New electrics to new porch

[Jake2021]

Hi ,

I’ve just dig
My
Foundations to
The new porch but the original porch had no Electricity in it.

What would The best way to get electrics to the porch
Please. The socket that’s in the living room is the last socket
On the ring main can I take a feed from that upto a mother rcd to the porch then run a socket , internal
Light and the small external light from That( it’s not a 1000w light)

I know someone one will say its
Pointless having two RCD’s on the same
Ring main
But thought this
Would
Be easier to Run 2.5 and 1.5 cable from it

It will be armoured cable used,

Thanks
Jake

 

[ericmark]

The image in my mind for a porch does not seem to line up with your description, so basics.
1) We want any power to outside to have an option to turn off both line and neutral, so we can isolate if there is water ingress.
2) The length and size of cable has to be so the volt drop is not exceeded, and the overload will work on the magnetic part of the trip, this can be calculated, but need some start figures.
3) It is quite acceptable to arrange RCD's so each one is approx 1/3 the size of the preceding one, i.e. a 30 mA feeds a 10 mA, and also using active RCD's is a good way to auto disconnect a supply with a power failure.
4) Outside lights without planning consent limited to 150 watt. May have now changed to lumen?
5) taking a supply from a socket, either one uses a plug with 13 amp fuse, or you need to ascertain what the supply to the socket is, we have ring finals, radials, unfused spurs, and fused spurs, it is not simply connect and trust to the lord.
6) Many types of light, but be protected by 16 amp or less overloads, and often down to 5 or 6 amp.

So what size overload feeds the socket, and how to you intend to connect SWA to a socket?

 

[Jake2021]

Hi thanks for your reply and questions.

The socket in the living room I think is on a 16A trip

I was hoping to come off the livong
Room socket with a piece of 2.5 2 core plus earth through the wall going through conduit through the wall and cavity and into a junction box like attached the the armoured cable upto the rcd / mcb .

The light we have is a 2 metre aluminium
Lamppost with a single 60w bulb

The blue on the pic is where my internal
Socket is located,

The red line is where the brick porch is going to come up to
Many thanks
Jake

 

[ericmark]

Personally I would consider the Screwfix LAP range of grid switches which will allow in a double socket face plate a single socket, switch and fuse holder, so you can easy fuse down, and for outside lamp would use LED bulbs as when a tungsten bulb heats and cools it can draw in water, it sucks it in as it cools, so LED are cooler so better option.

I can't see why you want SWA? Cable needs to be out door rated, so normally black, as less affected with UV, but every junction box is another place for water to get in, so unless likely to be physically damaged would not go for SWA.

 

[Jake2021]

Hi
Thanks for your reply and advise which I’ll take on board and use thanks .

Re the armoured cable I was thinking of burying it under my foundations then up through the cavity of the new walls
Thanks
Jake

 

[Taylortwocities]

3) It is quite acceptable to arrange RCD's so each one is approx 1/3 the size of the preceding one, i.e. a 30 mA feeds a 10 mA,

I’m sorry but it is not.
If you chain several RCDs as you suggest.
Let’s say a 100mA > 30mA > 10mA and a larger than 100mA earth fault occurs
(this is the usual situation!)
then there is no telling which will trip. It might be all of them, it might be the one with the fastest trip characteristic. This is not good practice.

To achieve discrimination of RCDs you need to use time-delayed RCDs (type S) and arrange them on the basis of trip time, not necessarily trip current.

Longest trip time nearest the source.

 

[Jake2021]

Hi Eric thanks for the info.. could you confirm if I am correct to use armoured cable and would it be acceptable to be placed at the bottom of my footings if in conduit
Thanks
Jake

 

[Taylortwocities]

Yes. And armoured cable does not need to be in conduit. But it needs to be properly installed.