It is not recommended because an oil, propane, or gas furnace uses a blower that generates between 1,000 and 2,500 CFM. Most of the time, the Kuuma Vapor-Fire will operate at low speed with only 600 CFM to deliver continuous yet gentle heat throughout the house. A high-volume blower is intended for periodic operation and not continuous like the Kuuma Vapor-Fire, which will provide more stable and comfortable heat. It’s ideal to common the furnaces in parallel and not in series, for information on how to common (click here).
