RV furnaces such as Atwood do no need an inverter. They run on 12 volts DC from a battery.
Expect to consume about 8 amp-hour of battery power. A typical Group 24 battery has about 80 amp-hour of capacity with only 50% usable since you do not want to go below 50% state of discharge (it shorts battery life a lot). If
So for a 2 nights of heater use if you are sleeping in it, your best bet is to use tow golf cart batteries wired in series for 12 volts. This will give you about 110 amp hours of battery capacity.
To run the heater on a generator you will need a converter which converts 120 volts AC from the generator to 12 volts DC. A progressive dynamics converter will allow this and also recharge your batteries.
An inverter converts 12 volts DC to 120 volts AC. Use the smallest inverter possible since inverters have a parasitic load that increases with capacity. Also, a 2000 watt inverter to power a TV will consume more electricity then a 1000 watter inverter to power the same TV because inverters are more efficient at near max load capacity.
30k BTU should be plenty and mount on side wall high or low depends on your preference and trailer use and ducting can take care of the rest. Most folks build a shelf to mount the heater.
You will need a propane tank, a line with connector two a 2 stage propane gas regulator. It must be 2 stage. RV heaters use only .4 psi of gas pressure and the tank pressure is anywhere from 130 to 350 psi depending on temperature.
From the regulator you can use black pipe which is on my RV or copper pipe which is what is found on newer RVs.
Use of a propane heater in a trailer requires a propane leak detector, a carbon monoxide and smoke detector. Mount propane gas leak detector on floor since propane is heavier then air.
Propane tanks to feed heater must be mounted outside.
Here is a good website with more info:
http://www.hardcoresledder.com/foru...stall-heater-enclosed-snowmobile-trailer.html I do not agree with only plumbing the heater exhaust to the outside. You need to plumb air intake for heater to outside also or you can risk consuming all of the oxygen in your trailer when it is in use and doors are closed.
Feel free to contact me regarding electricity and stuff. I have a fifth wheel RV and installed a very impressive solar system with all of the bells and whistles.