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l. The economizer shall maintain minimum airflow into the building during occupied period and provide
design ventilation rate for full occupancy. A remote potentiometer may be used to override the damper set
point.
m. Dampers shall be completely closed when the unit is in the unoccupied mode.
n. Economizer controller shall accept a 2--10Vdc CO2 sensor input for IAQ/DCV control. In this mode,
dampers shall modulate the outdoor --air damper to provide ventilation based on the sensor input.
o. Compressor lockout sensor shall open at 35_F(2_C) and close closes at 50_F(10_C).
p. Actuator shall be direct coupled to economizer gear. No linkage arms or control rods shall be acceptable.
q. Economizer controller shall provide indications when in free cooling mode, in the DCV mode, or the ex-
haust fan contact is closed.
2. Two--Position Damper
a. Damper shall be a Two-- Position Damper. Damper travel shall be from the full closed position to the field
adjustable %--open setpoint.
b. Damper shal l include adjustable damper travel from 25% to 100% (full open).
c. Damper shall include single or dual blade, gear driven dampers and actuator motor.
d. Actuator shall be direct coupled to economizer gear. No linkage arms or control rods shall be acceptable.
e. Damper will admit up to 100% outdoor air for applicable rooftop units.
f. Damper shal l close upon indoor (evaporator) fan shutoff and/or loss of power.
g. Design shall incorporate inherent barometric relief capabilities for barometric relief of rooftop unit return
air.
h. The damper actuator shall plug into the rooftop unit’s wiring harness plug. No hard wiring shall be re-
quired.
i. Outside air hood shall include aluminum water entrainment filter
3. Manual damper
a. Manual damper package shall consist of damper, air inlet sc reen, and ra in hood which can be preset to
admit up to 50% outdoor air for year round ventilation.
4. Head Pressure Control Package
a. Controller shal l control coil head pressure by condenser--fan speed modulation or condenser--fan cycling
and wind baffles.
b. Shall consist of solid--state control and condenser--coil temperature sensor to maintain condensing temper-
ature between 90_F(32_C) and 110_F(43_C) a t outdoor ambient temperatures down to --20_F(--29_C).
5. Condenser Coil Ha il Guard Assembl y
a. Shall protect against damage from hail.
b. Shall be either hood style or louvered.
6. Unit--Mounted, Non--Fused Disconnect Switch:
a. Switch shall be factory--installed, internally mounted.
b. National Electric Code (NEC) and UL approved non--fused switch shall provide unit power shutoff.
c. Shall be accessible from outside the unit
d. Shall provide local shutdown and lockout capability.
7. Convenience Outlet :
a. Powered convenience outlet.
b. Outlet shall be powered from main line power to the rooftop uni t.
c. Outlet shall be powered from line side or load side of disconnect by installing contractor, as required by
code. If outlet is powered from load side of disconnect, unit electrical ratings shall be UL certified and
rated for additional outlet amperage.
d. Outlet shall be factory--installed and internally mounted with easily accessible 115 --v female receptacle.
e. Outlet shall include 15 amp GFI receptacles with independent fuse protection.
f. Voltage required to operate convenience outlet shall be provided by a factory--installed step--down trans-
former.
g. Outlet shall be accessible from outside the unit.
h. Non--Powered convenience outle t.
i. Outlet shall be powered from a separate 115--120v power source.
j. A transforme r shall not be included.
k. Outlet shall be factory--installed and internally mounted with easily accessible 115 --v female receptacle.
l. Outlet shall include 15 amp GFI receptacles with independent fuse protection.
558J