Moving ceiling light

[Jeff Layman]

Well, although not twin and earth, there is 0.5mm^2 cable:

I see this is rated at 3 amps, which is much more than is needed for LED lighting. I reckon you'd be hard-pushed to use even 1 amp for LED domestic lighting. The price is £19.00 for 100 metres. Compare that to the 0.75mm^2 equivalent which is £29.00 per 100 metres

or the 1.5 mm^2 cable which is £42.00 per 100 metres

Quite a lot of savings to be made if you were wiring up hundreds of new homes.

Unfortunately, as far as I can see 0.5mm^2 T&E is not made - or at least is not available in the UK.

[John Rumm]

That's flex and not really suitable for fixed wiring.

Unless they house is wired with low energy fittings that preclude the use of other lamp types, then you still need to provision assuming 100W at each location (or the actual wattage if greater).

Not very practical though is it?

If we use a B3 MCB and assume a maximum circuit load of 3A that means we will drop around 264mV per metre of cable. We are allowed 3% of 230V or

6.9V, hence we have a maximum circuit length of only 26m (and note that includes the drops to the switch wire as well)

[tabbypurr]

So 7 lighting points per 3A feed.

1mm2 drops 44mV per metre of both conductors, 0.5 would thus be 88mV. 6.9v drop is thus 78m for a radial circuit, 156m for a ring.

There are certainly properties where such circuits would be practical.

I'm not convinced of the need, but if more robustness were wanted the coppe r conductors could contain a thin steel centre.

NT

[John Rumm]

Per meter *per amp*

[tabbypurr]

Oh yes :) So it's 26m radial, 52m ring. That's workable in many flats.

I suspect the future will see incadescents disappear more or less entirely, and the 100w per fitting drop to half or less.

NT

[ARW]

How high are the ceilings?

Care to post a photo of them and the existing light fittings? That way the next time I see something similar (or work on something similar) that has been redone with LEDs I can take some photos and give you some ideas to pinch for future use.

I do from time to time work in church halls, village halls and similar buildings. I always find them to be one of the most rewarding of jobs.

[ARW]

That would have been a posh install:-)

[ARW]

About right. My parents 1969 build was 2 single sockets per room (only one in the small bedroom). Gas CH was an optional extra (the coal fire was included in the price).

All sockets done on one 4mm radial circuit.

[dennis]

But those drops assume tungsten lights and current 240V LEDs will work down to about 130 volts and they could be made to work a lot lower. If you were hard wiring LED lamps you could ignore the 3% rule and not have any problems.

Once we go back to all tungsten lights after brexit the 3% rule will be essential.

[ARW]

Why would we do that? Is electricity going to be free after Brexit?

[tabbypurr]

You can ignore lots of rules and not have problems, old buildings do, but you've still got to follow them.

NT

[John Rumm]

You could, although a deviation from the current regs. However you then rely on the user to not change the lamps unless you use low energy fittings only to force their choice.

[dennis]

Isn't everything going to be cheap after brexit?

[Max Demian]

CFLs were never about saving us money, or it would have been left up to us which sort of light we use.