On Monday, 24 April 2017 20:24:12 UTC+1, dennis@home wrote:
On 24/04/2017 16:48, John Rumm wrote:

If we use a B3 MCB and assume a maximum circuit load of 3A that means we
will drop around 264mV per metre of cable. We are allowed 3% of 230V or
6.9V, hence we have a maximum circuit length of only 26m (and note that
includes the drops to the switch wire as well)



But those drops assume tungsten lights and current 240V LEDs will work
down to about 130 volts and they could be made to work a lot lower.
If you were hard wiring LED lamps you could ignore the 3% rule and not
have any problems.

Once we go back to all tungsten lights after brexit the 3% rule will be
essential.

You can ignore lots of rules and not have problems, old buildings do, but you've still got to follow them.


NT