Electrical question (please)

[robb]

Any electricians out there who can help please?
I am fitting fog and spots switched seperately from the dip and main beam circuits via relays. For neatness I was thinking of using 3 core cable to each pair using two of the wires for the separate live feeds and a common earth. I've seen amps = watts/volts which gives me approx 4.5 amps to each light and the cable I've seen is rated 6amps.

Now the potentially daft question - would the common earth have to take 4.5 or 9 amps?

thanks in advance...Rob

 

[Egon]

It would need to be able to cope with 9 amps.

 

[robb]

It would need to be able to cope with 9 amps.

supplementary dafter question - would 6 amp wire for a common earth blow then or do the bulbs consume the "energy"

 

[Egon]

supplementary dafter question - would 6 amp wire for a common earth blow then or do the bulbs consume the "energy"

Your cable would overheat and subsequently melt the insulation.

 

[robb]

Your cable would overheat and subsequently melt the insulation.

cheers - best not do that then, I'll source something 9amps plus.

 

[jimbo]

For many applications you don't need to run the earth far. Remember you don't have to run it back to the battery - the bike is negative earth. Mine are attached to the lamp bracket where they bolt to the bike.

 

[robb]

For many applications you don't need to run the earth far. Remember you don't have to run it back to the battery - the bike is negative earth. Mine are attached to the lamp bracket where they bolt to the bike.

I will probably stick with what I was planning and run a separate earth wire as you suggest.

 

[davegs]

Wiring.

Use the thickest cable that you can, it is always the best option to run a separtae earth to the battery as even a small resitance in the circuit will make a diffrence to,light no light output. Remember there's only 12 volts to sart with so even if you loose half a volt thats a big drop. Try it both ways and you will see the differance.
dave gs.