What is the minimum size ("Amps") Circuit breaker for lights circuit in a house?

Hi everyone,

So I had a qualified Electrician out today to do an inspection in preparation for doing a CoC for me. He had a look at the main DB in the house where I’ve got 5 x separate 5A Circuit Breakers for all the “Lights” circuits in the house, been like that since the house was built in the late 80’s and passed a CoC in 2010 when we bought.

He says they need to all be replaced by 10A Circuit breakers as 5A is too small.

Is there such a requirement where light circuits need to have a 10A breaker?

I cannot see the logic behind that as we have LED light bulbs in any way (5-7 Watt each) and even if the entire house’s lights is on one 5A breaker it will still not trip as we don’t use a lot of watts for lights, even traditional tungsten filament globes would have worked fine if we used 60 Watt globes back in the days as 5 Aps would require more than 1.1 KW of power to be used before it would trip.

Thanks if anyone has clarity on that :slight_smile:

The only requirement is that the breaker must protect the cable. If the breakers are functional, and not tripping, why bother? The trend is from incandescent towards LED lighting which means lighting requirements became less… not more.

If I needed some space in that DB… well then that’s probably one of the first things I’d do. Lump those 4 circuits into 2, on 10A breakers :slight_smile:

Thanks a lot,

so from a “COC” perspective there’s nothing forcing one to HAVE to go to 10A per breaker for “lights” circuits?

I checked SANS10142 quickly, but since I am not a trained sparky I cannot say for sure. I cannot IMAGINE there would be a reason that a breaker MUST be upsized. I mean, if it was nuisance-tripping, or if it is no longer functional, or if you were planning on installing that big 1kW chandelier in the ballroom… sure… and maybe 5A breakers on lighting circuits are indeed rare, the convention is 10A. But I cannot think of a reason why it MUST be so.

Thanks plonkster, much appreciated.

I totally agree, there’s no logic in having to go bigger, if the 5A is not tripping why would I want to allow that same circuit to now allow for twice as much amps if it has never tripped in 12 years…

I agree, the electrician is just commenting that 10A is the smallest breaker currently available, but there is no need to upgrade your 5A breakers.

Hogwash. Get a different electrician. Like all too many electricians I’ve had the misfortune of dealing with, this one is likely out to bleed you dry.

Just ask him to show it to you in the SANS standard… then watch him dance around it.

Can go lower breakers on bigger wires, not bigger breakers on lower specced wires.

Have stove circuit in place on a 40a breaker. The stove is long gone.

Asked the sparkie, that big mother of a wire, can we slap on a 5a breaker? The breaker must trip on ± 1.5kW draw … it is done.

Know your customers “they” said. They plug stuff into outlets connected to Critical Loads DB without thinking. I don’t like red warning LEDs on inverters.

So if I understand correctly then SANS 10142-1 (also known as the Code of Practice for the Wiring of Premises with low voltages), currently Edition 3.1 – Released October 2021 dictates all of those “rules” when it comes to circuit breaker sizes etc. and I should be able to read though that and find what I’m looking for?

The relevant section in SANS 10142 is “6.7 Protection”:



Note that a maximum protection rating is specified based on the cross-sectional area of the conductor. There is no minimum specified in the standard.

If I have a load with a fixed and known draw on the other side of the wire, like a pump, I would normally pick a breaker with a trip current that is sized just large enough to avoid nuisance tripping, but that will trip if e.g. the rotor gets stuck.

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Thank you, that makes 100% sense, my common sense also tells me there cannot be “minimum” size breaker as it all depends on what you are trying to protect and the breaker must suit that need.

Thanks for everyone’s input and helping with clarity, much appreciated.

In fact, the spec says the breaker must not exceed the LOWEST of the capacities of any of the conductors. That means, before you can up it to a 10A… you will have to inspect all the downstream wiring and make sure there is no 5A wiring there. There might be a reason smaller breakers were used, and you cannot increase the rating unless you know everything downstream is fine.

I agree that the trip threshold has a maximum setting, but a lesser setting can be selected.
As the issue has been described, it sounds like the electrician is wrong.
But, things are not always clear-cut.

There are instances where the short-circuit rating of an MCB is too small, this depends on the fault level assessment. ( different ratings like 10kA, 6kA or 3kA). This capability is regardless of the MCB’s trip setting and refers to the constructional integrity of the MCB
This 5A MCB may be physically too small.

There are also instances where MCBs that feed downstream MCBs have to cascade in the trip threshold setting so that the MCB that is most local to the fault trips before the upstream MCB.
Starting upstream with a 5A MCB doesn’t leave much room to cascade down further.
(That doesn’t sound like the case here, but I include it to show there are other things to be considered).

Is there a future space requirement for additional MCBs in the DB being anticipated? So ganging two circuits through one larger MCB is a logical step. Has the electrician spotted other ganged circuits that need splitting and he needs the space?


In my case it was an Electrician who did not check any wiring, he simply opened up the Main DB, had a look, asked me if those particular MCB’s were for “lights”, I said yes, and his immediate reaction was that “5A breakers for light circuits are not allowed, they must all be 10A and he suggests I replace them with 10A MCBs”.

I questioned this saying that we’ve lived here for 12 years, the MCB’s for the lights never tripped, and in fact we replaced all bulbs with LEDs, so they are now only drawing 5-7 watt (much less than before) and I cannot understand how there could be a “mininum” 10A requirement as it’s just lights (simple maths: 5A x 220v is already 1.1 KW, my lights will NEVER draw 1.1KW even if the entire house’s lights were on a single 5A breaker, and in my case it’s split across 5 x 5A breakers (and was probably done so by whom ever wired the house at the time it was built and for good reason).

His final comment is that we “probably got away with it” (with the previous COC 12 years ago when we bought the place) because there were 5 x breakers for the lights but still it is not allowed and should be 10A each.

He’s either dishonest or incompetent. Do you really want to pay to find out which it is?