Sockets - extending ring and adding unfused spur

[robato]

Hi everyone.

Doing a DIY kitchen refit and currently I only have a single 2-gang socket!
(Small kitchen but that's not enough!)

Just wanted to check if there's any words of advice on my plan below or if I've got it horribly wrong.

1) Add 2-gang DP socket by extending the ring final as pictured.
It's close enough to the existing socket that I can connect the existing cable straight to it.
It will be above the wall units to power an extractor hood and some LED cabinet lights with 3-pin fused plugs.

2) Spur off the new socket, for a 1-gang socket near the fridge.
This is so the fridge's cable doesn't need to go behind/across the cooker!

3) All cables and sockets are currently surface mounted. For the existing countertop socket, I want to sink it into the wall so plan to chase a channel vertically for the existing cables and feed them through an oval conduit, then plaster over. I'll leave the rest surface mounted as they are generally out of sight or use existing trunking.

I'm not planning on touching the 32A cooker circuit and control unit (the one with red switch).

Thanks
robato

 

[ericmark]

You start with the loop impedance or R1 + R2. A ring final can be up to 106 meters, step one is work out how long it already is. For a B32 MCB/RCBO you are allowed up to 1.38 Ω for the loop impedance to ensure it will trip within the required time with a short circuit.

If you have an installation certificate or an EICR then that should have the info your need.

An electrician will normally extend the ring, he has the testers to know if the limits will be exceeded or not, DIY tends to be the fused spur, as they have not got the test gear required for a ring. The tester like this

with a loop test cost around £40 - £50 and will pass anything better than around 1.9 Ω, a tester like this

will cost around £300 and can measure down to 0.01 Ω and that's the problem, even to hire likely with cost £60 as it needs recalibration after each hire.

 

[ebee]

Unless I misunderstand you then it appears your existing socket on a ring final circuit.
That, initially, seems a strange set up unless it was intentional to do so and leave in place a point for easy access for future expension of the ring to accommodate future additions and alterations without the need to take cables from that area back to the consumer unit.
I it is indeed a ring with only one socket on it whether twin or single and I would suggest all future sockets be wired as on the ring itself and perhaps a lot later on consider additions as either asnother extension of the ring or , if you prefer for some reason, those could be a spur on the ring (of one per existing point) unless fused down from the ring to the first point of the radial spur.
So long as you keep any likely loads not excessive (by floor space could be a sensible way or deliberately not using too much power simultaneously) you might find this works out ok too.
It is the "heavy" loads you need to consider - usually heating loads and the time they might cycle for - the number of "light loads" such as phone chargers etc could be largely ignored in most cases.


Eric you put your comments in whilst I was typing my answer.
Now I shall have to read thru what you just wrote.

 

[EFLImpudence]

Robato:

What you are proposing is fine.

 

[robato]

You start with the loop impedance or R1 + R2. A ring final can be up to 106 meters, step one is work out how long it already is. For a B32 MCB/RCBO you are allowed up to 1.38 Ω for the loop impedance to ensure it will trip within the required time with a short circuit.

If you have an installation certificate or an EICR then that should have the info your need.

An electrician will normally extend the ring, he has the testers to know if the limits will be exceeded or not, DIY tends to be the fused spur, as they have not got the test gear required for a ring. The tester like this View attachment 352771 with a loop test cost around £40 - £50 and will pass anything better than around 1.9 Ω, a tester like this View attachment 352772will cost around £300 and can measure down to 0.01 Ω and that's the problem, even to hire likely with cost £60 as it needs recalibration after each hire.

So my most recent report when the consumer unit was changed has the R1+R2 on this circuit at 0.68 Ω, if I read the report correctly. I plan to add no more than 3 metres of cabling.

 

[robato]

Unless I misunderstand you then it appears your existing socket on a ring final circuit.
That, initially, seems a strange set up unless it was intentional to do so and leave in place a point for easy access for future expension of the ring to accommodate future additions and alterations without the need to take cables from that area back to the consumer unit.
I it is indeed a ring with only one socket on it whether twin or single and I would suggest all future sockets be wired as on the ring itself and perhaps a lot later on consider additions as either asnother extension of the ring or , if you prefer for some reason, those could be a spur on the ring (of one per existing point) unless fused down from the ring to the first point of the radial spur.
So long as you keep any likely loads not excessive (by floor space could be a sensible way or deliberately not using too much power simultaneously) you might find this works out ok too.
It is the "heavy" loads you need to consider - usually heating loads and the time they might cycle for - the number of "light loads" such as phone chargers etc could be largely ignored in most cases.


Eric you put your comments in whilst I was typing my answer.
Now I shall have to read thru what you just wrote.

I believe there are 6 sockets on this circuit. It's just that there is only 1 socket in the kitchen itself.

These kitchen sockets are just for the existing fridge, kettle and toaster, plus a new cooker hood (100W) and LED cabinet lights (15W). The only other significant loads would be the hair dryer in the bedroom and freezer/washing machine in the utility room.

 

[ebee]

OK, right, looks fine to me.

 

[flameport]

The RCDs are Type AC which are not permitted for any new circuits or additions to circuits.

 

[ebee]

Good point there by Flameport, I failed to consider it, I was thinking about the gen circuit layout in itself as one example of a way forward, that is not an excuse but merely an explanation.