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I blew a switch nearly killed the cat

Postby Darkspark » Thu Nov 18, 2021 7:29 am

Hi in need of advice.
Right yesterday I was wiping a wall in the kitchen. Above a simple light switch plate that powers the outside floodlight and mains down to my Summerhouse.
i didn’t see a drip of water run down the wall. It got under the plate and bang, flash of lightening right in-front of my face and electrics trip out. I flip the mcb switch and all comes back on. Except when I let the dogs out that night. No outside light works nor green or summerhouse has power.
Now I’ve got an old Wylex fuse box which has served me perfectly well over the years. So I pulled them all out and made sure they had fuse wire. They did except the 15 amp blue one. So replaced the missing wire with more of the same. Stil not working. So I replaced the wall switch in the kitchen wired it exactly to mirror the original, still not working.
Running off this mains line to the outside I have two boxes. One a single weatherproof fuse box and the the other a waterproof switch which jointly powers both the outside light and summerhouse. So I changed the fuse. Still no power. The only thing I haven’t checked is the outside switch box to see if the wiring is still ok inside it. It’s like the switch in the kitchen is dead. Cannot attached pics to make things clearer as it says files to big.
what have I missed? Or does anyone have any suggestions. And I have changed the bulb in the floodlight. No power.
thank you for any advice
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Postby Mr White » Thu Nov 18, 2021 11:13 am

Without being able to test it, you are going to need to get someone in to test it for you.
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Postby ericmark » Thu Nov 18, 2021 11:15 am

Son did same, Cillit Bang and the switch was gone. Likely fault is between switch and fuse box, but current to blow a 15 amp rewire-able fuse is quite high, so could be any junction between the fuse and switch.

I would guess if 15 amp likely originally the immersion heater, did same with my old house, gas boiler fitted so hot water direct from boiler, cistern removed, and the immersion heater supply was turned into extra sockets, so look where the immersion heater would have been see if socket there.

I would also say time for upgrade, today RCD and SPD are standard in most consumer units (type tested distribution unit which replaces the fuse box) the RCD detects imbalance and in the main will trip before you get damage as you have had.

And the surge protection device (SPD) we are told stops the new LED bulbs blowing due to thunder storms and the like, personally not convinced they are required, but LED bulbs are expensive so personally not taking a chance, I fitted a SPD.

At the moment you can still get the MCB to fit the old fuse boards, around £11 each so they trip faster so less damage but main point is you can just flick back on. Personally I would say waste of money as may as well replace whole box, but not everyone can afford that.

They are an easy DIY fit, one screw and cover left off the board, should cut a hole in cover, but easy to smash, note do turn off mains before fitting parts are live behind the base which needs changing.
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Postby Darkspark » Fri Nov 19, 2021 7:13 am

Not even sure the 15 amp fuse wire hadn’t gone years ago as theres nothing else not working before I replaced the wire.
I am going to get a Multimeter to check the wiring. Thanks.
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Postby Darkspark » Sun Nov 21, 2021 12:26 pm

Ok so I got a Multimeter one brown wire is live the other is showing no reading so guessing it’s dead. So will need to replace the cable. The outside switch is corroded and the live terminal basically crumbling with corrosion. So my question is. What ampage replacement weatherproof switch do I get a 10A or 20A the voltage is 240 so assuming the 20A.
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Postby Mr White » Sun Nov 21, 2021 11:09 pm

Cables etc are protected by the "up stream" protective device. As you seem to have a 15A fuse, a 20A switch would be a good choice.
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