Old Wooden backed Wylex CU's - The position???

[333rocky333]

Prior to 16th Amendment 1 2002, the requirement was for the cable capacity to be 0.67 x In. Has there always been a correction factor for rewirable fuses? When they were all that were ever used (in homes) it seems a bit AAF for you to have needed a correction factor all the time

In the 14th you had

"close protection",
will operate within 4 hours at 1.5 times the designed load current of the circuit.

and
"coarse protection"
will not operate within 4 hours at 1.5 times the designed load current of the circuit

Rewirable fuses were coarse protection
All the tables for cable ratings were for coarse protection

Above each table was-
The tabulated ratings may be multiplied by1.33 if close excess current protection could be assured

A 2.5 T+E enclosed cable in the table was rated at 18 amps for coarse,
so if an mcb was used 18 x1.33 was 23.94 amps

 

[333rocky333]

3036 fuses have long been recognised, and continue to be recognised in the regulations.

The fact that there is a derating factor for the 3036 proves it is still current and recognised

As well as reg 533.1.1.3 and table 53.1

 

[ban-all-sheds]

So what was the requirement then for ring finals?

18 < 30x0.67.....

 

[333rocky333]

In the 14th 1976

From table A.3M 2.5mm is minima, and shall be increased , taking account of the class of excess current protection, in such circumstances it must be ensured that

for ring final sub-circuits, the current rating of the conductors forming the ring is not less than 0.67 times the rating of the fuse or circuit breaker

 

[333rocky333]

it was

18 amp for enclosed, but goes on to say enclosed in conduit or trunking

the only alternative is

21 amp for clipped direct to a surface or on a cable tray, and unenclosed.