can I join 2 different size wires?

mallardtone-man

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Sep 22, 2008
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hey guys I have a boat I am working on but I am NOT an experienced electrician I have wired in my bilge pump and running lights along with a bunch of interior LEDs and a breaker panel with switches I am doing most of it with remnant wire I purchased and don't always have the right size in some cases I have gone heavier than what the accessory called for like joining a 10 gauge wire To a 16 all the acessories have the proper size coming from them just not all the way to the battery am i risking damaging the acessories or blowing breakers by using this larger wire? all of my breakers are 10 Amp. Also in some cases I have run several grounds back to a common ground or several light to 1 positive wire I wanted to know if when I do this Am i supposed to use the same size wire that the acessories calls for or should I be doubling or tripling the size in the case of running two or three lights to one positive? also curious to know whether or not joining my ground wires is a good idea? do I need to have A ground running directly to the battery for everything assesory or can I join groups of assessories or even all of them 21 common ground? I am installing bus bars just before the battery just haven't gotten around to it. Thanks in advance for any help James
 

poconojoe

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So many questions! You seem to need a good lesson in electricity! Normally using a larger gauge wire won't harm anything, in fact if you are running a certain distance, you sometimes need to increase the size. ( depending on the distance).
As far as what gauge to use for 1,2,3,4 etc. Loads, you need to calculate the amperage draw of all those loads and use the proper gauge wire to support that amperage.
So, it's kind of complicated. You need to be careful not to overload the wires with too much amperage. You can start a fire. And to quote someone on this forum (sorry, I don't remember who it was) " there is nowhere to run when your boat is on fire".
Another related subject is fusing ( or circuit breakers). Place them as close to the battery as you can. They protect the wires from overload and melting. They also need to be sized according to the load and more importantly the size of the wires they are supposedly protecting.
Maybe you should read up on basic wiring. Or more specifically boat wiring. I think there is a sticky here somewhere on a generic boat wiring.
Good luck and makke sure your connections are good. A lose connection can also cause a fire.
 

poconojoe

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At the top of the electrical section is some stickies for boat wiring. Check all that out. If you have more questions, just ask.
 

poconojoe

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Oh, Idk if you are aware, but marine wire is special. It is not your normal house wire. It is tinned throughout to prevent premature corrosion.
 

poconojoe

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Oh, your original question on connecting different size wires....yes you can. There are several ways to splice wires. Buss bars, as you mentioned, are great for this. You can attach wires to the buss bars with stak-on crimps. You can solder wires together and use heat shrink tubing. Many ways depending on the wires and situation.
 

Grandad

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Hi James, I?ll try to answer some of your questions.

Am i risking damaging the acessories or blowing breakers by using this larger wire? all of my breakers are 10 Amp.
No, you?ll not cause damage by oversizing wires. Breakers (or fuses) should be sized to the weakest link in the circuit. The 10 amp breaker size is suitable for most loads suitably fed from #16 wire. Please note that negative wires must also be of adequate size as they?re protected by the same breaker that protects the positive wire.

Also in some cases I have run several grounds back to a common ground or several light to 1 positive wire I wanted to know if when I do this Am i supposed to use the same size wire that the acessories calls for or should I be doubling or tripling the size in the case of running two or three lights to one positive?
As poconojoe said, to know what minimum size wire you need, you need to total all the currents by every accessory connected common to that wire.

also curious to know whether or not joining my ground wires is a good idea?
Not sure what you mean exactly, but the number of joints should be minimized wherever possible. Making additional joints to allow use of several pieces of wire to get adequate length creates additional future failure points. Depending upon where you?re using your boat, trading safe reliability for economy may be unwise.

do I need to have A ground running directly to the battery for everything assesory or can I join groups of assessories or even all of them 21 common ground? I am installing bus bars just before the battery just haven't gotten around to it.
I wouldn?t run separate negative wires to the battery. Use a common bus bar or splitter located at a convenient location and then connect the bar to the battery via a wire large enough to carry the total current of all the connected accessories.

OK. I?m gonna stick my chin out about a couple of additional things. Unless you?re boating around salt water or if the boat sits continuously in dampness near the water, tinned wire is not a necessity. My 43 year old Starcraft has numerous untinned original wires and there?s no evidence of corrosion anywhere, including where the bare copper is exposed. That said, I recommend coating every joint and terminal with a dielectric grease or sealer to avoid the potential of corrosion.

A second point is that many folks take the approach that breakers and fuses only protect the wires, not the devices that the wires feed. This is a principal that can be taken too literally. It may be an accurate statement only if wires are not unduly oversized, since components also require protection. The manufacturer of a component often recommends a maximum fuse size without knowing what size wire you?ll be installing. Just because you used an oversized #10 wire to feed your fuel gauge is not justification to use a 30 amp breaker to protect the circuit. - Grandad
 

mallardtone-man

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awesome guys thanks for the advice. Especially you grandad very thorough I appreciate you taking the time to write it.

happy boating all
 

mallardtone-man

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here is another question my battery is at least 10 feet from my console where the breaker panel is so in this case should I be running inline fuses as well close to the battery? Or does this defeat the purpose of the breakers?

Also by joining grounds I meant say I have 3 LED lights I am hooking up instead of running each individual ground wire to the battery can I run all three 16 gauge wires into a 10 gauge wire and run that to the battery?
 

Grandad

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here is another question my battery is at least 10 feet from my console where the breaker panel is so in this case should I be running inline fuses as well close to the battery? Or does this defeat the purpose of the breakers?

Also by joining grounds I meant say I have 3 LED lights I am hooking up instead of running each individual ground wire to the battery can I run all three 16 gauge wires into a 10 gauge wire and run that to the battery?

Yes, you should have a main fuse in the wire feeding the console located as close as practical to the battery positive. There is no need to run separate negative wires for each component unless the total current draw exceeds the capacity of the wire size. Especially with LED's, the total current for lighting will likely be much less than the capacity of a #16 wire, so don't unnecessarily increase to a #10 that will in many cases just add physical bulk to the system.
Here's a link to the US Coast Guard's Boaters Handbook that has a lot of helpful info, though some of the diagrams in the electrical section can be a little confusing. - Grandad
http://uscgboating.org/regulations/builders-handbook-downloads.php
 

mallardtone-man

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great thank you so if all the breakers in my panel are 10 amps does that mean I will need a 10 amp fuse in that wire feeding the panel? Or should I go bigger?
 

Grandad

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great thank you so if all the breakers in my panel are 10 amps does that mean I will need a 10 amp fuse in that wire feeding the panel? Or should I go bigger?

I'd suggest that you feed the panel with a #10 wire and fuse that wire near the battery with a 30 amp fuse. This should be more than enough current for everything a small boat might carry, with the exception of a trolling motor. - Grandad
 

Silvertip

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Here is one way (typical for boat wiring) to wire your boat. In this example, the positive and negative feed from the battery to the helm is 10 gauge. All other wiring can be 16 gauge. Anything larger is overkill and anything less will result in smoke since your breakers are all 10A and they would not open before the wire overheated and began to melt due to overload.
 

gm280

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I personally would not connect multiple size wires together to make runs in the boat. If you don't have the proper gauge wire or the correct length, stop. Buy quality marine tinned wires in the proper gauges and wire it correctly and forget about it then. Every wired connection you make, is another possible corrosion problem later on. So correct proper gauge wires are the best way possible to wire your boat...or any other wiring effort as well. And honestly, a spool of marine wire is really not very expensive if you look... JMHO!
 
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