Spur with two sfcu on it

[Lighting]

Hi all is this ok to run two sfcu like this ?


Or should i run it like this

 

[ezzzekiel]

All this chatter for installing a couple of points , you'd think domestic work is complex reading all this lol.

Really makes you wonder what's going on out there!

 

[TaffyDuck]

Sorry Taffy you lost me on that one i don't see any difference at all Appendix 15 shows spur protecting sockets? You dont need a FCU protecting a FCU where would it end?

Ok, the part of the diagram on page 425 shows a spur off the ring main at 9 oclock. The 13A FCU is limiting the current that can flow through to 13A therefore protecting the cable. The OP diagram 1 shows a spur going straight to the first FCU and then on to another FCU. Therefore with 13A fuses put in each it is possible that the total draw could be 26 Amps thus overloading the cable. The 3 amp fuses fitted to the FCU`s are irrelevant as they are protecting the cable going out from the FCU to the appliance.

Now I appreciate that 6 amps, or the load from a boiler and a light (which is going to be less in all likleyhood) is not going to damage the supply cable however the light and the boiler are " fixed equipment" therefore the relevant part of the diagram is at 6 oclock where only 1 fixed item is allowed.

The reasoning for this reg IMHO is that should the fixed equipment be changed in the future, say an immersion for a boiler and a socket for the FCU running the light then you have an overloaded cable.

I refer to my previous post regarding fixed equipment on spurs.

 

[Guest55]

Really makes you wonder what's going on out there!

very little if it takes hours of debate to fit 2 fcu's :-D

 

[TaffyDuck]

very little if it takes hours of debate to fit 2 fcu's :-D

Ok we will all shut up until we can have a debate about something that you consider appropriate your highness.

 

[pencilpusher]

Ok, the part of the diagram on page 425 shows a spur off the ring main at 9 oclock. The 13A FCU is limiting the current that can flow through to 13A therefore protecting the cable. The OP diagram 1 shows a spur going straight to the first FCU and then on to another FCU. Therefore with 13A fuses put in each it is possible that the total draw could be 26 Amps thus overloading the cable. The 3 amp fuses fitted to the FCU`s are irrelevant as they are protecting the cable going out from the FCU to the appliance.

Now I appreciate that 6 amps, or the load from a boiler and a light (which is going to be less in all likleyhood) is not going to damage the supply cable however the light and the boiler are " fixed equipment" therefore the relevant part of the diagram is at 6 oclock where only 1 fixed item is allowed.

The reasoning for this reg IMHO is that should the fixed equipment be changed in the future, say an immersion for a boiler and a socket for the FCU running the light then you have an overloaded cable.

I refer to my previous post regarding fixed equipment on spurs.

I actually think this is an interesting debate and it has got me thinking TBH. I think Taffy is right here. The 13 amp FCU protects the whole of this spur cable in the future no matter what DIY Dan adds to it (and he will). The FCU's downstream could allow 26 amps to be pulled through and damage the spur cable upstream. Hmm

 

[Lighting]

Thanks for all the reply's i think i best put the 13a sfcu in as it will only take 5 mins

 

[mickys86]

Ok, the part of the diagram on page 425 shows a spur off the ring main at 9 oclock. The 13A FCU is limiting the current that can flow through to 13A therefore protecting the cable. The OP diagram 1 shows a spur going straight to the first FCU and then on to another FCU. Therefore with 13A fuses put in each it is possible that the total draw could be 26 Amps thus overloading the cable. The 3 amp fuses fitted to the FCU`s are irrelevant as they are protecting the cable going out from the FCU to the appliance.

Now I appreciate that 6 amps, or the load from a boiler and a light (which is going to be less in all likleyhood) is not going to damage the supply cable however the light and the boiler are " fixed equipment" therefore the relevant part of the diagram is at 6 oclock where only 1 fixed item is allowed.

The reasoning for this reg IMHO is that should the fixed equipment be changed in the future, say an immersion for a boiler and a socket for the FCU running the light then you have an overloaded cable.

I refer to my previous post regarding fixed equipment on spurs.

I get it now. That and what ipf explained. It'd be best to incorporate the spur as part of the ring or put the 13a spur in.


We only do new builds or complete refurbs when we do domestic, the rest is commercial work and in both circumstances I'm supervised. Always learning and even thou this wasn't my post I learned something today.

Sorry to bore you ez and biff. Was there nothing else on the forum you could've read??

 

[ezzzekiel]

 

[Simlec]

First pic a no go, second pic correct.
not sure why this has got to fourth page.

 

[TaffyDuck]

ezzzekiel, yes as I said.

 

[TaffyDuck]

First pic a no go, second pic correct.
not sure why this has got to fourth page.

Well its sorted now

 

[ezzzekiel]

Either option would be ok unlimited outlets allowed as the first fcu limits the total draw to 13a from that leg of the ring

 

[pencilpusher]

Either option would be ok unlimited outlets allowed as the first fcu limits the total draw to 13a from that leg of the ring

Sorry but there is no 13 amp FCU on the first drawing???

 

[TaffyDuck]

Said my piece Pic 1 is wrong, bored now.

 

[pencilpusher]

Said my piece Pic 1 is wrong, bored now.

Chill Taffy, I am not arguing with you, I am agreeing!

 

[ezzzekiel]

No it's not your right it's fused at 3a which still makes the circuit correct
everything from the fcu in picture one is limiting the draw to 3a

 

[mickys86]

Either option would be ok unlimited outlets allowed as the first fcu limits the total draw to 13a from that leg of the ring

That's what I was thinking at first but if second spur was connected to supply side of first spur then it would be wrong.

Why is everyone getting uptight about this?? It's Sunday..... Chill day

 

[pencilpusher]

No it's not your right it's fused at 3a which still makes the circuit correct
everything from the fcu in picture one is limiting the draw to 3a

OK but he stated it would be "looped". I take it that means the second FCU is fed from the supply of the first FCU and not the load side. That would mean the 3 amp fuse would protect the light and not the spur cable and that the second FCU could draw up to 13 amps?? That's my take on it but I may have read it wrong.

 

[ezzzekiel]

Yes but then the circuit wouldn't be wired correctly so not a design fault, not uptight about it but to say the circuit is wrong is not true, it may not be ideal or suitable for the use intended but it is correct as far as design goes, outlets are unlimited from fcu taken from the ring as the fcu be it 3,5,13a will limit the loading from the leg to the rating of the fuse.

As PP says above looping would be incorrect but ops original post was just a block diagram

 

[pencilpusher]

Guys, I think this is interesting even if some do not! I am certainly not uptight about any of it.

 

[mickys86]

Not saying you was uptight....but there was a few others.... I never said pic 1 was wrong but I came round to taffys way of thinking.

I can't remember seeing he was going to loop the fcu's I may have read it wrong too

 

[pencilpusher]

Hi all right the socket is on a ring final then going to the 1st sfcu then looping out to the 2nd sfcu o know you can only have 1 socket off a spur but both sfcu will be at 3a so i don't think i need a sfcu by the socket.

Looping! :smile5:

 

[ezzzekiel]

Maybe taffy was thinking that way too which would explain why he said 26a could be drawn, however just going by the ops drawing there is nothing to suggest it would be looped through so in my opinion it was worth 5 pages just to clarify the point that,
yes his circuit is correct providing he wires from the load side of the fcu and not looping from the feed.

Everybody happy with the clarification now?

 

[mickys86]

Maybe taffy was thinking that way too which would explain why he said 26a could be drawn, however just going by the ops drawing there is nothing to suggest it would be looped through so in my opinion it was worth 5 pages just to clarify the point that,
yes his circuit is correct providing he wires from the load side of the fcu and not looping from the feed.

Everybody happy with the clarification now?

Another pint please barman

 

[pencilpusher]

I am always happy! I think it was worth it because he was clearly going to loop from one to the next. If he now understands, then it's sorted.