shower circuit 6ml or 10ml

[Scott F]

client has old shower he wants replacing with 9 maybe 10kw.He has 6ml cable under floorboards which will be covered by 40 amp rcbo >now this is the part im struggling with according to table 4d5 ref meth c rating is 47 amps but if the cable runs under the floor with other cables does this make it ref meth 100* in which case it woukld be 34amps so would need either upgrading to 10ml or lowerd output on the shower hope this makes sense

 

[ian.settle1]

client has old shower he wants replacing with 9 maybe 10kw.He has 6ml cable under floorboards which will be covered by 40 amp rcbo >now this is the part im struggling with according to table 4d5 ref meth c rating is 47 amps but if the cable runs under the floor with other cables does this make it ref meth 100* in which case it woukld be 34amps so would need either upgrading to 10ml or lowerd output on the shower hope this makes sense

Replace it with a 10mm as 10Kw is 43amps.

 

[KillerWatt]

As above, replace it with 10mm² as 6mm² will only be good for up to 7KW when it is enclosed.
As far as protection goes, use a 40A RCBO for 9KW and a 45A RCBO if going up to 10KW.