Underwater lights wiring question

[mklearl]

Hi all! Just got a pair of Seablaze x underwater lights. I have just a basic wiring question which I'm sure there is an easy explanation.
I'm running both lights off of one switch. I went with 12/2 marine wire which is probably overkill but given the length (15 feet switch to light) I figured more was better. The lights draw 3.6 amps each. I was going to wire them off a fuse block with a 10 amp fuse. This should be good protection for the entire circut. However the manufacturer recommends a 5 amp fuse for the light. So my question is how do I protect the circuit which needs 10 amps and each individual light which needs 5 amps? I suppose I could run one length of wire to the lights and when I split the lights off the wire at the stern I could put a 5amp inline fuse to each light. I'm trying to avoid an inline fuse though. I know I would be fine with just a 10amp fuse and avoid any fires which is the main goal but with $800 in lights if kind of like to protect those as well.
Thanks in advance!

 

[Bondo]

Ayuh,.... Just change the 10 amp fuse to a 5 amp fuse,....

 

[mklearl]

3.6 amps each draw so I should have 5 amps fuse to each light. If I put a 5 amp fuse on the whole circuit then I'll be popping the fuse as it will be drawing 7.2 amps. 10 amps to protect the wiring. But I want to protect the lights.

 

[Redtruck12]

Are you planning on wiring them as a series or parallel circuit?

 

[mklearl]

Either or... I can easily run 2 wires piggybacked off the out terminal on the switch. So could I run 2 separate wires from 2 separate 5 amp fuse on the fuse block piggybacked to the +in on the switch and then another 2 piggybacked from the +out terminal in the switch to each individual light?

 

[Redtruck12]

Maybe refresh your knowledge of high school before you hook it up.
i understand your hesitation considering the cost of the lights.

i would likely go 1 - 5 amp fuse wired in series and negative switched.

found this quote, may help


"Charge flows together through the external circuit at a rate that is everywhere the same. The current is no greater at one location as it is at another location. The actual amount of current varies inversely with the amount of overall resistance. There is a clear relationship between the resistance of the individual resistors and the overall resistance of the collection of resistors. As far as the battery that is pumping the charge is concerned, the presence of two 6-Ω ;resistors in series would be equivalent to having one 12-Ω resistor in the circuit. The presence of three 6-Ω resistors in series would be equivalent to having one 18-Ω resistor in the circuit. And the presence of four 6-Ω resistors in series would be equivalent to having one 24-Ω resistor in the circuit.

The only drawback is if one goes out both will go out as opposed to a parallel circuit that could allow each to work individually

 

[mklearl]

Maybe refresh your knowledge of high school before you hook it up.
i understand your hesitation considering the cost of the lights.

i would likely go 1 - 5 amp fuse wired in series and negative switched.

I havent been in high school for 30 years but I can honestly say I don't remember any classes on marine wiring... Must have been all the partying in college why I don't remeber.

At any rate I understand the basics of wiring but negative switches in series wiring I'll admit is beyond my knowledge... Which is why I'm here. I'll look into it further. Thanks for the input! Your quote makes sense and is what I am looking for. I don't care if they both go out of there is a problem as long as the lights are protected.

Any chance you can put that into layman's terms for me? I will be looking elsewhere also... Always learning. Thanks!

 

[Redtruck12]

I did a quick search for a simple circuit this only has 1 bulb though;

of course you can switch switch either power or ground, I just prefer ground.
you will likely want a switched (key energized) power supply. Remember though that you will be adding load to whatever power source you are using.
remember that if l.e.d. Lamps are connected backwards they will not work.

i would go :
- power supply to fuse
- fuse to light #1 positive
- light #1 negative to light #2 positive
- light #2 negative to switch
- switch to ground.

 

[StingrayMike]

12/2 is not overkill. to determine wire size you have to include the to and from the light. so 12/2 would be appropriate for your application. Instead of doing inline fuses, why not have 1 wire from the switch to a fuse block, then each light can have its own 5 amp fuse?

You could do 1 10 amp fuse as Bondo suggested, but at least you would know if one light was bad/light wiring was bad.

 

[fishrdan]

I'd run both light off a 10 amp fuse and call it a day...

Or, fuse each lights + wire with a 5 amp fuse, before connecting it to your 12ga run, and fuse 12ga run with a 10 amp fuse.

Or, run individual 14ga wire runs and fuse each with a 5amp fuse.

 

[mklearl]

Thank you for the replies. After researching some more I think I'm going to run a length of 12 ga wire to the stern off a 10 amp fuse then put an online fuse of 5 amps between the 12 GA wire and the individual lights. Thanks again

 

[lmuss53]

MK, IMO your last solution is the best one, it protects the entire circuit as well as the lights individually. I would ground them individually too, that way if you pop a 5A fuse you don't kill both and the troubleshooting gets easier.