pdemarest wrote: I want to carry a small space heater and most of them pull 12.5 amps when running on "High". Will the 110 volt outlets in my 2003 Premier handle that?
Yes they should. The outlets (with the exception of the dedicated microwave outlet) are all on one 15 amp circuit. Thus 12.5 amps should be fine. The caveat would be are you running anything else on the outlets circuit, and how many amps is/are they consuming.
pdemarest wrote: Is there any particular outlet I should use and will I be able to simultaneously use my microwave without blowing a fuse?
As mentioned above, all of the AC outlets are on the same circuit, fused at 15 amps (14 gauge wire). The exception being the dedicated microwave outlet (in the dining upper cabinet in my rig), which has its own circuit and a 20 amp fuse (12 gauge wire).
So, presuming you want to keep the microwave plugged in to the microwave outlet, and presuming you have 30 amp service, then you need to add together the draw of the microwave (which is more than the "watts" it can cook with - look at the power label to check how many it draws), and the draw of the heater, plus anything else you are running, and those can't exceed 30 amps (nor can you exceed 15 amps on all of the non-microwave outlets added together).
I carry a small electric heater that is the common type you can buy at Walmart or anywhere (something like 10" x 11" x 3"), and it has three heat settings (just fan, low heat, medium heat, high heat). I find that handy for managing not just heat but also power consumption. For example high is 1500 watts, hence about 13 amps; medium is, IIRC, 1,000 watts or about 9 amps; low is 750 watts, or about 6.5 amps. I don't use the dial that acts like a thermostat, but simply turn that one all the way up and then select either low, medium, or high depending on how much heat I want or how much power I can spare.
I can't remember the exact figures for my stock microwave, but just for example if it were a "1500 watt" unit, that might mean it draws 1800 watts and outputs 1500 watts - because it's not 100% efficient (will specify on label probably on the rear). 1500 watts รท 115 volts would mean it would draw around 13 amps. So if that were the case, and you didn't have other large loads going, you could theoretically run microwave and heater on high on a 30 amp service. I say theoretically because I can't speak to surges, etc. You can also just turn the heater down to low.
BG
PS: Slightly off topic, but I re-purposed my microwave outlet by moving it down to the floor by the stove kick space. That way it's a dedicated electric heater outlet, with all the other outlets being on a separate circuit. So I have a theoretical 35 amps available for outlets (obvs could only use 30 tho). That's only useful if you don't want the microwave though.