Lighting Fuse question

awec

I have 2 fuses in my fuse box, ground floor lighting and first floor lighting.

If i turn ground floor lighting off, the ground floor lights work.

If i turn first floor lighting off, the first floor lights work.

If i turn both off, no lights work.


Does this sound correct? Both fuses have to be off to kill the lights?

Cerco

The labels are swapped.

2011

awec wrote: »

If i turn ground floor lighting off, the ground floor lights work.

But will the 1st floor lights work?

If i turn first floor lighting off, the first floor lights work.

But will the ground floor lights work?

If the answer is no to both of the above then Cerco is correct.
If the answer is yes to both of the above then the fuses are wired in series.

awec

No, the only way to turn off ground floor lights is both fuses down.

Only way to turn off first floor lights is both fuses down.

One single fuse down does nothing, either upstairs or downstairs.

Any issue with them being wired in series?

2011

awec wrote: »

No, the only way to turn off ground floor lights is both fuses down.

Then the fuses are wired in series (bad) or in parallel (much worse).

awec

2011 wrote: »

Then the fuses are wired in series (bad) or in parallel (much worse).

Any way of determining which?

The house alarm is also on the downstairs light circuit so I’m wondering if the alarm installers screwed something up.

2011

awec wrote: »

Any way of determining which?

Yes, take the cover off the board and look (but to do that would be illegal).

Because something as fundamental as this is wrong I would be concerned about what else could wrong. You really need to get an experienced electrician to check everything over.

awec

Thanks all for the help, electrician coming tomorrow.

He thinks it could be caused by one of the switches cause as of them are fed by multiple feeds, so in my completely novice opinion I guess this could mean that the downstairs and upstairs circuits are joined into what is really one big circuit at a certain point, and this seems less than ideal. No idea if this possibility is better or worse than your ideas.

Bruthal

It's probably likely the 2 circuits are linked at a switch. But ye just never know what some might have done.

2011

If it is due to a problem at the switch it is easy to fix.

Gashmuncher

Erroneous Connection between circuits. Rule 613.4 of ET 101 requires that a test is carried out to identify this highly dangerous wiring error.
Good explanation in post 5 here https://www.electriciansforums.net/threads/erroneous-connections.30846/
Most electricians think the only cause of this fault is incorrectly connected ring main lives. They are wrong, it's common were two lighting circuits are present in the same switch. Easy to miss unless test is correctly done as all MCBs are up and everything is working and looks normal. Extreme Fire hazard as overload protection is compromised on each lighting circuit. Two parallel MCBs feeding each circuit. Ask your self how much current it would take to trip two parallel 10 amp MCBs ?.
OP need to get his entire electrical installation fully tested as it is clear the installing electrician didn't test it.

Bruthal

Although its a very bad mistake or setup, I wouldn't say it's an extreme fire hazard myself, I doubt lighting circuits are overloaded too often.

The op could switch one of the lighting mcbs off for now though, to remove the parallel mcb setup until the problem is found.

I doubt even 1 10 amp mcb will be near fully loaded with all lights in an average house.