Exhaust Fan/Damper Operation; Valve Operation - Trane Tracer ZN.520 Manual

Exhaust fan is turned off/on based on the
target position of the econimizing damper.
Whenever the Tracer ZN.520 zone
controller generates a valve position
request of zero or 100%, the unit calibrates
modulating valves by overdriving the
valves.
CNT-SVX04A-EN
Sequence of operation

Exhaust fan/damper operation

This binary point is a shared point with medium fan speed. For exhaust control,
configure the controller for a 1-or 2-speed fan. The exhaust fan/damper is
coordinated with the unit fan and outdoor damper operation. The exhaust
output is energized only when the unit fan is operating and the outdoor damper
position is greater than or equal to the configurable exhaust enable point. The
exhaust fan output is disabled when the outdoor air damper position drops 10%
below the exhaust enable point. If the enable point is less than 10%, the unit
turns on at the enable point and off at 0.

Valve operation

Modulating valve operation
The Tracer ZN.520 zone controller supports one or two modulating valves for
hydronic heating and cooling operation. The main valve/coil is used for heating
only, cooling only, or heat/cool changeover. The auxiliary valve/coil only
provides heating for the following applications:
I 4-pipe heat/cool
I 4-pipe heat/cool changeover
The auxiliary valve/coil is capable of providing only heating (4-pipe operation).
Typical 2-pipe changeover configurations allow for both cooling (summer
mode) and heating (winter mode) with the main valve/coil.
Four-pipe configurations normally utilize the main valve/coil as the cooling
source and the auxiliary valve/coil as the heating source. The controller also
supports main coil changeover for 4-pipe configurations.
Modulating valve calibration
Calibrating modulating valves is a part of the controller's normal operation,
whether at power-up or during heating and cooling. At power-up, the Tracer
ZN.520 zone controller drives modulating valves and dampers to the closed
position. The controller calibrates to the full closed position by overdriving the
actuator (135% of drive time).
The controller moves the modulating valve to the desired positions based on
calculated capacity. Whenever the controller requests a valve position of either
zero or 100%, the controller overdrives the output by 135% of the stroke time,
regardless of the current valve position.
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