Adding sockets

[ewanrob]

Is it ok to add sockets onto an existing 4mm twin / earth radial circuit using 2.5mm twin and earth.

 

[ban-all-sheds]

If you go via an FCU, yes.

 

[ewanrob]

Please expand

 

[breezer]

this is an fcu

because you want to use 2.5 cable you must insert a fuse to protect the new smaller cable, hence fcu, how ever you can add more sockets with no fcu if you use 4mm

 

[ewanrob]

I am assuming this can be situated beneath the floorboards. I am a mechanical engineer and know a reasonable amount about electrics, but want to make sure everything is ok first.

Many thanks

 

[breezer]

no, sorry it cant becuse you will need access to it, stick with 4 mm cable

 

[plugwash]

how is running a 2.5mm spur from a 4mm 32A radial any different from running one from a 2.5mm 32A ring?

 

[breezer]

because thats not what it was designed to do. i see what you are saying though.

 

[andy]

how is running a 2.5mm spur from a 4mm 32A radial any different from running one from a 2.5mm 32A ring?

i agree. altho 2.5mm from a 32A ring is wrong since the breaker will only protect the cable to 32A, 5A above the limit

back to the main question, unless its the last socket you intend to take a feed from, itll be pretty tight gettin 3 4mm cables into one socket

 

[Damocles]

He's quite right: there is no sense allowing a 2.5mm spur off a 32A ring and forbidding one off a 32A radial. Of course, the other conditions re spurs would apply. No further spurs off the spur. Only one socket.

There is some cable protection, because the biggest thing allowed on the end is a double socket...with two 13A fused plugs=26A

The OSG seems quite happy in principle to have unfused spurs off 32A radials wired in 4mm. Unfortunately from the wording it does not say you can use a smaller cable size. But if you use the same size cable off a radial, how is that a spur?

 

[ewanrob]

Thanks for the responses, maybe I should explain a little better where I am upto.
My front room had only 2 sockets in it, she who must be obeyed decided 3 more sockets were needed. I knocked out the walls and fixed in the sockets fed the 2.5mm wire down under the floor leaving plenty of spare cable to cut to size ( at this point I hadn't been under the floor). Once all the cables had been fed down I got under the floor and connected each one to the next socket where possible & jointed at a junction box where the existing cable was. Thats when I noticed the ex cable was larger 4mm, the problem I have is all the cables are installed & I have plastered up where I chased out. What next.
Someone has told me I could change the 30amp fuse in the consumer for a 20amp, is this correct.

 

[plugwash]

Someone has told me I could change the 30amp fuse in the consumer for a 20amp, is this correct.

yes that would make the install safe but you may get neusense tripping problems (and you probablly would want to put a warning by the CU not to change it back)

 

[ban-all-sheds]

because thats not what it was designed to do. i see what you are saying though.

Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.
Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.

 

[ban-all-sheds]

He's quite right: there is no sense allowing a 2.5mm spur off a 32A ring and forbidding one off a 32A radial.

Do not look for logic, consistency or reason in the wiring regulations. That way lies madness.

etc..

There is some cable protection, because the biggest thing allowed on the end is a double socket...with two 13A fused plugs=26A

Until of course your socket bursts into flames - you mustn't take 26A from a double socket, they are only rated at 13A.

But if you use the same size cable off a radial, how is that a spur?

It's not - it's called a branch, or a leg, AFAIK...

 

[ban-all-sheds]

My front room had only 2 sockets in it, she who must be obeyed decided 3 more sockets were needed. I knocked out the walls and fixed in the sockets fed the 2.5mm wire down under the floor leaving plenty of spare cable to cut to size ( at this point I hadn't been under the floor). Once all the cables had been fed down I got under the floor and connected each one to the next socket where possible & jointed at a junction box where the existing cable was.

So all along, despite the fact that you were knocking holes, and chasing the walls, and you have access to the circuit cable under the floor, you planned to install these sockets as spurs, rather than properly extending the ring that I guess you assumed you had?

That's pretty shabby.