Table 7.1(ii) of the OSG includes Installation type B* which is "Enclosed in conduit or trunking on a wall, etc." This isn't included in any of the allowed installation methods of Table 7.1(i).
What "installation method" classification do you use when installing T&E on a blockwork wall in oval conduit, in a chase for subsequent plastering over? Equally, when the wires are just chased in and plastered over, or do you just consider that type C "clipped direct"?
length of circuit will be defined by the size of the building, and will feed into a check of voltage drop and far point Zs or R1+R2. If the resistance is excessive then a larger cable will be needed.
Cable resistance is only weakly affected by mounting method - unless you actually stretch the copper, the resistance is un affected by what is outside the insulation 
Cable cooling and therefore the thermal current rating is however dramatically affected by where and how the cable is routed and what else it is grouped with.
It is quite possible to rock up on site, realize that the thermal insulation or grouping conditions are far worse than originally expected, and have to either step up a cable size or re-route something to avoid a potential hotspot.
Mike.
length of circuit will be defined by the size of the building, and will feed into a check of voltage drop and far point Zs or R1+R2. If the resistance is excessive then a larger cable will be needed.
Cable resistance is only weakly affected by mounting method - unless you actually stretch the copper, the resistance is un affected by what is outside the insulation Cable cooling and therefore the thermal current rating is however dramatically affected by where and how the cable is routed and what else it is grouped with.
It is quite possible to rock up on site, realize that the thermal insulation or grouping conditions are far worse than originally expected, and have to either step up a cable size or re-route something to avoid a potential hotspot.
Mike.
