Wire Size

[rlongfield]

What gauge of wire should I be looking at? And what is the preferred connection method?
My wiring experience is either with AC wires or 22 awg DC wires. So either I’m using wire nuts or I’m soldiering and shrink wrapping, neither of which applies here I’m sure.

 

[Leeward Rail]

Gauge of wire for what application ?

You question cannot be answered without more information.

Wire size depends on the max wattage the devices on the circuit would use, and the length of the cable.

So a.question would be... I have to run 12 volt devices that need X amount of watts at the end of a cable x feet long.. what wire size do I need ?

So you need to add more info to your question.

 

[Davidasailor26]

Like Leeward said, the wire size depends primarily on amperage and run length, with some other factors as well. Blue Seas has a helpful calculator at Circuit Wizard - Blue Sea Systems. You’ll want tinned marine wire, which is stranded and very different from household AC wire. The preferred method for connections is properly crimping and heat shrinking.

 

[kappykaplan]

I’m using wire nuts

Wire nuts have no place on a boat.

 

[Justin_NSA]

Mainsail has good info on wire connections in his site. I bought a crimper from him many moons ago. I have one each for heat shrink covered fittings and standard fittings.

 

[rlongfield]

Wire nuts have no place on a boat.

Correct! My wire nut comment was in reference to my work with AC wires, soldiering for my small DC projects.

 

[kappykaplan]

Correct! My wire nut comment was in reference to my work with AC wires, soldiering for my small DC projects.

Okay.

 

[rlongfield]

Gauge of wire for what application ?

You question cannot be answered without more information.

That's what I get for posting past my bedtime, half baked thoughts

What I was really trying to ask was is it better to sort out the load and select the wire gauge for each circuit based on that, or do you just go with say 12 gauge (assuming that covers the highest load circuit) and use that for all circuits?

 

[Maine Sail]

The marine safety standards do not allow wire nuts . they also require a mechanical connection eg: crimp and solder does not count as a form of mechanical connection..
https://marinehowto.com/marine-wire-termination/

 

[rlongfield]

Wire nuts have no place on a boat.

Correct! My wire nut comment was in reference to my work with AC wires, soldiering for my small DC projects.

Okay.

That being said, I did pull some out of the boat from the previous owner. Shore power was apparently a long extension cord attached (with wire nuts) to 3 house outlets. It's ok though, the outlets have cover plates attached to them

 

[rlongfield]

The marine safety standards do not allow wire nuts . they also require a mechanical connection eg: crimp and solder does not count as a form of mechanical connection..
https://marinehowto.com/marine-wire-termination/

Thanks for the link, that answered a few un-asked questions about crimping (tool and connectors) I had

 

[kappykaplan]

That being said, I did pull some out of the boat from the previous owner.

Yeah, me too, 15 seasons ago.

 

[Ralph Johnstone]

This will give you a better idea of exactly WHAT a selected wire will do for you. Whether it's got the capacity to carry the desired current and won't burn up or whether it will safely carry the desired current but result in a large voltage drop.

 

[Project_Mayhem]

Regardless of temperature rating I would never attempt to push 20 amps through an 18 awg wire. It's too hot to handle even at 1500 watts

 

[sailme88]

Wire nuts have no place on a boat.

I beg to differ... wire nuts are the best way to connect speakers... when the give up the ghost, it is much easier to rewire the replacements...

 

[rlongfield]

Regardless of temperature rating I would never attempt to push 20 amps through an 18 awg wire. It's too hot to handle even at 1500 watts
View attachment 206104

I don't think I understand this table, I'm assuming that an 18awg wire can handle 10amps at 75C, 20amps at 90C, and 20amps at 105C? I would have thought that the hotter the environment the less amps the wire could handle since it is unable to dump heat it generates. Or is it at 10amps an 18AWG wire will heat up to 75C and in an EngRm it only take 8amps to reach the same temp?

 

[rlongfield]

wire nuts are the best way to connect speakers...

This is so much easier, I've always used banana plugs for my DIY speaker connections since they have the pinch screws for the plug and receptacle, wire nuts would be way easier.....

 

[Justin_NSA]

I beg to differ... wire nuts are the best way to connect speakers... when the give up the ghost, it is much easier to rewire the replacements...

If that's the concern, I would use heat shrink spade or bullet splices.

 

[Davidasailor26]

I don't think I understand this table, I'm assuming that an 18awg wire can handle 10amps at 75C, 20amps at 90C, and 20amps at 105C? I would have thought that the hotter the environment the less amps the wire could handle since it is unable to dump heat it generates. Or is it at 10amps an 18AWG wire will heat up to 75C and in an EngRm it only take 8amps to reach the same temp?

The temperatures are the heat rating of the wire insulator. For example - AWG 18 wire that’s rated for 75C can safely carry 10 amps (or 8 in an engine compartment). A different wire, also 18 AWG but manufactured with insulation rated for 90C can safely carry 20 amps (or 16 if in an engine compartment).

What you’ll also find is that most wire runs on a boat are long enough that voltage drop matters more than maximum amperage. Even though an AWG 18 wire can safely carry 10 amps, the voltage drop carrying those 10 amps for a 20 foot circuit would be 3.2 volts - way more than the limit for effective operation of equipment. So when you size the wire you need to consider both maximum ampacity and voltage drop.

 

[DayDreamer41]

The temperature is in reference to insulation of the wire and not the ambient temperature of the space the wire is in.