Trane Tracer Uc page 54

Calibration, Operation Modes, and Control
ECM Fan
This controller supports an electronically commutated motor (ECM). The controller turns the ECM
fan ON and OFF . It does not change the ECM fan airflow dynamically. The fan operates at a single
speed to match the fan flow setpoint. The fan flow correction factor is a direct multiplier used to
determine fan speed, and can be adjusted if the measured flow rate does not meet the fan flow
setpoint. To assist with flow balancing the fan flow rate is stored as a configuration item. The
minimum and maximum flow settings are predetermined at the factory and should not be adjusted
in the field. For units configured in the field, the maximum flow should not be set higher than the
nominal airflow of the VAV box.
Series Fan
The series fan is always controlled as a one-speed ON/OFF fan. The fan continuously operates in
the occupied or occupied standby mode and cycles ON and OFF with calls for heating or cooling
in the unoccupied mode. The series fan operates in a manner that prevents reverse rotational
operation. The series fan is turned ON whenever one of the following occurs:
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Series Fan Operation During Calibration
During calibration, the series fan is OFF for 10 seconds during calibration after the air valve closes
all the way. It remains OFF after the 10 seconds expires if:
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Otherwise the series fan is turned ON when the 10-second period expires.
Parallel Fan
The parallel fan is the first stage of heat. When the supply air temperature is cold, the parallel fan:
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When the supply air temperature is warm or hot, the parallel fan is OFF , unless the local reheat is
ON. Two (2) methods of control are supported for energizing the parallel fan:
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The parallel fan start points for each method of control are able to be configured.
Parallel Fan Start based on Space Temperature
The parallel fan turns ON when the space temperature falls below the heat setpoint, plus the
configured parallel fan temperature enable setpoint. It turns OFF when the space temperature rises
above the heat setpoint, plus the configured parallel fan temperature enable setpoint by 0.5°F
(0.28°C).
Parallel Fan Start Based on Supply Airflow
The parallel fan turns ON when the supply airflow falls below the configured parallel fan airflow
enable setpoint, or the supply airflow is less than the active minimum flow setpoint, plus 2% of the
configured nominal airflow. The parallel fan turns OFF when:
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Target airflow control point is greater than zero.
Target air valve position is not Closed.
Actual air valve position is not Closed.
System mode (communicated application mode or communicated heat/cool mode) is OFF .
Occupancy mode status is unoccupied.
Cycles ON as the first stage of heat during occupied mode or occupied standby mode.
Cycles ON with a call for heat during unoccupied mode.
One method is based on space temperature.
One method is based on supply airflow.
The supply airflow rises above the configured parallel fan airflow enable setpoint, plus 5% of
the configured nominal airflow.
VAV-SVX07B-EN