Extending A Lighting Circuit

[GrahamJ]

Hi.

I'd like to put in an extra light fitting upstairs.

There are currently 13 light fittings on the circuit - 2 of them with extractor fans wired in.  All the bulbs are CFL, so even with the extractor fans (60W apiece) included, total wattage is less than 250W.

I've read that a standard lighting circuit can support up to 11 light fittings, each of 100W, so does this mean I've loads of headroom for an extension?

Thanks for your time.

 

[Technician]

Is there such a thing as a "standard" lighting circuit?

What do you understand by that terminology?

I think some more information on circuit breakers/fuses

and ratings would assist, as well as conductor sizes.

 

[SPECIAL LOCATION]

Short answer:-  Most likely YES

Longer answer:-

Basic bit of maths...

Power = Current x Voltage...

the nominal voltage is 230v

the current would be your fuse rating...

probably either 5A or 6A or 10A......

so if 5A power = 1150Watts

so if 6A power = 1380Watts

so if 10A power = 2300Watts

so if you take off your existing 250w...

you have probably got somewhere between 900w and 2050w spare to work with....

*** IF EVERYTHING IS ON SIMULTANEOUSLY ***

However

Lighting circuits normally allow for the fact that not every light is on at the same time

A thing called Diversity...

It is NOT an exact science but one rule of thumb is 66% of total wattage of the connected load...

Guinness

 

[SLIPSHOD & SLAPDASH]

Is there such a thing as a "standard" lighting circuit?

In the good old days it was more 'good workmanship' to have a maximum number of lighting points per circuit. That went out the window with spotlights & Thatcher.

 

[Technician]

 maximum number of lighting points per circuit.

Hmmm......and when my Dad had his house rewired every light

was a radial circuit to one light only and fused line AND neutral.

 

[GrahamJ]

Thanks everyone for your help.

The circuit is 5A.

Much appreciated.