Does anyone know much about lightning protection systems?  I am in the middle of a falling out between two experts(!) and while I now know more than I did about lightning, I can't decide who is believable. Our facilities team have decided I'll be the best person to resolve the issue.

We own a building, which has lightning conductor, with an 'early streamer emission' spiky thing, which (as far as I can make out) actively induces the lightning to strike at a particular place by dumping a charged capacitor through a transformer sooner than a 'natural' strike would occur, which is interesting, but I'm not sure if that's relevant to the argument.

It is earthed to reinforcement bar connection in our basement car park, via the normal sort of flat strap down the outside of the building.

For some reason, we seem to have two maintenance / inspection contracts in place. 

We have the company that installed it (I'm not sure when, at least five years ago) who have recently provided a test certificate declaring "that the lightning protection earthling [sic] system at the above site has been tested for ohmic resistance in accordance with recommendations of the NF C 17 102-2011 and BSEN 62305-2011.  The resistance values obtained are satisfactory, and comply with section three item 16, 1 of this document"  The stated resistance is 1.09 ohms at the earth position in the car park.

Meanwhile, we have an inspection by our insurer, who have more recently issued a report staing "immediate danger" and that "The earth rod is measuring an excessive resistance, which is above the allowable value of 10 Ohmns [sic]. This requires immediate attention to ensure that the lightning protection system will provide adequate protection to this premise in the event of a lightning strike."

Outfit B say they "carried out a test of the down conductor by placing a Stakeless earth clamp meter around the down conductor. This clamp meter is calibrated and checked against a known source before each use. Unfortunately, I was unable to achieve any measurement yesterday as the meter indicated that the reading was above the scale of this test equipment i.e. >1550 Ohms."

Outfit A say "You can not test a single earth with a clamp meter, to use a clamp meter you will require 3 or more earth to gain a reading, this should of been test with a megger and tested from a none earth as it a single earth (Re-Bar Piles as the earthing system) or to put 2No subs earth away from the building of which will give a reading for a single earth.  Sorry but I do not think they know how to test a single earth."

I've tried to make the two organisations talk to each other, but I'm getting reported that one hung up the phone on the other and now the other are declining to try again.

Normally I'd side with the more specialist outfit, but in this case that's the installer, who (arguably) has an interest in their work not being condemned.  Maybe I should go with our insurer's outfit, but I do have my niggling doubts there - they seem very good with our (aged, idiosyncratic) lift, but I'm not sure they are lightning specialists.

I can't even pick who to believe on the basis of the number of spelling mistakes in their certificates - that's one all. 

Suggestions?

BS EN 62305 is another one of those standards with parts (BS EN 62305-)

Part 1 - General Principles

Part 2 - Risk Management 

Part 3 - Physical damage to structures and life hazard

Part 4 - Electrical and electronic systems within structures

So perhaps the installer can explain which part contains "Section 3 Item 16 which the resistance values are in compliance with".

Similarly the insurer should advise which published method they have used to make their determination as a qualified electrician.

Originally Posted by: achrn

Does anyone know much about lightning protection systems?  I am in the middle of a falling out between two experts(!) and while I now know more than I did about lightning, I can't decide who is believable. Our facilities team have decided I'll be the best person to resolve the issue.

We own a building, which has lightning conductor, with an 'early streamer emission' spiky thing, which (as far as I can make out) actively induces the lightning to strike at a particular place by dumping a charged capacitor through a transformer sooner than a 'natural' strike would occur, which is interesting, but I'm not sure if that's relevant to the argument.

It is earthed to reinforcement bar connection in our basement car park, via the normal sort of flat strap down the outside of the building.

For some reason, we seem to have two maintenance / inspection contracts in place. 

We have the company that installed it (I'm not sure when, at least five years ago) who have recently provided a test certificate declaring "that the lightning protection earthling [sic] system at the above site has been tested for ohmic resistance in accordance with recommendations of the NF C 17 102-2011 and BSEN 62305-2011.  The resistance values obtained are satisfactory, and comply with section three item 16, 1 of this document"  The stated resistance is 1.09 ohms at the earth position in the car park.

Meanwhile, we have an inspection by our insurer, who have more recently issued a report staing "immediate danger" and that "The earth rod is measuring an excessive resistance, which is above the allowable value of 10 Ohmns [sic]. This requires immediate attention to ensure that the lightning protection system will provide adequate protection to this premise in the event of a lightning strike."

Outfit B say they "carried out a test of the down conductor by placing a Stakeless earth clamp meter around the down conductor. This clamp meter is calibrated and checked against a known source before each use. Unfortunately, I was unable to achieve any measurement yesterday as the meter indicated that the reading was above the scale of this test equipment i.e. >1550 Ohms."

Outfit A say "You can not test a single earth with a clamp meter, to use a clamp meter you will require 3 or more earth to gain a reading, this should of been test with a megger and tested from a none earth as it a single earth (Re-Bar Piles as the earthing system) or to put 2No subs earth away from the building of which will give a reading for a single earth.  Sorry but I do not think they know how to test a single earth."

I've tried to make the two organisations talk to each other, but I'm getting reported that one hung up the phone on the other and now the other are declining to try again.

Normally I'd side with the more specialist outfit, but in this case that's the installer, who (arguably) has an interest in their work not being condemned.  Maybe I should go with our insurer's outfit, but I do have my niggling doubts there - they seem very good with our (aged, idiosyncratic) lift, but I'm not sure they are lightning specialists.

I can't even pick who to believe on the basis of the number of spelling mistakes in their certificates - that's one all. 

Suggestions?

Please PM me if you want to discuss in detail, and it would be good to know the two LPS organisations.

I have just done a similar procedure on a job for a client.

The organisation that stated you cannot use a stateless earth tester for a single electrode is correct.

1.55 k Ohms is way too much for an electrode.  Was that your measurement?  How did you measure it, and with what instrument?

It is on the edge of my ability, but I do have a general knowledge of LPS and an in-depth knowledge of electrical systems.