a. Casing: Provide removable full bottom access panels for servicing
internal components without disturbing duct connections. Insulate
inside of casing with manufacturer's standard insulation. Units shall
have recirculating air inlet equipped with filter frame, round primary
damper or valve, and unit mounting brackets.
b. Fans and motors: Provide centrifugal, forward curved, multiblade,
fan wheels with direct-drive motors. Motors shall be high efficiency
permanent-split capacitor type with thermal overload protection and
permanently lubricated bearings. Motors shall have three speeds or be
equipped with solid state speed controllers. Provide isolation between
fan motor assembly and unit casing. Fan and motor shall be removable
through casing access panel.
c. Flow sensor: Sensor shall be ring or cross type with minimum of two
pickup points which average the velocity across the inlet. Flow
measurement shall be within plus or minus 5 percent of rated airflow
with 1.5 diameters of straight duct upstream of unit and inlet static
variation of 124 to 1240 Pa (gage) 0.5 to 5.0 inches water gauge. Flow
measuring taps and calibration flowchart shall be supplied with each
unit for field balancing airflows.
d. Primary VAV damper or valve: Galvanized steel damper blade shall
close against gasket inside unit. Connect damper to operating shaft
with a positive mechanical connection. Provide nylon bearing for
damper shaft. Cylindrical die cast aluminum valve inlet tapered to fit
round flexible ducts with integral flow diffuser and beveled
self-centering disc. Damper or valve leakage at shutoff shall not
exceed 2 percent of capacity at 249 Pa (gage) 1 inch water gauge
pressure.
e. Regulator: Volume regulator shall be electronic. Electronic
controls contained in NEMA ICS 6, Type 1 enclosure sealed from airflow.
Controls shall be mounted on side of unit or on air valve. System
powered regulators shall not be permitted. Volume regulator shall
reset primary air volume as determined by thermostat, within upstream
static pressure variation noted in paragraph entitled "Flow Sensor."
Volume regulators shall be field adjustable and factory set and
calibrated to indicated maximum and minimum primary airflows. Volume
regulators shall be direct acting and normally [open] [closed] upon
loss of pneumatic pressure.
f. Electrical: Unit shall incorporate single point electrical
connection with electrical disconnect. Electrical components shall be
UL or ETL listed and installed in accordance with NFPA 70. Electrical
components shall be mounted in control box. Units UL or ETL listed as
an assembly do not require airflow switch interlock with electric
heating coil when factory assembled.
g. Filters: Provide UL listed throwaway 25 mm one inch thick
fiberglass filters, standard dust-holding capacity.
2.9.3.7
Reheat Units
a. Hot Water Coils: Hot-water coils shall be fin-and-tube type
constructed of seamless copper tubes and copper or aluminum fins
mechanically bonded or soldered to the tubes. Headers shall be
constructed of cast iron, welded steel or copper. Casing and tube
support sheets shall be 1.6 mm 16 gauge, galvanized steel, formed
SECTION 15895
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