Cooker cable upgrading?

[EricP]

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

[cynic]

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 money

HTH

[Roger Mills]

If you use TLC's cable size calculator at:

seems to suggest that a 10 metre 6mm^2 cable is good for about 10kW (43.5A) if open, or about 8.5kW if in trunking.

Play with the calculator yourself to find the limits for 10mm^2 cable.

[EricP]

It certainly does. :)))

many thanks.