I have not installed my
furnace yet, but I would think that 45 minutes would not be enough time to heat it up.
I just picked up and original heater and tested it sitting on my work bench, it took about an hour or so to really start to pump out some heat, ...........enough heat that i couldn't hold my hand above the grate, ......
so if it took about an hour to get just hot enough to prevent my hand from being held close to the vents, I would think it would take even longer to warm the entire trailer, ........
just for giggles i would turn it on around dinner time, and then come and check it before you go to bed, and see how it does then!!!!
something I have been thinking about since purchasing this little heater is to add a small 12V computer fan behind the heater (there is a small opening behind the regulator/gas hook up area) that i think would help push hot air a little better out of the vents which may aid in circulating the heat into the trailer, ......but I am not sure how this would affect the air flow of exhaust and fresh air intake?, ..............going to be experimenting shortly as out annual family thanksgiving camping weekend is coming up fast........