Where am I going wrong with my loft light?

[Meehog]

I'm trying to install a 2ft 18w Fluorescent strip light in my loft, but obviously, I've run into problems, which is why I'm here. I'll describe how I've set it up it in as much detail as I can, then maybe somebody will be able to tell me what I've done wrong.

I've used 1.0 mm twin and earth lighting cable, and connected the live, neutral and earth wires to the appropriate terminals in the light, then ran a cable down to a switch. I found a cable in my loft which goes from one ceiling rose to another (kids bedroom to bathroom in next room) and added a 30 amp, 3 terminal junction box to this cable. Then I ran a cable from this junction box to the switch, and put both reds to the switch's com terminal, both blacks to the L1 terminal, and both earths to the plastic mounting box's earth terminal.

The first time I turned the electricity back on, the upstairs lights all worked ok, then I tried the switch in the loft, the switch blew and tripped the upstairs lights on the consumer unit. So I turned the mains back off, checked all my connections, and fitted a new switch, but when I tried to turn the mains back on, the master switch on the consumer unit didn't want to co-operate, along with the switch for the upstairs lights. So I disconnected the switch and the new cable, but left the existing cable still passing through the junction box. I turned the mains back on, and everything was fine, the upstairs lights all worked, apart from a rather useless loft light.

Thanks for any help, it will be much appreciated. If what I've done wrong is really dumb, please try your best not to flame me too viciously.

 

[breezer]

see for refernce you have wired it wrong

 

[deejay d]

hi m8 what you have done is youve connected into the wrong cable although its a red and black its sounds like you have connected to the switch wire and feed to your light switch ,,on new installation we use twin red to the switchs ..well now its brown brown you need to find a perment live and neutral if you have a loopin system in youre celing roses you will have 3 terminals switch live perment live and neutral ,,

hope this helps

 

[Adam_151]

Put the red from the junction box in com, the red to the light in L1, and join both blacks together with a terminal block, leave the earths in the earth block, that bit is correct

 

[plugwash]

it amazes me how many people there are doing diy wiring without even the fundamental concept of what a cuircuit is.

i mean ffs thats high school stuff not rocket science.

 

[breezer]

thats why i point them to the refernce section, if they can not figure it out they shouldnt be doing it

 

[deejay d]

dont forget part P of the regs you shouldnt be doing home diy electrics anyway

 

[securespark]

DJD

There is a great deal that you can do without notification. Before you go scaring people away, read the Part P document for yourself.

For example, you can replace anything around the house like light fittings sockets etc. You can replace one circuit cable if damaged by fire impact or rodent as long as you follow the same route. You can fit extra sockets, lights etc as long as they are not in special locations (and that includes outside lighting as long as it is attached to the house and you do not have to run a cable across the garden to feed it).

As regulars say until they are blue in the face, "Familiarise yourself with Part P!"

 

[plugwash]

please get your facts straight

the only works notifyable under part P are new cuircuits works in the regs defined special locations (including garden power) and works in kitchens

 

[securespark]

JINX!!

 

[Meehog]

it amazes me how many people there are doing diy wiring without even the fundamental concept of what a cuircuit is.

i mean ffs thats high school stuff not rocket science.

You were really lucky to get taught how to install loft lighting etc in high school, your teachers were miles better than mine, they only taught us how to change a plug.

Put the red from the junction box in com, the red to the light in L1, and join both blacks together with a terminal block, leave the earths in the earth block, that bit is correct

Cheers mate, that worked a charm.

 

[plugwash]

it amazes me how many people there are doing diy wiring without even the fundamental concept of what a cuircuit is.

i mean ffs thats high school stuff not rocket science.

You were really lucky to get taught how to install loft lighting etc in high school, your teachers were miles better than mine, they only taught us how to change a plug.

no we weren't taught how to do home wiring but we WERE taught that electricity flows in cuircuits

knowing this it is obvious that the way you wired it can't work.

i'm not trying to pick on you individually but i find the number of people who make this f*ckup frankly scary it shows people are doing wiring by playing match the colors rather than having any clue whats going on

 

[felix]

Ah yes, classic booboo. As I hope you've figured out by now Meehog you had your switch and light in parallel instead of series. My father did this many years ago and him a science teacher too!

If you're still stuck, Adam_151 has already posted one correct answer to your problem but there was a better way from the outset. You should have got a 20 amp 4 terminal box.

From this box you run separate cables out to the light and the switch. Red from the switch goes to red in the box but black from the switch goes to that fourth terminal. You put a bit of red sleeving on it to indicate that this is switched live and not neutral. Red from the light also goes in the fourth terminal and black from the light goes to black in the box. All earths go in the same terminal.

If you've done it right your four terminals will contain:

1) Three red wires
2) Three black wires
3) Four earth wires
4) One red wire + one red sleeved black wire.