Fan operation
The SimplyVAV controllers support both series and parallel fan powered VAV units. For
either type of fan operation, the fan is controlled through the following terminals.
l A binary output triac controls a 24-volt fan starting circuit. See the topic Configuring
the VAV Box options on page 27 for the procedure to configure the controller for a
fan.
l A 0-10 volt DC analog output controls the speed of the fan. The output controls fan
speed at either Min Fan Speed or Max Fan Speed. See the topic Set the airflow
setpoints on page 29 for the procedure to set the fan speeds.
If the VAV unit is not configured for a fan, the two outputs are not used and remain inactive
regardless of the occupancy state.
Series Fan
If the controller is configured for a series fan, any time the Occupancy mode of the controller
is set to either OCCUPIED or STANDBY, the fan runs continuously. The fan speed is set to
Maximum Fan Speed when the state is OCCUPIED and set to Minimum Fan Speed when
the state is STANDBY.
When the Occupancy state is UNOCCUPIED, the fan starts and runs at minimum speed
only on a call for heating. The fan starts when the Heating loop is greater than 5% and stops
when the Heating loop is less than 1%.
Illustration 7–2 Series fan operation
UNOCCUPIED/
STANDBY
STANDBY
MAX FAN SPEED
MIN FAN SPEED
FAN OFF
OCCUPIED
HTG SP ROOM TEMP INCREASE
Parallel Fan
If the controller is configured for a parallel fan, any time the Occupancy mode of the
controller is set to either OCCUPIED or STANDBY and there is a call for heat, the fan runs
continuously. The fan starts when the Heating loop is greater than 5% and stops when the
Heating loop is less than 1%.
Section 7: Sequences of operation KMC Controls, Inc.
56 Revision H
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