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a. Shall be a direct--driven propeller type fan.
b. Shall have aluminum blades riveted to corrosion--resistant steel spiders and shall be dynamically bal anced.
23 81 19.13.O. Special Features, Options and Accessories
1. Integrated Economizers:
a. Integra ted, gear--driven parallel modulating blade design type c apable of simultaneous economizer and com-
pressor operation.
b. Inde pendent m odules for verti cal or horizontal return configurations shall be available. Vertical return modules
shall be avail able as a factory installed option.
c. Damper blades shall be galvanized steel with composite gears. Plastic or composite blades on intake or return
shall not be acceptable.
d. Shall include all hardware and controls to provide free cooling with outdoor air when temperature and/or hu-
midity are below setpoints.
e. Shall be e quipped with gear driven dampers for both t he outdoor ventilation air and the return air for positive
air stream control.
f. Shall be equipped with low--leakage dampers, not to exceed 2% leakage at 1 in. wg pressure differential.
g. Shall be ca pable of introducing up to 100% outdoor air.
h. Shall be equipped with a barometric relief damper capa ble of rel ieving up t o 100% return air.
i. Shall be designed to c lose damper(s) during loss--of--power situations with spring return built into motor.
j. Dry bul b outdoor --air temperature sensor shall be provided as standard. Outdoor air sensor setpoint shall be
adjustable and shal l range from 40 to 100_F/4to38_C. Additi onal sensor options shall be available as ac-
cessories.
k. The economizer controller shall also provide control of an accessory power exhaust unit. function. Factory set
at 100%, with a range of 0% to 100%.
l. The economizer shall maintain minimum airflow into the building during occupied period and provi de design
ventilation rate for full occupancy. A remote potentiometer may be used to override the damper setpoint.
m. Da mpers shall be completely closed when the unit is in the unoccupi ed mode.
n. Economizer controller shall accept a 2--10Vdc CO
2
sensor input for IAQ/DCV control. In this mode, dampers
shall m odulate 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 t he DCV mode, or the exhaust
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 ad-
justable %--open setpoint.
b. Damper shall i nclude 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 damper gear. No linkage arms or control rods shall be acceptable.
e. Damper wil l admit up to 100% outdoor a ir for applicable rooftop units.
f. Damper shall close upon indoor (evaporator) fan shutoff and/or loss of power.
g. The dampe r actuator shall plug into the rooftop unit’s wiring harness plug. No hard wiring shall be required.
h. Outside air hood shall include aluminum water ent rainment filter
3. Manua l damper
a. Manual da mper package shall consist of damper, air inlet scre en, and rain hood which c an be preset to admit
up to 50% outdoor air for year round ventilation.
4. Humidi --MiZer Adaptive Dehumidification System:
a. The Humidi --MiZer dehumidification system shall be factory--installed in the 50TC04--07 rooftop units, and
shall provide great er dehumidification of the occupied space by t wo m odes of dehumidi fication operations
beside i ts normal de sign cooling m ode:
(1.) Subcooling mode furt her subcools the hot liquid re frigerant leavi ng the condenser coil when both temperat-
ure and humidity in the space are not satisfied.
(2.) Hot ga s reheat m ode shall mix a porti on of the hot gas from the discha rge of the compressor with the hot
liquid refrigerant leaving the condenser coil to create a two--phase heat transfer in the system, resulting in a
neutral leaving-- air temperature when only humidity in the space is not satisfied.
50TC
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