How To Calculate Open Fireplace Flue Size. They use far less fuel (compared to an. If rectangular/square flues are used the minimum dimension should not be not less than 200mm.
19 revised select fireplace opening dimensions a and b and the corresponding flue liner size, l and m. To calculate what size of fire or stove you will need, measure the width, length, and height of the room or space and multiply the three figures together to obtain the cubic area of the space to be heated. When sizing a fireplace for a square or rectangular liner the 1/10 ratio should be used.
If a chimney’s diameter is six inches, then the flue should also measure six inches.
Round flues are always designated by their actual inside diameter. The rule of thumb for sizing a chimney liner is that you never want it to be smaller than the appliance exhaust hole and you don't want the liner to be three times the area of the exhaust hole of the appliance. In an open combustion fireplace there is no control over combustion air, thus accelerating the combustion air intake as the temperature in the fireplace increases, resulting in heat loss through the flue outlet. If you have a hood above your fireplace then your need to add up the lengths of all sides of the hood that are open (usually the front and sides) and enter that in the width box.