Forced air outside wood furnaces ?

Folks at our local consignment auction have had 1 for years. They have several, looks like hanging furnaces in the shop and office area, they have fans blowing out air. But they are hooked into the outdoor furnace. It looks like some sorta fluid is pumped thru lines to these "registers". The first furnace they had blew hot air into the building.   This Is a former car dealership, large building. The heated fluid furnace is warmer than the forced air unit they previously had.

Edited by HD6GTOM - 04 Aug 2021 at 7:31pm

everywhere i've seen people that have them, i don't ever see where they keep the wood under cover, always covered with snow or wet from rain. i guess that if i was to have one i would put a roof over it with the wood under the roof too, sure should make it easier to load each time. i have thought of placing a shipping container outside with the wood furnace in it, filling the rest of the container with the wood. could have it blow hot air or pump hot water either way. kinda nice to put a hole in a side wall instead of a roof of what is being heated. 

Been seeing a number of the older forced air wood furnaces at the local HVAC company, most have cracked heat exchangers they said were due to wider temperature cycling and wood moisture issues as opposed to LP or NG furnaces.  Were too costly as near to expense of complete new unit to just replace the heat exchanger.  Boilers can have freeze issues if not kept running in winter where if have to go elsewhere for a period of time can freeze and burst piping near the boiler, also need to purchase temperature control system with these(Optional) or end up too hot in open run regions and can damage concrete or discharge coils.

If you have an unlimited supply of wood or very cheap access, they work well especially if set up to load with loader bucket.