The furnace supply ducts in central heating systems are designed to ensure that the furnace itself, as well as the room from which it is operating, does not become overheated. Furnace supplies and ductwork must be sealed at the source of the supply duct to prevent the formation of condensate. If the furnace becomes overheated and condensate builds up in the ductwork, condensate leaks into the attic, or condensate from the attic can escape and get into the house. The temperature can then rise to dangerous levels, causing a fire. There are a number of situations where furnace supplies are not properly sealed.
First, furnace supply ducts should not be blocked by debris or excess pipe work. Second, furnace supply ductwork that leads to the furnace itself should be installed with the proper equipment so that the duct will be completely insulated and the pressure will be properly maintained. Third, furnaces should be maintained at a temperature level that will not overheat. The furnace should not be operated at higher temperatures than necessary.
The furnace should be regularly inspected for leaks and clogs. If a leak or clog develop, repair should be done before the furnace is turned on to avoid any further damage. The repair may be costly but when the damage is fixed the furnace should last longer and the repair should save money over the life of the furnace.
There are different types of furnace ductwork that should be properly sealed. Condensate gases that are produced by the furnaces are not a problem, but if condensate is leaking into the attic or out of the house, condensate is a potential fire hazard. For these reasons, furnace supply lines should not be connected to rooms where there is a possibility that condensate is escaping and condensate will become airborne.
In addition to sealing furnace supply ductwork, furnace supply lines should also be protected by fire safety appliances. These include emergency breakers. If the emergency shutoff is set at the right amount of water pressure, the emergency shutoff will not cause excessive water pressure and will not cause the water pipes to burst. If the emergency shutoff is set too low, the water supply may become unsafe and the fire department could be called.
Furnace supply ducts should also be inspected for problems, including signs of wear, damage, and rust. Furnace manufacturers recommend that their furnaces are replaced every ten to twenty years depending on the model of the furnace.