Help with wall lights

[Graham Mackie]

Hi,

I have recently had a wall re-papered by a decorator who took two wall lights down to put the wallpaper up but then left them off for me to put them back as he wasn't 'qualified'.

The wall lights are wired to a single way dimmer switch.

Before I wired them backup up I checked the circuit with a multimeter and I get a live circuit on Wall light 'A' whether the switch is on or off. On Wall light B I get a permanent feed as well - but only 132v.

Wall light 'A' has two choc blocks and four standard electrical cables coming out of the wall.

Choc block 1. Has three red wires connected together, three black wires connected and the three earths. This is permanently live and doesn't seem to be affected by the operation of the switch. I have tried swapping for a new dimmer switch and this doesn't make a difference. The switch is wired correctly

Chock block 2. The second joins a red and a black wire together.

Wall light 'B' has the expected red,black and earth.

There are no obvious markings to highlight a switched live.

I think that some of the wires came out of the 'choc' block when the decorator removed the lights and I suspect he has put them back wrongly. Other than trial and error is there an easy way to find out what he has done wrong using a meter ?

 

[securespark]

Where were you testing between when you got 132V? If it was not a two pole tester, go out and get one!

The individual block on Light A that has a red and a black wire in is the switched live: only live when the switch is on.
The black is the switch return and the red is the feed to Light B.

The other block with reds in is the live loop: live all the time.

With power off, check for dead with a two pole tester. Ensure that all terminations are tight and all conductors are secured with the terminal screws on the copper.

With the power restored, check with your two pole tester that you have:

230V between the Loop and Neutral.

230V between the Loop and Earth.

0V between Earth and Neutral.

230V between the Switched Live (terminal block with red and black together) and Neutral, but only when the wall light switch is closed.

230V between the Switched Live and Earth, but only when the wall light switch is closed (ON).

0V between the Switched Live and Earth, when the wall light switch is open (OFF).

 

[John D v2.0]

If you're using a high impedence multimeter, you can read stray voltages from capacitance which are not useful.
As above a two pole tester would work, or if it's only for a one off job you can temporarily connect a resistive load eg low wattage 240v filament bulb, and measure across that. If you still get voltage, then it's not stray. Also the bulb should light up, but don't rely on that fact.

 

[Graham Mackie]

Thanks for your help guys, two pole meter on order Amazon for delivery tomorrow. Will let you know how I get on

regards

 

[securespark]

What were you using to measure the voltage?

 

[ban-all-sheds]

a multimeter

 

[securespark]

O.
K.

 

[Graham Mackie]

Where were you testing between when you got 132V? If it was not a two pole tester, go out and get one!

The individual block on Light A that has a red and a black wire in is the switched live: only live when the switch is on.
The black is the switch return and the red is the feed to Light B.

The other block with reds in is the live loop: live all the time.

With power off, check for dead with a two pole tester. Ensure that all terminations are tight and all conductors are secured with the terminal screws on the copper.

With the power restored, check with your two pole tester that you have:

230V between the Loop and Neutral.

230V between the Loop and Earth.

0V between Earth and Neutral.

230V between the Switched Live (terminal block with red and black together) and Neutral, but only when the wall light switch is closed.

230V between the Switched Live and Earth, but only when the wall light switch is closed (ON).

0V between the Switched Live and Earth, when the wall light switch is open (OFF).

Hi Securespark,

I have this evening done all the above tests and the results are all as expected. However when I connect the wall lights to the neutral & switched live they still don't work. I have swapped light fittings and tried new bulbs and still nothing. I definitely get 240v (using a two pole tester) on this circuit when the switch is closed and 0v when it isn't. However if I touch the screwheads on the choc block once the light is wired in I just get the continuity buzzer and LED. I am sure I am missing something obvious here - I just can't work out what it is

regards

 

[securespark]

Is there something loose or in intermittent contact?

Power down and check all terminations again. Also check the light fitting works on another supply.

Check also the terminations at the switch(es) controlling those lights.

...when I connect the wall lights to the neutral & switched live they still don't work.

Neither fitting works at either point?

 

[Doggit]

As to decorator, if he was okay to take them off, then it was also okay for him to put them back on; you don't need to be regulated or part P to replace and existing fitting, but I suspect he didn't bother taking a note of what went where.

As to the problem, you have 3 wire in the first light fitting, but only one in the second, so the first one has a feed, a switch wire, and then feed to the other fitting. You may need to take the wiring apart, and first find the live feed, then find the switch feed, and then you'd be left with the feed to the other fitting. Once you isolated the live, then the other two should be dead, so you can connect then switch the light switch on and check for continuity, and then connect the earth and neutral on the other fitting, and prove that wire as well.

The live feed will go to the switch wire, and the feed coming back will go to the live connector in the fitting, and the neutral from the live feed will go to the other side of the fitting. The feed to the other fitting will be connected to both of these wires, and if I'm right, this should solve the problem, and if I'm wrong, some one here will rip me to shreds.

 

[securespark]

Dog, there are 4 cables not 3.

OP gets 240V at the terminals when using the two pole tester, but that goes to 0V when the light fittings are connected. I reckon there must be a dodgy connection somewhere, probably at a point downstream of the light point, maybe the switch.

GM: have you rechecked the connections and checked the switch connections are secure?

 

[Doggit]

Thanks Secure, I can see three cables, but yes, 4 reds, so what do you think the extra cable is used for; possibly a loop to another fitting. So do you think he's got the cable layout set up properly yet.

 

[securespark]

I have this evening done all the above tests and the results are all as expected.

I definitely get 240v (using a two pole tester) on this circuit when the switch is closed and 0v when it isn't.

However if I touch the screwheads on the choc block once the light is wired in I just get the continuity buzzer and LED.

So it seems there's a problem with an intermittent connection somewhere.

Just a silly thought...I wonder if the OP is testing the same terminals that he has connected the light fittings to?

 

[Graham Mackie]

Not had much time to get to this today due to family commitments. However I connected another light fitting (took the 13a plug off a table lamp) and got a flickering CFL/energy saving bulb. Swapped this for a standard filament bulb and got nothing. I think that this suggests an induced voltage rather than a full one, could it also mean that the wall switch is switched neutral rather than live ?

 

[ban-all-sheds]

could it also mean that the wall switch is switched neutral rather than live ?

No.