Central Boiler manufactures and distributes the Classic, Classic Edge and E-Classic outdoor wood furnaces. These outdoor wood-fired hydronic heaters can heat multiple buildings, hot tubs, pools, greenhouses and more. While burning a wood stove indoors can mean many problems, there is an alternative...a Central Boiler outdoor wood furnace. Also known as an outdoor wood boiler or outdoor hydronic heater, an outdoor wood furnace eliminates the problems associated with indoor burning and allows you to get even more benefits from wood heat. Central Boiler outdoor wood furnaces can actually improve the indoor environment, while eliminating the time-consuming chore of tending a traditional wood stove.