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Sequence of operation
Equipment fan off detection
The VVT Bypass Controller continuously monitors its damper's position and the supply duct static pressure. If
the pressure drops below 10% of the nominal setpoint and the bypass damper is fully closed (or VFD is
commanded to maximum speed), after 1 minute the controller assumes that the equipment fan turned off.
The bypass damper then modulates to 65% open and the VFD speed is commanded to 35% (3.5 volts) to
facilitate a fan restart. The controller monitors the static pressure to determine when the equipment fan
restarts. If it rises above 10% of the nominal pressure setpoint, the controller assumes the fan restarted and
controls to maintain the duct static pressure setpoint. If Linkage is active, the air source mode is provided to
the VVT Bypass Controller.
Supply Air Temperature Alarm
The VVT Bypass Controller generates an alarm if the supply air temperature remains above the configured
Maximum Heating SAT or below the configured Minimum Cooling SAT for more than 5 minutes.
Airside linkage
When the VVT Bypass Controller is part of a linked system, it uses data received through Linkage (equipment
SAT and mode) to detect excessive leaving air temperature (LAT) conditions at the equipment and equipment
operating mode.
20
VVT Bypass Controller
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