Cable rating for halogen downlights

[ste6085]

please excuse me if this has already been answered in another topic:

I am installing 5 x 50w 240v downlights, i have some heat resistant 0.75mm 3 core cable (white), is this ok to use? (as i find this easier to work with) or do i need to run 1.00mm 3 core (grey) to each lamp? I have already done another room (although only 2 lamps and works fine, but would rather know for this and future work.)

Many thanks guys.

 

[ban-all-sheds]

What current does 1 light draw?

What current does all 5 draw?

Will you be running all the lights from one cable, or one cable per light?

What is the rating of 0.75mm² cable?

What is the rating of 0.75mm² cable given your particular installation method (i.e. insulation, grouping, ambient temperature)?

How long will the cable(s) be?


http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

[ste6085]

Hi
What current does 1 light draw? What current does all 5 draw?

they are standard GU10 50w mains lights

Will you be running all the lights from one cable, or one cable per light?

I had planned to run cable to first light, 2nd etc etc would one cable per light be better
What is the rating of 0.75mm² cable?

6amp

What is the rating of 0.75mm² cable given your particular installation method (i.e. insulation, grouping, ambient temperature)?

I live in a bungalow so the wiring will be in the loft

How long will the cable(s) be?

The room is 5 m x 3m and the lights are evenly spaced

Many thanks for your help.

 

[ste6085]

Thanks for the help

 

[ban-all-sheds]

np.

 

[bongos]

they are standard GU10 50w mains lights

So for 5 x 50W they will be draw ~1.1A

I had planned to run cable to first light, 2nd etc etc would one cable per light be better

Run cable to the first, then onto the second and then onto the third etc.

I live in a bungalow so the wiring will be in the loft

Unfortunately you haven't provided enough information for the cable route. Will it be under loft insulation with one side touching the ceiling, straight through the middle of loft insualtion or will it be in 'free air'? What length of the cable (if any) would run through insulation?

You need to know the answer to this to make sure you derate the cable adequately. You also need to make sure that the cable is stilll rated high enough after taking this into account to be protected by the fuse/MCB rating for that circuit.

I believe this new circuit would be notifiable.

 

[roberta1000]

Normally you would 'daisy-chain' the lighting ie run the cable from light to light. You would generally only run separate cabling to each unit if the loads were significant such as for instance to storage heating and the like.

In terms of the lighting load (approximately 250 watts) the cable you mention would be more than adequate even allowing for lots of loft insulation and a loft temperature of say 40 degrees.

HOWEVER the cable should be protected by a circuit breaker of some sort to no more than its maximum current capacity (in case of faults) and this depends on where it is installed (because this affects the rate at which is is able to dissipate any heat it generates). In your case you would be OK at 3 amps but probably not at 6 which is what a lighting circuit is normally protected at.

 

[ste6085]

The cable lays on top of the loft insulation in places and where this is not the case its just laying on the bare plaster boards. The loft does get warm (never hot) in the summer and very cold in the winter (Bungalow).

Is there any advantage to running a single cable to each individual light ?

When using daisy chain - do i have to loop back from the last light to the junction box or finish the cable at the last light.

I have already wired these lights and they work fine, just need to be sure that i have done an ok job before i plaster ceiling.

Cheers for the ehlp

 

[bongos]

Is there any advantage to running a single cable to each individual light ?

When using daisy chain - do i have to loop back from the last light to the junction box or finish the cable at the last light.

You finish the last cable feeding the last light. The benefit of this method of installation over taking a feed from the junction box to each light is that it means you have alot more room in your junction box as you only have one cabel to terminate there.

What is the fuse/MCB protecting the lighting circuit? As long as it is 5/6A you should be ok.

 

[ste6085]

The MCB on the lighting ciruit is 16a.

Is there a problem running a single cable to each individual light ?

Cheers

 

[sparkyspike]

The MCB on the lighting ciruit is 16a.

What is the rating of 0.75mm² cable?
6amp

 

[ste6085]

I take from the last post that my cable should be stronger with a 16a MCB.

Could anyone tell me if its acceptable to run .75mm 3 core cable to each individual light therefore reducing the load on the cable, the max length of a cable would be 2m.

 

[ban-all-sheds]

It's not.

 

[Master of None]

Why is the lighting circuit protected by a 16A MCB? Surely the switches and fittings on the circuit are rated lower than this?

 

[ste6085]

There are some 6A MCB's but the lighting for the main house is 16A, Garage lighting is 6A.