Wiring regs re Spurs

[mikehardy]

Hi all, My Conservatory is being built, the total area is 10M sq. The electrician has installed wiring (1st fix) but I was a bit surprised that the power ring main is not continuous but merely a spur to the two double power sockets. This spur looks as if it will be wired into an existing socket on the house power ring main. Is this legal? and to IEE regs, there is no mention of a 20A spur fuse! (is this item needed?) Do you think this approach is cost cutting - IE no return ring wiring. The installation is due to be completed next Thursday 9th June.

I would appreciate any comments.

Regards, Mike

 

[Jurasic Spark]

Your electrician should be familiar with BS7671 so ask him why his circuit is not inaccordance with Appendix 15.

 

[mikehardy]

Thanks Jurasic Spark, Is there any chance this could be a 'radial' in formation?

 

[Jurasic Spark]

The way you have described it, it sounds as though the intention is to connect the 2 new sockets spurred from the house ring. A none fused spur can only be used to supply 1 double socket.
Maybe he intends to fit a Fused Spur or run it straight back to the consumer unit as a new radial with a 20A breaker.
Speak to him to find out the plan.

 

[Electro-tech]

A radial unfused spur should feed one single or one twin socket outlet. A fused spur connection unit would then limit your load to 13 Amps/Although you can have a number of socket outlets. Also the cable first fixed may need to be 4mm if dropped down the cavity with the insulation touching or surrounded.

 

[Des 56]

This spur looks as if it will be wired into an existing socket on the house power ring main.

There are two end products available
The existing socket is part of the ring main. then fitting a fused spur off that socket will permit umpteen others to be wired in a radial from that fused spur

The existing socket is itself a spur off the ring main.in this case he will have to fit the fused spur before that socket which will become the first in the line of the new items

 

[mikehardy]

Thanks Electro-tech, The cable inside the cavity is 2.5mm with the insulation surrounded. If this spur is wired to the ring via a spur fuse what should be the fuse rating? bearing in mind the circuit contains two double switched sockets.

The cable size is by sight, the cable overall width is the same as the lighting circuit cable which contains 3 cores and the earth trace.

 

[Graeme Harrold]

The cable size is usually stamped on the outer sheath, just make sure you see BASEC along its length too.............You can get away with wiring in 1.5mm, as long as its correctly fused down. not recommended though.....

 

[mikehardy]

The lighting feed (3 cores and earth) looks as if it will be terminated at the same double socket on the original house power ring - does this circuit need a spur fuse as well?

 

[mikehardy]

Graeme, there is no markings on the cable sheath and the cable drum(s) were blank, how often are these markings repeated? I have looked over a 5m length - nothing marked!!

 

[Electro-tech]

The fused spur- holds a maximum fuse of 13 Amps the same as a plug and it can feed the two double switched sockets.But you are limited to 13 Amps! You really need to know what loads you are going to plug in the conservatory.The circuit should be designed around your needs and the size cable, or type of circuit, with the outcome a Design Current/ load.Then you will have rating factors as mentioned on insulation to take into consideration.This should all be within the scope of the electrician or the Conservatory Design Team.

 

[malcolmsanford]

To be honest it is nearly impossible to 2nd guess what the electrician as designed for you.

There is a myriad of circuits he could be doing for you. he maybe fusing down via a spur, he may even be extending the ring from the house into the conservatory using that existing socket as a type of junction box, what is intriguing though is the 3 core cable for the light.

 

[mikehardy]

The fused spur- holds a maximum fuse of 13 Amps the same as a plug and it can feed the two double switched sockets.But you are limited to 13 Amps! You really need to know what loads you are going to plug in the conservatory.The circuit should be designed around your needs and the size cable, or type of circuit, with the outcome a Design Current/ load.Then you will have rating factors as mentioned on insulation to take into consideration.This should all be within the scope of the electrician or the Conservatory Design Team.

This was not discussed - we were told 'two double sockets and a light/fan point' in fact I was surprised that the house ring was not to be extended into the Conservatory - cost cutting do you think?
​

 

[mikehardy]

To be honest it is nearly impossible to 2nd guess what the electrician as designed for you.

There is a myriad of circuits he could be doing for you. he maybe fusing down via a spur, he may even be extending the ring from the house into the conservatory using that existing socket as a type of junction box, what is intriguing though is the 3 core cable for the light.

There are only two cables entering the house from the Conservatory - the twin and earth (2.5mm) and the 3 core and earth (lighting) Am I correct in assuming these two cables will be connected to the existing house ring via two separate fuse spur units and this will comply with the latest regs?

 

[Jurasic Spark]

There are only two cables entering the house from the Conservatory - the twin and earth (2.5mm) and the 3 core and earth (lighting) Am I correct in assuming these two cables will be connected to the existing house ring via two separate fuse spur units and this will comply with the latest regs?

Yes this would comply but we can't assume what the elctrician intends to do. You need to discuss it with him.