"Andy Pandy" wrote in message
...
On Tue, 04 Oct 2005 22:29:21 +0100, Andy Wade
wrote:

Jim Ingram wrote:

Could someone please expain to me what the requirements are for
ensuring a balanced road on a ring main.

The essential requirements are in Reg. 433-02-04 and can be summarised
thus:

- min. conductor size is 2.5 mm^2 (with one exception: 1.5 mm^2 is
permitted for 2-core MI cables);

- the as-installed cable rating (Iz), taking into account the
installation method and grouping factors, etc., must not be less than 20
amps;

SNIPPED

This is all well and good in theory but what happens when new
occupants move into a house, with various load appliances ?
Are the regs soon going to tell us where we can place our appliances?
Have there been cases of houses being damaged by misplaced appliances
on properly installed ring mains ?
This issue seems on the surface, to be getting out of hand.

Andy

I find it surprising, will the IEE and authorities hell bent on reducing
risk - Part P and all that, that a ring main based on 2.5mmT+E is still
allowed. In most environments 2.5mm is not up to passing 32A which is an
every day possibility. Excusing this on the basis of diversity really isn't
good enough unless the MCB rating suits the rating of the cable, ie worst
case scenario.

The very fact that this is not seen as a problem gives me opinion it's quite
acceptable to exceed a cable working temperature of 70 deg C.