Cable carrying cal

[dave992]

Hi, looking through an EICR report and have a issue with the MDP.

We have

4x240 - on a 1440 breaker
3x240 - on a 1250 breaker
2x240 - on a 630 breaker

All cables are ducted within the ground. Am i right in thinking that there are breakers are over rated for the cable size. Just double checking cables in parallel, do you work out the cable carrying capacity of one cable then times it by how many cable.

Thanks

 

[telectrix]

if they're over ratted, i'd consider some mechanical protection them rats BITE.

 

[Richard Burns]

Yes you would sum the current carrying capacities of the cables (not totally accurate but is stated in BS7671), the cables should be of the same size, length, route and construction.
Have a look at appendix 10 in BS7671 for details for protection advice for conductors in parallel.