Increasing Lighting Circuit Capacity

[Steve]

Significant Other wants to festoon the whole house with zillions of 20W low voltage downlights. To fulfil her wishes I either have to split both upstairs and downstairs into 2 circuits each giving 4 separate lighting circuits of 1200W max each or preferably have just 2 circuits as normal but with increased capacity.

I'm re-wiring the whole house any way but don't currently have enough spare way's for the extra circuits.

Can I double the capacity of each circuit by making them into lighting ring-mains? If not, what gain can I get by using 1.5 or 2.5 sq. mm cable for the lighting circuits rather than 1 sq. mm as normal.

F.Y.I., I'm assuming each normal circuit using 1 sq. mm can carry 1200W.

For her requirements I need 1340W upstairs, including 240W on a 2-way for the downstairs hall, and 1260 downstairs.

[Owain]

The problem is not primarily one of cable size as 1mm is rather generous for 6A anyway and will carry 10A quite happily in most circumstances. Changing to a ring would be a non-standard circuit and would be rather unnesccessary. Many lighting circuits aren't wired as a straightforward radial anyway but have spurs upon spurs - which is permissible on a radial.

Voltage drop on 1mm cable may be an issue if cable length is greater than about 20 metres.

You can probbaly change to a 10A MCB provided all the switches and other accessories are rated for this and you do not have any SBC or SES lampholders, as these must not be used on cirvuits >6A.

Actually it can do well above that.

Owain

[mike ring]

Owain wrote in news: [e-mail]:

That raises an issue I've been trying to solve for ages.

I just checked your statement, and it appears 1mm will do 11 amps!

In a refurbishment I ditched a manky 1kw I/R bathroom heater, which was on the lighting circuit, but have since not ben able to find a 1kw replacement, but loads of 2kw I/Rs and fans.

Does this mean I can put a 2kw fan or I/R on the wall? If necessary fusing up on the mcb. Or would that compromise the lighting circuit?

Please say yes

[meow2222]

2kW ~ 8A. On a 10A light circuit that leaves 2A for all the lighting. Seems a bit tight!

I'm surprised you've not found a 1kW appliance. I've got one sitting in a box here fwiw, a white switchable 1kW/2kW bathroom fan heater.

NT

email addy not valid

[Andrew Gabriel]

I would no longer put such heaters on a lighting circuit. It was done back in the days of the 750W silica glass tube bathroom heaters, but people tend to want more power than that nowadays. When I added heaters to my bathrooms, I put in a 20A RCD-protected radial circuit for them (which also includes a couple of socket outlets in the loft which have been handy from time-to-time).

If you increase the lighting circuit above 6A, you should make sure you have no SES or SBC lampholders on it, which require fusing at 6A max. You will also have to take more notice of where the cable runs go, e.g. you could be overloading the cable where it's buried in loft insulation and needs derating.

[mike ring]

[e-mail] wrote in news: [e-mail]:

A presettable, (not switchable) 1kw; pull cord operated, wall mounted, not too butt-ugly device?

That's what I can't find.

[David Hansen]

On 14 Feb 2006 19:17:28 GMT someone who may be mike ring wrote this:-

A small company called Poole Heating, based in ISTR the English West Midlands, certainly makes such things. I'm sure others do. Beauty is in the eye of the beholder.

I would disconnect it from the lighting circuit though. Although slightly frowned upon I would connect it to a ring main, unless it is heavily loaded. I would also ensure that the bonding is all present and correct.

[Owain]

AIUI the Dimplex one is internally settable to 1kW or 2kW

Owain

[meow2222]

yep, all those exactly. The 1 or 2 kW switch is internal, not accessible to the end user.

Yup, its square, white plastic, and looks fine to me. Its not your curvaceous windows-logo styled thing. I dont need it.

NT

[<me9]

I was thinking of getting one from tlc-direct the other week for my bathroom, pre-settable on installation to 1 or 2 Kw. I need to replace the 750w dimplex radiant one in my bathroom, which is on the lighting circuit.

[Gary Cavie]

Dimplex FX20V is switchable inside to 1 or 2kW, and looks quite nice in a bathroom.

[Christian McArdle]

Yes, and make sure it is an RCD protected ring, too. If not, add RCD to the ring or use an RCD FCU.

Christian.

[mike ring]

Gary Cavie wrote in news: [e-mail]:

Hey, that's better than the ones Í've seen, it might fix it for me.

And just in time for summer, too!

TYhanks

[meow2222]

Mines a Dimplex FX20, in case someone wants to see what it looks like.

NT