Electrical "load" advice...

[TonyK]

Hi

Continueing on from my search for "black" T&E I'm probably going to end up using the Hi-Tuf cable previously recommended. However I think a few eyebrows were raised at the thought of wiring 12 x 50w mains halogens in series. Basically I have an existing light fixture (3x80w spot) which I intend to replace with a junction box. From this I plan to run a a single cable about 20-22 metres long. Approx. every 1.5 metres along its length or so there would be a junction box with a spur about 2m long with a 50w halogen on the end.

Ignoring the practicalities of wiring ths upside down, 4m up in the air, trying to conceal the cable and drilling through timbers 12" thick what are the electical implications? Will it work?

I've googled and can't find anything particularly relevant or imformative. Anyone got any ideas?

Tony

[Bob Eager]

I think the eyebrows were because you said 'in series' when you actually mean 'in parallel'.

Nothing particularly wrong with it AFAICS...

[Set Square]

As others have pointed out, they'll actually be in parallel - with the cable taking progressively less of the load the further along it you go.

12 x 50 watts (600 watts = 2.5 amps @ 240v) is actually a pretty light electrical load. I don't know what size your cable is, but 1mm^2 or above should handle it quite easily. [It would, of course, be a totally different story if they were LV halogens - since you'd then be dealing with a total current of about 50 amps].

[Dave Plowman]

Series wiring is like fairy lights - ie volts have to pass through one lamp before the next. So if you wired up 12 identical mains halogens like this, they'd be running on 20 volts or so and be rather dim. There's also the problem that if one or more blows, you'd not know which it was, as they'd all go out.

All equipment designed to run off 230 volts is parallel wired.

[Mike Tomlinson]

In article , TonyK writes

I hope you mean in parallel, otherwise you won't have much light. :)

12 x 50w = 600W, a fairish load. What else is on the circuit? Fused? MCB?

My problem with this is the number of joints you will be making; twelve for the lights plus one for the existing connection. Can you run the cable up and down to each light to minimise joints - this would be considered good practice.

To reduce voltage drop, which may cause the light at the furthest end of the chain to be slightly dimmer, I'd suggest using 1.5mm2 cable.

[Owain]

"Mike Tomlinson" wrote | >However I think a few | >eyebrows were raised at the thought of wiring 12 x 50w mains halogens in | >series. | I hope you mean in parallel, otherwise you won't have much light. :) | 12 x 50w = 600W, a fairish load. What else is on the circuit? Fused? | MCB?

However IEE regs require each lighting point to be assessed at 100W minimum, or actual load if greater. So the 12 points would represent a pretty much fully loaded 6A lighting circuit. And I don't know if the dinky mains halogens are permitted under the regs (or allowed in the manufacturer's instructions) to be fused at >6A - SES and SBC aren't.

Owain

[Dave Liquorice]

The only thing that occurs to me is that switching on 12 x 50W mains halogens from cold is going to have quite a switch on surge. May well be big enough to trip an ordinary 6A MCB...

[Alan]

It's probably not much different from switching the 500W rectangular spotlights with the PIR that people fit for 'security', or to light the garden.

[TonyK]

Thanks all

I didn't think it would be a problem with my unique style of "series wiring". And if you think thats bad wait till you see my parallel plumbing!

Tony

[Sparks]

Paralell plumbing, that's quite normal!

Series pluming would be very bad though..

As you can see, THAT would be BAD!

Sparks...

[TonyK]

Sh*t!

Knew I'd gone wrong on those showers!

Oh well....

[Sparks]

....Saves on the water bill (If metered) though!

Sparks...

[N. Thornton]

It can be done actually, tho not in that order!

Regards, NT

[SantaUK]

No shit! (ho ho ho!)

[Christian McArdle]

I was under the impression that the 100W allowance is for ES and BC fittings. If the fitting takes a specific size bulb (such as a fluorescent tube or halogen bulb) then you could substitute the maximum wattage that the fitting is capable of.

Christian.

[Owain]

"Christian McArdle" wrote | > However IEE regs require each lighting point to be assessed at | > 100W minimum, or actual load if greater. | I was under the impression that the 100W allowance is for ES and BC | fittings. If the fitting takes a specific size bulb (such as a | fluorescent tube or halogen bulb) then you could substitute the | maximum wattage that the fitting is capable of.

I would always work on the 100W per point minimum on the basis that a fitting might be substituted at a later date with one having an incandescent.

However IIRC the OP is talking about a commercial installation where the Electricity at Work Regs will apply, so a 16A lighting circuit will be possible if the individual fittings allow use on a 16A cct and the terminals are adequately sized. The requirement that any alterations to the installation will be carried out by a 'competent' person should mean that SBC/SES luminaires aren't substituted contrary to Regs. I don't like 16A lighting in domestics because of the liklihood that SBS/SES luminaires will be used.

Owain

[ARWadsworth]

My NIC inspector used 60W each for the downlighters in a newbuild as the transformers were 60VA.

-- Adam

adamwadsworth@(REMOVETHIS)blueyonder.co.uk