Wiring Advice Sought

[PeteW]

I'm rebuilding and therefore rewiring a 29' 1992 Excella Classic Airstream. All of my lighting, including running lights, will be 12VDC and it will all be LED. The running lights will be on their own individual circuits for the 7 pin connector. House lighting will be separate and may also be on more than one circuit. The original wiring was 14 AWG, but everything was incandescent. At this point I'm only talking about lighting. Is there any reason I want to run larger wire than 16 AWG? I'm pretty well versed in single phase 120/ 240 AC wiring, but I'm still learning DC. Where can I do some educational reading on wire gauge sizing for DC loads and circuits?

 

[John Frum]

For the lighting will you be running a return wire or using the the chassis?

 

[John Frum]

You will need to consider the total ampacity of your circuits and the voltage drop over the round trip distance of the circuit.
Ancor https://www.ancorproducts.com/en/products/Wire-and-Cable/Multi-Conductor/Flat-Duplex-Cable
makes flat duplex cable that is great for this use case.

 

[Vigo]

Generically speaking the LEDs will draw so little in comparison to the old incandescents that all the existing wiring would be oversized, but to no harm. I would leave it all in place and wait for problems to present themselves, which they may not!

DC wire sizing calculators are roughly as available as AC wire sizing calculators online. I have not looked to see if they actually recommend different things! I am newer to the AC side but i assume that DC would require a larger conductor at same voltage because it would flow 'peak' amps continuously, rather than averaging some smaller current because of the sinusoidal voltage waveform.

DC wire size calculator google results

 

[12VoltInstalls]

There is no problem using 14ga
16ga is smaller but you already have 14- use it

 

[PeteW]

For the lighting will you be running a return wire or using the the chassis?

You will need to consider the total ampacity of your circuits and the voltage drop over the round trip distance of the circuit.
Ancor https://www.ancorproducts.com/en/products/Wire-and-Cable/Multi-Conductor/Flat-Duplex-Cable
makes flat duplex cable that is great for this use case.

Generically speaking the LEDs will draw so little in comparison to the old incandescents that all the existing wiring would be oversized, but to no harm. I would leave it all in place and wait for problems to present themselves, which they may not!

DC wire sizing calculators are roughly as available as AC wire sizing calculators online. I have not looked to see if they actually recommend different things! I am newer to the AC side but i assume that DC would require a larger conductor at same voltage because it would flow 'peak' amps continuously, rather than averaging some smaller current because of the sinusoidal voltage waveform.

DC wire size calculator google results

There is no problem using 14ga
16ga is smaller but you already have 14- use it

Sorry, I should have been more clear. There will be a dedicated ground wire the backbone of which will be 10AWG. I've measured all of the running lights and their current draw is very low. They measure in the milliamps, all below one amp, that includes when they are combined as some of them will be. The duplex cable John Frum linked to is what I'm looking at for connecting the solar panels on the roof with.

The reason I posted my initial question is because I'm re-wiring with all new wire. The Airstream had water damage and I did not want to reuse any of the original 30 year old wire. It will be recycled. All of the new wire I'll be using will be marine grade, tinned wire.

Thank you all for your comments and links. With the additional information I provided please feel free to comment further.

Thanks,
Pete

 

[HRTKD]

Sorry, I should have been more clear. There will be a dedicated ground wire the backbone of which will be 10AWG. I've measured all of the running lights and their current draw is very low. They measure in the milliamps, all below one amp, that includes when they are combined as some of them will be. The duplex cable John Frum linked to is what I'm looking at for connecting the solar panels on the roof with.

If the cable used to connect the PV panels will be exposed, then it should be actual PV cable. Look for UL 4703 rated cable.

 

[12VoltInstalls]

new wire I'll be using will be marine grade

I’d still be inclined to use 14ga and I’d use paired wire home runs to a blue sea box and not common perimeter ground.

 

[PeteW]

If the cable used to connect the PV panels will be exposed, then it should be actual PV cable. Look for UL 4703 rated cable.

Great tip! Thank you. I've definitely wondered about UV and how to know it was accounted for.
Pete