Historical question WRT 15 amp sockets.

broadgage: 
 

ISTR that in an old edition of the then IEE regs, that two socket outlets each of the unfused 15 amp type could be connected to a 25 amp fuse.

Have found a number wired thus in a large old house. Possibly pre-war, wired in MICC and still in good condition. 

I can not put my hand on anything prior to 1955 (13th Edition) at present where the assumed current demand for a 15 Amp socket was in fact, wait for it, wait for it…………………………. fifteen Amps…………………..

Z.

In his little pocket book entitled “Electric Wiring Diagrams”  (First edition 1946, my copy 2nd. Edition 1956) G.E. Stubbs in his preamble to ring circuits says, “Normally a final sub-circuit having a rated capacity above 15 Amps must not be arranged to supply more than one point to comply with regulations."

Z.

Take a look at regulation 201 (page 19) 11th edition.

Regards 

Geoff Blackwell

Indeed, in the 1939 11th edition, see below.

But this was short-lived rule as by the 1950 12th edition this had gone to be replaced by advice about 13A sockets, fused plugs, rings  and floor areas, more or less the modern era.

So it was once allowed ! And fairly sensibly since it permitted use of two portable heaters on one circuit.

Most rooms  in this house have no electricity supply at all, open fires for heating and gas lights, or candles. Who needs electricity in a bedroom ? For once a year polishing of the oak floorboards, a long extension lead suffices for the polishing machine.

Ones children might be allowed electricity for modern electronic entertainments,  but an extension lead from the “radiator plug” on the landing will serve.

Where would you get a 25 amp fuse from? I've never seen such a beast maybe 2 bits of 10 amp wire and one of 5 all twisted together all seems a bit hit and miss for Mr average householder 

I suspect that in practice that 30 amp fuse wire was often used.

25 amp fuse wire was certainly available, even if not sold specifically as fuse wire. Every good supplier of electrical sundries offered tinned copper wire in many sizes, and generally with a list of “the rating when used as fuse wire” Old fuse boxes also had a list inside the lid giving the correct size fuse wire in SWG for different amp circuits.

Old style fuse carriers were often marked with the  SWG size fuse wire to be used as well as the ampere rating. 22 SWG was used for 25 amp fuse wire, or should have been.

It has been decided to leave the existing wiring largely as is. Works fine, insulation resistance and earth loop tests all good. New 25 amp fuse wire fitted in each fuse carrier.

Where the existing socket outlets do not meet present day needs, then extension leads, rather reluctantly. Installing extra outlets is not realistic in most areas due to an historic interior.

If the wiring is OK, as a 4mm - well more like 4.5mm2 - radial,  you could probably add as many 13A sockets as you like, either hard-wired or plugged into the 15A socket, fit a 32A RCBO and declare compliance to a much later version of the regs..

Mike

broadgage: 
 

It has been decided to leave the existing wiring largely as is. Works fine, insulation resistance and earth loop tests all good. New 25 amp fuse wire fitted in each fuse carrier.

Where the existing socket outlets do not meet present day needs, then extension leads, rather reluctantly. Installing extra outlets is not realistic in most areas due to an historic interior.