5.
15604-7
AUTOMATIC TEMPERATURE CONTROL (ELECTRIC)
b. Economizer cooling: When the temperature at the outside air temperature
sensor falls below 60°F and the outside air enthalpy is less than the return
air enthalpy during occupied periods; the supply fan shall be in the
occupied mode; and the outside air, exhaust air, and return air dampers
shall modulate from minimum to 100% as necessary to maintain a
discharge air temperature of 60°F (adj.) at the discharge air temperature
sensor.
Safeties:
a. Smoke: If the associated duct smoke detector senses smoke in the air
stream; the RTU fans and compressors shall be de-energized; the return,
exhaust, and outside air dampers shall close; and an alarm and detailed
notification shall be sent to the SCADA system alerting the operator to the
condition.
b. Freeze protection: When the temperature at the discharge air temperature
sensor falls below 45°F (adj.), the outside air and exhaust air dampers shall
close, the return air damper shall open fully, and an alarm and detailed
notification shall be sent to the SCADA system alerting the operator to the
condition. When the temperature at the discharge air temperature sensor
rises above 45°F (adj.), normal operation shall resume.
B. Variable Air Volume Terminal Units (VAV):
1.
Integral digital controls shall operate the unit per the following sequence:
a. Occupied/unoccupied schedule shall be interlocked with CRTU-1.
b. Heating: When the temperature falls below 50°F at the outside air
temperature sensor, the VAV units shall be in heating mode.
i. Occupied operation: The primary air damper shall open to minimum
position.
ii. | Unoccupied operation: The primary air damper shall be closed.
c. Cooling: When the temperature at the outside air temperature sensor rises
above 50°F, VAV units shall be in cooling mode.
i. Occupied operation: The primary air damper shall modulate
between minimum and maximum position as necessary to maintain
the cooling setpoint, 74°F (adj.), at the zone temperature sensor.
ii. | Unoccupied operation: The primary air damper shall be closed. If
the temperature at the zone temperature sensor rises above 85°F
(adj.) The primary air damper shall open to maximum position and
a signal shall be sent to CRTU-1 that unoccupied cooling is required.
C. Packaged Heat Pump Air Handling Unit (CRTU-2&3):
l.
2.
Occupied/unoccupied schedule shall be programmed as provided by the owner.
Supply fan:
a. Occupied operation: the fan shall be energized and operating
continuously.
b. Unoccupied operation: the fan shall be de-energized.
Ventilation:
a. Occupied operation: The outside air damper shall be open to minimum
position and the return air damper open to maximum position to provide
ventilation air.
13089K
