Description
This function block set is used to control an on-off fan. After an AHU turns on, the damper is ON immediately. The fan turns on after a delay of 60...120 seconds in a bid to prevent air duct damage and low temperature freeze. When low limit temperature protection is activated, the fan is stopped immediately.
Function
When "Fan Start/Stop" is "1" (0-OFF/1-ON) and starts timing until "Fan Start Time Delay" is elapsed, "Fan Command" is "1".
At any time when "Fan Fault Alarm" is "1" (0-OK/1-FLT), "Fan Command" is "0".
When "Low limit Temperature Alarm" is "1", "Fan Command" is "0".
Internal logic
Input
PIN | Data type | Unit | Default value | Value/range |
|---|---|---|---|---|
FAN_SS | BOOL | - | 0 | 0-OFF / 1-ON |
FAN_FA | BOOL | - | 0 | 0-OK / 1-FLT |
LLT_ALM | BOOL | - | 0 | 0-OK / 1-FLT |
TIME_DELAY | FLOAT | s | 60 | 0...65535 |
Output
PIN | Data type | Unit | Default value | Value/range |
|---|---|---|---|---|
FAN_CMD | BOOL | - | - | 0-OFF / 1-ON |
Example
