Raidial and Ring from same fuse?

[Electrifying]

To the OP, there's nothing wrong with 2.5mm spurs off your 30A BS3036 Fuse - as long as each spur only feeds one single or one double socket outlet.

What is Iz for a 2.5mm² spur running in conduit in plaster?

20 Amps - which is why I wrote:

(Subject to installation/reference methods, of course - before anyone starts )

 

[ban-all-sheds]

4mm TE cable supports a 30 amp radial.

Not with rewirable fuses.

Not getting this comment, BAS

I'm not having a go, I just don't get what you are trying to say.

4mm cable won't carry 30A because it's overload protection is via a 30 A fuse?

A 30 A fuse can't protect 4mm cable from overload? - but it can protect a 2.5mm ring final?

If a 32 A MCB is suitable overload protection for a 2.5mm ring final or a 4mm radial, then it stands to reason that if a 30 A BS3036 is suitable overload protection for a 2.5mm ring final, it must be suitable for a 4mm radial.....

...or do you know something I don't?

I've never actually done the calcs, but does the fusing factor affect the 4mm radial, but not the 2.5mm ring final?

The 0.725 factor affects everything.

So for Ref Method 3, 4mm² is rated at 27A.
[edit].. . . . . . . . . . . . . . . . ↑
. . . . . . . . . . . . I meant C [/edit]


2.5mm² becomes 20A, which just scrapes in for a ring final. For any other installation method it's not. e.g. A, which would be OK for a B32, drops to 14.5A.....

 

[Electrifying]

You are annoying, BAS, because now you've got me looking things up and it's making even less sense.

The onsite guide:

Pg 158, Table 8A gives...

An A2 Radial - 30/32 Amp overload protection - 4mm conductor.

Pg 159 - 8.2.2 states....

'Table 8A is applicable to circuits protected by:

fuses to BS3036, BS1361 and BS88

circuit breakers......'

So this, in effect, is allowing a 4mm radial on a 30 A BS3036.


Then, lower down pg 159, it states....

For protection by a fuse to BS3036, the current carrying capacity for an A2 radial must be at least 41A??


Which we know isn't possible with 4mm

 

[ban-all-sheds]