nor less than thickness of stack, whichever is larger. Plastic materials
polyetherimide (PEI) and polyethersulfone (PES) are forbidden to be used
for vent piping of combustion gases. The clear distance between any
portion of the breeching surface and any combustible material shall not be
less than that specified in NFPA 211. Joints and seams shall be securely
fastened and made airtight. Suitable hinged and gasketed cleanouts shall
be provided, which will permit cleaning the entire smoke connection without
dismantling. Flexible-type expansion joints shall be provided as required
and shall not require packing.
2.11.4.2
Stacks
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NOTE: Frequently boiler outlets are designed to
support no more than the weight of a 6 m (20 foot)
stack section, when installed directly above the
boiler outlet. Ensure that the stack is properly
supported.
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[Individual stub stacks shall extend above the roof to the heights
indicated. Individual stub stacks shall be [6] [_____] m [20] [_____] feet
in height when assembled on the boiler and measured from the ground line.
Stack section shall be sheet steel having a thickness of not less than 2.47
mm 0.0972 inch.] [Prefabricated double wall stacks system shall extend
above the roof to the height indicated. The stacks shall be [6] [_____] m
[20] [_____] feet in height when assembled on the boiler and measured from
the ground line. The inner stack shall be [304 stainless steel] [316
stainless steel] having a thickness of not less than 0.89 mm 0.035 inch.
The outer stack shall be sheet steel having a thickness of not less than
0.635 mm 0.025 inch. A method of maintaining concentricity between the
inner and outer stacks shall be incorporated. The joints between the stack
sections shall be sealed to prevent flue gas leakage.] A 7.92 mm 0.3125
inch diameter hole shall be provided in the stack not greater than 150 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 boiler room when samples are not being taken. Each stack
shall be provided complete with rain hood. Plastic materials
polyetherimide (PEI) and polyethersulfone (PES) are forbidden to be used
for vent piping of combustion gases.
2.11.5
Direct Vents
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NOTE: Delete this paragraph if condensing boilers
are not used. A conventional stack is not needed
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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SECTION 15569A
Page 43
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