FCU on a lighting circuit

[bel83]

Hi Guys,

Please could someone throw some help in my general direction?!

We've been rewiring our house under the supervision of a qualified sparky as I want to become an electrician. However he has gone on holiday for 2 weeks and has left me a list of things to get done in his absence. Nothing is connected to a CSU so there's no risk in that regard and he's also checking everything meticulously when he gets back.

We've got three outside lights, all in the same set up (i.e. they're part of the main lighting radial and attached to a switch). He has recommended that we future proof them by attaching switched FCUs to the circuit, in case at some point we want PIRs. They are already wired to a switch as we are going to put the FCUs up at ceiling height.

I'm trying to work out how I need to wire this in. I understand it from a socket, and without a separate light switch, but I'm struggling to work it out from it coming off the lighting radial. I think I have it sorted and then get myself in a muddle. We are using a wago box in the wall space to limit the number of wires having to go out of the house.

The picture is what I think I need to do... but I keep changing my mind between the FCU connecting to the switch or to the WAGO.. because somewhere a circuit line gets discontinued.. and now I'm thinking I need 3 core.. connect the neutral line in the FCU with terminal block, extend a switched live and a com.. do the same in the switch? and again extend the switched live and comm to the WAGO and on to the luminere?

http://www.dropbox.com/s/0xy7rx9204q9bh6/electrics.png



Please could someone advise. And before you all have a go at me for not being qualified.. I am doing this with an electrician. He'll check it all when he's back but I need it in place for him to do it..

Thanks in advance..

 

[bel83]

rather than being unhelpful maybe suggest what you're not understanding and offer help...?

 

[Spoon]

So what you are saying is that you are going to add 3 outside lights to the lighting circuit?
So why do you need FCU's?
What is the wattage of the outside lights?
If you buy PIR lights can't you buy the LED ones?

 

[Simonslimline]

It would be a good idea to have double pole isolation for the outside lights. That way if a fault occurs you can isolate the neutral as well.

 

[trev]

I'm with Spoon on this, you can buy LED flood lights with PIRs.

 

[bel83]

basically our outside lights are wired into the lighting circuit and all have individual switches (not FCUs). Our electrician came to wire things in last week and said that as they are PIR they need to be on FCUs. We are replacing the lights with non PIR lights anyway (10W LEDs) but he said that to future proof them (in case we want PIRs in the future) and in order to isolate them, we have to have each one on a FCU.

We have put non maintained junction boxes in the wall spaces so only the power cable to the light goes outside. Without the FCU these are wired the same as any other junction box or ceiling rose, i,e, line in and out, switched live and comm from the switch and the neutral and live from the light. However, I don't know where I need to put the FCU in- is it before or after the switch.. I assume before, so that all power in is cut off.

if so, do I need 3core to connect it to the switch so that comm/ live/ neutral connections are maintained, or am I missing something? I get what I need to do if I was connecting it as a spur from a socket. I think the whole 'double switching' element is the bit that's confusing me..

@Carlos- you're really not being any more helpful. If you have nothing useful to say, go and bother somebody else.
@Spon- thank you. As to why we need FCUs, who knows. Like I said, he has said futureproofing..

 

[Deleted member 72666]

Did you not think to ask your 'holidaying' sparky friend before he went away?

 

[bel83]

unfortunately he was in a bit of a rush.. we'd previously come to the decision that we didn't need them as we weren't having PIRs and then he changed his mind and said to put them in just in case we changed our minds in the future.

@stan- I take it that this means that you think I'm bullsh*tting about having a sparky in.. think what you like.. We started this with the intention of having one sign off stuff after we'd installed as my f-i-l is an electrical engineer but was never domestic and things have moved on rather, so i said that i wanted it all to regs etc. The sparky is a friend of a friend and has agreed that so long as he oversees every step and has conversations with us about plans, he's happy to come and test etc. He was impressed with how fast i grasped what i was doing and was confident in my abilities. We both assumed that I knew what I was doing with the FCU, and like I said, if there was no switch already in the line, then this would make more sense to me.. Doing it as a 3 way switch won't work according to my logic as the point is to isolate it..

Please could someone actually offer me some help, as opposed to just questioning my honesty.

He's back on the 31st so I can ask him before he comes to test but I'd much rather have it sorted as I'm renovating the whole house and don't really want to get caught up on this..

Thanks

 

[Spoon]

Hi mate.
In your case above you would only use the FCU for isolation & maintenance.
Therefore put the FCU in where you would think it would go. Any electrician should know where it goes.
I'm not giving you the full answer cause really you should now know.

 

[bel83]

Hi Spoon,

Thanks.. Can I just clarify this with you- If it's there purely for isolation and maintenance it should cut the power to the permanent live. So therefore I want it to go in before the switch.

I understand your reticence to reply completely.. And like I said, if it's in the wrong place he'll take it out and put it where it needs to be when he comes to connect it all.. I'm essentially minimising the time spent on bits he has to do..

Cheers

 

[DPG]

Seems a bit over the top having individual isolation for each outside light. Or is it just me? Daz

 

[Spoon]

If it's there purely for isolation and maintenance it should cut the power to the permanent live.

Read post 6 mate.

 

[bel83]

My original diagram, which my husband questioned, causing my head spin was as follows...

Lighting radial in- FCU- Non maintained connection unit- leading (separately) to the switch and the light itself.

I believe that is right... (she says, hopefully!)

 

[bel83]

and yes.. on the neutral.. sorry Spoon! i tell you, head spin.. trying to do audits while working this out too.. no electric at home so no wifi!! and yes.. it does seem ott but they're in very different places so unless they had a radial all to themselves (which in hindsight would have made things SO much easier.. ) they need them if they are to be isolated..

 

[Spoon]

Does the outside light manual say that it need isolation?

 

[bel83]

not these ones, no.. but ssparky has requested that we wire in fcus in case we change our minds and put in floods in the future.. or the next people do etc.. as we've rewired everythign is being concealed.. no trunking.. so i think he's trying to save us the hassle of having to chase in the future or have to have trunking..

 

[amckay]

I'm not sure I understand what you are having trouble with. Taking a feed from the end of the internal lighting radial and extending it to the exterior for outside lighting?
It would make more sense and less work to install led pir lights outside, with the addition of a switch so its either on the pir or on full if you know what I mean. Can't get much more future proof than that. I agree with a dp isolator too. But if you say its a rewire, why don't you properly future proof it by giving the said circuit its own MCB in the board?

 

[Spoon]

You are wiring to the lighting circuit therefore any 'future' lights will be limited to your 6A breaker.
Get the LED floods in future then you are sorted.

 

[DPG]

I can't believe it's worth you doing these bits anyway to be honest. Your sparky is going to have to check all of your work when he gets back - he may as well just do it himself really. Sorry if that's a bit negative. Wouldn't be so bad if you knew what you were doing, but you don't. Daz

 

[bel83]

Everything else has been fine and zero problems. it's just this FCU that has caused problems as he's asked us to do it last minute and not really explained why.. the lights are already wired into the circuit and under floorboards etc so the hassle of digging it out now to put on its own ring is a pain. we originally wanted the outside lights on their own mcb but he said there was no need.. now i'm getting the feeling that there is a need, otherwise we wouldn't need to isolate them..
he's been perfectly happy with everything else that i've wired in..

ultimately it would have been difficult to have someone come in and rewire because the house has needed building up from nothing.. there is only one mcb for the whole house as it stood.. we've had to move in and so there was no way we could really get someone in to rewire it.. like i said, it's just this bit that has had me thrown as it's ended up a bit of a contradiction.

Carlos.. i see you're intent on trolling this thread without actually contributing anything of use.. you're clearly a self aggrandised twit with nothing better to do.. go and make yourself useful- electrocute yourself..

 

[DPG]

But he shouldn't be asking you to do it. And you shouldn't be doing it if you aren't competent to do it. Daz

 

[Spoon]

So you are saying that the outside light are already wired in and the electrician has asked you to hack into the circuit and fit a FCU?
I wouldn't bother. Just keep the outside lights as they are.

 

[amckay]

Everything else has been fine and zero problems. it's just this FCU that has caused problems as he's asked us to do it last minute and not really explained why.. the lights are already wired into the circuit and under floorboards etc so the hassle of digging it out now to put on its own ring is a pain. we originally wanted the outside lights on their own mcb but he said there was no need.. now i'm getting the feeling that there is a need, otherwise we wouldn't need to isolate them..
he's been perfectly happy with everything else that i've wired in..

ultimately it would have been difficult to have someone come in and rewire because the house has needed building up from nothing.. there is only one mcb for the whole house as it stood.. we've had to move in and so there was no way we could really get someone in to rewire it.. like i said, it's just this bit that has had me thrown as it's ended up a bit of a contradiction.

Carlos.. i see you're intent on trolling this thread without actually contributing anything of use.. you're clearly a self aggrandised twit with nothing better to do.. go and make yourself useful- electrocute yourself..

You live and learn. Nothing substitutes a good well thought design with an understanding and competent installer!

 

[malcolmsanford]

Do not feed the troll

 

[trev]

Do not feed the troll

MALCOLM!!!!!!!!
Welcome back mate, I was just about to start athread asking if anyone had heard from you recently.
How the hell are you?

 

[malcolmsanford]

Trev!!!!! How the devil are you? I'm still hanging in there mate back in the UK and sort of semi retired but keeping my hand in. How are you ?

 

[trev]

I'm very well mate, busy but could be busier but the bills are paid there's grub in our bellys and beer in the fridge so it must be pretty much ok.
So no more foreign excursions for you?

 

[Octopus]

basically our outside lights are wired into the lighting circuit and all have individual switches (not FCUs). Our electrician came to wire things in last week and said that as they are PIR they need to be on FCUs. We are replacing the lights with non PIR lights anyway (10W LEDs) but he said that to future proof them (in case we want PIRs in the future) and in order to isolate them, we have to have each one on a FCU.

We have put non maintained junction boxes in the wall spaces so only the power cable to the light goes outside. Without the FCU these are wired the same as any other junction box or ceiling rose, i,e, line in and out, switched live and comm from the switch and the neutral and live from the light. However, I don't know where I need to put the FCU in- is it before or after the switch.. I assume before, so that all power in is cut off.

if so, do I need 3core to connect it to the switch so that comm/ live/ neutral connections are maintained, or am I missing something? I get what I need to do if I was connecting it as a spur from a socket. I think the whole 'double switching' element is the bit that's confusing me..

@Carlos- you're really not being any more helpful. If you have nothing useful to say, go and bother somebody else.
@Spon- thank you. As to why we need FCUs, who knows. Like I said, he has said futureproofing..

Can you expand on this as it doesn't make sense.

 

[Deleted member 72666]

Can you expand on this as it doesn't make sense.

I took that to mean 'maintenance free'.

 

[Octopus]

I took that to mean 'maintenance free'.

I took it that he may have placed JB's in the cavity!

 

[telectrix]

Trev!!!!! How the devil are you? I'm still hanging in there mate back in the UK and sort of semi retired but keeping my hand in. How are you ?

malc!!!! welcome back.

 

[Richard Burns]

(Hi Malcolm)

Bel

I can see no reason for an FCU in this situation. Fusing down the outside light (say to 3A from 6A) will have very little effect, I cannot think of any lights that have needed limiting on the current they could take (and if they did then they should be internally fused).
The switching effect of the FCU could be to have double pole switching (though the FCU may not be double pole), this could be achieved more easily by swapping the light switch for a double pole switch.
The switching effect of the FCU could be to have an overall off situation, so that the PIR was un-powered, perhaps for maintenance, but really you could just switch off the lighting circuit. This FCU could also be intended as a PIR off and use the light switch as a manual override ON, whilst the PIR is powered, but this could be achieved without the fuse and just use a double gang switch (double pole if desired for the PIR off) in place of the existing single gang.

From your diagram, unless the output from the maintenance free wago box had a three core cable to the light PL, SL, N then none of the override functions would be possible, so there would be no need for the permanent line to go to the Wagobox, since it is inaccessible later modifications would need to rip things apart anyway.

Leave the FCU out and change the single gang switch to a double gang if required (grid switches if other functions needed, Click grid switches if you need a fuse as well)