COOLING OPERATION 末 On a call for cooling, the chilled water valve will begin to modulate open. As the cooling demand increases, the valve will continue to open until the discharge air temperature reaches 52ーF. When the discharge air reaches 52ーF. the fan will begin to modulate toward the maximum cooling fan airflow as the chilled water valve continues to modulate open. This process will continue until the fan reaches the cooling maximum airflow and the chilled water valve reaches the maximum allowed water flow.
DEAD BAND OPERATION 末 With no demand in the space, there will be no call for heating or cooling. The fan will be at dead band airflow. The chilled water valve will be off. The hot water valve or the electric heater relay will be off.
HEATING OPERATION 末 On a call for heating, the heating valve shall open or the heating relay shall close to activate the heater. The fan shall begin to modulate from the dead band airflow toward the maximum heating airflow. As the demand for heat increases, the fan shall continue to modulate upward until it reaches the maximum heating airflow. For 2 stage heating, there will be 2 defined heating airflows, first stage heating airflow and maximum heating airflow. When the demand exceeds the first stage heating condition, the second stage heating will be activated and the fan will continue to modulate toward the maximum heating airflow.
Chilled Water Coil: 400 - 500 fpm 末 higher velocities will result in water blow-off.
Hot Water Coil: 400 - 800 fpm 末 higher velocities are permissible, but air pressure drop will probably be excessive.