Supply tail query

[LlandrilloSpark]

Guys

Inspection i did about two weeks ago and im going back to do the remedial work tomorrow, next to the main ccu there is a one module unit plus 61008 rcd main switch, inside the unit is a 32A MCB protecting an armoured outside supply, the module unit is fed by 6mm single spured of the incoming side of the main switch in the main ccu.

my query is - should the tails theoretically be 16mm to match the main 60amp cut out fuse as technically this is a supply split, or are the little 6mm tails protected by the 32A mcb only allowing that much current to flow?

I see a lot of this and wanted other peopled opinion on it, personally i always put in henleys and split it correctly

cheers

 

[KFH]

Reg 434.2.1 allows reduced conductor size up to 3m before the reduced protective device as long as a maze of other regs apply. Typically branches off a rising main supplying flats.

However in this situation I am with you and would put in proper tails.

 

[johnboy6083]

backfusing is allowed, and as the fella above mentioned the 3m rule applies. Read 433.2.2

 

[LlandrilloSpark]

Cheers guys I suppose this covers the temporary supply issue also, 3m ext lead with 5 sockets on it plugged into the meter whilst doing a rewire??!!

 

[johnboy6083]

That would only be safe if the amount of CCc of the cable was less than what the fuses in the sockets added upto. So for 2.5mm2 which can take 27a before derating, then you could only have 2 sockets max (2x13a= 26a). If you then plug more into them, then your relying on the 13a fuse to provide over current protection.

 

[LlandrilloSpark]

I made a little device with a 3 inch plastic moulded box with 25 tails coming out of one end and the 3m lead out of the other, inside the box is a 20A mcb