Adding a new light and switch to an existing circuit HELP!

[Friedkoala]

Hi,

I have spent today helping a friend add a couple of low voltage down lights to his kitchen which, he wants on a separate switch. I broke into the existing lighting loop and followed the wiring directions to the letter adding in the switch and lights at the correct circuit points.
When I turning the power back on and switched the kitchen light on all good. I then turned the down lights on and nothing..
However, when I turn the kitchen light off the down lights come on and the kitchen light comes on but very dim.
No other lights in the house come on dim just the kitchen light.

I have double checked the lighting diagram, checked the web and shouted at it but it still wont work correctly.

Where did I go wrong and what do I do to get it working right and earn my promised beer?

Many thanks in advance.

 

[ban-all-sheds]

I have spent today helping a friend add a couple of low voltage down lights

//www.diynot.com/wiki/electrics:voltage-bands

to his kitchen

Did either of you apply for Building Regulations approval first?

I broke into the existing lighting loop and followed the wiring directions to the letter adding in the switch and lights at the correct circuit points.

No you didn't.

Where did I go wrong

Sounds like you connected the N for the new lights to the switched live of the existing kitchen light.

and what do I do to get it working right and earn my promised beer?

//www.diynot.com/wiki/electrics:lighting

 

[Friedkoala]

Sounds like you connected the N for the new lights to the switched live of the existing kitchen light.

OK I'm a dumba$$
Could you go into a little more detail for me please?

 

[pjcomp]

I assume you've put in a 2-gang switch? Sounds as though you've connected the new lights into the switch drop rather than the power cable. AS the kitchen is a "special location" in the terminology of the regulations, you should have Building Control permission for the work or have it done by a "competent person" (that's a term from the regs, not just a description); based on what you've done it doesn't appear that you count as a CP, s obest if you forego the beer and get in someone who knows.

PJ

 

[Friedkoala]

I assume you've put in a 2-gang switch? Sounds as though you've connected the new lights into the switch drop rather than the power cable.

New switch in a different location to the main light switch.
Junction box used to break into the lighting loop before the main light (about 5 feet away).
No connections directly to any of the main light cables/switches etc.
Kitchen light had 3 cables. Loop In/Out and switch. The switch cable is easy to spot as a CP used single core Red wire with no earth "because it was easier"
True I am not a CP but at least I am using the correct spec cable.
Not all CP's are like that I hasten to add.

 

[1john]

CP's can connect lights correctly that work, and do proper tests to ensure they will before they connect to a cable, they also dont use junction boxes which may be in inaccessable positions and they comply with the law and inform BC of the work so there are no problems when the house comes to be sold. I suggest you employ one to sort this out properly.

 

[Risteard]

Not sure why you think that there's anything wrong with a single-core cable with no earth if used correctly. It wouldn't be made to British Standards if it couldn't be used.

 

[nelectric]

Yes, you really should get a competent electrician to sort this out. But so you can understand what the problem might be...

IF you have connected the LV transformer into the switched live for the main kitchen light instead of into the main light circuit AND you connected the neutral for the LV transformer into this switched live the following is occurring:

When you switch on the main kitchen light, this is applying 240V up the switched live to the main light, so the current then flows through the main light and back via the main light neutral (because that is at 0V), so the main light works. Because you have also connected the neutral of the LV transformer to this main light switched live, there is now 240V on the neutral side of your LVT. There is also 240V on the live side of the LVT because you have a constant, unswitched live connection to it, therefore the LV lights don't work because the potential voltage difference on the transformer is 0V. When you switch off the main light, you have 0V in the main switched live so you now have 0V on the neutral side of the LVT. So now the LV lights work. But the current path is now LVT live --> LVT --> LVT neutral --> main switched live --> main light (which is a resistive load)--> main light neutral. The LV transformer has not drained much power, which leaves just enough power to partially energise the main light.

This is making assumptions about what you have done, but there are now two problems. Firstly you have an unswitched live connection to the LVT (potentially very dangerous). Secondly you have tapped into the wrong part of the circuit.

I know it means losing face, but for the sake of safety of your friend/relatives you really should get someone in who knows what they are doing.