen between the modules and the grounding electrode system, not upstream of the modules..
Click to expand...
Therein lies the nuance. From my reading, there are two ways to ground a lightning protection system; with individual ground rods or tied into a ground ring for the entire facility. This particular facility does not have a ground ring, so by bonding the PV system to the lightning system, you are now bonding the PV array at two seperate points (the lightning systems ground rods, and the building steel) which is a no-no.

The purpose of lightning aerials and a lightning protection system is to divert the surge to ground so it does not follow a path through the building. By bonding to the PV array, you are encourgaing exactly that.
 
petersonra said:
so you don't get lightning jumping between the two conductors. it is safer if they are bonded together.

if you do not want him to bond to your stuff just don't put your stuff within 6 feet of his down conductors.

NFPA 780 has a whole section on solar arrays.

View attachment 2558144
Click to expand...

I wish it were that simple. He put his stuff within 6' of my stuff.

How would it be safer to encourage a lightning surge to dissipate [proportionally] through the #6 GEC rather than the engineered lighting protection system?
 
BandGap1.1eV said:
I wish it were that simple. He put his stuff within 6' of my stuff.

How would it be safer to encourage a lightning surge to dissipate [proportionally] through the #6 GEC rather than the engineered lighting protection system?
Click to expand...
I think it is safer to avoid flashover if they are in close proximity.
 
BandGap1.1eV said:
This particular facility does not have a ground ring, so by bonding the PV system to the lightning system, you are now bonding the PV array at two separate points (the lightning systems ground rods, and the building steel) which is a no-no.
Click to expand...
Not super familiar with the typical connectivity of these system, but the lightning system ground rods are connected to the building steel and the Grounding Electrode System, since all ground rods present need to be connected to the GES? If so, can you bond the PV array to the lightning system and disconnect your other PV to GES bond? That would avoid the double bonding.

Cheers, Wayne
 
wwhitney said:
Not super familiar with the typical connectivity of these system, but the lightning system ground rods are connected to the building steel and the Grounding Electrode System, since all ground rods present need to be connected to the GES? If so, can you bond the PV array to the lightning system and disconnect your other PV to GES bond? That would avoid the double bonding.

Cheers, Wayne
Click to expand...
how would this help anything?
 
wwhitney said:
Not super familiar with the typical connectivity of these system, but the lightning system ground rods are connected to the building steel and the Grounding Electrode System, since all ground rods present need to be connected to the GES? If so, can you bond the PV array to the lightning system and disconnect your other PV to GES bond? That would avoid the double bonding.

Cheers, Wayne
Click to expand...
Probably he can't do this because the 'other PV to GES bond' is an EGC that is needed for ground fault protection and other such safety issues that have nothing to do with lightning. It could be dangerous, and would certainly be a code violation.
 
petersonra said:
how would this help anything?
Click to expand...
By ensuring that the only bonding involving the PV is to an adjacent object likely to be at a similar (lightning-induced) potential, and the PV system is not part of a path between two locations at significantly different potential. The latter being what I took "bonding twice is a no-no" to mean.

Cheers, Wayne
 
jaggedben said:
Probably he can't do this because the 'other PV to GES bond' is an EGC that is needed for ground fault protection and other such safety issues that have nothing to do with lightning. It could be dangerous, and would certainly be a code violation.
Click to expand...
I guess it could only work then if the lightning system down conductor could fulfill the role of the EGC, which seems challenging.

How about adding a high-frequency choke to the regular PV EGC so it's at a high impedance for lightning? [Just brainstorming here.]

Anyway, sounds like the solution is to get the lightning installer to move their stuff to more than 6' away from the PV, so the PV doesn't need to be bonded to it.

Cheers, Wayne
 
According to the NEC anything thing that is built, other than equipment, is a structure. The building codes have much more nuanced definitions.
 
pv_n00b said:
According to the NEC anything thing that is built, other than equipment, is a structure. The building codes have much more nuanced definitions.
Click to expand...
Ok, so in RJ's photo, that is a structure because of the concrete base which is not "equipment"? Now what about the same thing but with a driven post.....is the entire thing equipment then? Or is the post not equipment? ;)
 
electrofelon said:
Ok, so in RJ's photo, that is a structure because of the concrete base which is not "equipment"? Now what about the same thing but with a driven post.....is the entire thing equipment then? Or is the post not equipment? ;)
Click to expand...
on that note, we're required to ground a pole mounted temp service electro.....~RJ~
 
Ok, so in RJ's photo, that is a structure because of the concrete base which is not "equipment"? Now what about the same thing but with a driven post.....is the entire thing equipment then? Or is the post not equipment? ;)
Click to expand...

I would say the post is the structure, equipment such as PV modules and inverters are attached to the post. But it's a point of interpretation. From the NEC:
Equipment. A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation.
Click to expand...
 
Status
Not open for further replies.
Top