64 CNT-SVX17G-EN
Sequence of Operations
Note: The nvoUnitStatus.mode and nvoHeatCool both report Cool when
nvoSpaceTemp is 0.01°C above the configured unoccupied cooling setpoint. The
nvoUnit Status.mode and nvoHeatCool both report Heat when nvoSpaceTemp is
0.01°C less than the configured unoccupied heating setpoint. Otherwise, there is
no change in nvoUnitStatus.mode and nvoHeatCool. There is no change on the
transition from occupied to unoccupied.
Fan Control
The Tracer
®
VV550/VV551 controllers provide three fan options when in space
temperature control mode:
•None;
• One-speed ON/OF
F series fan;
• One-speed ON/OF
F parallel fan.
This Comm5 controller supports an electronically commutated motor (ECM) fan similar
to
the way that the Comm4 VAV controller does. The controller turns the ECM fan On and
Off. It does not change the ECM fan airflow. To assist with flow balancing the fan flow
rate is stored as a configuration item.
Series Fan
The series fan is always controlled as a one-speed ON/OFF fan. The fan operates
continuously in the occupied or occupied standby mode. The fan cycles ON and OFF with
calls for heating or cooling in the unoccupied mode.
Operation to prevent reverse rotation of fan
The series fan operates in a manner that prevents re
verse rotational operation. The series
fan is turned ON whenever one of the following occurs:
• Target airflow control point is greater than zero;
• Target air valve position is not closed;
• Actual air valve position is not
closed.
Series fan operation during calibration
During calibration, the series fan is OF
F unless the power-up control wait timer reaches
zero. When the power-up control wait timer reaches zero, the controller uses the normal
series fan control logic. The series fan is turned OFF for 10 seconds during calibration
after the air valve closes all the way. And, it remains OFF after the 10 seconds expires if:
• Power-up control wait time is still active;
• System mode (communicated application mode or communicated heat/cool mode)
is
ON;
• Effective occupancy mode is unoccupied.
Otherwise the series fan is turned ON
when the 10-second period expires.
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