Lighting protection via 10mm bonding cable

[D Skelton]

So, I'll start by saying that my knowledge of the regulations surrounding lightning protection systems are limited, it simply isn't work that we as a company carry out as we leave it to the specialists.

During an EICR I find what looks to be an old aerial pole on the roof of the building, looks like a 3m scaffold pole just bolted vertically into the roof structure. Now this has been bonded back to the MET with 10mm bonding cable. It's clearly not an extraneous conductive part and so the bonding needs removing. My question is regarding the code to give it. The chances of it being struck by lighting are slim as there are higher buildings next door with proper lightning protection systems and charge dissipators atop. That said, without experience in lighting protection, is it up to me to make this judgement call and give it a C3 or should I just play it safe and C2 it? My gut tells me the latter may well be the best approach.

 

[HappyHippyDad]

Why would taking the bonding off make it safer Mr DS?
Is it because it is clearly not the correct method of lightning protection so would be better not to attract the lightning to that point?
I think Darkwood knows quite abit about lightning so I hope he replies.

 

[D Skelton]

Why would taking the bonding off make it safer Mr DS?
Is it because it is clearly not the correct method of lightning protection so would be better not to attract the lightning to that point?
I think Darkwood knows quite abit about lightning so I hope he replies.

Bonding needs to be applied to lighting protection systems as they are extraneous conductive parts, however when a part isn't extraneous, and bonding the said part essentially turns your 10mm bonding conductor into a potential lightning conductor, this just ain't good really is it lol

 

[Rockingit]

Wasn't it a fashion though a while back to go bonding aerial masts and satellite dishes? Might be worthwhile asking if there was ever anything on it!

 

[Hobsoni]

I think that because you are aware of the potential hazards that it has to be noted as a C2. Is there no access for you to at least cut the 10mm (outside the property) off?

 

[davesparks]

Could it be an old CB or HAM aerial installation which would have required an earth connection to work? Although I'd have expected it to go to a rod rather than the MET.

 

[LeeH]

Could it be an old CB or HAM aerial installation which would have required an earth connection to work? Although I'd have expected it to go to a rod rather than the MET.

The only earth they needed Dave was through the coax shield.

 

[D Skelton]

I think that because you are aware of the potential hazards that it has to be noted as a C2. Is there no access for you to at least cut the 10mm (outside the property) off?

I could have done, but I was there to provide a report only, not to start chopping bonding conductors, regardless of any potential danger.

I gave it a C2 in the end but basically said that they needed to gain the advice of a lightning protection specialist.

Probably the best way to deal with it in my eyes. I've covered my backside but at the same time told them that it needs further investigation by someone who knows better than I do whether it should be there or not.

 

[Marvo]

If you decide to disconnect it I'd suggest a full risk assessment first including referring to whether charts for strike frequencies etc. I'd personally leave it connected to the MET. Is it against the UK regs to have an item connected to the MET if it doesn't qualify as extraneous conductive?

 

[D Skelton]

If you decide to disconnect it I'd suggest a full risk assessment first including referring to whether charts for strike frequencies etc. I'd personally leave it connected to the MET. Is it against the UK regs to have an item connected to the MET if it doesn't qualify as extraneous conductive?

I wouldn't know where to start with a strike frequency risk assessment, nor would I know whether the conductor's existence is actually dangerous, hence why I won't be touching it until a specialist in that area has given their advice.

 

[Marvo]

Maybe I'm misunderstanding, was the pole installed as lightning protection or is it just a pole bolted to the roof for some other obscure reason?

 

[Richard Burns]

UK has less than 25 thunderstorm days per year so becomes a low risk situation.
Connection of non extraneous parts to the main bonding (or MET) only means that the part could now become live in the case of a fault whereas it would not before, because the pole is well out of reach there should be no likely risk present.
Lightning conductors connected to the earthing system just provide a good path to earth, without this they may well "side strike" into the earthing system anyway.
However I do not know enough to make a sound judgment.

 

[D Skelton]

Maybe I'm misunderstanding, was the pole installed as lightning protection or is it just a pole bolted to the roof for some other obscure reason?

Just a pole bolted to the roof mate lol

 

[tazz]

No expert on this, but can quote what i see on construction buildings, And that is on large copper strap, covering the complete circumference of the building. With completed straps being taken down the building into dedicated earth rods.....on saying this, I was always informed that lighting hits the highest point...Liberia, when two high hotels were missed and the lightning hit a lower construction crane...So there must be some design aspects involved here

 

[Rockingit]

Go here, and ask for the guide to BS EN 62305. You wont be disappointed with what arrives in your post.

Furse Literature

 

[amckay]

I'm pretty sure its a requirement to earth TV aerials and sat dishes. Maybe that's what it was for? 3m pole tho does sound like it could have been a radio mast?
I'm sure if it was lightning protection the installation requires surge protection but I'm no expert on lightning protection

 

[ferg]

I'm pretty sure its a requirement to earth TV aerials and sat dishes. Maybe that's what it was for? 3m pole tho does sound like it could have been a radio mast?
I'm sure if it was lightning protection the installation requires surge protection but I'm no expert on lightning protection

You had better tell SKY then

 

[UNG]

Also some good info to download here

A N Wallis

In the past I've had some good information and help from the technical support people over the phone from both Wallis and Furse so may be worth a call. Had a chat with a guy at Furse once after I had faxed some info to him phoned him to discuss the project and his response was it would be more dangerous to install lightning protection than not installing it so lightning protection ain't the be all and end all solution on some sites

With regard to the OP it sounds like this has possibly been some sort of comms installation at some time, it is not clear in the post if there is actually a lightning protection system installed and this is just a bond to the MET or if this conductor is the sole earthing point if it is the latter it would be better disconnected.

I've seen quite a few iffy installations on sites when I was installing a lot of comms kit a number of years ago including a failed ground termination on a lightning protection system on one site and the whole of the roof system was earthed on two coax shields from a couple of other radios on the roof, only became apparent because the kit we were installing suffered some interesting interference problems