10A on lighting circuit ???

[BillyMac]

Getting myself a little worried here - any input would be greatly appreciated (including any corrections to my maths)

Currently have 5 rooms on a single lighting circuit with about 200W of bulbs in each room (and boy are some of the rooms dark!!)

I make that 1.1KW and therefore about 4.8A if everything was on.

Having played around with options, we've worked out we need to stick almost 30 halogen downlighters (mains) in one room to light the whole area which, mixing 50W and 35W bulbs, comes to about 1200W.

Also an external light is also on this circuit which I wanted to uprate to a 500W halogen with PIR. (I think this should really be on a different circuit but ....)

All told, that gives me almost 2KW, or almost 2.4KW (10A) if I include the outside light.

The cabling is 1.5mm which I understand will handle 3KW (13A).

Is it ok to just change the MCB from 5A to 10A, or is there something I'm missing ????

Cheers,

 

[ban-all-sheds]

Getting myself a little worried here - any input would be greatly appreciated (including any corrections to my maths)

You should do the calcs using 230V, not 240.

Having played around with options, we've worked out we need to stick almost 30 halogen downlighters (mains) in one room to light the whole area which, mixing 50W and 35W bulbs, comes to about 1200W.

Have you thought about some different types of light fittings? I'm not saying that it would be attractive, but can you imagine how bright the room would be with 12 100W GLS pendant lights dangling down? Downlighters are not good at illuminating whole rooms, as you've discovered. Have you thought about maybe having some wall mounted uplighters as well?

All told, that gives me almost 2KW, or almost 2.4KW (10A) if I include the outside light.

See above - 2400 ÷ 230 = 10.43. Not that it matters in practice here, but it's good to get into the habit of using the right values.

The cabling is 1.5mm which I understand will handle 3KW (13A).

Up to 20A, actually, depending on how it's installed.

Is it ok to just change the MCB from 5A to 10A, or is there something I'm missing ????

Volt drop. - How long is the lighting circuit?

 

[BillyMac]

BAS - thanks for the reply.

You should do the calcs using 230V, not 240.

Thanks. I was being lazy

Have you thought about some different types of light fittings? I'm not saying that it would be attractive, but can you imagine how bright the room would be with 12 100W GLS pendant lights dangling down? Downlighters are not good at illuminating whole rooms, as you've discovered. Have you thought about maybe having some wall mounted uplighters as well?

Well, have discovered that the effect we get is about equivalent to 4x100w GLS (put the downlighters up temporarily on a 13A plug to see the effect before I put the new plasterboard in). All the walls are in use and the ceiling's only about 6'8" from the floor. Have used 40 degree GU10 floods in wall wash fittings and the lights fairly even without being blinding as much of it is reflected back from the walls.

The irony is we're unlikely to light the whole room, just sections of it, but I need to make sure the circuits won't trip if all the lights get turned on.

Volt drop. - How long is the lighting circuit?

There is a shared supply lead to 5 terminal blocks of about 4m. Each block serves 5 lights having a lead back out to the switch of about 4m, then an onward lead to another terminal block of up to 5m, then fans out to 5 lights with each on a run of max 2m.

I thought that distance (15m) wouldn't be too great

 

[ban-all-sheds]

No problem - VD on 15m of 1.5mm² is about 4.5V at 10.43A

 

[securespark]

From a practical POV, you could do worse than install two circuits for lighting with the security lights on a third or run off the ring. Not a bon idee to put 500W floods on ordinary lighting circ.

 

[breezer]

i think 500w flood lights are over rated (no punn intended)

most of them you see are put up above a back door, blinding all who look the wrong way, and lighting up neighbours gardens (some times bedrooms)

i think small is marvelous, in the right place (big farm, fields, etc) they are fine but houses , no thanks

 

[BillyMac]

I'd agree with you about the floodlights in town ... but we are a farm and half a mile from the nearest road, let alone neighbour