GU10 fitting with 0.5mm cable is it OK on 6A circuit

happyhero

I have some Gu10 fittings that come with 50watt lamps and I've noticed the electrician is connecting them with 0.5mm flex. I have some electrical background and so can understand some of any installation. He has said it will be fine as the lamp won't draw anywhere near the cable rating.

I know that 0.5mm cable can take 3A so over 700watts and the lamp is only 50watts but is it accepted to have a cable that can only cope with 3A on a 6Amp circuit

Any answers/ advice appreciated.

Carrot007

It would probably be best practice to have an inline fuse for a lower rating where the change to the smaller wire occurs.

Risteard

I'm not clear whether you are referring to final connections to the luminaires or whether you are talking about cables between luminaires.

If we are just talking about the final connections then as stated the load (i.e. the halogen lamps) cannot overload the cable and so so our consideration is then with whether fault protection is afforded by the circuit protective device to the cable.

happyhero

Risteard wrote: »

I'm not clear whether you are referring to final connections to the luminaires or whether you are talking about cables between luminaires.

If we are just talking about the final connections then as stated the load (i.e. the halogen lamps) cannot overload the cable and so so our consideration is then with whether fault protection is afforded by the circuit protective device to the cable.

The circuit I wired in 1.5mm Twin&E but he has fitted connectors on this to allow easy removal of the fitting and from these connectors to the luminaries is where the 0.5mm flex has been used.

Ectophile

It's perfectly normal for the last bit of flex from the junction box/ceiling rose/whatever to the light fitting to be much less than 1.5mm. Just look at the bit of flex going down to a traditional pendant light socket.

The load at the end of it is a single lamp, so it won't overload the flex. And if there is a short circuit, the breaker will trip before the flex melts and catches fire.

happyhero

I'm probably being stupid but its just the logic of it, ie what if the lamp went faulty and started drawing more current than normal, potentialy it could draw close to 6A and not trip the breaker and then the cable could cook.

You are right though the cable that goes from from a pendant is often 0.5mm ish and the cables on the GU10 fitting that go from its own connector (mounted on the GU10 casing) to the GU10 bayonet type connector are small too, although they are funny stiff wire so not sure what they could cope with.

Ectophile

If a lamp that's supposed to be only 50W suddenly starts dissipating about 1.3kW, then you've probably got bigger things to worry about than the state of the flex - the whole fitting will probably be either melting or catching fire.

In practice, it's very unlikely to happen. Traditional light bulbs may take a surge of power when they blow, but stop pretty quickly. New energy saving ones are likely to have a component in that will blow if there's a current surge.