12v question

I am in the process of adding a 12v outlet in my rv that is more convenient to use with my s9 autoset.
My question would be when the unit has a peak draw of between 5-7.25 amps depending on the heat settings etc, what sized fuse should i put in the inline fuse im wiring in? Too close to the peak draw and ill be replacing fuses, too much over and there is risk to the machine itself.
Im am referencing the Resmed battery guide if anyone wants more info.
By the way i have the resmed 12v/24v DC converter.

I'd use a 10 amp fuse. If you start blowing them, go with a slow blow fuse.

It looks like the adapter itself is already equipped with a 20A fuse. If that's the case I would probably use a 15A unless it was specified differently. Maybe 10A if you're paranoid, or if your equipment specifies something else then whatever that spec says.

The purpose of the fuse is to protect the wiring, that is, to prevent a fire. You should size the fuse according to the wire you use, which should be sized according to the highest load you could possibly have on the circuit, the length of the run, and the acceptable voltage drop for the application. I have about a dozen 12v outlets on my boat (it seems like I add 1 or 2 every year) and I usually use 12 gauge wire and most of them go to one of two 15 Amp circuit breakers.

If you're using a lot of wire (over 10 feet, which is 20 feet round trip) you should consult a chart like this to size the wire:
http://www.westmarine.com/WestAdvisor/M ... d-Ampacity

And remember, you may be intending a socket for a cpap, but someone else is likely to plug in an inverter and then put a tv, computer, and space heater on that!