Fan-Powered Units - Trane Symbio 210 Installation, Operation And Maintenance Manual

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Fan-Powered Units

The Symbio 500 controllers provide the following three (3) fan options when in space temperature
control mode:
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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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BAS-SVX091A-EN
Refer to on/off electric heat for operation. The main difference with ON/OFF hot water heating is
the control of a two position hot water valve instead of the contact energizing an electric heat
strip. Refer to and .
Modulating
Proportional hot water reheat uses 3-wire, floating-point-actuator technology. It is enabled if
there is no valid supply air temperature and disabled if the supply air temperature is greater than
the configured reheat enable setpoint.
When the space requires cooling, the air valve modulates between Airflow Setpoint Maximum
and Airflow Setpoint Minimum, to maintain space temperature at the active cooling setpoint; and
the water valve is closed. When the cooling load has decreased to the point where the air valve
has reached Airflow Setpoint Minimum, space temperature is allowed to drift downward, in the
deadband between the active cooling setpoint and active heating setpoint.
When the space temperature drops below the active heating setpoint, the air valve opens to the
Airflow Setpoint Reset Minimum Local Heat and the reheat valve modulates to maintain space
temperature at the active heating setpoint. Control of the water valve uses a separate
proportional plus integral control loop, and its position is dependent on the degree that the space
temperature is below the active heating setpoint and the amount of time that the space
temperature has been below the active heating setpoint.
If the discharge air temperature reaches the Discharge Air Temperature Design Setpoint, the air
valve opens further and modulates between Airflow Setpoint Reset Minimum Local Heat and
Airflow Setpoint Reset Maximum Local Heat to maintain space temperature at the active heating
setpoint, while the water valve modulates to maintain discharge air temperature at the Discharge
Air Temperature Design Setpoint. If the air valve reaches Airflow Setpoint Reset Maximum Local
Heat, the water valve opens further and modulates to maintain space temperature at the active
heating setpoint, while the air valve remains at Airflow Setpoint Reset Maximum Local Heat.
An additional ON/OFF remote heat output is available and energized when the water valve is
driven 100% open and de-energized when the water valve reaches 50% open.
When reheat is de-energized, the cooling Airflow Minimum Setpoint is enforced.
Note: Steam is not supported.
One-speed ON/OFF series fan
One-speed ON/OFF parallel fan
Flow control parallel fan
Target airflow control point is greater than zero.
Target air valve position is not Closed.
Actual air valve position is not Closed.
Calibration, Operation Modes, and Control
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