Electrical question for PigletJohn - if you don't mind. xxx

[jalopy]

Needed to replace our battery in the mains-connected smoke alarm.

Isolated and turned off the power switch on the Fuse board to do that particular job.

Turned it back on and somehow another fuse button has flipped. The one affected supplies our downstairs loo. I assume it the lights or the extractor fan of that room. Cant reset it now.

What's the problem likely to be?

Thanks in advance. xxxxx

unusual.

if it won't reset, the MCB might be at fault, or something could have gone wrong on the circuit.

if we presume that some fault occurred to trip it (or did you touch it by mistake?) and is still present, I wonder if you have a filament-type (incandescent light bulb) that has melted as it blew.

If this is possible, take out all lightbulbs on that circuit and see if the MCB will now reset.

photos of the breakers in your consumer unit would help.

BTW, when it's light, turn off the main switch (so all circuits are dead) and see if the troublesome breaker will now reset. Toggle the switch manually all the way to the "off" position before you try to put it "on". If not, the breaker is at fault.

If you have actual buttons it may be a very old type of breaker and can be replaced with a new one.

Thank you, PigletJohn.

I got the detail slightly wrong. The downstairs loo button was flipped off before we realised there was a dedicated fuse button for the smoke alarm circuit. Once the battery was replaced, the fuse buttons were reset but the downstairs loo one didn't flip up. Hope that makes sense.

We will try your suggestion tomorrow in daylight.

I'll let you know the outcome. Many thanks again.

Update for piglet.

Followed your instructions and found that the downstairs loo's ventilation and lights are actually working but when we reset all the switches, the loo one isn't quite in alignment with the others but is working. I can only assume it must be a problem with that particular fuse in the master fuse box? We probably need to get an electrician in at some point, as something has upset it.

Thanks for your prompt advice.

photo please.

I read this as “ethical question for pigletjohn”
Personally I think that should be a section all of its own.

As you can see, the switch would not go to the top when the mains was turned off. It has not tripped since. Does this need to be replaced?

yes. A mechanical defect like that is fairly unusual but if it were ever to jam in the "on" position that would be worrying.

If you get hold of a qualified electrician and give him the part number beginning "NS" it should be an easy swap for a new one. I'd try the movement of all the others in case another is faulty. It is not a safe DIY repair because live parts will be exposed.

(the new one will be a different part no as Wylex have updated it). it must be Wylex brand, not a substitute make.

It will be very helpful if you can find the installation date, as some around 2009/10 were recalled.

Thank you so much, PigletJohn. Very helpful indeed. x