Electricians...

[dinny_g]

Our Boiler and Washing Machine have a dedicated Isolation Switch on the kitchen wall.

About tea-time yesterday, there was a loud bang, sparks from switch and then, the fuse box tripped.

I turned the switches off (the Boiler one was fried), turned off the boiler and washing machine separately and re-set the fuse box.

Here’s the thing -

the isolation switch has a fuse, why didn’t this blow first??

Despite the sparks and the burned melted switch, it all still functions the boiler will work, so will the washing machine (Obviously we’re not using them)

I’m no expert but This doesn’t seem right and I’m concerned if the Sparky just replaces the switch, there’s an underlying issue undiagnosed??

There have been other electrical issues (garage sockets connected to Lights Ring...

[Beany]

Have you checked the switch itself to make sure that, for example, there isn't an exploded insect in there?

Also, arcing is a thing if the switch didn't close/open properly or got moisture in it, etc. Kill the power, pull them out, and physically inspect them.

Switches *can* fail - they're very simple but they're not infallible.

[dinny_g]

Have you checked the switch itself to make sure that, for example, there isn't an exploded insect in there?

Also, arcing is a thing if the switch didn't close/open properly or got moisture in it, etc. Kill the power, pull them out, and physically inspect them.

Switches *can* fail - they're very simple but they're not infallible.

Cheers Beany... should the fuse not go first though to prevent the switch from melting??

[Beany]

Arcing might not cause enough current to blow the fuse, but arcing will generate a fuckton of heat, so it's not impossible. A dead short would pop the fuse, but arcing isn't a dead short

Circuit breakers have 'quenches' in them (basically a series of plates to 'catch' the arc) to prevent exactly this from happening in the fuse box. Switches? Less so.

[dinny_g]

Cool - makes perfect sense now it’s explained.

Sparky should confirm this and all will be gravy!

[Carlos]

the isolation switch has a fuse, why didn’t this blow first??

The fuse in a plug or spur pretty much never trip before the rcd or cicuit breaker in a modern electrical set up.

They are more sensitive and faster by design.

[V8Granite]

What Carlos said.

Also, all fuses are not equal and I’ve had some fuses that melt the body but not the wire and also a fuse that seemingly wouldn’t blow if you plugged it directly into a nuclear power station.

Dave!

[Beany]

In the last place my brother lived in, the fuse board used fuse wire.

Like these


https://www.diynot.com/pages/el/el009.php

RCDs are for pussies and people who don't like seeing smoke coming out of sockets.

[McSwede]

In the last place my brother lived in, the fuse board used fuse wire.

Like these


https://www.diynot.com/pages/el/el009.php

RCDs are for pussies and people who don't like seeing smoke coming out of sockets.

The house we moved into earlier this year had a wylex board with these cartridges in. I had that swapped out pretty quick and updated all the sockets to a mix of usb-c rapid charge twins and normal twins. Far better. Also added an outdoor supply for garage and shoffice project that may happen next year.

[jamcg]

Our Boiler and Washing Machine have a dedicated Isolation Switch on the kitchen wall.

About tea-time yesterday, there was a loud bang, sparks from switch and then, the fuse box tripped.

I turned the switches off (the Boiler one was fried), turned off the boiler and washing machine separately and re-set the fuse box.

Here’s the thing -

the isolation switch has a fuse, why didn’t this blow first??

Despite the sparks and the burned melted switch, it all still functions the boiler will work, so will the washing machine (Obviously we’re not using them)

I’m no expert but This doesn’t seem right and I’m concerned if the Sparky just replaces the switch, there’s an underlying issue undiagnosed??

There have been other electrical issues (garage sockets connected to Lights Ring...

The fuse will only blow based on a surge in power- if this had happened your boiler probably wouldn’t be working as it has lower rated fuses protecting the circuit board (2amp quick blow vs a 3amp in the fused spur)

What you’re describing sounds like arcing inside the switch- either as Brant suggested a now expired insect or possibly a leak that’s gone unnoticed, for instance if your wall is of dot and dab construction and it’s going down the back of the plasterboard

What can also happen is if a connection is even slightly loose it will arc to the terminal and heat up- this will melt the wires insulation and eventually you can get a proper arc between 2 of the 3 wires and then instant bang- which without rcd protection will be big loud and sometimes quite dramatic

[Beany]

What @jamcg said is what I reckon has occurred. Sparky arcy bang bang!

New switch will likely be just fine

[V8Granite]

It’s not just insects....

In Uganda we were running 64 x 1MW sets at a 0.8 power factor so needed to run roughly 60 to make 50MW. During the 4 hour load runs an engine wouldn’t synchronise so I fired another one up and marked it to look at once the test was over.
After the test I had a look and couldn’t see anything but the breaker had not re-wound so I knew there was a fault. I thought it was an alternator failure so tried to turn the engine over with the barring gear and it wouldn’t engage, the flywheel was too low.

Upon stripping down the breaker to let me separate the engine and alternator a dead rat was found inside the breaker. When it got the signal to close we think the rat got slowly chopped in pieces, the engine was out of phase and sheared off, 12 x 12.9 grade M16 bolts snapped like twigs

Also there was a power outage in Hampton Loade last Tuesday. They found a squirrel and Crow on a transformer a bit black, I’m guessing the squirrel got a belt and the crow went down later for an eyeball snack and took out the who,e water treatment works.

Electricity is fun.

Dave!

[Beany]

Oof, I mean, you'd think this shit would be reasonably well protected from wildlife looking for somewhere warm to hide, but then the CERN LHR had an issue where a scorrie dropped a fucking baguette across some contacts, so what do I know?

https://www.theregister.com/2009/11/05/ ... _incident/

[Rich B]

[jamcg]