Can Someone Help? RCD Keeps Tripping.

[eskimo39]

Hi Guys, I am not yet a qualified electrician and am currently on my C&G 2330 course.
My mums house had a small outside light which she wanted changing to 2 x 500w Halogen spotlights.

I bought a IP66 1 Gang 2 Way switch, some sheilded flex 3 core, 2 x Halogen 500w lights and some conduit and appropriate fixings.

I removed the old light and used the 3 wires from that to go into the switch. I then connected the live (Brown) to the Common terminal and put the Neutral (Blue) into a chocbox, then the earth into the terminal on the switch.

I then wired the 2 lights up and then ran the cables down from these into the switch ( I have run 1 wire from each directly into the switch, not ran 1 wire from the switch to 1 light and then piggybacked from this to the other light)

I then twisted the 2 neutral cables together and put them into the other side of the chocbox, twisted the 2 live and put them into the L1 terminal in the swith and then twisted the 2 earth cables and added them to the earth terminal in the switch.

The problem I have is now when i try to swich the lights on it trips the switch labled 'Downstairs Lights' on the RCD. I then tried disconnecting 1 of the lights and it works fine.

Is there anyway to use both lights without blowing the trip switch?? I wondered if I can get a less sensitive trip switch on the RCD or if I just ran 1 set of wires from the switch into 1 light and then ran a wire from 1 light to the other, would this work.

Any ideas????? Thanks in advance??

P.S Don't worry I am not going to bodge this, I am going to have a qualified electrician who lives on our street check this over before keeping it live.

 

[tony.towa]

When you say it works fine with just one fitting have you tried both fittings individually or just one fitting on its own to "test" the circuit?

 

[eskimo39]

Many Thanks for the reply. I have tried each unit seperatly and they work fine. The problem seems to be caused when both are connected at the same time which leads me to think it's either too much load (Would this cause a trip?) or I have them wired up in the wrong way.

Is there any difference between having 2 seperate wires from the switch (1 to each light unit) , and having 1 wire which then goes into 1 light and then that light is wired into the next light. I can think of three ways to wire these lights in but am unsure if any of these are right or wrong and also if the different wiring types would affect the power requirements perhaps causing the trip.

I have added 3 diagrams (Sorry about bad quality) to show what I mean.

http://www.eskimo-design.com/plan1.jpg This is how it is currently wired & blowing

http://www.eskimo-design.com/plan2.jpg This is with the piggyback idea.

http://www.eskimo-design.com/plan3.jpg This is adding a 3 way junction box.

Many Thanks for all the help.

 

[ElectricMick]

Hi eskimo39, running 2 x 500w halogens on the downstairs lighting circuit seems a bit excessive to me. If its all on a 6A mcb the two halogens are virtually at the limit on there own (4.35 amps = 1000 watts). I would put these two lights on circuit of their own (if theres room in the CU), if not I would run a fused spur from the ringmain. 1000 watts is alot to add to a lighting circuit that is probably already pulling anywhere between 700 and 1000 watts. If the circuit is on 1.5mm cable you could try putting a 10A rcbo in it. If its on 1.0mm I would not add another 1000 watts to it. Hope this helps a bit.