efficiency, condensing type furnaces are not used.
Conventional vents are not needed for condensing
furnaces due to the low exhaust air temperature.
Precautions should be taken due to the acidic
condition of the condensate. The location and size
of the vents should be shown on the drawings.
Consult NFPA 54, UL 1738, and available vendor data
to design the vents. The vents can be mounted on
the roof or exterior wall with proper separation.
The vents should be extended above the typical snow
level. Vents should be located in such a manner as
to prevent vandalism and to prevent discharge of
condensate across walkways.
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Direct venting shall be used for condensing type furnaces. Both the air
intake and exhaust vents shall be sized and located as indicated on the
drawings and as recommended by the boiler manufacturer. A separate
combustion air intake vent and exhaust shall be provided for each furnace.
Plastic materials polyetherimide (PEI) and polyethersulfone (PES) are
forbidden to be used for vent piping of combustion gases.
2.2.6.1
Combustion Air Intake Vent
The combustion air intake piping shall be constructed of Schedule 40 PVC in
accordance with ASTM D 1784. The vent shall be suitable for the
temperature at the furnace combustion air intake connection point. Each
intake shall be provided complete with bird screen.
2.2.6.2
Exhaust Vent
The exhaust vent piping shall be constructed of Schedule 40 CPVC or
stainless steel in accordance with UL 1738 and the furnace manufacturer's
recommendations. The exhaust vent shall be suitable for the maximum
anticipated furnace exhaust temperature and shall withstand the corrosive
effects of the condensate. A 8 mm 0.3125 inch diameter hole shall be
provided in the stack not greater than 152 mm 6 inches from the furnace
flue outlet for sampling of the exit gases. A method shall be provided to
seal the hole to prevent exhaust gases from entering the indoor space when
samples are not being taken. Each exhaust stack shall be provided complete
with bird screen.
2.3
AIR CONDITIONING EQUIPMENT
Cooling coils, condensers and related equipment shall be as specified in
Section [15700A UNITARY HEATING AND COOLING EQUIPMENT] [[_____]].
2.4
CONTROLS
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NOTE: The designer should indicate the desired
sequence of operation on the drawings. Depending on
the fuel type and size, some manufacturers offer
single stage, two stage, or variable speed
operation. Prior to specifying two stage or
variable speed operation, the designer should
coordinate the selection with furnace manufacturers.
The designer should consider the use of
programmable thermostats for facilities that will
SECTION 15566A
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