Can work out why my new light isnt turning on!

[Yukster]

I replaced my light fixture and wired it like the old one. But the light isnt turning on so i must have made a mistake. Unfortunately, I cant follow the wires in th eloft to figure out what's what. When the light switch is on i've got 1. a pair of black wires, one with electricity and the other without. 2. a single black wire with electricity. 3. three red wires in a clamp solved in the ceiling cavity. There no electricity in any of the black wires when the light switch is off. I connected the pair of blacks to the live and the single black to the neutral but no cigar. Any advice will be appreciated

 

[WabbitPoo]

Any advice? Stop messing with stuff you don't understand! *

An electrician will be along in a minute.






















* Not being snide - it was meant as good advice.

 

[Yukster]

Any advice? Stop messing with stuff you don't understand! *

An electrician will be along in a minute.

* Not being snide - it was meant as good advice.

I could get an electrician but then everyone else posting questions about stuff they don't understand would need to call a tradesman rather than having stuff explained on the forum

I'm not a complete novice and I rewired lights before. I would be able to work it out myself if I could track the wires in my loft but it's got thermally insulation laid down so getting to the wires is a major pain. Can anyone offer advice based on the info in my original post?

 

[stillp]

When you say "with electricity", what are you testing with?

 

[EFLImpudence]

//www.diynot.com/wiki/Electrics:Lighting-Circuit-layouts

 

[Yukster]

When you say "with electricity", what are you testing with?

I'm testing with Fluke Volt Alert

 

[Taylortwocities]

The VoltAlert gives an "indication" that there is some voltage present but not how much voltage. So some of the "electricity" may be induced voltage from other circuits.
It does not show if there is a neutral present, or which or the three blacks is the neutral, and which is the switched live.,

So you'll need a mutimeter or a proper two-probe voltage tester. Using anything else is just guess work.

 

[Yukster]

The VoltAlert gives an "indication" that there is some voltage present but not how much voltage. So some of the "electricity" may be induced voltage from other circuits.
It does not show if there is a neutral present, or which or the three blacks is the neutral, and which is the switched live.,

So you'll need a mutimeter or a proper two-probe voltage tester. Using anything else is just guess work.

Righty o. I've got a multimeter. Should I measure ac voltage between the 3 combinations with the light switch on until i get a 220v reading?

 

[PrenticeBoyofDerry]

I replaced my light fixture and wired it like the old one.

Did the old one work?

But the light isnt turning on so i must have made a mistake.

Possibly

Unfortunately, I cant follow the wires in th eloft to figure out what's what.

Is that necessary?

When the light switch is on i've got 1. a pair of black wires, one with electricity and the other without.

That sounds like one is possibly switch live and one is neutral, and the term is voltage not electricity!

2. a single black wire with electricity.

How much?

3. three red wires in a clamp solved in the ceiling cavity.

That sounds like the live loop

There no electricity in any of the black wires when the light switch is off.

That is what is expected

I connected the pair of blacks to the live and the single black to the neutral but no cigar. Any advice will be appreciated

You need an approved two pole/probe voltage indicator and test between the live loop and the blacks for voltage and also test blacks to CPC/earth and live loop to cpc/earth, take a note of the results and identify which blacks are showing around 240 volts. These tests can be done with the switch closed/on. Be careful as you are testing a live installation.
Then post your results back.

 

[PrenticeBoyofDerry]

Righty o. I've got a multimeter. Should I measure ac voltage between the 3 combinations with the light switch on until i get a 220v reading?

You should be measuring for AC voltage and an expected reading would be something between 230V-250V between live-neutral, live-CPC/earth and 0V between neutral and CPC/earth.

 

[EFLImpudence]

It would be safer to test with the circuit dead.

Determine which is the switch wire by continuity between the conductors of a cable and make sure by operating the switch.

If only a single light then all the other cables are line and neutral.

If there is a second light determine which cable runs to it.

 

[Yukster]

You need an approved two pole/probe voltage indicator and test between the live loop and the blacks for voltage and also test blacks to CPC/earth and live loop to cpc/earth, take a note of the results and identify which blacks are showing around 240 volts. These tests can be done with the switch closed/on. Be careful as you are testing a live installation. Then post your results back

I measure 240v between the live loop and black wire no 2 and very low voltage (circa 5v) between the live loop and the other two blacks.

I measure 240v between the live loop and earth

I measure 240v between the earth wire and black wire no 3

 

[PrenticeBoyofDerry]

I measure 240v between the live loop and black wire no 2 and very low voltage (circa 5v) between the live loop and the other two blacks.

240V does that then reduce to near zero when switch is opened?
Edit this, incorrect info given!

I measure 240v between the live loop and earth

That's what is expected

I measure 240v between the earth wire and black wire no 3

Is black wire number three different to the conductors described in the ones tested above?

The live loop if poked up in the ceiling, should be encased in an insulated enclosure, such as a choc box.

 

[Yukster]

Is black wire number three different to the conductors described in the ones tested above?

black wire no 3 doesn't look ny different. As far as I can remember, black wire 2 and 3 were paired when connected to the previous light fitting

 

[PrenticeBoyofDerry]

Need clarification on
* Number in total of black conductors
* If you are referring to them as number 1,2,3...... etc. Need to know which are live when switched, which are not and if unswitched how those results change. As you stated number 2 was at 240V and the other were at 5V, but then stated number 3 was reading 240V!