17th Edition - Cable Capacity - Which Method ?

[Spark123]

Yes

 

[self builder 123]

Hi Sparks

Thanks for your quick answer.

In my case I happen to have a 6 sq.mm cable supplying an induction hob. The dedicated circuit is protected by a 32A MK Type B MCB.

The PVC T+E cable runs is clipped in the centre of timber ceiling joists and is covered with mineral wool insualtion at the side. The cable does not touch the rear of the plasterboard ceiling.

As a test we powered up all the rings on the hob to maximum and used a clamp meter on the live wire at the CU and measured that 34A was drawn.

As it is unlikely ( if ever ) that all 5 rings will be turned up to maximum ( diversity ) would you say that it would be safe to leave the 32A MCB in place ?

 

[Spark123]

As the loading is cyclic then I don't see the problem with applying diversity.
I haven't worked out the CCC of the cable tho - if it is covered in wool insulation then that has to have an impact on it.

 

[self builder 123]

We have been working on the house for several years now and when we started it was wired in accordnace with the 16th Edition.

Am I correct to say that the 47A cable has to be derated to 35A in accorance with Installation Method 15 for Table 4D5A ?

The ambient temperature will not exceed 30 deg C and the cable is run on its own.