Location of boiler external fuse

26 Oct 2008
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United Kingdom
I installed a new thermostat for the boiler. I basically need to know where the external fuse is located.

Whoever did the wiring originally for the boiler did a poor job, as the outer sheath for the mains supply was stripped so much that the individual wires were outside the housing of the control PCB. When I folded up the panel as I finished the job, the live supply wire got snagged between the PCB housing and case, making electrical contact. When I turned the power on, I heard a small bang with sparks on the water pipes where they were earthed. I could see it was the live wire that had been cut as I could see the burn marks.

So I recut the mains wire properly. I also checked the internal 2A fuse on the PCB, as I assumed that it would have blown when the case became live. But I tested it with a connectivity meter and it was fine. I closed up the boiler and turned on the mains. The boiler did not turn on, no light, nothing.

Apart from damage to the boiler PCB itself, I assume that the external 3A fuse required for the boiler has blown. This is because the internal 2A fuse is still intact and no RCDs were tripped.

The boiler mains supply runs straight under the floorboards. There is not fusebox visible there. There is also the main electrical board next to the boiler, but I still can't see a 3A boiler fuse there.

So where could the 3A external fuse be?


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Can you one of these near the boiler or in airing cupboard ?
The switch fused spur as pictured above is meant to be fitted close to the boiler!

Of course cowboys dont bother to do anything properly.

It turns out it was connected via a regular 3-pin plug (the wire ran down one side of the cupboard under the floorboards then back up the other side) rather than a fused spur. Replaced the fuse, everything is working.

Thanks for the help.
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Although supplying from a plug is frowned upon, I think its a better way in many respects.

At least it can be positively disconnected !

I agree Tony untill up in the airing cupboard a cowboy "borrows" a neutral for an Attic light or similar meaning that as soon as you pull the plug it all livens up in your hand (yes I have had that experience!) :evil:

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