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TL;DR we have a hot tub in a covered area outside and want to take measures to mitigate against harm to us or the electrics if a storm strikes us unawares. (We’d get straight out of course.)

What measures can I take to reduce the risk of harm?

More context / background:

We have built a pergola which is a simple wooden structure at the end of a high-walled garden. The wooden roof with corrugated plastic on top spans between the end garden wall and four posts, and clears the side walls by a couple of inches. It is mostly dry except for the side walls (driving rain comes in but is managed by drains under decking floor). We have run some cables under the roof and around the outside for mains lighting and data (external grade lighting, wireless, some automation sensors) terminated in suitably protected IP rated boxes.

Inside the pergola is a jacuzzi style hot tub made from acrylic. It is powered from a consumer unit and 32A mains isolator located in a brick-built cupboard within the pergola, of course this was carefully designed to be dry at all times. 240V mains is fed from the house, the underground wire is suitably protected SWA. We have other appliances (fridge etc) in the covered area.

In London we have fair weather: rainy sometimes but very rarely do we have electric storms. My point is that if there is an electric storm we won’t be expecting it, it may happen once every two years. I understand the hot tub must not be used in an electric storm, but we use it regularly during rainy periods under the dry pergola.

There is a small chance that we may be in the hot tub when a storm strikes, likewise it could be in the night time and I would therefore not be able to turn off the feed to the pergola to protect equipment.

I have also run 4x CAT6 external cable to the area and installed wireless. I mention this in case these incoming cables can be protected.

What measures can I take to protect the wiring, the equipment, and us, from an unexpected electric storm?

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  • I am curious do you get out of the bath tub / shower during a lightning storm? Nothing will protect agents a very close strike like hitting a tree on the other side of the driveway the lightning can still jump so a small switch gap is not going to do much good, your best bet is to have a quality earthing system to protect your equipment with surge protection at your service.
    – Ed Beal
    Jan 21 '21 at 1:30
  • That lightning bolt just traveled about a 1.6km or more to land in your yard and you wonder what you can do to be safe from it? Don't be there! What's 1.6km plus 2m? Still electrocuted!
    – Aaron
    Jan 21 '21 at 2:14
  • If lightning strikes nearby, that few mm of contact distance inside an off switch means nothing. It's all about potential differences radiating outward from the epicenter and it averages around 300MV.
    – Aaron
    Jan 21 '21 at 2:22
  • Check out the part about the tree roots: quora.com/….
    – Aaron
    Jan 21 '21 at 2:23
  • A lightning rod placed nearby might be able to mitigate the risk?
    – Drew
    Jan 21 '21 at 6:13
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As I read your question, you're looking for protection against a lightening strike during a very rare electrical storm. I'm going to assume you're looking for personal protection more than full on protection for your house/electronics/etc - things can be replaced, people, not so much, but that protection for the things would be a definite bonus.

  • I live in the Midwest US. 99.999% of the electrical storms we get (and we get a lot of 'em) come with rumbling thunder from distant lightening long before we get any strikes anywhere near us. When you hear the thunder, party's over - get out and move inside. NOW! Watch the show from a window if you want to watch. (I'll often watch distant lightening from our covered, generally dry front porch, it can be quite spectacular! But, once it starts getting close, I head inside.)
    • Some "pop-up thunderstorms" do happen. Those are the 0.001% not covered above. Just get out as quickly as possible and head inside.
    • If a strike really does come out of nowhere and hits your house/pergola/hot tub, there's really not much you can do about it.
  • Install a properly grounded/earthed lightning rod on the top of the house/highest point around. A proper lightning rod (system, more than one rod may be necessary) will most likely attract most of the strikes that come near your house and will properly dissipate the charge into the ground instead of you, your house and your electric devices.
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  • Thank you, @TPE... I seem to always get that wrong... It seems to be my Achiles heal of spelling. :D
    – FreeMan
    Jan 22 '21 at 11:58

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