underwater lights

[davemaskell]

there's an owner who is looking into installing underwater lights. i looked up the stats and these lights draw 18 amps for 25 sec. then taper off to just a couple of amps.they're 12v. he wants 10. if you do that it will draw 180 amps for 25 sec. ,that doesn't sound to go. they also make them in 110v. if i did the 12v i guess i could get a starter solenoid, hook up something like a #2wire, feed it to a fuse buss, and then feed each light on a 20amp fuse. then the switch would only have the amp draw of the solenoid. what do you say.

[GordMay]

Dave:
What kind of underwater lights are these. The HID lamps that I’m familiar with have a starting inrush current, but nothing like what you describe (18:1) - and incandescents actually increase their resistance (& amperage) as they heat up.
I’d be curious to see the product information.
Gord

[davemaskell]

its runs by a xenon bulb. a boat just last week had two put in but another company did it. go to "aqualights.org " and click to underwater yacht lights. the model is
al50x.they cost $900 each. wow.

[Rick]

Xenon HID start-up circuits actually ramp up to the peak (say 18A in your case) for about 3 secs then fall off to half of the peak about 5 secs later then almost linearly fall off to the steady-state run current for the next 15 sec or so. You, therefore, will not experience a full 180A load that entire time, only for about a second. Regardless, you need to plan out the wiring to take off from a battery directly and not go through a distribution panel serving other needs.

Rick

[Alan Wheeler]

What the heck, with that sort of light, they are going to atract giant squid. What some people will waste their money on

Dave, you could also look at selected delayed starting. Basicaly, you have say four seperate circuits of the lights. The first circuit energises instantly and the next 1 sec behind and the next at 2 sec and so on. I used to use this technique when starting multiple racks of Amplifiers drawing huge inrush starting currents.

[davemaskell]

i still have to come up with a way to switch on the lights. you have a beautiful yacht, you don't want some big battery type switch to turn them on. what do you think about my solenoid idea.

[GordMay]

Your proposed use of a Solenoid, to switch high amperage loads, is an elegant and conventional solution.
I also like your proposed breaking of the (switched) high amp bus into individual 20 Fused circuits.

For reliability, I’d use a higher amperage rated switch, than the actual loads demand.
ie:
250 A Electronic Solenoid Switch - Blue Sea Systems # 9012 (about $125): http://www.bluesea.com/product.asp?P...1=7459&l2=7491
vs
65 A Solenoid Switch - Cole Hersee #24059-08-BP (about $40)

Regards,
Gord May