Derating Factors

[DominicB]

Hi guys,

Might be a silly question but getting really confused.
Table 4D5 for choosing cable size for different installation methods, does this already have de-rating factors applied for the different methods? If so, then if you calculated your current capacity using specific de-rating factors which table do you use?

 

[Wilko]

I'm not sure I've understood you correctly but yes, those are the ccc values for that installation method. There are different installation methods detailed in other spots, e.g. Table 4A2.
Does that help?

 

[Richard Burns]

Each column has the cable rating applicable for that particular method of installation.
So there is no need to apply further derating for say, a cable in conduit in an insulated wall, just use the value given in the table.
However there may be a need to consider additional derating factors such as grouping and ambient temperature that would be combined with the tabulated value to give a final current carrying capacity.