Boyertown Regal Oil Furnace Nrg Max - Manual (Page 13)

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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 furnace 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.
Evidence of potential or existing chimney damage should be determined by visual inspection of the
chimney and liner. Exterior indicators such as missing or loose mortar/bricks, white deposits on the
brick or water stains on the interior building walls should be investigated further. The operational flue
temperatures for furnaces range from 350
º F to 550 º F at the outlet of the furnace. These temperatures
are further reduced before reaching the chimney due to heat loss through the vent connector and
dilution from the draft regulator. The resulting flue gas temperatures may become low enough to
form condensation on the chimney liner walls.
To prevent condensation, it is necessary that the internal chimney wall temperature always be kept
above the dew point of the flue gasses. If the chimney is a masonry type, it may have to be lined with
a flue liner, if the temperature loss is too great for the furnace. A liner will act as an insulator and
reduce the flue gas temperature loss. Insulation may be added around the liner for further temperature
stability. Refer to NFPA-31 for recommended liner sizing tables as developed by the Oil Heat Vent
Analysis Program.
Chimney Connector
The chimney connector pipe between the furnace and chimney shall be of equal diameter as the flue
outlet of the furnace. Refer to furnace specifications in this manual for proper size flue pipe for your
model furnace. Any reduction in size required for the chimney must be made at the chimney
connector. The vent connector pipe must be made of 24 gauge (or thicker) corrosion-resistant steel.
The vent connector pipe should be as short as possible and installed so that it has a continuous rise
from the furnace to the chimney. Long horizontal vent runs can result in the possibility of
condensation in the flue pipe or the chimney. All horizontal runs of vent connector pipe should be
pitched upward a minimum of 1/4 inch per foot of run. The horizontal length of the vent pipe
connector shall not exceed 10 feet. The chimney connector shall be installed so as to minimize the