Boyertown Regal Oil Fired Furnace Variable Speed 2 Stage ECM Motor - Manual (Page 13)

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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
number of elbows and to avoid sharp turns or other construction features that would create excessive
resistance to the flow of flue gasses. Tees may be used in a straight section in conjunction with a
barometric draft regulator; however, they must not be used for a 90° turn. No device that will obstruct
the free flow of flue gasses shall be installed in the chimney connector. This does not exclude the use
of devices specifically designed for the use in chimney connectors such as automatic dampers. The
vent pipe should be joined with metal screws and supported by straps. A thimble should be used to
connect the vent connector pipe to the chimney so the pipe may be readily removed in case of
inspection or replacement.
No chimney connector shall pass through any floor or ceiling. The vent connector pipe must not pass
through a combustible wall or partition unless they are guarded at the point of passage by a ventilated
metal thimble not less than 12 inches larger in diameter than the connector, on metal or fireclay
thimbles adequate protection is provided at the passageway. An acceptable passageway could be
either an approved, ventilated metal thimble which is at least 12 inches larger in diameter than the
vent connector pipe, or brick work which is at least 8 inches thick constructed into the wall and
surrounding the vent connector
Clearances from combustible materials or materials shall be in accordance with the clearances given
in Tables 1 or 2. The vent connector pipe should extend only to (and not beyond) the inside wall of
the chimney. A thimble should be used to connect the vent connector pipe to the chimney so that the
vent connector pipe may be readily removed in case of inspection or replacement.
Connection to the chimney must be made above the bottom of the chimney to avoid blockage. Vent
piping should extend just into the chimney far enough to expel flue gasses. Inserting the vent piping
too far into the chimney will cause undue obstruction. Use a thimble or a slip joint where vent pipe
enters the chimney to allow easy removal for cleaning.