Accessory Amp/Watts Wire Question

[JustMrWill]

I have been reading for about 2 days now...and I understand that a simple "use #14 wire for accessory X" is not the correct answer. I have printed out all kinds of charts saying that the wire gauge should be X if the run is Y and the amp draw is Z but, what I can't seem to locate is the average/max amps used for accessories that I already have on my boat. I understand that simular but differnt items will have different needs (a double air horn vs a single air horn...led vs reg bulbs). Is there a chart/link that shows Nav light = 1 amp, horn = 5 amp, etc? I have been searching various manufacture's sites to try to get the specs but most dont say anything about amps or watts...just that it is a 12 volt item.

Am I worrying too much? Should I just copy the wire size that the accessory came with (the 4" tails) and figure "close enough"?

Here is what I have (all existing with no markings on them):

Nav light (single bulb).
Single horn (looks like.. http://www.iboats.com/AFI_Mini_Comp...68938908--list_time.1181322117--view_id.37987 )
Anchor light (on pole)
Bilge pump (Rule 450 gph)
Humminbird WIDE Onehundred depth/fish finder.

If anybody can tell me the amps I can figure out the wire I need to buy.

Thanks.
-JMW

 

[PondTunes]

Re: Accessory Amp/Watts Wire Question

I assume you're not powering all of these items off of a single wire. Nav lights, Fish finders, electric horns and such will all have light gauge wire #12-#14 in most cases. These wires would need to be routed into a fuse block and fused to protect the battery.

The actual function of the fuse block is to break the connection from the battery to the accessory in the event of a short thus why each items individual load rating would become important.

CD Player/Radios are normally fused 10a

Fish Finders Normally come with an in-line fuse and can vary depending on the features but 1-5 amps should be fine there.

Your entire nav light setup if using "bulbs" should be fine on 5 amps (less if its LED)

Your horn should be happy on no more than 5a
Bilge pump could be 5a - 15a depending on make/model/size

These figures could vary a bit based on who made the item in question, so consulting the user manual/installation guide that came with the item should be able to clear up any questions about amperage draw.

The fuse block however will need to be supplied power by a wire that is large enough to accommodate the entire current draw for every item powered by the fuse panel.

IE just using the above maximums as an example:
10+5+5+15 = 35 amps.

You can check your charts that you downloaded but a #10 AWG wire should be plenty to supply the fuse block with some room for expansion.

*REMEMBER ground gauge should equal your primary gauge never use a smaller ground than positive lead.

 

[jtexas]

Re: Accessory Amp/Watts Wire Question

amps = watts ? volts, so for light bulbs, divide their stated wattage by 12.
The pump is a different animal, as its current draw varies according to the load, but Rule will have recommended a fuse size - you just need to make sure the wire won't burn up *before* the fuse blows. No doubt its on their website.
Same with the AFI horn.
The fishfinder...if it used any less power, it'd be charging the battery.

I have 3amp fuses on all my pumps (incl the 1000 gph bilge), and the nav/anchor lights on the same 5A circuit. Don't recall what wire size I used - pretty sure it's all 12 or 14. except the fuse box supply line is 10.


hope that helps

 

[JustMrWill]

Re: Accessory Amp/Watts Wire Question

Thanks for the replies. I don't have the manuals for the stuff I mentioned...and I have spent many hours looking at their websites and cant find anything. These devices came with the boat and the wiring was un-salvagable so it got cut out.

I just needed a "general" guide as to how much each draws so I can start planning the wiring. I am going to run a #8 or #10 from the battery to the fuse box (about a 12' run) then to either switches or the devices. I figure...when in doubt..go with a bigger wire but I wanted to be close to start with.

Thanks again.

-JMW