Can central heating wiring to...valves, stats, programmers etc be classed as Control Circuits 514.6 Table 51, therefore none of line conductors will need brown sleeve ?
I'd say no. Simply because the spirit of the Regs would, I believe, class control circuits as those which indirectly control items of equipment via contactors, relays or pcb boards. If said wiring directly controls said items of equip/etc then not? I may be wrong, but that's how I see it currently.
I always sleeve, but have also wondered TBH. You always see on new builds that the T+E's have been sleeved at timeclock, room stat etc, but never the flexes on the cyl stat, valves etc. I find this a tad odd....or lazy?