Lighting Circuits

[Howarth]

Hi All,

I have a problem with downlighter circuits. 9 down lights on one MCB but 2 circuits on one double dimmer switch. One circuit is not working the other is and the switch is working. Have check wiring at consumer unit and switch nothing loose,next stage would be look at each downlighter individual before wiring under the floor board is this the best way or I am missing something?? PS the downlighters are 240v ie no transformer.

 

[Doc Hudson]

Hi All,

I have a problem with downlighter circuits. 9 down lights on one MCB but 2 circuits on one double dimmer switch. One circuit is not working the other is and the switch is working. Have check wiring at consumer unit and switch nothing loose,next stage would be look at each downlighter individual before wiring under the floor board is this the best way or I am missing something?? PS the downlighters are 240v ie no transformer.

I am unclear what you are describing here? Do you mean two groups of lights supplied from the same MCB, or two independent MCB's supplying lights through a shared double dimmer switch? If it is just multiple cables coming from the same MCB at the consumer unit, it is all one circuit. The circuit would be defined by the protective device, not the number of branches in the cables. With regard to the lighting fault finding, especially decorative or downlighters that are a nuisance to remove to access wires, then some light mate adapters can speedup your investigations a lot. http://isswww.co.uk/...-Lightmate-Kit/ our forum sponsor may be able to do you a decent deal if you want a full set. Is the power present in and out of the switch. Do the lamps have sufficient load to work the dimmer? Dimmers have min & max ratings, if low wattage lamps have been fitted sometimes it can be below a dimmers rating (e.g. 60w-250w). As you have no transformers in circuit, I would prove if the neutral has continuity through to all the lights, using the plug in test adapters linked above, before dismantling anything, i.e. try to establish if it is a single conductor open circuit or both line and neutral.

Doc H.

 

[Howarth]

Thanks Doc H

It is multiple cables from one MCB I will look at switch and the lightmate look a good idea.

 

[kerching]

Not knowing your level of skill...but you must have some idea if you are taking covers off consumer units.

What happens if you remove the dimmers and fit a standard 2 gang switch?

If this makes the lights work then It is the dimmer that is faulty. Cheap lamps [and sometimes dearer ones] can blow the dimmer when they fail...but the switch part of it will still often work

Your description is a bit vague really

 

[Howarth]

Thanks for this.

My skill level is reasonable as I am training at the moment. However the dimmer switch works on 1 set of lights but not the other so i am assuming that the transformer for one set of lights could have blown so it is a good idea to try the standard 2 gangway.

BTW it is one circuit with multiple cables on one MCB if that makes it a bit clearer, sorry slowly getting to grips with this.

Thanks

 

[kerching]

Have you tried swapping the 2 dimmers over? this will prove if it is the dimmer that is faulty. My money is on one of the 2 dimmers being moody

post #1 no transformer

post #5 transformer................................errrrrrrrrm

 

[Doc Hudson]

Thanks for this.

BTW it is one circuit with multiple cables on one MCB if that makes it a bit clearer, sorry slowly getting to grips with this.

Thanks

One MCB is one circuit protective device, so one circuit. Many people make the mistake of thinking a radial circuit branched at the MCB is two circuits, but it is not. A radial circuit can be branched at an accessory, junction box or MCB. If the lights branched onto two cables at an accessory they are still all the same circuit not multiple circuits. The definitions in part 2 of BS7671 clarifies this. Simple rule is if an MCB can de energise a group of cables then they are all the same circuit. Problems arise where people cross circuits so that two MCB's can energies the same section of cable, as in the borrowed neutral landing/hall light scenario.

Doc H.

 

[Doc Hudson]

Have you tried swapping the 2 dimmers over? this will prove if it is the dimmer that is faulty. My money is on one of the 2 dimmers being moody

I thought the opening post said the switch was working?

Doc H.

 

[kerching]

I thought the opening post said the switch was working?

Doc H.

Mmmmm....brain is still mashed at present [you know why :innocent ]

I was working on assumption of 2 gang dimmer. each dimmer with in built switch. one side is working fine on,,dim,,off. Other side is on...off dim not working. dim blown by dodgy lamp. swap dimmers over to prove if it is dimmer or transformer since a transformer has appeared inbetween post 1 and pos 5. If you see what I am sort of getting at in a F roundabout way

 

[Howarth]

Thanks for this Doc and K.

Good thoughts and makes it clear the switch is the sensible route. I assumed that if one set of lights worked from the total switch it meant the switch was working for both sets but obviously one switch may be work and the the other not, so I will swap or change.

Thanks for your help and advice

 

[steptoe]

9 downlights on one dimmer?

Are they 50w lamps?

Is it a 400w dimmer?

 

[ProDave]

2 gang dimmers are two completely independent units on one front plate.

Have you actually tried measuring with a volt meter to see what voltage (if any) is coming out of the two dimmer switches (wrt neutral)?

That is surely the first step. If you have a proper output and the lights don't work, then it's the wiring

If you get no output voltage then it's the dimmer that's at fault.

 

[Doc Hudson]

2 gang dimmers are two completely independent units on one front plate.

Have you actually tried measuring with a volt meter to see what voltage (if any) is coming out of the two dimmer switches (wrt neutral)?

That is surely the first step. If you have a proper output and the lights don't work, then it's the wiring

If you get no output voltage then it's the dimmer that's at fault.

+1,

I has assumed that the OP had done this, but after reading post#10 I am not so sure now? how can anyone say a switch is working without proving it either with a meter or under load.

Doc H.

 

[Howarth]

Thanks guys for all the info. I will try all suggested and let you know. Just getting used to the forum will be better next time.

Cheers

 

[paul b b]

my money is on the dimmer blown, to many lamps for a 250w dimmer. as said befor, stick a normal switch on to see if it solves the problem, if it does get the correct rated dimmer for the install.

 

[CRAZE]

welcomne