I have been working out cable sizes for a new install, for the cooker I was always told to use a 32 breaker (or the older 40amp fuse) incase the cooker was upgraded in the future. However this install has 3m pvc trunking above the consumer unit (as its on a wall on the stairs, in a flat) because the cable will be grouped with 8 other cables it ups the cable required considerably (60ish amps!) the cooker is only 2000kw. (8.69amps) 7671 says 6.0mm cable will take 38amps so I was going to run the cable in its own trunking. In theory I could use a 16amp breaker and 2.5mm cable (I won't!), just wondered if i'm correct.
In theory you'd be surprized what you could do!
There would also be factors required to be worked out, regarding the size of the trunking in which these cables are routed dependant on the CSA of cables.
But that's another can of worms!
If you run cable on it's own ring with 6mm cable protected by 32amp mcb should be okay. The reason being is if was ever decide to change cooker to a higher output one that circuit could still be used.
But part p regs comply see docs projects on part p.
kbrownie said ring think that was slip and he is referring to radial and if you are planning make sure the rating you use is for that cable "6mm Twin & Earth 6242YH" is rated 47amp by AEI Cables who make it. Yet 70deg PVC in 16th edition is a lot lower the number at the back of the cable is important as they all look the same but differ slightly so always identify what cable you are using. As to grouping because the total amps for all cables is limited to 100 amps it can be higher than as a single. Table 4A in 16th Edition gives all installation method reference numbers you are looking at method 3 giving 0.52 correction factor so about 24 amps but that is with all other cables also at max amps which can't happen because of 100 amp feed. As to future a hob with 4 x 2.4Kw rings is 41amp but unlikely that all 4 rings will be on together for more than couple on minuets only if you also included an oven on same circuit could you have problems with 6mm cable. And even then if on a 32amp MCB it would still not cause a problem. So all things considered 6mm on 32 amp MCB routed with other cables is very unlikely to cause any problems. You are on site and you must make final judgment. But I think your looking for a problem which does not exist. I am assuming you are qualified and are aware of Part P etc.
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