On 2 Feb, 18:25, EricP wrote:
Although we do not have an electric cooker/oven in the kitchen, that
may change with the nice new appliances now available.

The present cable is 6mm and access is open for all it's length except
in the walls where it's in conduit. I would like a ball-park figure
for the current carrying capacity of 6mm and 10mm cable with a view to
up rating as good housekeeping for the future, before access is
closed.

From the CU, 0.20m is in plaster, 8.00m is tacked to a joist in the
ceiling and the last 1.50m to the cooker box is in wall conduit.

Most grateful for any help


6 mm Twin and cpc enclosed in conduit in a thermally insulating wall
32A
10mm Twin and cpc " " " " " "
" " " 43A
Plastered in should be the same

However this is probably above the actual rating you will need for a
cooker as diversity is applicable

To apply diversity as per On site guide
Add up all the loads on the cooker and calculate the current required
at 230 volts
for example a cooker with 16kW worth of load would work out at 70 Amps
Take the first 10 Amps plus 30% of the remaining load
So 10 + (60 x 30%) = 10 + 18 = 28 Amps
If a 13A socket is present on the cooker switch add another 5 Amps to
allow for the short time load likely on this (time to boil a kettle)

So you are looking at either a 28 A design current or a 33 A design
current depending on the presence or not of a 13A socket

If you do have a socket the disconnection time will be 0.4 seconds in
the event of an earth fault or 5 seconds (16th edition) without a
socket.
For a type B circuit breaker both conditions are fulfilled anyway but
a fuse will behave differently.

6mm will have a volt drop of 7.3mV per A per metre so with 10 metres
of 6mm cable at 32A you will drop 2.4 volts (less with 10mm at 4.4mV/A/
m) Which is well within the 4% permitted volt drop of 16th edition and
certainly within the increased 5% drop for power circuits of the 17th

Likely the new cooker will be less than 16kW in total so your existing
cable should be ok if protected by a 32A type B circuit breaker. It
really comes down to your desire to spend moneyg

HTH