Damper enable signal
On startup, the heating valve and pump assume normal control. When the outside air temperature is below the low limit frost protection, which is defined by parameter OAT-03, the return water temperature should reach the calculated return water temperature setpoint (minus 1/2 P-band RWT-04), before the damper enable signal is set to "on". This feature reduces the risk of frost damage on initial plant startup. If the time, to reach the mentioned temperature, exceeds the delay, defined by parameter DME-01, an alarm will be generated via the output "DamperEnableAlm".
Frost protection does not influence the damper enable signal.
During frost protection the dampers will be overridden by the plant mode signal to the following positions:
Notes:
As long as the outside air temperature is below the value of OAT-03 and the coil return water temperature sensor is not configured, the heating coil will enable the damper after the delay, as defined by parameter DME-01.
As long as the outside air temperature is above the value of OAT-03 plus the fixed differential of 1K, the coil will enable the dampers immediately (without delay).
To disable the damper enable alarm even at low temperatures, set DME-01 to a value of "0".
AHU stops on pump-off alarm at low outside air temperature
If the outside air temperature is below the value of the parameter OAT-03 and the pump would fail, which means that no adequate frost protection can be done, the total air handling unit will be stopped when this function ALM-03 is enabled. In this specific case, the module will disable its "DamperEnable" output immediately and the output "DamperEnableAlm" will be set into the alarm condition. For this case connect one of the pump alarms from pump macro to the "FailCmdAlarm" or "OffAlarm" input.
Description |
Default value |
DME-01: damper enable or alarm delay; 0=alarm disable |
300 sec |
ALM-03: AHU stops at pump off alarm at low outdoor temperature; 1 = yes |
1 |
RWT-04: return water temperature P-band |
10 K |
OAT-03: low limit frost protection |
6 °C |