e.alleg wrote:What is the problem with having a gravity forced air system? I'm talking about having a heat exchanger in the ductwork with hot water flowing through it, or just the furnace hooked to the ductwork and no blower fan. The heat should rise steadily and constantly through the ductwork, no? I hate my 1500cfm blower, I feel that it is too loud.
As Greg says it's a problem with the design size of the duct work. The water analogy would be a fire hose with gravity flow vs. a garden hose with a pump. Both can deliver the same amount of water. Unfortunately you have a duct system designed for use with a blower. With a coal furnace or coal boiler with and air coil you will always have heat in your duct but you still need to move it with a blower. The blower speed will need to be reduced, perhaps unsubstantially. Depending on how fancy a system you want the blower could be replaced with a multi-speed blower or even a variable speed blower. Then you could select the appropriate speed based on the fuel in use. Higher speed for propane, lower speed for coal. Depending on your budget it can all be made automatic. A proportional room thermostat that varies blower speed as a function of the difference between the set point and the current room temperature. At low speed and any reasonable installation it will very quiet. As Greg says try it without the blower on. If you don't like the results AND IF it's a 220V blower AND IF you know what you are doing you could test it at half voltage temporarily, which would lower the speed.