Mains power during lightning -was it a wind up

dencol · 03-07-2008, 09:24 PM

I am having problems with leisure battery so at the moment have been on sites using mains hook up. The other week looked like due for thunder and lightning in the area and I noticed next door removing his hook up from the power point. When speaking to him he suggested that the van would be ok as it was a Faraday cage (heard about that fellow) but by connecting to the power point I was in effect negating this. Decided it was safer to go read a book in my panel van that stand around on wet grass holding a long length of electrical cable. But now he has got me thinking is it true and should I disconnect the electrical?
He was in a caravan and I was going to point out the fact that the metal corner stays were down but decided to let it pass.

Wildman · 03-07-2008, 10:05 PM

to my way of thinking, the van and site would have a trip but a path to earth is a good thing in the event of a lightning strike. Modern electronics are easily destroyed by static charge an unearthed vehicle is a faraday cage but will still charge with static. So what is the answer? I dont use sites and never been out in the middle of an electric storm but am sure someone here will have the answer.

shortcircuit · 04-07-2008, 06:55 AM

A plastic Faraday cage? Naw! (Unless an RV which could be aluminium?)

Dont think it would make any difference if it was connected to EHU.

G2EWS · 04-07-2008, 08:11 AM

Hi Dencol,

Lightning is a strange beast and the main damage is caused by what hits the ground and travels until it finds something to eat!

You will also get surges coming along the power lines and even more prevalent the telephone lines.

As mentioned the most important thing is to get the surge to earth by it's shortest path. Anything in it's way will be taken out, as recently happened in my house where I lost my telephone system, two multi function printers, hot tub and a few other bits.

A MH plugged into the mains does indeed have a quick route to earth in the unlikely event that the vehicle gets a direct strike. However, a direct strike will mean you don't really have a chance anyway as the force will take out the vehicle. You must have seen trees that have felt the full force, or indeed craters in the ground. The good news is the likelihood of this is very remote.

So if the MH is not plugged into the mains and it does not get a direct strike (praise be to Allah/Lord/insert your own saviour) then where will the surge come from? Well there is not really any other likely source. Unless you have a satellite dish on the ground and plugged into your tv? You are of course insulated from the ground by 4 or 6 rubber tyres.

But with it plugged into the mains this is your only likely source of a surge. If the campsite has a good electrical system with the necessary working trips and a good earth then it is very unlikely that you will have any problems. If however any of the safety measures are not up to scratch then a surge coming through your mains cable has the ability to not only take out any equipment in your MH but depending on the severity of the surge it could take out the MH out as well.

The mention of a faraday cage is relevant for a direct strike only. I cannot speak for all MH's but reckon that a lot of them have a framework of metal on which the various wood and grp bits are bolted. This metal framework may act as a faraday cage but it is unlikely, which you can see by this definition I have just goggled:

...if the conductor is thick enough and any holes are significantly smaller than the radiation's wavelength...

So what would I do if caught in the open during a thunderstorm? If it was all around me, I would head for the nearest pub and enjoy the spectacle from inside. If it was in the distance I would pull up a chair outside the MH open a bottle of London Pride or some such substance and enjoy the spectacle!

Best regards

Chris