by Pmullen503 » Tue Mar 03, 2020 11:20 am
I'd run a 10 or 15 amp fuse. If it's good silicone wire you'd be good to 20A continuous in open air. If it's cheap copper coated aluminum in a plastic sheath, buried in foam insulation, I'd go down to 10A.
The problem is heat generation. You could theoretically run undersized wire, overfused to allow high current enough to melt the insulation on the wire. An often overlooked problem is the connections. A poor connection (splice or terminal) has the same effect of running too small a wire. SO DON'T BURY YOUR CONNECTIONS! Make sure place your splices and connections where you can inspect and repair if necessary.
Lastly, there is a lot of cheap Chinese wire out there that is not pure copper or is copper coated aluminum and it tends to fail at connection points. I've had to rewire my trailer twice in five years due to the wiring corroding to powder. This was supposedly marine rated wiring from a reputable trailer parts supplier.