UK Can someone help me wire a new light fitting into an old house with old wiring systems.

[JayLynch712]

I’m a junior electrician, fresh out of college. I did some minor electrical work for a friend buI tried to put up a new chandelier I came across:

• Two Line wires (RED), going into one connector block
• Two Neutrals (BLACK), separated into different connector blocks

- Two CPC wires, going into one connector block.
The chandelier has one line, one neutral and one earth.

I wired it up putting the neutral in one neutral block. When turned on the bulbs barely lit up.
When i switched the wire to the other neutral block it lit up greatly, however could not be turned off.
When i put both neutrals in one block, the light lit up, but tripped the fuse when I attempted to turn it off.
I know little about old domestic systems. Can someone please advise.

 

[westward10]

Is that how they were originally connected.

 

[Midwest]

Think you may have crossed wires.

 

[SJD]

The two black wires are likely NOT both neutrals!

The fact that they were in separate connectors blocks, rather than connected together should be a clue.

Perhaps one is switched live, and one neutral, which would be typical for a lot of domestic wiring.

 

[Moley]

The answer is in your own post. You need to wire it exactly as it was.

 

[Pretty Mouth]

Research 3 plate wiring systems, there's plenty of info on the internet, youtube etc. This should help you understand what is going on in this situation.

 

[Midwest]

If there’s two cables, with one light and one switch. Theres only one way to connect the wires up @JayLynch712

 

[Pete999]

I’m a junior electrician, fresh out of college. I did some minor electrical work for a friend buI tried to put up a new chandelier I came across:

• Two Line wires (RED), going into one connector block
• Two Neutrals (BLACK), separated into different connector blocks

- Two CPC wires, going into one connector block.
The chandelier has one line, one neutral and one earth.

I wired it up putting the neutral in one neutral block. When turned on the bulbs barely lit up.
When i switched the wire to the other neutral block it lit up greatly, however could not be turned off.
When i put both neutrals in one block, the light lit up, but tripped the fuse when I attempted to turn it off.
I know little about old domestic systems. Can someone please advise.

Where do you live Mate?????

 

[Julie.]

I’m a junior electrician, fresh out of college. I did some minor electrical work for a friend buI tried to put up a new chandelier I came across:

• Two Line wires (RED), going into one connector block
• Two Neutrals (BLACK), separated into different connector blocks

- Two CPC wires, going into one connector block.
The chandelier has one line, one neutral and one earth.

I wired it up putting the neutral in one neutral block. When turned on the bulbs barely lit up.
When i switched the wire to the other neutral block it lit up greatly, however could not be turned off.
When i put both neutrals in one block, the light lit up, but tripped the fuse when I attempted to turn it off.
I know little about old domestic systems. Can someone please advise.

It's a three plate wiring system, one of the red/black/cpc cables is the live feed, the other is the switch.

Both lives (reds) together, to nothing else, the earths (cpc) together to all metal that can be touched when in use, the one switch wire (black) to the live of the lamp fitting, and the other neutral (black) wire to the neutral of the light fitting.

This isn't old, this is still current practice, only the colours have changed.

 

[Dave OCD]

I expect the black switch wire didn't have red sleeving to identify it and that won't have helped the OP, but why isn't this method being taught at college now- that's the impression I'm getting from this ?

 

[Julie.]

Even if the switch wire isn't identified, the fact that you use both black (or now blue) to the lamp means it doesn't actually matter (unless it's an edison screw) - although it's clearly preferable to identify the actual live to the lamp fitting.

 

[Dave OCD]

Of course it should be right, I'd say not checking and identifying the switched live clearly is a definite non compliance.

 

[Midwest]

Even if the switch wire isn't identified, the fact that you use both black (or now blue) to the lamp means it doesn't actually matter (unless it's an edison screw) - although it's clearly preferable to identify the actual live to the lamp fitting.

Egggh, I’m full of sunday roast, but I still don’t follow you.

 

[westward10]

Modern Edison screw lampholders if made to the correct standard are not polarity biased.

 

[Dave OCD]

Yes but the brown of the flex to the lampholder should still be connected to the switched live of the fixed wiring, suitably identified.

 

[Julie.]

Egggh, I’m full of sunday roast, but I still don’t follow you.

Which bit the es?

It's because with the es lamp fitting, it does matter, the switched live (which could be a red wire from the switch - if twin red, the black wire from the switch - if standard t&e,
Or black with red sleeve if std t&e done correctly) must go to the centre pin on an es fitting as it's polarised - and a test requirement.

But with a standard bayonet fitting, it doesn't really matter whether the black neutral goes to either connection, as long as the other black switch wire goes to the other connection on the lamp as they are not polarised.

(read brown/blue for new colours red/black - just kept with the old colours as that's what the original question was in)

 

[westward10]

Which bit the es?

It's because with the es lamp fitting, it does matter, the switched live (which could be a red wire from the switch - if twin red, the black wire from the switch - if standard t&e,
Or black with red sleeve if std t&e done correctly) must go to the centre pin on an es fitting as it's polarised - and a test requirement.

But with a standard bayonet fitting, it doesn't really matter whether the black neutral goes to either connection, as long as the other black switch wire goes to the other connection on the lamp as they are not polarised.

(read brown/blue for new colours red/black - just kept with the old colours as that's what the original question was in)

Modern ES holders are not polarity biased.

 

[Dave OCD]

I gave a disagree Julie because you seem to be saying that it doesn't matter whether the black [or blue] switched live is clearly marked or not. Ok it'll work at the end of a loop in system with only two cables at the light but elsewhere you'd have a 1 in 3 chance of it working or not.

 

[Julie.]

I gave a disagree Julie because you seem to be saying that it doesn't matter whether the black [or blue] switched live is clearly marked or not. Ok it'll work at the end of a loop in system with only two cables at the light but elsewhere you'd have a 1 in 3 chance of it working or not.

Yes, but I was referring to the op's question, which is at the end of the loop.

In addition, although not applicable to this case, when I first learned, there were strict placements for each wire, on the first three it would be: neutral to drop wire, neutral from supply, neutral to next fitting; on the next three: live from supply, live to next fitting, switch live to switch, then on the last two: switch wire from switch, live to drop wire.

The actual marking of the switch wire wasn't commonplace as you could easily identify it from the strict connection placement, and the way that cable was identified during first fix, don't think it is so strict these days, and of course lost when you fit another type of luminaire - which just wasn't likely back then!

 

[Dave OCD]

The point I was making though was that a switched live unless already red or brown should always be clearly marked, otherwise it doesn't comply with BS7671.