2 red cores in a lighting fuseholder

[AS]

Have been mapping out the lighting circuit from a consumer unit in extension part of house.

(the old part of house has lights going off 3 seperate multi terminal boxes)

Extension part of house has different consumer unit and 2 lighting fuse holders.

Lighting fuse holder A which seems to control all the lighting in the extensions - has 2 live cores going into it - what does this suggest as i thought all lighting circuits were radial and that there should only be one live core going into the fuseholder (old MEM unit).

Lighting fuse holder B in this unit has one red core going into it but i can not fathom out what this is doing as everything seems to work when I take fuse B out of the unit.

Any thoughts?

 

[plugwash]

Lighting fuse holder A which seems to control all the lighting in the extensions - has 2 live cores going into it - what does this suggest as i thought all lighting circuits were radial and that there should only be one live core going into the fuseholder (old MEM unit).

two possibilities:
1: they are two branches from the fuseholder (nothing wrong with having the first split in a radial at the fusebox)
2: someone has wired the lights in a ring for some reason (most likely ignorance).
edit: forgot the second possibility

Lighting fuse holder B in this unit has one red core going into it but i can not fathom out what this is doing as everything seems to work when I take fuse B out of the unit.

outside pir floodlight?
loft light?
boiler?
shower pump?
fridge? (at a push)

 

[Lectrician]

doorbell?

 

[kendor]

A Situation i had in my old house when i first moved in was that i bought it off a plumber and he advised me that the electrics were newly refurbed and done by a "qualified electrician".
Those days people didn't bother with test certificates etc and the survey was "good enough".
Visually it all looked a good job done 2 consumer units adequate seperate ring circuits blah blah blah.
also noticed several 15a breakers which i was told covered various plumbing installations around the house.
wasn't till i moved in that i needed to ident the circuits at the cu and got the missus to tell me what went off as i methodically went through each breaker in turn, all ok until we got to the kitchen, I told her to let me know when the microwave 's clock went out and proceeded to turn each breaker off and back on, imagine my surprise when she didn't answer, and i said you must have missed it going out, anyway to cut a long story short I ended up taking the cover off the cu and to my horror the ring circuits for the kitchen were spread across 2 15a breakers whereupon it clicked that the "qualified electrician" was in fact the plumber himself who obviously had a surplus of 15a breakers and probably thought to himself that 2x15a breakers =1x 30a breaker
Not saying that might be your case but i thought i'd mention it as you see some classics around.

 

[AS]

Is there any way I can check wether the cores are 2 radials or if infact someone has wired the lights in a ring?

 

[plugwash]

remove both from the fuseholder/breaker and check for continuity between them with a multimeter.

if you have continuity then its a ring otherwise two radials.

 

[mapj1]

Or for those without a meter, unhitch one core, note which lights don't work, call this branch A,
now unhitch the other core, reconnecting the first, note down the lights no longer working as branch B.
If A+B = all lights in house, its totally conventional, with two branches to the radial tree. (if you ever wanted to add more lights you can then separate them across two breakers if you like.)
If no lights at all go off until both are removed at once its a ring !

- of course do turn it off while connecting and disconnecting wires in this way, and while 'on test' make sure the free end can't do any harm - if in doubt treat it as potentially live, and cover it with something like a bit of choc block, or if desperate a fold of tape.. or a screwit - tape is not for permanent use though, at least not as an insulator.

M.

 

[dingbat]

wasn't till i moved in that i needed to ident the circuits at the cu

It's actually a requirement that circuits are identified. BS7671 calls for a circuit schedule to be available at, or close to distribution boards. In a new installation or rewire, labelling each breaker is usually enough. Amazing how often even this isn't done though. Worst case is usually the Wylex fuseboard that's been added-to over the years then 'upgraded' to plug-in MCB's. The old fuse cover is discarded... and this was where the circuit ID's used to be written!

Many householders simply have no idea what 'those funny little switches' do.

 

[kendor]

wasn't till i moved in that i needed to ident the circuits at the cu

It's actually a requirement that circuits are identified. BS7671 calls for a circuit schedule to be available at, or close to distribution boards. In a new installation or rewire, labelling each breaker is usually enough. Amazing how often even this isn't done though. Worst case is usually the Wylex fuseboard that's been added-to over the years then 'upgraded' to plug-in MCB's. The old fuse cover is discarded... and this was where the circuit ID's used to be written!

Many householders simply have no idea what 'those funny little switches' do.

Yep I know but as i said this was quite a few years back and the "electrician" hadn't bothered hence why i had to get my hands dirty

 

[dingbat]

I wasn't having a pop; merely commenting on how common this non-compliance is.