Pre-Cool
Pre-Cool is a mode often used during building unoccupied periods and optimal start applications to rapidly decrease the space temperature, as efficiently as possible, before building occupancy. Pre-Cool mode of operation can be enabled and disabled via Pre-Cool Enable Command. Pre-Cool is reported via Heat Cool Mode Status when active. Ventilation air is not provided during Pre-Cool operation.
VVDA
VVDA equipment types, a transition from Unoccupied to Occupied mode or Off/Shutdown to Occupied, if a valid space temperature input is above the Pre-Cool Setpoint + 1.5°F Pre-Cool Mode will initiate. Symbio™ 700 operates in a discharge air control mode providing discharge air per Discharge Air Cooling Setpoint Active until space temperature drops equal or below the Pre-Cool Setpoint. In this cooling mode the outdoor air damper minimum position is 0%, but the controller will use compressor and/or economizer cooling when suitable. VVDA units will modulate fan speed and manage to the duct static pressure setpoint.
Pre-Cool mode can also be commanded via Heat Cool Mode Request. In this case, the Symbio 700 remains in Pre-Cool indefinitely until the commanded mode is removed. When space temperature is equal or less than Pre-Cool Setpoint, cooling capacity is disabled but the supply fan continues to circulate air until the Pre-Cool command is removed. Cooling capacity control will enable if space temperature rises above Pre-Cool Setpoint + 1.5°F.
Space Temperature Control
Space temperature control units must be in Cool or Auto mode to allow Pre-Cool operation. A transition from Unoccupied to Occupied mode, the controls will initiate Pre-Cool if a valid space temperature input is above the Pre-Cool Setpoint + 1.5°F. The Symbio™ 700 operates in a space temperature control mode controlling space temperature to the Pre-Cool Setpoint. The supply fan operates at maximum speed. When 60 minutes expires or when space temperature is equal or below the Pre-Cool Setpoint, Pre-Cool mode will terminate.
Pre-Cool mode can also be commanded via Heat Cool Mode Request from a building automation system or external control. The Symbio 700 controller will continuously control space temperature to the Pre-Cool setpoint until the mode is released or changed.
Application Guide Link
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.