TranSystems Corporation - LGM Construction

501070099 Federal Express Oakland Sort Expansion Issued for Bid 10/11
F. Night Economize Mode [Night Purge Mode]
The AHU shall not be used for Night Heat mode.
1. The BAS time-of-day scheduling application shall support Night Economize functionality.
The Night Economize mode shall be scheduled during the daily block of time when the
outdoor air enthalpy is typically the most effective for economizing.
2. The BAS shall command the VAV Air System to Night economize when all three of the
following conditions are met: temperature of the space is greater than the space’s
occupied cooling setpoint, and the temperature of the space is greater than the Outdoor
Air temperature plus the Minimum Indoor/Outdoor Temperature differential (15 deg F,
adj.), and night economize mode is enabled by the time-of-day schedule.
3. Each VAV box that is associated with the VAS shall control to its occupied cooling
setpoint, and shall modulate box airflow to meet the airflow requirements to cool the
space to the Occupied Cooling setpoint minus the occupied cooling deadband (4 deg F,
adj.).
4. The air handler shall modulate its airflow to maintain the duct static pressure setpoint.
5. Mechanical cooling shall not be used during Night Economize mode.
4.2 DX VAV ROOFTOP UNITS, COOLING ONLY, ECONOMIZER, DDC CONTROLLER (DIRECT DIGITAL
CONTROL)
A. Building Automation System Interface:
1. The Building Automation System (BAS) will send the controller Occupied, Unoccupied,
Optimal Start, Night Heat / Cool, and Timed Override commands. If a BAS is not present,
or communication is lost with the BAS, the controller will operate using its local schedule
and setpoints.
B. Unoccupied Mode:
1. In the unoccupied mode the rooftop unit (RTU) will cycle as required to maintain the
adjustable (adj) unoccupied space heating and cooling setpoints. The variable frequency
drive (VFD) will operate as necessary to maintain duct static pressure setpoint (adj)
during morning warm up or cool down modes. The outside air damper will remain closed,
and the return air damper will remain open during unoccupied mode.
C. Cool-Down Mode:
1. On a transition from the unoccupied mode to occupied mode, if the zone average
temperature is 3°F above the occupied setpoint a morning cool-down mode will be
activated. When morning cool-down is initiated the RTU will enable the fan and DX
cooling or economizer. The outside air damper will remain closed. When the zone
average temperature reaches setpoint (adj), the RTU will transition to the occupied mode.
D. Occupied Mode:
DIRECT DIGITAL CONTROL SYSTEM 15900-22