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10
VENTING
Failure to follow all instructions can result in flue gas spillage and carbon monoxide
emissions, causing severe personal injury or death. All chimneys must meet the requirements of
NFPA 211 and NFPA 31
WARNING
Chimney
The boiler must be connected to an adequate chimney or an approved venting system in accordance with
these instructions. An adequate chimney or venting system is one that is sealed and lined with the capability
of producing a -.04" W.C. flue draft and having the capacity to handle the amount of flue gas that is
introduced. A chimney with an internal construction of corrosion resistant tile, stainless steel, or some other
material that will withstand flue gas temperatures up to 1000
0
F is required.
Masonry and metal chimneys shall be constructed in accordance with applicable building code
requirements. Masonry chimneys shall be lined with an approved clay tile liner or a listed chimney lining
system installed in accordance with manufacturers’ instructions and also meeting the requirements of
NFPA-211 Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances. Metal chimneys
also shall meet the requirements of NFPA-211. Factory built chimneys shall be listed and shall be installed
in accordance with their listing and NFPA-211.
Prior to installation of the boiler, the chimney or venting system shall be examined by the installer and
determined to be in good condition. All joints of the chimney must be tightly sealed. The inside of the
chimney should be free of all obstruction, such as loose brick, broken pieces of tile, or corroded metal. If
chimney flues are divided or there are multiple flues within one chimney, make sure there are no openings
in the partition separating the divided or individual flues. When a new appliance is connected to an existing
chimney, that chimney shall be brought up to current requirements. Chimneys which are relined shall be
done so with an approved liner that will resist corrosion, softening, or cracking from the flue gasses.
All chimney clean-out doors and flue connections must fit tightly so they will seal to avoid air
leakage.
The inside area of the chimney liner should equal, at a minimum,
the area of the vent pipe exiting the
furnace. If more than one appliance is installed, the area of both appliances shall be used in determining the
required inside area of the chimney.
The flue gas exit of a chimney shall be at least 3 feet above the highest point where it passes through the
roof of a building and at least 2 feet higher than any portion of a building within 10 feet of such chimney.
The chimney height will also be determined by the height of the surrounding trees, buildings and terrain.
When chimney downdraft conditions cause faulty operation that creates a hazard, corrective steps must be
taken.
When altering the surrounding obstructions is not possible, a chimney cap can be constructed on the top of
the chimney to avoid downdrafts. The chimney cap should be pyramid shaped on the top with a perfectly
flat surface immediately above the chimney outlet. The hood should be attached by four (4) iron supports.
The four iron supports should be equal in height to the width of the chimney opening. Four plates, flaring
down, can be added to help insure that the wind will pass straight over the chimney outlet.
Chimney Relining
A tile lined masonry chimney serving an oil fired boiler should comply with applicable building codes such
as NFPA-211. An additional listed lining may be required to reduce transient low draft during startup and
acid water condensation during cyclic operation. This is particularly true for high mass masonry chimneys
serving oil fired furnaces of higher efficiency. For masonry chimneys, local experience can indicate how
well construction has withstood the lower temperatures produced by higher efficiency furnaces.