Adding sockets to ring main - load? temperature? etc.

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Hi, I want to add 7 sockets to a ring main with five sockets. I have seen articles on the Internet indicating that adding sockets into the ring is a simple task, but others talk about calculating load, voltage drop, cable temperature, etc. Will a ring of 12 sockets require such calculations?

The ring will have a double socket added alongside each of two existing double sockets (making two groups of four), a single socket will be replaced by a double socket and two new sockets will be added about 3m from nearest socket.

The consumer unit is old so presumably I must add an RCD.

Any advice gratefully received.
Thanks
 
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All new wiring which is buried less than 50mm needs either RCD protection or be one of the special cables. All new sockets must be RCD protected.

Although in theory you could wire with Ali-tube cable and fit sockets with built in RCD's the cost would be rather high.

So options are protect whole ring with RCD or use RCD FCU to feed a set of sockets as a fused spur.

I would say latter is most cost effective way in most cases but may be better to swap consumer unit and get full protection.
 
Thanks for your reply.

The cables will run under the floorboards where they currently reside.

Will the upgrade from 5 to 12 sockets create any load problems?
 
You can add as many sockets as you want - the socket itself does not add any load.

What is plugged into the sockets is another matter.
12 mobile phone chargers would be virtually nothing.
12 kettles would be more than the capacity of the supply to your whole house.
 
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I have seen articles on the Internet indicating that adding sockets into the ring is a simple task, but others talk about calculating load, voltage drop, cable temperature, etc. Will a ring of 12 sockets require such calculations?
Yes it would, you need to consider loading, voltage drop and the method in which the cable is installed, to calculate whether the circuit would be overloaded or cable sizing would need increasing.
Although there are some rule of thumb designs of The ring final but if you had a demand of in excess of 7.36kW then you would need to consider an extra circuit and if cable was buried in thermal insulation, then an increase of cable CSA would be likely. Also if the ring final covered a large linear loop then voltage drop again needs to be considered.
The ring will have a double socket added alongside each of two existing double sockets (making two groups of four), a single socket will be replaced by a double socket and two new sockets will be added about 3m from nearest socket.

The consumer unit is old so presumably I must add an RCD.
30mA RCD protection would be required on any new cabling buried less than 50mm within wall and not mechanically protected (be aware there are limitations to the depths of chases allowed within solid walls, so often the 50mm depth cannot be achieved) but regardless of that socket outlet will also require the 30mA protection.
 

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