Electric Heating
The individual stages of electric heat will be sequenced on the zone demand. The number of available stages will depend on the unit size and heat capacity selected.
Hot Water or Steam Heating
Upon a call for heat, the UCM will send a varying voltage signal to the valve actuator. The valve will modulate to meet building demand as indicated by the voltage signal. When heating is satisfied, the valve will modulate closed. A temperature sensor is located on the coldest section of the coil. When it senses an impending freeze condition, a signal is sent to the hydronic valve to drive it full open. If the supply fan is on, or if the outside air damper is open when this freezing condition is sensed, the supply fan is turned off and the fresh air damper is closed.
Supply Air Tempering
For staged gas and electric heat units in the occupied Heating mode but not actively heating, if the supply air temperature drops to 10°F below the Occupied zone heating temperature setpoint, one stage of heat will be brought on to maintain a minimum supply air temperature. The heat stage is turned off if the supply air temperature rises to 10°F above the Occupied zone heating temperature setpoint.
On units with hot water or steam heating, if the supply air temperature drops below 48°F, the heating valve is modulated to maintain 50°F supply air temperature with a 4°F deadband.
Controls Constant Volume (CV) Only
Auto Changeover
When the System Mode is “Auto,” the mode will change to cooling or heating as necessary to satisfy the zone cooling and heating setpoints. The zone cooling and heating setpoints can be as close as 2°F apart.
Unoccupied Zone
Temperature Control
Cooling and Heating
Cooling and/or heating modes can be selected to maintain Unoccupied zone temperature setpoints. For Unoccupied periods, heating, economizer operation or primary cooling operation can be selectively locked out at the Human Interface Panels.
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