Wiring walllights/ceiling rose in the loft

[aidan1979]

Hi All

I am trying to wire 4 wall lights and 1 ceiling rose in the loft (i.e. 4 lights in each corner of the loft and 1 ceiling rose in the middle - its a pretty large loft and less lights than this wouldn't really do the job).

However, qwhen I wired them up, the bulbs (each 100W) were really dim. However, when I removed them (one by one) the remaining ones got brighter. I'm not sure why this is happening but I'm sure its more a case of wiring them up incorrectly rather than that it can't be done - please advise.

I have run the mains cable (from consumer unit) into a 20A JB. From the JB there's a cable running to a 10A switch and another running to the first wall light (which has wiring blocks identical to those found in ceiling roses). In the first wall light I have put the live wire into the live block and the switch live (i.e. the blue wire with the red sleeve) on the switched live block. However, where I think I've made a mistake is that from light to light I have wired them up with the neutral to the neutral block but all the lives go to the switched live(i.e. both the wire going into the light and the one coming out of it going to the next light).

Should I have connected the wire coming into the lights to the neutral block and switched live block and the wire coming out of the light and going to the next light to the neutral block and the live block?

PLEASE HELP!!!

THANKS!!!

 

[didthathurt]

Yes, it is a wiring cock up! You've, basically, wired them in series.

You need a 4 terminal JB for starters, do you have one?

3 wires come in from the CU, a Brown, Blue and a bare core which should have a yellow and green sleeve over it. These go into 3 of the terminals. From the JB a 3 core wire to the switch. Brown from brown in the JB to 1 of the switch terminals. To the other switch terminal connect the Blue with a Brown, NOT Red, sleeve. This goes back to terminal 4 (the unused one) in the JB, where it is brown sleeved again. This is, now, your live supply to the lights which you connect in parallel, as depicted here:
//www.diynot.com/forums/viewtopic.php?t=7553
Throughout, all the bare cores must be green and yellow sleeved and connected togather via earthing terminals in switches and fittings.

500W of lighting needs only 2.5A to operate - so cable size is no problem. I AM concerned, however as to where in the CU you have run this from and what sort of MCB/fuse is protecting this circuit.

Now, at the risk of offending you (as last time I wrote this I appear to have created mortal offence!) Time to be honest with yourself, this is such a basic piece of standard cct construction if you are not sure of this do you really know enough to guarantee the lives of your family on the standard of the job you'll do? Just because electrcity doesn't smell when it leaks or make a puddle it seems so easy to do. Cock up's kill people very quickly.

It's part P time again! This is notifiable work, the addition of a new cct, that must be declared to the LABC.

 

[aidan1979]

Thanks for your post didthathurt.

I may not have explained it properly but the wiring you explained re the 4-terminal JB is as i have done it (albeit that I used red sleeving as opposed to brown). Its how to connect from the JB to the lights and then from one light to the other (i.e. in parallel) that I'm unsure of and cannot find on that link you gave.

The lighting to the loft is on its own 6A MCB.

Please note that the lights will be checked by a qualified electrician who will be asked to issue a certificate that they're ok (or to correct it if its not).

I'm not offended by your comment; its a fair point to make. Personally, however, I would say that simply because I'm unsure as to how to wire the lights together doesn't necessarily call into question how competent I might be at actually wiring everything together once I have been advised how this should be done - I understand that you may not necessarily agree with this! It is as a result of my inexperience and the potential dangers that may arise thereof that I call upon the advice of those more qualified than myself - such as yourself!

Anyway, thanks a lot for your help!

 

[johnny_t]

I'm not sure that they are in series, as then taking any bulb out would cause them all to go off. Maybe the configuration is more like.....


o---------L---------------------------------
I I I
I I I
L L L
I I I
I I I
o--------------------------------------------


where the L's represent a light. Is there one light bulb that if you take it out then it makes all the others go off ?

The first light in your circuit wants to be wired 'as normal' and everything else wants to be run from the switched live on that first light and the neutral.

Incidentally, your first light wants to be between switched live and neutral. It is not entirely clear that that is how you have it.


EDIT: Oh - That didn't work. Basically what I am trying to draw is three bulbs in parallel, and then one bulb in series with that whole combination. This gives you a potential divider presenting a reduced voltage across all bulbs. Removing any one of the parallel bulbs increases the resistance of that section, thus upping its 'share' of the voltage and making them brighter, though this should also make the Series one dimmer. Removing the series one will cause all to go off......

 

[aidan1979]

HI Johnny T and thanks for your time.

The first light I have wired "as normal" (i.e. the switched live from the switch goes to the switched live in the light and the live goes to the live block. I think the mistake might lie in that to go from this first light to the second (and so on) I have wired the live from the switched live to the next light's switched live (neutrals to the neutral block).

Perhaps I should have wired from the first light's live block to the second light's switched live (all neutrals to the neutral block)?

Removing any bulb does not make the others go off, it simply affects the brightness of the bulbs which remain connected.

 

[johnny_t]

If no one light makes the others go off then my theory above is incorrect. It almost sounds as if there is some large resistance on the live (or neutral) feed in, so it might be worth checking that you haven't got a dodgy connection on the live (or neutral) to the first light, or got the insulation trapped under the screw or something (though this would be a very large resistance and would normally make the whole thing not work).

From the first light, you need to run from the switched live on that light to the live of the next light, to the live of the next light, to the live of the next light, and each light wants to be run between this live and its neutral. All neutrals are connected together.

(I am assuming you want them all off or all on at the same time)



(I would also point out that I am not a proper electrician, just an electronics dude so I am approaching this from an Ohm's Law viewpoint - It may be safer to wait for a proper electrician to offer some advice here)

 

[didthathurt]

the switched live from the switch goes to the switched live in the light and the live goes to the live block

If you've wired the 4 terminal JB as described then you have carried out the functions that the 3 separate terminal blocks in a loop ceiling rose do, so you shouldn't have a sleeved blue live coming from the JB. You should have the brown core of a cable from the switched live in the JB (Brown sleeved Blue) running to the first lamp fittings live connection. The Brown of this cable you need to connect into 1 of the 3 loop terminals at the light fitting. Connect the lamp live to another of the loop terminals in that fitting and then the lamp neutral and the neutral of the JB cable into 2 of the 3 neutral fittings on the first rose. Remove all other cables and check that works.

If it does, and it should!, then connect the cable to the next rose into the remaining loop and neutral fittings in the 1st rose and then into the loop and neutral of the second. Then replicate what you've just done in the first rose. This will parallel all the lights.

 

[didthathurt]

If you find it's getting stickier, e-mail me a contact no and I'll call you and try to sort it out with you.

 

[aidan1979]

Didthathurt and Johnny G

Thanks a lot for your help. I will try your suggestions tonight or tomorrow night and will let you know how I get on. If I'm getting nowhere, I will post you my no. didthathurt and take you up on your kind offer.

Thanks again.

Aidan

 

[aidan1979]

Thanks for your help didthathurt.

I had wired the cable from the JB to the first light incorrectly. I did as you suggested and now it all works fine.

Thanks a lot!

 

[dingbat]

Please note that the lights will be checked by a qualified electrician who will be asked to issue a certificate that they're ok (or to correct it if its not).

And did you call in this qualified electrician?
Did he give you a certificate?

I only mention this because so many posters say this is what they intend to do, but we never hear about the outcome. A reputable electrician is highly unlikely to certify work he has not done himself.

 

[aidan1979]

Not yet but we will do. Not sure if you've seen any of my other posts but it seems that our builders screwed through a ring main cable when putting up some plasterboard so we need to get that fixed. We will therefore be etting someone in to do that and certify all the house electrics - if nothing else because we've done aocmplete renovation and building control and involved and know about it all we need to get everything "in order" before we can sell it and move on. If we do decide to stay by GF won't have them staying uncertified anyways!!!

Its a small price to pay for piece of mind and everyone, particularly those who do any amount of work on the electrics themselves, should get it checked out by a qualified electrician.