Effect of Lightning Strikes on a Building

[Tim]

Good evening guys,

I have just had a call to go and have a look at a hotel tomorrow that was hit by lightning yesterday morning. All i know is that its a 2 story building and was hit and now has a hole in the roof and that there is no lightning protection system in place.

They are worried that the strike may have damaged the electrics in the building and therefore voided their insurance. I have no experiance with lighting protection systems or the effects of a lightning strike on a building, I'm hoping someone on here has some insight on the main things to check. I will be recommending that they have the site assessed for an LPS by a specialist contractor as this is not something I or anyone in the company i am working for is competent to do.

My plan is as follows:
Go to site, ask the manager that was on duty at the time what happened and if anything went down/caught fire/made funny noises etc.
Then check out a sample of RCBO's/RCD to ensure the electronics in them were not damaged by the EMP.
Check Bonding and Earthing conductors and clamps for signs of overheating.
Do the usual Ze and Pfc test to check the main earthing conductor has not been damaged.

Can anyone suggest anything else that would likely have been damaged by a strike? I am working on the assumption that the strike hit some metal work on the roof (AC unit??) that was connected to the MET and that was the route to earth for the strike.

Any advice would be appreciated as this is not one of the things you come up against on a daily basis. And of course i will post up pictures when i get to site.

Cheers,
Tim

 

[Tim]

Ive just seen your edit, any speculation as to why the rods are installed but no conductors to the roof?

 

[Engineer54]

Right, ive found something interesting.

View attachment 19945

As previously stated i know very little about lightning protection systems.

The pic is of what i think (and judging by the company name i am right) is a pit to send the lightning strike to the ground directly and not through the building.

My question is where is the conductor (i believe they are lead usually) that goes around the building to capture the strike? Could it be buried with the rod? There is no evidence one is fitted and i have accounted for all the cables from the met so if there is an lps its not bonded.

If i am right in thinking the rod pits have been installed but not connected, why would this be?

Cheers,
Tim

Going by what i can see, the rod in this earth pit is connected by what looks to be a copper tape. And ''NO'', ...LP systems do not use lead conductors they will all be of high conductivity copper, usually hard drawn copper too, for strength/longevity etc, being exposed to the elements.


Hard to tell what this earth pit is being connected too, the earthing system could be a TT system or maybe was a TT system now converted to a PME system (as darkwood suggests)!! Hopefully they left the TT earth in place at the MET if it is a converted system...

 

[Darkwood]

You have a phone number on the lid .....can't do any harm to ring it and query what its purpose serves explaning what site you are on???? Let us know....

 

[Engineer54]

Ive just seen your edit, any speculation as to why the rods are installed but no conductors to the roof?

From what little i can see of the roof, there seems to be no indication of any LP system in place. Maybe it was originally planned to provide LP to this hotel but got dropped later, (are there several of these earth rod pits around the building?) after the ground works had already been completed. Which could mean an easy LP retro-fit if they so choose to fit!! lol!!

 

[Tim]

From what little i can see of the roof, there seems to be no indication of any LP system in place. Maybe it was originally planned to provide LP to this hotel but got dropped later, (are there several of these earth rod pits around the building?) after the ground works had already been completed. Which could mean an easy LP retro-fit if they so choose to fit!! lol!!

There are 7 of the pits around, i think as you said, the pits were there for the lps but it was never installed for some reason.

Ive tried to trace the copper tape with no luck. There is no structure on the roof that resembles an lps system.

Darkwood, i have tried phoning the number but it forwards to a mobile voicemail. Ill try again later.

Cheers guys

 

[Engineer54]

There are 7 of the pits around, i think as you said, the pits were there for the lps but it was never installed for some reason.

Ive tried to trace the copper tape with no luck. There is no structure on the roof that resembles an lps system.

Darkwood, i have tried phoning the number but it forwards to a mobile voicemail. Ill try again later.

Cheers guys

Sounds to me as though a provision has been made for an LP system for this hotel. The Tapes will/maybe be rolled up at the seven locations at the base of the building walls adjacent to the earth pit locations....

 

[Tim]

Well it looks like my information was wrong, the manager has just got in an confimed that there was an lps but doesnt know wether it 'works' or not.

I am poking around the hard to access parts of the loft now and look what ive found

 

[Darkwood]

Forecast is isolated thunderstorms all day...... Do you really want to be up there lol!......as you say it sticks out like a sore thumb ..... if your hair tingles get worried!!!! :sick:

 

[Engineer54]

Well it won't be doing any good below the roof tiles!! lol!! Unless you can see air conductors on the roof, be they spikes or external flat tape runs, then this building does not have an LP system... Should also be able to see down conductor test points about 1.3m from FGL on each down conductor.

Also, if that copper tape is for LP purposes, the fixing installation does not comply in any way shape or form to LP installation regulations.... The plot thickens!! lol!!

 

[Tim]

Forecast is isolated thunderstorms all day...... Do you really want to be up there lol!......as you say it sticks out like a sore thumb ..... if your hair tingles get worried!!!! :sick:

The sky is a bit dark round here, i think ill take shelter in the van, i know they say it never strikes the same place twice but i dont want to be the exception that proves the rule lol

Well it won't be doing any good below the roof tiles!! lol!! Unless you can see air conductors on the roof, be they spikes or external flat tape runs, then this building does not have an LP system... Should also be able to see down conductor test points about 1.3m from FGL on each down conductor.

Also, if that copper tape is for LP purposes, the fixing installation does not comply in any way shape or form to LP installation regulations.... The plot thickens!! lol!!

Looks like they need a proper inspection of the lp system then. I can see what looks like copper tape poking up from the apex of the roof about 8", is this a version of an air conductor?
Its too far for me to see in detail, but it looks like there are 8or so of these 8" strips.

Cheers,
Tim

 

[Darkwood]

The construct/building and earthrods all look recent ,10yrs old ...You should be able to get building plans and subsequent LP system info to boot.

 

[Engineer54]

The sky is a bit dark round here, i think ill take shelter in the van, i know they say it never strikes the same place twice but i dont want to be the exception that proves the rule lol

It can and often does!! Lightning strikes always go for a weak point...




Looks like they need a proper inspection of the lp system then. I can see what looks like copper tape poking up from the apex of the roof about 8", is this a version of an air conductor?
Its too far for me to see in detail, but it looks like there are 8or so of these 8" strips.

Cheers,
Tim

Yep, get the so-called specialists in, because bits of tape sticking up out of the roof apex does not make for a working LP system. Air conductor spikes are around 12'' long with a prominant point to them. That or the tape needs to be completley external and follow the line of Apex as well as the edges of the roof complete with cross connections. (A bit difficult to explain fully here)

Save to say, from what your telling us, it sounds like a bit of a pig's ear of an LP installation!! ...lol!! And has already proved to be ineffective!!