Discuss Interesting Conundrum 1.5 power in the UK Electrical Forum area at ElectriciansForums.net
One cable at the board coming from each 16a mcbAre you quite sure these socket circuits are radials, and not 16A ring final circuits? (Yes yes, I know that would be rather non standard ...)
Your clearly being very optimistic with that comment on complianceCarp design for sure, but I'd be surprised if this was dangerous, or even non compliant, all other things being correct.
If there is any insulation does it really matter if it is significant or not for me you always calculate on the worst possible.Most recently built houses that I have worked on tend to have the cables for socket circuits run in the floor void between floors, dropping or rising to the sockets. There's not usually any need to run the cables through any significant insulation.
That's completely fine electrically speaking. It's literally what French regs specify. 8 sockets max on a 16a radial in 1.5mm.Defiantly 1.5 cable , and all on 16amp circuits. Feels very much European
I didn't have time to add up all the sockets but I would suspect that there is around 6 or 7 sockets on each 16amp radial , possibly 1 circuit for upstairs , 1 for downstairs and 1 for the kitchen , but this would require further investigation
But this house isn’t in France.That's completely fine electrically speaking. It's literally what French regs specify. 8 sockets max on a 16a radial in 1.5mm.
Normally over there they have freezer, washing machine, dryer, and dishwasher on their own runs but kitchen countertop sockets used to be fine on 16a, i think they now have to be on 20a.
Connect all the wires up and it can be fine electrically speaking whether it is compliant in the UK is a different matter and that is the pertinent point of this threadThat's completely fine electrically speaking. It's literally what French regs specify. 8 sockets max on a 16a radial in 1.5mm.
Normally over there they have freezer, washing machine, dryer, and dishwasher on their own runs but kitchen countertop sockets used to be fine on 16a, i think they now have to be on 20a.
Your clearly being very optimistic with that comment on compliance
If there is any insulation does it really matter if it is significant or not for me you always calculate on the worst possible.
If a cable is running in a floor void is that in free air or is it a duct and given that you can also have heating pipework running in the same void how do you assess the thermal effects of that on the cable
Where in BS7671 does it say you can't use 1.5mm cable with 16a breakers?But this house isn’t in France.
We have to work to BS7671, and have to design circuits with estimated load, installation method, current carrying capacity, length of circuit…..
If none of it mattered, it wouldn’t be there in the regs.
What does it matter whether you start at 240v or 230v, ok at 240v you have an extra 0.5v before you hit maximum allowed volt drop within the installation but if you are on the limit then potentially you are running equipment possibly below it's optimum voltageI think VD is, as you mentioned earlier, where it may fail. We're probably starting at 240V rather than 230, so perhaps not a big deal real world, but still.
2.5mm ran in a wall is only rated at ~18.5a yet everyone puts them on 20a breakers when doing a radial. Shouldn't your advice to the homeowner then apply to basically every building in Britain with a radial in it for sockets?The only way 1.5mm c.c.c is above 16A is if its clipped direct in open air. Bury it in a wall, or run it through insulation and youre down to 14 approx.
I did say real world rather than regulations world.What does it matter whether you start at 240v or 230v, ok at 240v you have an extra 0.5v before you hit maximum allowed volt drop within the installation but if you are on the limit then potentially you are running equipment possibly below it's optimum voltage
Which table/ref method are you taking this from?2.5mm ran in a wall is only rated at ~18.5a
Cable Ratings dot co dot uk i thinkWhich table/ref method are you taking this from?
It's better you take this info from the tables in the regs. The statement from NIC is true, but it's only part of the picture, there's a lot in between.Cable Ratings dot co dot uk i think
Some NIC site i've just been looking at states 'For a single cable likely to be totally surrounded by thermally insulating material for a length of 0.5 m or more, the current-carrying capacity must be taken as 0.5 times the current-carrying capacity for that cable clipped direct to a surface (Reference Method C).'
So ring finals should be only able to carry the 'normal' clipped current of a single 2.5mm cable at ~27a.
I just want to know why 16a + 1.5mm is apparently borderline dangerous but 32a + 2.5mm isn't? Eager to learn.
I don’t think anyone said exactly that. The speculation is about whether it passes through insulation.I just want to know why 16a + 1.5mm is apparently borderline dangerous
Like many rules and regulations, there has to be a defined point for acceptable or not. Our regs happen to say 5% drop (3% lights but that is another debate...) from the nominal 230V for calculation and if it less then OK, if not then you need to alter the design (usually thicker cable, as typically load is fixed and route has no shorter paths).For that reason, I find it difficult to take voltage drop in domestic installations tremendously seriously for the most part.
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