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Run Together operates both fans as one. Both fans are started and stopped together and if either fan fails, that fan is stopped until the alarm is cleared and the system is reset.
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Lead/Lag (only available for variable speed fans) operates the lead fan until its output reaches the stage up setpoint (SFSTG-SP, default value = 90%). If the lead fan is not able to maintain the static pressure setpoint, the lag fan is started and ramps up to the current control speed. You can change the lead fan by adjusting the value of the network input SF-LEAD (default value = Device 1). If the fan speed falls below the stage down setpoint (default value = 28%), the lag fan is stopped and the lead fan is controlled to carry the entire load. If either fan fails, that fan is stopped until the alarm is cleared and the system is reset.
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Run/Standby operates the lead fan, keeping the standby fan in reserve. If the lead fan fails, the standby fan is started. If either fan fails, that fan is stopped until the alarm is cleared and the system is reset.
There are three supported sequences of operation for dual fans.