2.9.3
Variable Air Volume (VAV) and Dual Duct Terminal Units
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NOTE: Delete reheat coils when not required.
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VAV and dual duct terminal units shall be the type, size, and capacity
shown and shall be mounted in the ceiling or wall cavity and shall be
suitable for single or dual duct system applications. Actuators and
controls shall be as specified in paragraph CONTROLS. Unit enclosures
shall be constructed of galvanized steel not lighter than 0.85 mm 22 gauge
or aluminum sheet not lighter than 1.3 mm 18 gauge. Single or multiple
discharge outlets shall be provided as required. Units with flow limiters
are not acceptable. Unit air volume shall be factory preset and readily
field adjustable without special tools. Provide reheat coils as indicated.
Attach a flow chart to each unit. Base acoustic performance of the
terminal units upon units tested according to ARI 880. Sound power level
shall be as indicated. Discharge sound power shall be shown for minimum
and [375] [_____] Pa [1-1/2] [_____] inches water gauge inlet static
pressure. Acoustical lining shall be according to NFPA 90A.
2.9.3.1
Constant Volume, Single Duct Terminal Units
Constant volume, single duct, terminal units shall contain within the
casing, a constant volume regulator. Volume regulators shall control air
delivery to within plus or minus 5 percent of specified air flow subjected
to inlet pressure from 200 to 1500 Pa 3/4 to 6 inch water gauge.
2.9.3.2
Variable Volume, Single Duct Terminal Units
Provide variable volume, single duct, terminal units with a calibrated air
volume sensing device, air valve or damper, actuator, and accessory relays.
Units shall control air volume to within plus or minus 5 percent of each
air set point volume as determined by the thermostat with variations in
inlet pressures from 200 to 1500 Pa 3/4 to 6 inch water gauge. Internal
resistance of units shall not exceed 100 Pa 0.4 inch water gauge at maximum
flow range. Provide external differential pressure taps separate from the
control pressure taps for air flow measurement with a 0 to 250 Pa 0 to 1
inch water gauge range.
2.9.3.3
Variable Volume, Single Duct, Fan-Powered Terminal Units
Provide variable volume, single duct, fan-powered terminal units with a
calibrated air volume sensing device, air valve or damper, actuator, fan
and motor, and accessory relays. Units shall control primary air volume to
within plus or minus 5 percent of each air set point as determined by the
thermostat with variations in inlet pressure from 200 to 1500 Pa 3/4 to 6
inch water gauge. Unit fan shall be centrifugal, direct-driven,
double-inlet type with forward curved blades. Fan motor shall be either
single speed with speed controller or three-speed, permanently lubricated,
permanent split-capacitor type. Isolate fan/motor assembly from the casing
to minimize vibration transmission. Fan control shall be factory furnished
and wired into the unit control system. Provide a factory-mounted pressure
switch to operate the unit fan whenever pressure exists at the unit primary
air inlet or when the control system fan operates.
2.9.3.4
Dual Duct Terminal Units
Provide dual duct terminal units with hot and cold inlet valve or dampers.
SECTION 15895
Page 46
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