Fuse and wire size

[skyhook]

Thanks guys. I have a little bit better understanding now.

The only question I have is about one recommendation of four lights per 15a fuse vs another of 7. Using the provided formula, and the fact that all seem to agree on 2a per light, it seems that 7 lights on each fuse is correct.

Should have mentioned the plan was to run four lights on one switch and two on another. The third would be empty for now.

I said 4 per fuse ( 8amps) for safety reasons, as stated, those are AC rated switches, not DC,
DC switches are more "bulkier" and are made to handle a steady flow of current as opposed to AC.
You will see more AC switches "fuse" themselves together from heat in a DC circuit than you will DC switches, thats why they cost more.
You could put 7 per fuse (14amps) but I wouldn't chance it myself.
Heck, you could also raise the fuse up to 20amps and put 9.

 

[Fallon]

I said 4 per fuse ( 8amps) for safety reasons, as stated, those are AC rated switches, not DC,
DC switches are more "bulkier" and are made to handle a steady flow of current as opposed to AC.
You will see more AC switches "fuse" themselves together from heat in a DC circuit than you will DC switches, thats why they cost more.
You could put 7 per fuse (14amps) but I wouldn't chance it myself.
Heck, you could also raise the fuse up to 20amps and put 9.

I wouldn't put more than 5 maybe 6 lights on the circuit. Loading a circuit beyond 75% or so is asking for issues. It just takes a little power fluctuation for some reason & you are blowing fuses. Leave yourself plenty of headroom on the wire gauge & fuse.

Its not even a bad idea to have a fuse smaller than the wire is rated for.

 

[DT86]

Thanks again for taking time to explain.

Still working on attachment of the lights and the switch panel. Once that is complete I'll start wiring it up.

 

[Scrambler82]

When setting up off road, incandestant lights, we use two lights per relay but you can use multiple relays per switch.
Reason being if one set of lights goes out you will still have the others to get home with.

Back to basics, 6, 27 watt lights can run on 15 amps, if you size the fuses, switches and really to handle the load.
But... Stick to the two lights per relay, 16 gauge will work (rated at 10 amp), use 14 gauge wire, fuse for 10 amps and switch with almost any switch you want to use.
Always use a relay, alway fuse the main power wire for the current rating of the smallest component and use standard automotive relays, unless they might get wet, then consider wet environment components.

I can go on and on but use that simple rule of two lights per circuit and make sure to ground properly and you should get years of service from the circuits.

 

[DT86]

Another stupid question. Why are switches like this rated for AC when most would be used for DC??

I think what I'll end up doing is installing solenoids near the lights and using the hot wire (hot with key) provided by Kubota for a work light to power the switches. That way I can eliminate the fuses at the switches (except for the power socket), not have to worry about over taxing the switches, only have to run one big hit wire to where the lights are and not have to worry about leaving the lights on when the tractor is off.

Anything wrong with this plan?

 

[PILOON]

If you look carefully, many switches will have both AC and DC ratings. At least many that I have seen, generally American makes.*
The DC rating will be much less as a rule but 10 amp DC switches are reasonably common. Certainly not the mini ones however.
*One brand is CH (Cuttler Hammer)

Another stupid question. Why are switches like this rated for AC when most would be used for DC??

 

[Scrambler82]

I for one do not know why switches are not rated for DC but switch in your case should only be used to control the relay, low amperage draw, not the full current of the circuit.

With lights you actuall have two parts for a circuit, part one is the low amperage switching of the relay, part two is the high amperage circuit of the lights.


I forgot to mention... if you go LED you can do a lot more lights one one relay/one switch or if you keep to the two light rule then you can eliminate the relays or not.
Think LEDs, the only thing is the price !

 

[DT86]

If you look carefully, many switches will have both AC and DC ratings. At least many that I have seen, generally American makes.*
The DC rating will be much less as a rule but 10 amp DC switches are reasonably common. Certainly not the mini ones however.
*One brand is CH (Cuttler Hammer)

I just looked through my "assorted electrical junk box", the switches found were either rated for AC or not at all.

 

[DT86]

I forgot to mention... if you go LED you can do a lot more lights one one relay/one switch or if you keep to the two light rule then you can eliminate the relays or not.
Think LEDs, the only thing is the price !

I already have the 27w LED lights. In fact I bought 4 for my RTV, then bought 10 more to use between the tractor and truck.
Buying in bulk has the price around $14 each. The first 4 were about $20 each.

 

[Scrambler82]

So are those LED Lights the ones you are going to use ?

If so, what is the manufacturer's requirements for amperage for each light ?

Do you have a manufacturer for these LEDs ?