This does not mean that this is the size piping needed for proper venting.
Sealed combustion furnace 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.
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.
Called high low vents one must terminate within a foot of the ceiling and the other within a foot of the floor.
The combustion air intake usually is piped from the exterior of the home to the furnace.
In a direct vent system you can readily see the two pipes emerge through the side of your house.
The gas flame is completely sealed inside away from all contact with room air.
Vents can also be terminated above the roof.
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.
Only clean gentle heat in continuous circulation is delivered into the room.
For clean comfortable heat when and where you want it the gas flame is completely sealed inside away from all contact with room air.
The highest performance combustion furnaces are sealed combustion direct vent condensing gas furnaces with an annual fuel utilization efficiency afue exceeding 94.
The installation manual will have a venting chart which gives maximum lengths for each size of piping allowable.
Air necessary for combustion is drawn into the chamber from outside through the vent and combustion products are vented directly to the outside.
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.
All penetrations must be air sealed as well.
The space saving direct vent furnace design mounts to an exterior wall and the adjustable vent assembly adjusts to fit walls from 4 1 2 in.
You must do the math.
Due to high efficiency furnaceshaving their own fresh air intake no air is drawn from inside your home.