How many lights on 1 circuit?

[v1k10]

Hi all, I want to know how many lights you can put on to 1 lighting circuit? The circuit is wired using 1.5mm twin and earth cable and is protected using a 6amp MCB?

thanks.

 

[flameport]

Whatever number of lights total 6A or less, or 1380W.

If the lights are 7W LEDs, then a couple of hundred.
If they are illegal 500W outside floodlights, then only two.
Unlimited other combinations of lighting are available.

There are also other considerations such as what area these lights are covering, and whether it is appropriate to have them all on a single circuit.

1.5mm cable was almost certainly not required.

 

[v1k10]

Hi thanks for that, 500W lights are illegal?

I had the house rewired a few years back and I remember the electrician used 1.5mm cable for the lighting circuits - is that not right?

 

[winston1]

It is not wrong and not necessary. 1.0mm is OK for lighting on a 6A MCB.

The answer to your original question is normally 10. This assumes each light point consumes approx 100W.

 

[big-all]

all the lights in my house are leds so out off the 12 amp available on the upstairs and downstairs circuits 11.90 amps are still free as my total use is between 35 and 80w illuminates the whole house like an xmas tree

 

[flameport]

500w floodlights do not meet building regulations, and haven't done for many years. They are grossly overpowered and in more than 99% of installations are totally unnecessary.

10 lights per circuit was correct back in the day, but as no one has 100W lamps any more, the actual number is generally far more than that.

 

[ericmark]

As already stated 150W is the maximum wattage for outside lights without planning permission and since most ceiling roses which double as junction boxes are rated 5 or 6 amp in most homes a 6A MCB is the largest that can be used based on 100W per lamp that equates to 12 lamps per circuit.

Back in the real world today a 5 lamp chandelier with 11W CFU's is still only 55W and even a kitchen florescent is likely only 60W so reasonable safe to consider 60W per lamp rather than 100W which means 23 lamps per circuit is quite reasonable.

However because lights in bathrooms are now RCD protected and cables buried in walls and ceilings under 50mm below surface also require RCD protection plus lamps blowing can cause ionisation within the lamp taking out the 6A MCB it is now normal to have at least two lighting circuits independently protected or emergency lights to comply with.

314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.

 

[securespark]

This 6A thing could be argued till the cows come home.

Sockets are effectively used as junction boxes on circuits and they have a face value rating of 13A, yet the CPD is anything up to 32A.

Roses on lighting circuits are the same, surely? You could have a 6A rose on a 10A breaker without contravening the regs?

As for the switches, that's a no brainer, as long as the switch is breaking no more than a 6A load.

 

[JohnW2]

Sockets are effectively used as junction boxes on circuits and they have a face value rating of 13A, yet the CPD is anything up to 32A. ... Roses on lighting circuits are the same, surely? You could have a 6A rose on a 10A breaker without contravening the regs?

AFAIAA, the regs are pretty silent on the matter of ratings/protection of accessories - their main interest is in protection of the cables. A problem could, of course, arise if the manufacturer's instructions for, say, a "6A rose" say something about a 6A OPD - in which case use of a 10A OPD could become non-compliant with the regs.

I'm not sure that I even understand exactly what is meant by a "6A rose" - presumably that it has been tested, and shown to be satisfactory, with 6A flowing through one or more of the terminal strips?

The situation with sockets is obviously a bit different. The 13A (or whatever) 'rating' relates to what goes through the switch mechansim (if present) and the socket's contacts. What current can be safely carried between two or more conductors terminated in its terminals is a different matter (clearly a lot more than 13A), but I'm not sure that is necessarily documented in the specs (usually only maximum cable accommodation capacity for the terminals).

Kind Regards, John