[quote="kirklehook"]So you're blowing directly into your cold-air return. Hmmm.... Thats a great idea! Preheating the air would definitely cut down on the run time of your other furnace. However, I plan on using my Koker as the main heat source, and only using propane if for some reason my Koker goes down. Which is why I was curious if the air would sometimes run backwards through my propane unit if it isn't blocked-off in some fashion.[/quote]
You see, if I pumped hot air into the hot air vents and the furnace came on, the 2 hot air currents coming from two different directions would create turbulence. The furnace blower would eventually win and cause the hot air from the coal stove to back up. That could cause my coal stove to overheat because it would not be able to wash the heat away from itself, thus losing the heat and wasting coal.
I'm not familiar with your unit, but if your blower is strong enough you can pump your heat through the main plenum and let the propain contols in the furnace plenum blow the heat throughout your home!