4mm radial

[sedgy34]

has anyone spured off a 4mm radial in 2.5mm on 75 mtrs circuit length on 32A mcb

 

[kingeri]

Doesn't really matter as it should be protected by an RCD anyway!

That's true but I've seen so many 4mm radials used for sockets in ex-council properties (that's one circuit for the whole house!) where the Zs are nothing like good enough and no RCDs in sight, just re-wireable fuses. Needed slightly upgrading!

 

[rich.250]

Answer appendix 15

My point sedgy. I'd be checking.

 

[Unswitched]

To spur off in 2.5mm feeding a max. of 1 x 13A Twin socket, although unconventional, is technically ok. The reason why this is ok is the max. amount of current that can be drawn by this twin socket is 13A (Well that is what they are designed to take, not 13+13 = 26A. Sockets, single or twin are designed to take 13A total).

2.5mm is rated max at 27A (clipped direct or in plaster) - Due to the plug top fuse being 'down stream' this limits the amount of current that can be drawn.

The 2.5mm is protected by fault current by the 32A MCB, this is where the adiabatic equation comes into platy to prove this. (However, we should already know that it is ok to spur off a 32A ring circuit with 2.5 to feed one point).

Fuse doesn't always have to be at origin. Downstream protection is common. Think Busbar chambers and meter tails....

 

[kingeri]

In real terms, I don't see the point of changing to 2.5 just for one 'spur'. Why not just use 4mm like the rest of the circuit? It is then just a branch off the radial, and also leaves the option of adding onto the end in the future.

 

[SPARTYKUS]

Doesn't really matter as it should be protected by an RCD anyway!

Unless its a grade 2 medical location!!! Or some such cobblers.

 

[telectrix]

page363, brb. perfectly acceptable for 1 outlet.

 

[SPARTYKUS]

To spur off in 2.5mm feeding a max. of 1 x 13A Twin socket, although unconventional, is technically ok. The reason why this is ok is the max. amount of current that can be drawn by this twin socket is 13A (Well that is what they are designed to take, not 13+13 = 26A. Sockets, single or twin are designed to take 13A total).

2.5mm is rated max at 27A (clipped direct or in plaster) - Due to the plug top fuse being 'down stream' this limits the amount of current that can be drawn.

The 2.5mm is protected by fault current by the 32A MCB, this is where the adiabatic equation comes into platy to prove this. (However, we should already know that it is ok to spur off a 32A ring circuit with 2.5 to feed one point).

Fuse doesn't always have to be at origin. Downstream protection is common. Think Busbar chambers and meter tails....

Eh? lost me there unswitched.

 

[Strima]

I was under the understanding that the max drawable from a 2G socket under normal domestic conditions was 26A? i.e. 2x 13A plug tops (with three 4G ext leads running of them).

 

[kingeri]

I was under the understanding that the max drawable from a 2G socket under normal domestic conditions was 26A? i.e. 2x 13A plug tops (with three 4G ext leads running of them).

Two gang sockets seem like a bit of a grey area to me. Nothing to stop someone drawing 26A through one yet most have 13A stamped on them but are actually rated up to 20A (?)....I always feel better using a decent quality socket like an MK or Contactum. I also find these will take 2 x 4mm quite easily. My dad gave me a big box of old but unused Contactum accessories, nearly used them up now, but they have been a joy to work with.

 

[Knobhead]

kingeri, just give up. Don't try to understand it

View attachment 12100

 

[kingeri]

kingeri, just give up. Don't try to understand it

View attachment 12100

Hehe, good idea Tony :shout:

 

[Engineer54]

When did this change, i cant see any difference now than 5 or 10 years ago years ago.

You need to be more observant then !! ...lol!!

 

[Top Cat]

You need to be more observant then !! ...lol!!

And if you were more observant you would have seen my earlier post!!!!!

MK Technical:-http://www.mkelectric.com/Documents/English/EN%20MK%20Technical%20Specifications/T02%20LOGIC%20PLUS%20Tech%20355-389.pdf .... Lol

 

[Guest55]

Your MK link doesnt work TC.
Anyways my 2p is that you'll never get 3 4mm wires in a standard socket terminal anyway.
And most BS double sockets are rated at least 20A.

 

[telectrix]

that's why 4mm is stranded. so you can snip a few off to make them fit. only joking, before i'm crucified)