That's obviously true, but I still think that a PF of 0.8 would probably be unnecessarily pessimistic as a 'rule of thumb' to use for all circuits in a domestic installation, don't you?Anything with a ballast, an induction motor or a transformer will have a power factor of less than 1 ...
You're right - I wasn't thinking straight In fact, now that I'm hopefully thinking a bit straighter, I'm not sure exactly how 'taking PF into account' would actually have any effect on the designing of most domestic installations. AFAICS, the main importance of considering PF in circuit design is in ensuring that cable CCCs (and, as you say, the corresponding OPD In) are adequate for the loads concerned. However, apart from fluorescent lighting (and even that may change) there are few 'known' (i.e. hard-wired) non-resistive loads that could be considered at design stage - and lighting circuits are generally so over-designed (in terms of CCC) that PF is hardly an issue. ... or am I missing something?No, as long as the cable rating is bigger than the over current protection, if you want to make your over current protection larger then you'll end up in a pickle.To use such a factor would essentially mean de-rating cable CCCs by 20% - which would mean, for example, that a 2.5mm² ring final (or 20A radial) would be non-compliant if any of the cable were not 'clipped direct', and that a 4mm² 32A radial would be non-compliant with any installation method.
Kind Regards, John