Downlights problem

[enigmatic]

just wired four downlights in a daisy chain system.

after finising off the wiring turned the power back on and the lights were on, without the switch being on.

turned them off and the breaker in the cu flipped.

i have two red, two black wires.

i tried using just the two and putting the other two in a terminal block this time they wouldnt go off!

what have i done wrong, im not dead yet so thats a good start.

im using 1.5 t&e, i was thinking if the original wire up there is 1.0m2 would that make a difference?

thanks

 

[Spark123]

Sounds like you have connected the switch wire in parallel with the lights, i.e. all the reds together, all the blacks together. How are the cables connected at the moment, are they in a Junction box?

 

[GaryMo]

The two blacks, one of them is a neutral and the other a switched live.
Have a look at the Wiki - http://www.diynot.com/wiki/electrics:lighting:lighting_circuit_layouts

Switch would have been off when the lights were lit, turn the switch on and place a dead short between live and neutral - MCB trips.

 

[Qedelec]

The size of cable will not be the problem. You dont sound like you understand lighting circuits. Look at the reference section.

 

[enigmatic]

Sounds like you have connected the switch wire in parallel with the lights, i.e. all the reds together, all the blacks together. How are the cables connected at the moment, are they in a Junction box?

not in a junction box, all daisy chained, i have the two red in L, and the two blacks in N, from there i chain another wire to the next light.

have i wired up the switched live wrongly?

 

[Spark123]

Yep, sounds like you have.
Turn off the electric and make sure it is off before doing anything.
Can you ID which cable is the switch cable, you may need to use a multimeter set to ohms. With the meter connected to the red and black of one cable get someone to operate the switch. If you are connected to the switch wire then you should see the resistance go from high to low or vice versa when the switch is operated.
Is the area accessable? If so then a Junction box can be used. It needs to be fitted before the first light so you will have a supply cable in, switch wire and a supply out to the first light. clicky (ignore the supply to next light wire).

 

[enigmatic]

ok i think i follow, once i've found the switched live and L1 as i have two black two red, can i then terminate the other two in a terminal block?

to make sure i have this right, i wire the switched live and L1 into seperate terminals then i can wire the first live with L1 and the N with switched live?

 

[Spark123]

Once you have ID'd the switch wire the other one is the supply wire. You need to have the two reds connected together but to nothing else, the black neutral (supply cable) to the lamp neutrals and the black switch live (should have red sleeve) to the lamp live. All the earths connect together. Not a good idea to have block floating about in a ceiling, it needs to be inside some sort of enclosure hence the reason for suggesting using a junction box.

 

[enigmatic]

Sorry to dreg this up but im desperate now and reluctant to get an electrician in to charge me £200 just to be frustrated at how easy it was.

plus the fact we have no lights in the bedroom

ok i couldnt id the switch live as i've not got a multimeter handy plus time is against me, any other way around this i have an ac tester but it does not show anything whilst the switch is being pressed testing for the switch wire.

im faced with two flex cables, both with 1 red and 1 black wire both held together by the earth wire (just to explain what im looking at)

the downlight has a 2 terminals to connect to blue and brown wires.

what can i do please??

i know most of you will just tell me to get the electrican but im hoping one of ya will show a peasent mercy!

again sorry to yam on but could it be a case that one of the red wires is actually the switch live as opposed to it being the black cable?

cheers

 

[enigmatic]

ok i've got myself a multimeter to find the switch live cable, how do i acheieve an accurate test?

is it touch each wire with both prongs or touch a red and black till i get a reading? i'll have someone to turn the switch on to check resistance.


once i've found the switch that goes into the lamp live correct?

and i can just terminate the other two reds on thier own?

 

[plugwash]

turn off power to the circuit before starting.

put your meter on resistance and put one probe on the red wire and one on the black wire from a cable. Get someone to turn the lightswitch on and off. If the resistance changes when the switch is turned on and off (it should go from open circuit to very low) then you have found the switch cable.