Which is the "correct" wiring size??

[23Sojourney45]

Hello experts, I've been out of the loop for a few months and took a hiatus on my trailer. I've been watching YT videos and reading up on some of the wiring concepts on here. My question is, what is the correct wiring size, if any? I've seen some on YT say that the wire gauge from the battery to the fuse should be in the single digits, 2 or 4 or something like that. Its been awhile but I do believe I heard 2 or 4 in some of those videos. Aren't those too big for a teardrop? From the fuse box to the usb ports, light switches, fans etc...I'ved heard anything from 10-14 gauge. What do I know 100% is to use multi strand wires, red/black. I'm still deciding on if I should use CCA wires or solid copper wires. I haven't checked on amazon on how much CCA wires are vs. Solid copper wires, again I've been out of the loop for months and building along the way. For now, my trailer will only be using usb ports, light switch/puck lights, 12volt plugs/socket. Also, some of those YT videos don't even mention grounding their electrical. My trailer lights are grounded to the trailer via screw. Is it a choice to ground the teardrop wires to the trailer?? even if its just a 12volt system? If I end up adding one or two 120 volts, those need to be grounded for sure?

 

[reaver]

First of all, stay away from CCA wires. CCA is less conductive, and more prone to breaking. In my build, I ran 12ga tinned marine wire from the battery to all my lights, switches, and outlets.

Now, 12awg ran everywhere is completely overkill.

I ran 4awg underneath to the dc-dc, and from the battery to the bus bars, and DC panel.

What you need to do is calculate what amps your device uses, how far of a run you need to make, and consult the blue sea wire size chart for what gauge you need to use.

Most likely, 16awg will be more than enough for 95% of what you need.

 

[Tom&Shelly]

First, I agree with everything reaver says.

My question is, what is the correct wiring size, if any? I've seen some on YT say that the wire gauge from the battery to the fuse should be in the single digits, 2 or 4 or something like that. Its been awhile but I do believe I heard 2 or 4 in some of those videos. Aren't those too big for a teardrop? From the fuse box to the usb ports, light switches, fans etc...I'ved heard anything from 10-14 gauge.

Yes, that is excessive. I used 10 gauge from the battery to the fuse panel. But the real answer is to compute the current draw (amperage) and wire run length and use the wire size that exceeds the max current draw.

What do I know 100% is to use multi strand wires, red/black.

That's probably best. I used mostly 14 gauge speaker wire from the fuse panel to the lights etc., because I have a large spool from the 1980's. It's possible modern speaker wire isn't made to the same quality. Anyway we haven't had any problems at all. There is one person on this forum, whom I respect highly in all matters electrical, who may even say it's okay to use solid wire. The theory is that stranded wire will better withstand repeated bending that occurs as the camper flexes while being pulled down the road.

For now, my trailer will only be using usb ports, light switch/puck lights, 12volt plugs/socket.

I did use 10 gauge wire to the cigarette lighter style sockets, since I don't know what high current devices might get plugged in. Hairdryers and electric blankets will draw a lot of current!

Also, some of those YT videos don't even mention grounding their electrical. My trailer lights are grounded to the trailer via screw. Is it a choice to ground the teardrop wires to the trailer?? even if its just a 12volt system?

Yes, as long as there is a return (black wire) you don't need to ground the 12 volt systems. I didn't ground either the 12 volt camper system or the vehicle safety lights. I believe running dedicated return wires are more reliable, and we haven't had any problems in 4+ years.

If I end up adding one or two 120 volts, those need to be grounded for sure?

Indeed! That's for safety. It's really a different concept than the "ground" for the 12 volt systems, which is really just the current path return. For 120 volts, you need to have the frame grounded so that if the line ("hot" wire) somehow touches the frame there is a better path for the electricity to flow than through you or a loved one. (Hopefully that situation will also trip a circuit breaker somewhere.)

Hope that helps!

Tom

 

[Pmullen503]

Do not use CCA. It can literally corrode and turn to powder inside the insulation. CCA is cheaper than pure copper so big box trailer harnesses are often made with the stuff. Maybe it's ok for some uses but not for trailer wiring.

Buy real copper wire from a trusted source. Expect to pay significantly more for it.

 

[Pmullen503]

Do not use CCA. It can literally corrode and turn to powder inside the insulation. CCA is cheaper than pure copper so big box trailer harnesses are often made with the stuff. Maybe it's ok for some uses but not for trailer wiring.

Buy real copper wire from a trusted source. Expect to pay significantly more for it.

 

[TimC-TNT]

Agree to all the above advice. The best "pure" copper is often referred to as "OFC" (oxygen free copper). If it is tinned that's even better. It is not necessary, but tinning will help preserve the wire from corrosion (turning green over time).

I used 10awg and 12awg for my long wire runs. Though they're not really long in a teardrop. I used 18awg OFC speaker wire in my short runs to various electrical equipment such as LED lights, 12V fans, USB ports, etc. Kind of overkill for some of that but I wanted to get a large spool of 18awg to cover all my low amp needs. My fridge is on 12awg.

I bought most of my wire from "Sky High Car Audio Cable" on ebay as the Menards/Home Depot types didn't carry OFC and Sky High had a good selection available.

 

[23Sojourney45]

First of all, stay away from CCA wires. CCA is less conductive, and more prone to breaking. In my build, I ran 12ga tinned marine wire from the battery to all my lights, switches, and outlets.

Now, 12awg ran everywhere is completely overkill.

I ran 4awg underneath to the dc-dc, and from the battery to the bus bars, and DC panel.

What you need to do is calculate what amps your device uses, how far of a run you need to make, and consult the blue sea wire size chart for what gauge you need to use.

Most likely, 16awg will be more than enough for 95% of what you need.

Really? CCA is less conductive? Good to know, I thought they were all the same. 12 gauge from the battery to the lights, switches, and outlets? You also ran a 4 gauge one? I'm confused at this part: "dc-dc and from the battery to the bus bars, and DC panel." My teardrop is 5x8 so I won't need a long cable run. Basically 12-16 gauge would be fine? Except for the 4 gauge one that confuses me, lol.

 

[23Sojourney45]

First, I agree with everything reaver says.

My question is, what is the correct wiring size, if any? I've seen some on YT say that the wire gauge from the battery to the fuse should be in the single digits, 2 or 4 or something like that. Its been awhile but I do believe I heard 2 or 4 in some of those videos. Aren't those too big for a teardrop? From the fuse box to the usb ports, light switches, fans etc...I'ved heard anything from 10-14 gauge.

Yes, that is excessive. I used 10 gauge from the battery to the fuse panel. But the real answer is to compute the current draw (amperage) and wire run length and use the wire size that exceeds the max current draw.

What do I know 100% is to use multi strand wires, red/black.

That's probably best. I used mostly 14 gauge speaker wire from the fuse panel to the lights etc., because I have a large spool from the 1980's. It's possible modern speaker wire isn't made to the same quality. Anyway we haven't had any problems at all. There is one person on this forum, whom I respect highly in all matters electrical, who may even say it's okay to use solid wire. The theory is that stranded wire will better withstand repeated bending that occurs as the camper flexes while being pulled down the road.

For now, my trailer will only be using usb ports, light switch/puck lights, 12volt plugs/socket.

I did use 10 gauge wire to the cigarette lighter style sockets, since I don't know what high current devices might get plugged in. Hairdryers and electric blankets will draw a lot of current!

Also, some of those YT videos don't even mention grounding their electrical. My trailer lights are grounded to the trailer via screw. Is it a choice to ground the teardrop wires to the trailer?? even if its just a 12volt system?

Yes, as long as there is a return (black wire) you don't need to ground the 12 volt systems. I didn't ground either the 12 volt camper system or the vehicle safety lights. I believe running dedicated return wires are more reliable, and we haven't had any problems in 4+ years.

If I end up adding one or two 120 volts, those need to be grounded for sure?

Indeed! That's for safety. It's really a different concept than the "ground" for the 12 volt systems, which is really just the current path return. For 120 volts, you need to have the frame grounded so that if the line ("hot" wire) somehow touches the frame there is a better path for the electricity to flow than through you or a loved one. (Hopefully that situation will also trip a circuit breaker somewhere.)

Hope that helps!

Tom

Thanks for the info! From what you guys are telling me, 10-16 gauge is good enough for my trailer. Again, its a 5x8 trailer, nothing too crazy. I was just researching the multi-strand wires on amazon and trying to figure out the "best" one. So your 10 gauge wires worked well using a hairdryer and heating blanket? you found 12v versions of those items? Do share!! I figure we can probably plug in the heating blanket for a bit, set it on a timer and problem not have to worry about turning it on the rest of the night.

 

[23Sojourney45]

Do not use CCA. It can literally corrode and turn to powder inside the insulation. CCA is cheaper than pure copper so big box trailer harnesses are often made with the stuff. Maybe it's ok for some uses but not for trailer wiring.

Buy real copper wire from a trusted source. Expect to pay significantly more for it.

Sounds good, Pmullen! I'm slowly research which ones to buy on amazon, lol. My trailer is 5x8 and I'm thinking of how long my total wire length will be if I added it up altogether, 100ft? 50ft? Idk.

 

[23Sojourney45]

Agree to all the above advice. The best "pure" copper is often referred to as "OFC" (oxygen free copper). If it is tinned that's even better. It is not necessary, but tinning will help preserve the wire from corrosion (turning green over time).

I used 10awg and 12awg for my long wire runs. Though they're not really long in a teardrop. I used 18awg OFC speaker wire in my short runs to various electrical equipment such as LED lights, 12V fans, USB ports, etc. Kind of overkill for some of that but I wanted to get a large spool of 18awg to cover all my low amp needs. My fridge is on 12awg.

I bought most of my wire from "Sky High Car Audio Cable" on ebay as the Menards/Home Depot types didn't carry OFC and Sky High had a good selection available.

Nice TimC! You used a variety of different sizes I see. Did that cost you a lot since you used different gauge wires instead of a single one? The fridge is 12v I'm assuming? you used only a 12 gauge one for that? oh wow, that's awesome. Is it a newer fridge?

 

[Tom&Shelly]

So your 10 gauge wires worked well using a hairdryer and heating blanket? you found 12v versions of those items? Do share!! I figure we can probably plug in the heating blanket for a bit, set it on a timer and problem not have to worry about turning it on the rest of the night.

Well, I tested the circuits with a 12 volt hair dryer. Then Shelly told me I could keep the hair dryer as it didn't work well enough to dry her hair. Not sure what brand it was or what happened to it, but it was a fundamental problem that it didn't heat enough to dry hair but pretty much maxed out the current draw on the circuit.

Tony Latham recommended the 12 volt electric blanket. IIRC, he and his wife would plug it in for a little while before they went to bed to warm it up, but wouldn't use it all night. Shelly and I never bought one, in the end, as we have a shore powered electric heater. Now Tony has a propane heater.

Sorry about not having more. Didn't mean to mislead--I was referring to our expected use cases as we designed the tear.

Tom

 

[TimC-TNT]

...
Nice TimC! You used a variety of different sizes I see. Did that cost you a lot since you used different gauge wires instead of a single one? The fridge is 12v I'm assuming? you used only a 12 gauge one for that? oh wow, that's awesome. Is it a newer fridge?

Not sure I fully understand your question, but, I believe it cost me less because I wanted a short run of large capacity wire for the charge controller to the battery and to the fuse block. The branch circuits, except the fridge, used mostly lower capacity 18awg where possible; even where it was overkill (LED lighting and 12v fans which would probably be fine with 20 or 22 awg). I bought a bulk reel of 18awg to accomplish that. Buying multiple short pieces would have likely cost more overall. No, I can't prove that theory. I value my time more than saving a couple bucks. 18awg was safe for my purposes and reasonably priced so I went with it.

The fridge is a 2017ish Alpicool 35 liter. So yes, it is very efficient. My only attempt to measure draw was a two day test in my garage where it used 14 aHr per 24 hour period.

 

[23Sojourney45]

So your 10 gauge wires worked well using a hairdryer and heating blanket? you found 12v versions of those items? Do share!! I figure we can probably plug in the heating blanket for a bit, set it on a timer and problem not have to worry about turning it on the rest of the night.

Well, I tested the circuits with a 12 volt hair dryer. Then Shelly told me I could keep the hair dryer as it didn't work well enough to dry her hair. Not sure what brand it was or what happened to it, but it was a fundamental problem that it didn't heat enough to dry hair but pretty much maxed out the current draw on the circuit.

Tony Latham recommended the 12 volt electric blanket. IIRC, he and his wife would plug it in for a little while before they went to bed to warm it up, but wouldn't use it all night. Shelly and I never bought one, in the end, as we have a shore powered electric heater. Now Tony has a propane heater.

Sorry about not having more. Didn't mean to mislead--I was referring to our expected use cases as we designed the tear.

Tom

I see, good point about the hair dryer! As for the heating blanket, we may go that route with the 12v or use shore power, not sure yet. I'm still in the beginning of the wiring planning and making sure that I don't leave anything out. Its not like we will be camping anywhere below 0 degree F, but at least its an option.

 

[23Sojourney45]

...
Nice TimC! You used a variety of different sizes I see. Did that cost you a lot since you used different gauge wires instead of a single one? The fridge is 12v I'm assuming? you used only a 12 gauge one for that? oh wow, that's awesome. Is it a newer fridge?

Not sure I fully understand your question, but, I believe it cost me less because I wanted a short run of large capacity wire for the charge controller to the battery and to the fuse block. The branch circuits, except the fridge, used mostly lower capacity 18awg where possible; even where it was overkill (LED lighting and 12v fans which would probably be fine with 20 or 22 awg). I bought a bulk reel of 18awg to accomplish that. Buying multiple short pieces would have likely cost more overall. No, I can't prove that theory. I value my time more than saving a couple bucks. 18awg was safe for my purposes and reasonably priced so I went with it.

The fridge is a 2017ish Alpicool 35 liter. So yes, it is very efficient. My only attempt to measure draw was a two day test in my garage where it used 14 aHr per 24 hour period.

TimC, you understood it 100%, thank you. I don't have any wires at all to rummage through like a lot of the TD builders, so I'm starting from scratch and weighing in all of my options. As for my TD, I will have LED puck lights for the cabin and the hatch, lights outside the doors, 12v Fan. I will have a few usb chargers in the cabin and probably in the hatch as well. I'm thinking of adding 1 quantiy of 120v in the cabin and 1 quantity of 120 v in the hatch, not sure yet. I will definitely run shore power connector. In the future, I may add solar and I may add a fridge. We shall see. I was just trying to figure out what size wire to get that will cover all my bases for now.

 

[Louis_189]

I know I'm late to the conversation, but I'm attaching a wire size chart for future reverence. I spent 50 years as an automotive electrician for new car dealers and a large city fleet repairing police and some fire vehicles as a certified EVT. The only recommendation I can make other than what I have read in the thread is you should always have a fuse or some type circuit breaker within 18 inches of the 12V power source for safety. I use a resettable circuit breaker similar to this link. I'll place it out of view near the battery box on the trailer tongue. Remember it should be rated 125% of the total circuit load. This doesn't replace the need to fuse the individual branches.

 

[swoody126]

I know I'm late to the conversation, but I'm attaching a wire size chart for future reverence. I spent 50 years as an automotive electrician for new car dealers and a large city fleet repairing police and some fire vehicles as a certified EVT. The only recommendation I can make other than what I have read in the thread is you should always have a fuse or some type circuit breaker within 18 inches of the 12V power source for safety. I use a resettable circuit breaker similar to this link. I'll place it out of view near the battery box on the trailer tongue. Remember it should be rated 125% of the total circuit load. This doesn't replace the need to fuse the individual branches.

GREAT CHART !

sw