Sealed Combustion Furnace Venting

Vents can also be terminated above the roof.

Sealed combustion furnace venting.

The combustion air intake usually is piped from the exterior of the home to the furnace. For clean comfortable heat when and where you want it the gas flame is completely sealed inside away from all contact with room air. This does not mean that this is the size piping needed for proper venting. These types of furnaces have a dedicated pipeline that runs directly from an outside vent into a sealed combustion chamber of the furnace and a sealed vent to the outside of the home for venting the toxic fumes from the combustion process.

Air necessary for combustion is drawn into the chamber from outside through the vent and combustion products are vented directly to the outside. The key is that you have to install air inlets so that the furnace or water heater gets the combustion air it needs when it s running. When a furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space containing the furnace the return air may also be handled by duct s sealed to the furnace casing and terminating outside the space containing the furnace. Most sealed combustion furnaces are provided with 2 intake and exhaust ports.

Called high low vents one must terminate within a foot of the ceiling and the other within a foot of the floor. These furnaces draw combustion air from and release combustion byproducts directly to the outdoors. Due to high efficiency furnaceshaving their own fresh air intake no air is drawn from inside your home. Only clean gentle heat in continuous circulation is delivered into the room.

All penetrations must be air sealed as well. It provides a direct intake vent that brings outside air to the sealed combustion chamber with one pipe while a second vent pipe provides sealed venting of exhaust gases back to the outside of your house. Unlike conventional furnaces a condensing furnace often uses a sealed combustion chamber and direct vent combustion air. This means the furnace does not take air already heated by the furnace and use it for combustion.

You must do the math. The installation manual will have a venting chart which gives maximum lengths for each size of piping allowable. The highest performance combustion furnaces are sealed combustion direct vent condensing gas furnaces with an annual fuel utilization efficiency afue exceeding 94.