OP
Smugley
Hi there, after reading this discussion it seems to me that some people are happy to use a cable size with a capacity barely above the nominal value of the MCB. Personally the reason I would go for a larger SWA in this case is because a 16A MCB may not trip until well over 20A, maybe 22A, according to Appendix 3 of the BRB. This brings your tolerance down significantly, and if there is any place along the run which causes the cable to derate, ie fed through bunches, under insulation etc, then the capacity of the cable may drop below the MCB trip current, and then you may have a problem. It's all about perceived risk I guess.