Applications Guide Tracer Graphical Programming - Trane

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Chapter 6 VAV AHU example
Figure 116: Controlling the cooling valve
Controlling the heating valve
Consider the following specifications from the sequence of operation when
writing the module for the heating valve.
Modulatetheheatingvalvetomaintainthedischargeairtemperatureat
the discharge air heating setpoint when both of the following are true:
• The supply fan is on.
• The air handler is in heating mode.
Open the heating valve completely when both ofthefollowingaretrue:
• The supply fan is off.
• The outdoor air temperature falls below the adjustable freeze avoidance
setpoint.
Close the heating valve when any of the following is true:
• The air handler is in cooling mode.
• The supply fan is off.
• The discharge air temperature sensor is failed.
Like the cooling valve, the control of the heating valve consists of two
parts: the decision and the control. However, a third requirement calls for
the heating valve to open when the outdoor air temperature falls below
the adjustable, low setpoint for the outdoor air temperature.
124 CNT-APG001-EN