lights working one day, off the next

[groves94]

Hi all,

Recently passed my AM2, so im fresh out there with a lot to learn.

Recently moved into a house that needs re-wiring. All lights in house are on one breaker and i am separating into upstairs and downstairs. I have found the upstairs lighting junction box in the and disconnected everything. I have traced all the cables and and found they have been wired with the permenant live in common at light switches. i am re-using the light switches, as the missus wants as little chasing as possible as we are living here and money is abit tight. I have rewired the power to the lights from switch with new 1.5 twin.

This is how i've wired it using the existing switch wires.

• Permanent live from 6A MCB ( separate to existing lighting MCB), to 5-way wago block in junction box.
• Common from each existing light switch at room 1, 2, 4 and 4, into wago block at junction box with permanent live.
• Wired new 1.5 twin to each light fitting back to junction box.
• Live for each light fitting in with each light switch L1 switch wire in 2-way wago at junction box
• Neutral for each light fitting, in with new lighting neutral from board at junction box with 5-way wago.
• All earth from light switches, light fittings and board connected together at junction box.

All upstairs lighting worked yesterday, not today and i'm struggling to understand why. I have 200v between live and earth at each light fitting when light switch is off, and 240v when switch is on. I have 60v at neutral in each fitting when switch off, and 120v when switch on.

I have repeatedly checked all connections at each switch, light fitting and junction and is wired how i feel correctly. I don't feel as though i am losing a neutral anywhere and all connections are mechanically sound. This is my first time working with a lighting circuit with the permanent live wired to commons first, i usually practice with permanent live in and out at each light fitting, daisy chaining until end of line.

I read something about phantom voltage but i have no idea what this is.

Could i have some advice please, whilst waiting, im gonna disconnect whole circuit and connect back up one light at a time until the circuit doesnt work.

Thanks in advance

 

[loz2754]

Definitely sounds like you've lost a neutral.
If all the lights are affected, then the fault is between the consumer unit and the junction box.

 

[littlespark]

It sounds like youve connected a few lights in series... The first bulb is taking the voltage away, basically halving what you need. Changing switches from on to off has changed voltages

Lights are notoriously difficult sometimes when it comes to figuring out whats what.


So what you have is 4 rooms, 4 switches, 4 lights? is that right? no two switching or anything?

Your switches all have one T&E at them? Brown to common, blue, with brown sleeve to 1 way.
Lights will be a brown and blue.

The corresponding blues at the joint box end should also be sleeved brown, to identify the switched lives.

If the switches and lights are right, it must be in your joint box.
You have the live and neutral supply? Take each room, one by one and connect the brown down to switch to live main joint.... the blue, with brown sleeve to brown to light, and blue from light to main neutral joint.
Get that room working... then work on the next.


For goodness sake, and I'm sure you're doing this, but isolate the supply inbetween working on it.



Another thought. Is the supply you're working from definitely a mains supply from the board, and not either a switchwire and neutral that should go to a light, or maybe strappers from a 2 way stair lighting?

 

[telectrix]

a scottish essay...macbeth was shorter than that. ??

 

[buzzlightyear]

TWO BEERS OR NOT TOO BEERS THATIS THE QUESTION .LOL.

 

[littlespark]

yas... and i got words of more than 3 syllables at times

 

[groves94]

Hi all,

Recently passed my AM2, so im fresh out there with a lot to learn.

Recently moved into a house that needs re-wiring. All lights in house are on one breaker and i am separating into upstairs and downstairs. I have found the upstairs lighting junction box in the and disconnected everything. I have traced all the cables and and found they have been wired with the permenant live in common at light switches. i am re-using the light switches, as the missus wants as little chasing as possible as we are living here and money is abit tight. I have rewired the power to the lights from switch with new 1.5 twin.

This is how i've wired it using the existing switch wires.

• Permanent live from 6A MCB ( separate to existing lighting MCB), to 5-way wago block in junction box.
• Common from each existing light switch at room 1, 2, 4 and 4, into wago block at junction box with permanent live.
• Wired new 1.5 twin to each light fitting back to junction box.
• Live for each light fitting in with each light switch L1 switch wire in 2-way wago at junction box
• Neutral for each light fitting, in with new lighting neutral from board at junction box with 5-way wago.
• All earth from light switches, light fittings and board connected together at junction box.

All upstairs lighting worked yesterday, not today and i'm struggling to understand why. I have 200v between live and earth at each light fitting when light switch is off, and 240v when switch is on. I have 60v at neutral in each fitting when switch off, and 120v when switch on.

I have repeatedly checked all connections at each switch, light fitting and junction and is wired how i feel correctly. I don't feel as though i am losing a neutral anywhere and all connections are mechanically sound. This is my first time working with a lighting circuit with the permanent live wired to commons first, i usually practice with permanent live in and out at each light fitting, daisy chaining until end of line.

I read something about phantom voltage but i have no idea what this is.

Could i have some advice please, whilst waiting, im gonna disconnect whole circuit and connect back up one light at a time until the circuit doesnt work.

Thanks in advance

Right i've gone iv wired up first light...

• Permanent live from board to common at switch.
• Switch wire in with live at light.
• Light neutral in with neutral at board.
• Switch, light and board earth all together.

Still nothing.....I have 240v across permanent live and earth when is switch is switched in both positions obviously. 0v across earth and switch live when switch is off then 240v when switch is on. 200v across live and neutral when switch is off, 60v when switch is on.

All i can think is that im possibly sharing a neutral somewhere are the board?? earth and neutral are in correct terminals at board corresponding with the MCB. I have no break in cable anywhere.

I'm lost.....

 

[UNG]

So working through this
What supply type do you have?
Have you done any loop tests on the supply?
Have you done an R1+Rn on the circuit
Have you done any loop tests at the light switch and / or fitting?

 

[MJPD29]

What testing have you carried out? Have you took continuity readings on the cable? It sounds like you have lost your neutral, how have you confirmed there are no breaks anywhere in the cable? Also, any pictures you have of your connections may help a as a second pair of eyes might spot something different.

 

[MJPD29]

I presume from how you are talking, you have a twin and earth from the board to the switch, and another twin and earth from the switch to the light. Is this correct?

 

[timhoward]

I presume from how you are talking, you have a twin and earth from the board to the switch, and another twin and earth from the switch to the light. Is this correct?

That is indeed the first thing to clarify.
Once this is established, I'd suggest (as others have) turning all power off and doing some continuity checks to establish how the cables are running and confirming they are not damaged.

Btw we've all been here at least once - lighting can be highly frustrating and it's particularly easy to assume it's been connected in a logical way and be blind to how it's actually been wired up.
Stay clam, make tea, and draw diagrams!

 

[timhoward]

This is how i've wired it using the existing switch wires.

• Permanent live from 6A MCB ( separate to existing lighting MCB), to 5-way wago block in junction box.
• Common from each existing light switch at room 1, 2, 4 and 4, into wago block at junction box with permanent live.
• Wired new 1.5 twin to each light fitting back to junction box.
• Live for each light fitting in with each light switch L1 switch wire in 2-way wago at junction box
• Neutral for each light fitting, in with new lighting neutral from board at junction box with 5-way wago.
• All earth from light switches, light fittings and board connected together at junction box.

All upstairs lighting worked yesterday, not today and i'm struggling to understand why. I have 200v between live and earth at each light fitting when light switch is off, and 240v when switch is on. I have 60v at neutral in each fitting when switch off, and 120v when switch on.

If you had actually wired it as you describe (which is fine), there is no PL at the light fittings, so there is no way you should be getting 200v at the light fitting with the switch off.

I suspect something has been mis-identified in the lighting junction box, and quite possibly a 2 plate 2 way switching arrangement for landing / stairs lighting has been unintentionally connected. This could also account for why it all worked yesterday and why you might have accidently created a potential divider circuit lowering the voltage.

I'm afraid you need to go back to first principles and prove one thing at a time. Power off, lots of continuity tests, label cables as you go. It's not nice but sometimes the only way.