Best practice for wiring recessed downlighter

Question

I'm looking to modernise a house with old (1950s) wiring. The original wiring is in conduit, with no separate earth conductor, but amazingly still functions! 
 In practical terms, I think the best thing to do is to remove the conduit - it's too small to accommodate cable and its earth continuity is poor - and start again. There has been some previous attempt at partial re-wiring; TW&E cables are forced into old conduits; this looks very shoddy and compromises cable ratings. 
 In terms of lighting circuits, the existing arrangement of looping via ceiling roses won't work, since it's intended to install modern recessed downlighters. 
 I want to avoid having any cable joins or terminal blocks in locations which will be inaccessible. All terminals need to be accessible for future inspection and test. (Am happy to pull out a recessed downlighter to check connections on the top). 
 I am proposing to run a single cable from the consumer unit to a connection box. From there, a cable for each lighting circuit would run to a switch and then on to the lights. The junction box would be accessible (with tools). There would be two such junction boxes, one for each floor, and each would have maybe four or five lighting circuits. 
 When I mentioned this to a friend (who once worked as an electrician) he asked me if that was allowed and my response was that I can't see where this would be prohibited. It may be unusual, but I reckon as long as the protection is appropriate there's nothing wrong with this approach. 
 This leads to a second issue. It seems that when interconnecting recessed downlighters, some might just run the cable between them on the ceiling, but I think this is poor practice and that the cable needs to be clipped to a joist or run in a conduit along a joist. Is there a good solution for this that minimises the need to lift floorboards? 
 Thanks!

mapj1 · Accepted Answer

Well 
 wiring lights at a central joint box is one of several common approaches These days the old ashley boxes have given way to things full of wago connectors . 
 The other easy way is slimline boxes behind each downlighter, and as much as possible loop through switch, rather than loop though rose - thog this needs deeper back boxes at the switch, it makes inspection easy. 
 Unless you expect the ceiling to collapse laying a wire over plasterboard is pretty standard - its a lot safer against damage from screws and nails if its not rigidly held, as anything poked through the ceiling can then shove it to one side. Clips only at access points if at all above a fixed celiing, A suspended ceiling on grid wires with loose panels is a different matter and here best practice puts cables in a basket or tray above the ceiling so that if can be lifted for maintainence. 
 Cables that could collapse in a fire and impede an exit need to be secured, but again, if they can only fall after the ceiling, which also obstructs an exit, the point becomes moot. 
 What else is being done at the same time as the lights ? you may as well do the lot. 
 Note you should have RCD or RCBO cover for ,most lighting circuits these days, to be up to current regs. 
 Mike

AJJewsbury · Answer

The 1-big-joint-box approach isn't that unusual - I've done just that in my own home - although with a slight modification which is easy as all the cables come back to a single point. That is to interleave adjacent rooms onto different circuits - e.g. hall and upstairs bedrooms on one circuit, downstairs rooms and upstairs landing on the other - that way if one circuit fails and you loose light in a room, you still have light through the doorway. 
 - Andy.

Best practice for wiring recessed downlighter

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