What Gauge Wire?

[l008com]

I'm re-doing all the non-engine wiring in my boat. Replacing the nav lights with bright LEDs, adding some LED courtesy lights, hopefully installing a stereo, plus a depth finder for sure.

So, for simplicity and to save money, I was just going to get one spool of 100feet duplex marine cable. The question is what gauge is good. The fuses in the switch panel are 20 amp fuses. However I know the LEDs will be using 1-5 watts max. Not sure how much power the stereo will use. That will likely be the biggest draw. The bilge pump will suck some power when it's active. I have no idea how much power a depth finder uses. It's a basic one with an numeric display, not a fancy one with a color LCD. So I came up with 14 gauge. Thicker than needed for the LEDs i know. Will that be enough to power the 200watt (speaker max) stereo? And the bilge pump? Or should I get something thicker? I do plan on using a short stretch of something thicker to connect the switch panel to the battery. This wiring is just going from the switch panel, do the end devices.

 

[Safebet]

Re: What Gauge Wire?

14 ga. should be adequate.

 

[l008com]

Re: What Gauge Wire?

This specifically is what I am tentatively planning on getting:
http://shop.genuinedealz.com/Items/...=14/2 AWG Marine Duplex - Flat Blk/Red 100 FT

 

[Silvertip]

Re: What Gauge Wire?

You have one device that is the highest draw and that's the stereo system. So why use 14 gauge wire to wire accessories, none of which come close to the current capacity of 14 gauge wire. 16 gauge is adequate for everything on the boat and 20 amp fuses are overkill for every circuit anyway. Circuits are fused for the items connected to each circuit.

 

[l008com]

Re: What Gauge Wire?

It will be cheaper to buy one spool, then to buy different spools of different gauge. No harm in over-gauging, right?

 

[TerryMSU]

Re: What Gauge Wire?

You have one device that is the highest draw and that's the stereo system. So why use 14 gauge wire to wire accessories, none of which come close to the current capacity of 14 gauge wire. 16 gauge is adequate for everything on the boat and 20 amp fuses are overkill for every circuit anyway. Circuits are fused for the items connected to each circuit.

Here is the math. 200 Watts / 12V = 16.7 Amps (for the stereo)
Maybe 80% efficient so assume 20.8 amps

Fish finder, maybe 35 watts so assume 3 amps

Bilge Pump 3A fuse (Johnson 1st Mate 400 Bilge Pump from Iboats add)

Ignore the LEDs - very small compared to everything else

Stereo is (as we all know) the worst steady state load.

However, the stereo will not be running at 100% rated power. How long are your wire runs? Remember that unlike home wiring where 1.2 volts is a 1% loss, in a 12v marine system, 1.2 volts is a 10% loss. For the bilge, there will be a large in-rush to start the motor spinning. If you starve it with too small wire, it may never start spinning.

I would say use the #14 wire to be safe. Fuse the stereo line at 20 Amps.

On second thought, fuse it for 5 amps. (That will limit you to about 60 watts and thus keep the volume down. Sorry, I just couldn't resist.)


TerryMSU

 

[l008com]

Re: What Gauge Wire?

The boat is 15 or 16' long, so the wires won't be that long. I was planning on having the radio and the depth finder on the same 20 amp fuse... would that be pushing it? I don't plan on listening to my radio at full volume much (or ever)?

 

[Silvertip]

Re: What Gauge Wire?

If you are running one circuit and intend to power everything off of that circuit it had better be 14 gauge. But a fish finder that draws little current does not need to be fed by a 14 gauge circuit. Nor does a bilge pump or LED lights. Use 14 gauge if you like -- no harm -- no foul. It is simply overkill.

 

[RicMic]

Re: What Gauge Wire?

Fuses or circuit breakers are to protect the wire(in case of a short circuit), its not so much that the wire needs protection, but if it gets to hot and melts the insulation, it becomes a dangerous fire hazard. SO the wire needs to have amperage appropriate fuse or c.b., you can have one smaller, if you also want to add some protection to devices on that circuit. There are lots of kinds of wire, which vary in their ratings and how they are routed is also a consideration, one wire in open air has a lot higher rating than a bunch crammed in a wireway or tied together. Also in a boat, I would always opt on the side of overkill, heavier wire is physically stronger wire and fire on a boat is a really bad deal. As a very general rule, if you have 20 amp fuses or circuit breakers(I would only use the manual test/reset kind), then a marine grade #14 wire should be fine. Always use crimped or soldered and taped or heat shruck connections on a boats, never wire nuts or simply twisted together and secure the wires so they are rubbing or moving around.

 

[l008com]

Re: What Gauge Wire?

So I have a spool of 14 gauge for everything else, but I'd still like to connect my distribution panel to my battery with 10 gauge. Anyone know where I can get about 15 feet of duplex 10 gauge on the cheapie? I don't need a spool. And West Marine's price for 10 gauge is about as much as a spool of it from anywhere else.

 

[seabob4]

Re: What Gauge Wire?

Why not just go back to genuinedealz? And frankly, I'd feed the helm with 8GA...

 

[l008com]

Re: What Gauge Wire?

Why not just go back to genuinedealz? And frankly, I'd feed the helm with 8GA...

I thought they only sold spools, do they also sell short lengths? Also I'm certain 10 gauges is sufficient. It's a very small boat, most of the switches are going to have LEDs attached to them

 

[seabob4]

Re: What Gauge Wire?

Let me see if I have some 10GA Red and Black laying around. Let you know...