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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthor39North
    • CommentTimeDec 9th 2009
     
    Our house in Spain was recently struck by lightning. We were lucky as we were around as the storm approached and disconnected everything. Even so it wiped out our hot water solar controller and boiler. I have started investigating what we can do to protect the property in the future and wondered if anyone had any experience/expertise they could share.

    Sorry if this is not under the correct subject, but wasn't sure where to place it.
  1.  
    There's not much you can do to protect from a direct hit, but fortunately most damage is caused by currents induced into cables.

    If your house is one of the highest in the area and there aren't trees nearby then you may want to fit lightning conductors to define a safe route to earth. However, the chances are that the lightening entered the house via electrical, aerial & telephone cables. If the lightening lands in your area then it can induce large currents into cables without even striking them. If it lands somewhere else it can travel a long way via cables.

    You can buy a range of transient suppressor devices designed to tackle lightening. You should have some basic spark gap & electrostatic discharge protection where the cables enter the house. If the cables are overhead this should have been fitted by the electrical or telephone company, you will need to do this yourself for the aerial cables. Then you should fit some more precise transient voltage protection closer to each valuable piece of electrical kit. You can get relatively expensive plug-in products aimed at modems & PCs, or you can buy individual transient suppressor components for fitting across the mains supply, for example, in a socket or junction box.

    http://www.maplin.co.uk/Module.aspx?moduleno=499#features

    David
    •  
      CommentAuthorjoe90
    • CommentTimeDec 9th 2009
     
    We were hit by lightning last year and it blew every electrical devise in the house including some light switches. Even the cast iron guttering leaked from every joint as the putty in the joints was blown away. An assessor was sent by the insurance company because it was such a large claim and I asked him about protection and he told me protection that you can buy is ok for induced voltages from nearby hits (as David says above) but no amount of protection will stop a direct hit from doing its worst to electrical equipment although structural damage can be limited by earth straps from the ground to the highest points.

    The lightning hit a chimney (although we have trees higher than the house) blowing the top to bits, melting the flashing around the base jumping to the cast iron guttering and generally dispersing through anything and everything. Still, we got all new equipment and despite being told by some people that it was "an act of God" the insurance company were very good and coffed up for the lot.
    • CommentAuthorchuckey
    • CommentTimeDec 9th 2009
     
    A lightning conductor placed above a gable end, connected via a 3/8"diam stainless steel cable or a decent sized piece of copper (normally 30mm X 3mm cross section) going straight down the wall to a buried copper earth rod. Lightning is funny stuff, it really does not like going round corners. I have seen where it has come out of the corner of a earthing bar where it had a right angle bend in it and tracked across the surface of a building. One cheap thing to do in your case is to make sure that the copperware in loft/solar kit is actually bonded to a decent earth. As mentioned, what has actually happened in your case was that the lightning strike hit your solar kit, so raising its potential to perhaps 20,000 volts (a very typical figure) and also due to surface leakage most of the house was raised to some other dramatic figure. So this'er high voltage was looking for an earth, the house was at, say 10,000 volts, but the mains feed to your solar controller has its "neutral" conductor earthed at your local substation. As the substation has not had any leakage to it it is still at earth potential, so this is where the lightning found its earth, frying the controllers internals.
    It is because of the remote "earths" on things like telephone cables and mains feeds that these always suffer during a lightning strike. TV aerials, er, no their wiring is within the confines (normally) of the house so they suffer less. It would still be good practise to put a good earth on them though, otherwise the strike could travel down the aerial into the back of a TV or amplifier THEN find a "proper" earth via their mains feeds.
    FWIW:
    I was having a pre-dinner party drink with my guests during a storm when suddenly there was a VERY loud bang and I saw a frizzy spark curve out of the chimney breast( about 7' from the floor) and sort of curve out into the room, looked about 3' long! We rubbed our eyes and made comments of "I'll have another one of those" ilk. The next morning I discovered that my 6 pot 6' high victorian chimney stack was beautifully split into a pair of 3 pot stack! No marks on the chimney breast though.
    Frank
    • CommentAuthorCWatters
    • CommentTimeDec 10th 2009
     
    If your house has been struck you certainly need an external lightening rod professionally installed. Problem with high voltage/currents is it can get in many ways that bypass protection devices. You can get transient/surge suppressors that are fitted in or before your consumer unit. I'd look at fitting those AND individual protection for appliances as David mentions. Don't forget your phone line.
    • CommentAuthor39North
    • CommentTimeDec 10th 2009
     
    Thanks for your comments and advice. We were hit on the roof and it travelled round the metal in the top floor ring beam (basically a continuous run of concrete reinforced with a rebar structure) and blew out the plaster indoors in a couple of places obviously looking for earth. Like I said we were lucky, and certainly didn't have anything as dramatic happen as you chuckey. We are not fitted to mains electric and the solar electric system appears to be well earthed. The hot water panels are a good way from the photovoltaic panels, but nearer the house, so must have acted as a conducter to the solar controller.

    Googling I have come across a company called Foudretech who claim that they can protect an area around the mast this gadget is mounted on, and attracts any lightening and safely conducts it to earth. Would like to know if it works and if it would be better to have a mast with this on, taller than the house.

    Will look into transient/surge suppressors. We have hager fuses and the catalogue shows some bits for lightning protection.
    • CommentAuthorCWatters
    • CommentTimeDec 10th 2009
     
    I had a look at the Foudretech web site and they just appear to sell standard (and some fancy looking) lightening rods and conductors. All correctly installed lightning rods "attract" lightning away from other nearby structures thereby protecting - so this maybe just marketing speak you were reading.

    As a thunder cloud passes overhead charge in the ground is attracted to charge in the cloud and it tries to get as close to the cloud as it can - so it all accumulates on any tall pointy objects like chimneys or church spires. Eventually the voltage between that object and the cloud is high enough for a spark to leap the gap. So the lightening conductor should be the highest thing around and pointed to ensure thats where the charge accumulates and where the lightening strike occurs. Normally they are mounted on and sticking up above your chimney as thats the highest thing on the house.

    Your lightening strike may not have gone directly through the controller. It's possible for the current in the lightening strike to induce a current/voltage in nearby wiring and for that to damage equipment. Ideally run the lightening conductor down the outside of your house as far away from other wiring as posible - for example don't clip your TV aerial downlead or anything like that to the lighening conductor!
    • CommentAuthorchuckey
    • CommentTimeDec 10th 2009 edited
     
    There are three basic methods for the terminal of your lightning conductor, they are, the old "spiky thing", an ion generator (Foudretech method) and the fakirs bed developed by Glasgow Uni. We found there to be no advantage with the ion generator over a "spiky thing"- some suppliers even use use industrial sized razor blades to get a very sharp edge! The fakirs bed is shrouded in mystery, a Prof from Glasgow supplied this thing which we installed on top of the Black Hill TV transmitting station mast, after some length of time -7 years? we returned it to him. It appeared to work very well, but the whole project just disappeared into a black hole.
    I would be more impressed with Foudretech site, if they had not shown the control tower's protection with a sharp right angled bend between the parapet conductors and the vertical section. P. 6 in their .pdf info bulletin was good it showed the leader, the initiation for a strike is a weak upwards strike from the mast etc which when it hits the clouds allows the passage of the big strike.
    Italy is the worst country for lightning strikes, people have measured currents of 60mA flowing into their TV transmitter masts from the earth and producing the ion current into the sky at the top. These currents flow for a couple of hours before the storm appears!!
    The theoretical area of protection for a lightning conductor is based on a rolling ball, of radius = height of conductor, anything lower then the ball is considered protected by the conductor. We found in practise that a 1000' TV mast with loads of lightning conductors on its highest surface, would often have damage about 10m down on the side of the white glassfibre aerial cylinder , very weird.
    Frank
    • CommentAuthorCWatters
    • CommentTimeDec 11th 2009
     
    Interesting stuff. I'd be interested to know if you've heard this tale... During WW2 the BBC broadcast propaganda messages in German to Germany. According to the story if you walked around the transmiter mast you could hear it wispering in German. Anyway the story continues... one night lightning struck the transmitter mast and a arc was formed at a horn gap. This somehow rectified the signal and caused the broadcast to be audible leading to some locals believing the Germans had landed. Any idea if it's true/possible?
  2.  
    Oh great! Thanks Chuckey!!! I live in Italy. A friend just (3 weeks ago) had a near miss and lost his main Electricity Company Meter, once they came (only took a day as he knew somebody who knew the last mayor!) and replaced the meter they found they had lost a random selection of lights and the electric gate controller. However, last year another friend suffered a direct hit which vaporised all the electrics in the house - everything - they were inside; it lasted several seconds and was very scary!

    As of now we have £31,000 of PV panels, 5 FPs, decent solar controller, new boiler, pumps etc....and a new earth for the house. We already have surge protectors on the PCs and TV and some funny little box you plug into a spare socket that claims to protect everything within 30 meters electric cable length but I seem to remember that the in-line surge protectors had some sort of maximum limit. Electricity comes down an overhead line into a std modern meter no earth. I am surrounded on 2 sides by trees close by and much taller than the house.

    Do I still need a house mounted razor blade - which would cost a fair bit?

    If I don't do this, might it be sufficient or might it add some braces to the presence of the trees if I mounted a bit of left over copper earthing rod out the top of the tallest tree and attached it to some heavy earth wire and then to the rebarred 4x50m wall?

    We are wireless to broadband but have digital TV via a cable - is there a way to send this signal wirelessly without having a sacrificial tuner?

    CWatters, would I need one individual transient suppressor per plug, per MCB, per Consumer Unit (of which I will have 4 in all soon)?

    There's no such thing as safe from lightening - but what might a cheap and easy to install DIY 95% assurance set up look like for my house?
  3.  
    <blockquote><cite>Posted By: Gotanewlife</cite>We are wireless to broadband but have digital TV via a cable - is there a way to send this signal wirelessly without having a sacrificial tuner?
    </blockquote>
    Wifi systems have the bandwidth for video, but aren't normally used for video distribution due to quality of service issues (the TV picture might break up if someone decides to download a big email attachment at the same time). If you only use your wifi for this connection then that shouldn't be an issue, but sounds like you're already using it for the connection from modem to PC.

    To overcome this problem the BT Broadband package includes a pair of mains Ethernet terminals for sending digital TV from modem to TV over the mains. Still requires mains at each end & assumes a British ring main, but it's one less lightening path to worry about.

    Alternatively you could use an optical fibre Ethernet connection from modem to TV.

    David
    • CommentAuthorchuckey
    • CommentTimeDec 11th 2009
     
    Cwatters, yes the "singing arc" is a well known phenomena. I have actually heard on myself. In the 60s there was a tweeter type loadspeaker, the "Ionosphone"(Sp.?), that used the singing arc - zero inertia to its "moving" parts, but loads of other electronics to put in added distortion.
    Frank
    • CommentAuthor39North
    • CommentTimeDec 11th 2009
     
    Chuckey - thanks for the info, especially about the theoretical area of protection.

    IanD - Thanks for the links. Looking at mrnathan.munichre.com we are at an average risk of lightning strikes. I am surprised as since living here I have seen some spectacular storms and a lot more lightning strikes than when I lived in the UK. The house is an an elevated position with plenty of trees around, and a bit higher risk than our neighbours. I will contact Furse and see if they can help me, but they do provide some very useful information. The insurance company seems to just pay up and don't seem to worry or be able to provide guidance/advice.

    CWatters - haven't heard the story before, but thanks for telling us about it. Hope someone can confirm/deny whether it is true or not.

    Gotanewlife - Good questions and hopefully someone answers. I think I prefer the idea of a lightning rod being attached to something else and not the house. Also easier to have the cable going in a straight line into the ground.
    • CommentAuthorCWatters
    • CommentTimeDec 11th 2009 edited
     
    Posted By: GotanewlifeCWatters, would I need one individual transient suppressor per plug, per MCB, per Consumer Unit (of which I will have 4 in all soon)?


    Try this guide or show them to your electrician..

    "How to protect your house and it's contents from Lightning"
    http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf

    It's published by the IEEE so has an American bias but the basic principles will apply in all countries.

    It refers to the use of "AC building entrance protectors" on page 11. These are surge protectors that are installed on the incoming supply to the house before the consumer unit(s). A good electrician will know what these are.

    I'd also use plug in surge/transient suppressors on things like PC's, Tv's and anything similarly expensive to replace as well. You can buy simple plug adaptors and mains extension leads with them built in.
    • CommentAuthorCWatters
    • CommentTimeDec 11th 2009
     
    Posted By: chuckeyCwatters, yes the "singing arc" is a well known phenomena. I have actually heard on myself. In the 60s there was a tweeter type loadspeaker, the "Ionosphone"(Sp.?), that used the singing arc - zero inertia to its "moving" parts, but loads of other electronics to put in added distortion.
    Frank


    Thanks.
    • CommentAuthorCWatters
    • CommentTimeDec 11th 2009 edited
     
    Another guide. This one might be easier to follow...

    http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf

    Again has an American bias but not too hard to translate "service panel" into "Consumer Unit" etc :-)
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