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.

 

[littlespark]

It doesn't fill you with confidence that a trainee couldn't work this out. (no offence, its just how you have been taught)

The OP gives no mention of the fitting being ES, but through dead testing with a simple multimeter you can work out which black is neutral and which is the switched live (and as others have mentioned, should have been identified with tape or sleeving) by taking the switch off.

Ive never known it as a "3 plate" system, just called a "loop in"

 

[davesparks]

Ive never known it as a "3 plate" system, just called a "loop in"

You'll find it described as such in all text books and other reference material.

Loop in could be used to describe any method of wiring lighting, but would originally have been used to describe a method of wiring in steel conduit generally used when the conduit is buried in the concrete slab. The back entry besa boxes used for this method are still know as loop in boxes.

 

[Anthony S]

Ive never known it as a "3 plate" system, just called a "loop in"

3 plate wiring as been a term used in the industry since I can remember going back to the mid 1980's

 

[littlespark]

well, I was taught in late 80's in the Scottish borders... where my college tutor and journeymen were all of the same era... it would be how they were taught and passed onto us.
Seriously never heard "3 plate" until I joined this forum

 

[Anthony S]

well, I was taught in late 80's in the Scottish borders... where my college tutor and journeymen were all of the same era... it would be how they were taught and passed onto us.
Seriously never heard "3 plate" until I joined this forum

You can call it the "loop in method" as well because that's how it's described in one of my training books that the CITB produced for JIB Apprentices back in 1984.

 

[westward10]

Three and two plate refer to the amount of terminals on the rose or batten back plate. Ignoring the cpcs two plate referred to a back plate with two terminals, line and neutral. Three plate came about when the loop in terminal was incorporated, three terminals hence three plate or three terminals on the back plate.

 

[JayLynch712]

Ok fixed the issue. Some people were correct. The power went from CCU to the light then to the switch (hence the two line cables) One neutral was fine The other was actually a line. I went back and put one neutral in a neutral block and a line in the other neutral block. Everything works fine ?.

 

[DPG]

Did you sort the earth?

 

[Moley]

I went back and put one neutral in a neutral block and a line in the other neutral block. Everything works fine ?.

Which is exactly how you said it was in your first post. Never be afraid to take photos or even sketch out how things are wired before you pull things apart. If you had made a little sketch and thought through what each wire is doing it can save a lot of hassle later on. I hope you sleeved the switched live so that the next person doesn't have the same problem?

 

[Dave OCD]

Ok fixed the issue. Some people were correct. The power went from CCU to the light then to the switch (hence the two line cables) One neutral was fine The other was actually a line. I went back and put one neutral in a neutral block and a line in the other neutral block. Everything works fine ?.

Jay, Good to hear that you've got the light working but I don't think you've fully grasped the circuit yet. The part highlighted above should say the neutral connects to the neutral [blue] connection on your light fitting and the switched live or line connects to the live connection [brown] on your fitting. You can't have two neutral blocks. All I'm trying to do is make it a little clearer for you.