connections, and access doors.
2.2.3.1
Test Holes
Provide factory fabricated, airtight, and noncorrosive test holes with
screw cap and gasket. Provide extended neck fittings to clear insulation.
2.2.3.2
Round Elbows
Provide 45 degree and 90 degree elbows of 2 piece die stamped construction
for ducts 200 mm 8 inches or less in diameter. For ducts over 200 mm 8
inches in diameter, provide 5 mitered piece for 90 degrees and 3 mitered
piece for 45 degrees.
2.2.4
Round and Oval Ducts
Make joints between sections of duct and fittings with mating angle rings,
beaded sleeve joints or slide-on gasketed flange connections. Slide-on
gasketed flange joints shall consist of two mating flange rings. The
flanges shall be fabricated with an integral mastic to make them
self-sealing. The flanges shall be joined to the duct with spot-welds or
self-tapping screws. A neoprene gasket shall be used between the flanges.
Final joining of the slide-on flange connection shall be made with four
bolts for flat-oval ducts. A single-bolt closure ring shall be used to
complete the round slide-on flange connection.
2.2.5
Rectangular Ducts
Except as specified or indicated otherwise, make joints between sections of
duct and between ducts and fittings with mating angle flange joints, other
joints recommended in SMACNA HVAC Duct Const Stds, Section 1, or slide-on
gasketed flange connections. Reinforce at the joints and between the
joints. The slide-on gasketed flange connections shall consist of two
mating flange frames. The frames shall be made up from four pieces of
straight roll formed flange and four corner pieces. The flange shall be
fabricated with an integral mastic to make them self sealing. The corner
pieces shall be made with a downset to allow the corner of the duct to
protrude past the corner piece. The frame shall be joined to the ductwall
with spotwelds or self-tapping screws. A butyl gasket shall be used
between the flanges. Gasket must pass UL 723 and shall not contain
vegetable oils, fish oils or any other type vehicle that will support
fungal and/or bacterial growth associated with dark areas of ductwork. The
connection shall be completed using drive-on corner clips and snap-on
cleat. Cleat spacing and fastener spacing shall be as dictated by the
manufacturer. For joint systems , follow the manufacturer's construction
and installation guidelines.
2.2.6
Sound Attenuators (Traps)
Provide factory fabricated attenuators that will reduce the rated sound
pressure level of the fan down to at least 65 decibels in the 250 Hz (3rd
octave band) center frequency by using a reference sound source calibrated
in decibels of sound power at 10-12 watts. Maximum permissible pressure
drop shall not exceed 160 Pa 0.63 inch of water. Attenuators to be
constructed air-tight when operating under an internal pressure of 2500 Pa
10 inches of water. The air-side surface shall be capable of withstanding
air velocity of 50 meters per second 10,000 feet per minute. When
attenuators are submitted for approval, provide manufacturer's
certification of the sound reduction values. Sound absorbing material
SECTION 15810N
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