Bonding

[D Skelton]

Ok chaps, so why do we bond lightning conductors???

I've asked quite a few people not one of which has got the foggiest?! Seems idiotic to me

 

[Engineer54]

If you stop and think about it for a minute or two, all would become clear. No bonding would almost always create a high degree of flash sparking between exposed (and sometimes even unexposed) earthed building metalwork and LP air conductors (roof area) and down conductors (walls) that can cause severe damage to the building structure and any earthed metallic equipment...


Bonding will virtually nullify any tendency to flash across as the two systems would be at virtually the same potential. The use of surge protectors helps protect any sensitive internal/external systems and equipments from damage, from direct or induced impressed high voltages due to an actual lightning strike to a protected building....

 

[D Skelton]

But what if there is no building metalwork, or, the building metalwork is nowhere near the lightning conductor? Wouldn't bonding it potentially introduce a lightning surge to all exposed conductive parts within the building?

 

[Engineer54]

But what if there is no building metalwork, or, the building metalwork is nowhere near the lightning conductor? Wouldn't bonding it potentially introduce a lightning surge to all exposed conductive parts within the building?

That's what Surge protectors are for!!! I've just read Tony's link above, it's basically confirming what i've stated, ....but far more eloquently than i...lol!!

There are VERY few buildings where Lightning Protection would have been installed, that doesn't have huge amounts of steelwork within the fabric of the building. In some cases the buildings steelwork is actually used as the down conductor, which makes equipotential bonding even more necessary....

 

[D Skelton]

There are VERY few buildings where Lightning Protection would have been installed, that doesn't have huge amounts of steelwork within the fabric of the building.

What about churches?

And forgive me, my knowledge of SPD's is very limited. Would you fit one in line between your earth bar and every CPC then? Or would you fit one in line on the bonding conductor between the lightning conductor and your earth bar? If so, how would that allow for equal potential?

 

[Engineer54]

What about churches?

And forgive me, my knowledge of SPD's is very limited. Would you fit one in line between your earth bar and every CPC then? Or would you fit one in line on the bonding conductor between the lightning conductor and your earth bar? If so, how would that allow for equal potential?

No, ...they would be connected to the DB's and/or at the origin of sensitive systems. I've seen connections from LP systems to HVAC roof plant with in line surge arresters, but never to the buildings bonding arrangements... Surge arresters allow free passage of electrons under normal circumstances, it's only when voltages reach a predetermined level that the protective device operates and hopefully dissipates the spike...

Check out surge arresters on the web, they can explain the theory and workings far better than i ...lol!!!!

 

[D Skelton]

Yes, but my understanding of SPD's is that they are never fitting in line on CPC's. I may be wrong there however.

 

[Engineer54]

Yes, but my understanding of SPD's is that they are never fitting in line on CPC's. I may be wrong there however.

Don't think i mentioned SPD's being connected in-line on CPC, I was talking about Lightning Protection roof air conductor grids connecting to the metal framework of large HVAC roof units and the like, via an in-line surge arrester. Only ever saw that once and supposedly, the LP system was designed by Furse for the customer... Can't say i would agree with it myself, but then i don't know the criteria Furse was working too...

 

[Deleted member 9648]

This was the first question I asked when I joined the forum...(2009)...!.....and I didnt really get a satisfactory answer then,my confusion being based on the fact that a LPC is invariably outside of the EPZ.
Do recall though that the guidance is that bonding of lightning conductors should only be undertaken in consultation with a lightning protection specialist....not like just bonding the gas then!