Lighting and sockets on same circuit?

purpleparrotuk

The property I moved into had a new fuse board installed a few years ago. Sometimes when installing new lights even though the lighting fuse is turned off on the fuse board the sockets keep tripping on the fuse board. Is there some dodgy wiring going on? Has someone wired the lights into the sockets?

Also if the sockets are off now how come the dishwasher in the kitchen extension is still going but the washing machine in the old utility room isn’t?

Edit. The lighting fuse is off and the lights definitely don’t work so not sure what’s happening.

Norman_Castle

Has someone wired the lights into the sockets?

Switch fuses off individually and see what still works.

Kitchen extension and utility room sockets may be on different fuses.

magn8p

The question you should really ask is why is replacing a light bulb tripping a fuse at all?

Also, when the fuse board is changed (assuming it has done properly), it should have a building regulations certificate provided along with a electrics install certificate.

With the above certificates, ideally the fuses (RCD/MCBs) must have also been individually labelled. Usually the the lights and sockets are isolated and so are upstairs and downstairs. But then this procedure isn't always followed, perhaps that's the case with your extension.

purpleparrotuk wrote: »

The property I moved into had a new fuse board installed a few years ago. Sometimes when installing new lights even though the lighting fuse is turned off on the fuse board the sockets keep tripping on the fuse board. Is there some dodgy wiring going on? Has someone wired the lights into the sockets?

Also if the sockets are off now how come the dishwasher in the kitchen extension is still going but the washing machine in the old utility room isn’t?

Edit. The lighting fuse is off and the lights definitely don’t work so not sure what’s happening.

john240870

It sounds like its tripping the RCD if that is the case their is nothing wrong the lighting and power are probably on different circuits but both controlled by RCD

purpleparrotuk

john240870 wrote: »

It sounds like its tripping the RCD if thats the case their is nothing wrong

But what’s tripping the RCD. That’s the question. When it happened we were not even touching the wiring. The fuse board was installed properly as far as I know and I have the appropriate certificate.

Maybe I will turn the fuse off for the lights and just wait an hour and see if it trips.

fezster

Even if a lighting circuit is switched off at the consumer unit, the RCD can still be tripped if there is any earth leakage. I'm not sure changing a bulb would trip this, but any faulty earth wiring would cause the RCD to trip and this in turn would mean any other circuits (eg. sockets) on that RCD will also switch off.

You can tell this has happened very easily because the RCD has it's own switch on the CU.

bris

A light blowing can and often does trip the RCD.


Your fuse board should have everything written on the individual MCB's telling you what's wired to them. There is no way a competent spark would ever wire a light circuit to the sockets. The kitchen will also have it's own circuit, often separate but not always, to the utility room.

EachPenny

purpleparrotuk wrote: »

The property I moved into had a new fuse board installed a few years ago. Sometimes when installing new lights even though the lighting fuse is turned off on the fuse board the sockets keep tripping on the fuse board. Is there some dodgy wiring going on? Has someone wired the lights into the sockets?

Are the light fittings metal? If so, have you ever tried changing the bulb without touching any of the external metal parts of the fitting with your bare hands? Do you have any plastic/ceramic light fittings? Does the same thing happen with them?

Jonesya

When you isolate a circuit by switching off the MCB or removing the fuse, you are normally only isolating the live conductor, the neutral and earth remain connected.

If you then short the neutral and earth together, you can get some neutral current from the other circuits flow to earth via this short. The RCD is normally protecting several circuits and the RCD sees the imbalance from that neutral current leaking to earth and will trip.