I found a Suburban NT-12SE furnace on the net that seems tiny but mentions the use of a 12 volt battery with a 2.8 amp draw....does this mean you need power for it? ?? I always though these Direct Discharge furnaces didn't need power?
I think that's the same model I have in my 12-1/2' Scotty. 12,000 BTU. I have stayed in it down to about +20°F and then it was only running at about a 50% duty cycle to keep it ~70°F inside. Should be good to zero at least without too much bother.
Yes, the drawback to those is that they need 12V power to run. There is an electric motor with a fan blade on each end; one to circulate the hot air from the heat exchanger out into the camper, the other for a forced draft to bring in outside combustion air and push out exhaust gasses. There is a "flag switch" which will prevent the burner from firing if there is insufficient airflow, either from a blocked vent or low battery
voltage. They include a circuit board which gives a pre and post purge.
The advantage is that they are very compact and can intake and exhaust directly through the side wall, no flue pipe required.
If you go with this model, let me know as I have information sheets and repair manuals in .pdf format that I'd be happy to E-mail to you.