A chimney sweep should service your furnace flue after each heating season. When he removes the connector pipe and opens the cleanout door, he can find one or more of the following:
-Small particles of the chimney liner that have fallen to the base of the chimney
-No chimney lining
-A cracked or broken flue tile
-A wet chimney
These are just some of the problems that can cause poor chimney performance. Most of them can be corrected by relining your chimney.
Old Appliances
The long term effects on the clay tile flue liners venting ol fired
appliances can be gradual deterioration of the liner due to acidic nature
of the chimney residue. This process can occur over many years. The
liner walls can soften and flake off material opening holes through
the liner walls. If this happens, the flue must be relined.
New Appliances
New high efficiency oil fired appliances require smaller flue sizes
than older units. Where an old unit may require an eight inch flue,
the replacement unit’s installation instructions may call for
a five inch flue. This is a 60% reduction in flue size. Couple that
with lower glass temperatures of new units and the flue size becomes
much more critical to the proper operation of the present day oil fired
appliance.
In cold, oversized masonry chimneys, the less hot flue gases of modern
appliances quickly expand and cool even more.
Draft is drastically reduced because it depends upon the buoyancy of the hot flue gases. The cooler the gases become, the slower they move up the flue and the more the draft is reduced. This will reduce an appliance’s efficiency and increase fuel consumption. The longer the flue gasses remain in the flue, the greater the risk of leakage into the home.
Water Vapor, a normal by product of combustion, condenses on the cool internal surfaces of oversized flues. This problem is worse in exterior chimneys and cold climates. The resulting moisture can be absorbed by the chimney and transferred through the walls. It may cause paint to peel, and wallpaper and plaster to fall. In winter, wet chimneys experience numerous freeze/thaw cycles causing bricks and clay tile liners to spall or flake, mortar joints to erode, and water leakage at te bottom of the chimney.
Dangerous Carbon Monoxide gases can be forced into your home through open mortar joints, cracked flue liners and flues blocked by debris.
Deterioration Of The Flue Liner can occur when venting oil fired appliances.
Chemical compounds such as sulfur residues from oil chlorides from the
laundry area, when combined with water, form a highly aggressive acids,
capable of causing considerable damage to flue tiles in masonry chimneys.
How Can These Problems Be Solved?
Retrofitting a chimney with a UL Listed, properly sized and properly
installed chimney lining system is the most important and easiest way
to prevent these problems.
A properly sized chimney lining system will insure correct draft by
preventing the flue gases from expanding and cooling more than they
should. Properly sizing a chimney liner will greatly reduce condensation
within the venting system. The hot and buoyant flue gases will remain
hot, exit the flue quicker, cool less and be much less likely to condense
on the chimney or liner walls.
By using a watertight flue liner any condensation that might form is
contained within the liner, thereby avoiding further damage to the chimney
from freeze/thaw cycles and corrosion from the highly acidic condensate.
A UL Listed stainless steel flue liner or a UL Listed, cast in place
chimney lining system designed to vent the flue gases of oil fired appliances
should be installed.
A Final Point Concerning Equipment Performance
And Efficiency
A new chimney lining system for your oil fired appliance can improve
its performance and increase the life of your chimney. Increased oil
burner efficiency means less oil is required to heat your home. This
reduces your phone bill.
