16A MCBs on Lighting Circuits

[opsman]

I was always taught that the max size mcb for domestic type lighting circuits is 10A due to the fact that accessories are rated no higher than 10A. When I recorded 16A MCBs on lighting circuits as a C2 departure my supervisor has corrected them as satisfactory as the current carrying capacity of the cable has not been exceeded. Anyone know which one of us is right?

 

[malcolmsanford]

You would have to assess the installation really, most ceiling roses for example are only rated at 6 amps, so a 10amp protection device as you say is often found, would that compromise the rose as well?

I have seen many lighting circuits on 16+ amps in industrial.commercial installations though in fairness most of them were under control of a contactor or relay.

You need to assess the installation really, if you have a bank of 40+ fluorescents on a 16amp breaker and all controlled by a single gang switch then yes I would seriously consider coding it, perhaps a 2, but if you have the same 40 lights spared over 5/6 switches then no problem

 

[ian.settle1]

I was always taught that the max size mcb for domestic type lighting circuits is 10A due to the fact that accessories are rated no higher than 10A. When I recorded 16A MCBs on lighting circuits as a C2 departure my supervisor has corrected them as satisfactory as the current carrying capacity of the cable has not been exceeded. Anyone know which one of us is right?

Unless the reg has changed you can put a lighting circuit up to and including a 16A protection device so your supervisor is correct.

 

[ackbarthestar]

Malcolm is correct see 559.6.1.6
things to check using a single pole or 3 pole linked B or C16A MCB are
1/ size of conductors
2/ Method switching

Don't be surprised to find a standard single pole 1 or 2 way 10A switch controlling a larger switching device such as a contactor.
Alternatively a bank of grid switches controlling sections of the lighting

 

[UKMeterman]

Hi,
You were correct, check the regs for SBC and SES bulb holders, some of them are even limited to 6A! Also check the switch rating.

 

[malcolmsanford]

Hi,
You were correct, check the regs for SBC and SES bulb holders, some of them are even limited to 6A! Also check the switch rating.

Who is correct the OP or the supervisor?

 

[PC Electrics]

The regulation governing this was changed at 17th. B15 and E14 lampholders were limited to 6A and B22, E27 & E40 limited to 16A ocpds by 553-03-01.

This was changed to 559.6.1.6 in 17th which now limits lighting containing these lampholders to 16A across the board.

The ocpd is there to protect the circuit and its cable. Each accessory should be protected from individual overload by limiting it's load by design (ie each switch limited to switching <10A).

Note that the regulation only applies to bayonet and screw type lampholders. So, in theory a large bank of florrys could be protected by a 40A ocpd. This would, of course, be impracticle as the circuit would need to be in 6mm

So, the supervisor is correct.

 

[Engineer54]

Think you'll find that most commercial premises of any size(say, medium to large) would be using 16A OCD, and that would also probably be the case for many industrial installations too. It's not uncommon at all to have a minimum size wiring requirement of 2.5mm for lighting circuits and 4mm for power outlets on specified contracts...

 

[DurhamSparky]

as E54 says 2.5 and 4 is common...! building i look after at is wired in exactly that! also not a ring in sight!!

all lighting circuits are on contactors with pir switching. pain in the arse when you want to turn the lights off to get some "lazy time" as the em switching banks is centrally located in the db room