Applications Guide Tracer Graphical Programming - Trane
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Applications Guide Tracer Graphical Programming - Trane

Applications Guide Tracer Graphical Programming - Trane Applications Guide Tracer Graphical Programming - Trane

trane.com
28.09.2014 Views

® Chapter 8 Constant-volume AHU with warm-up, pre-cool, and communications Figure 172: Controlling the cooling valve Controlling the heating valve Incorporate warm-up for the heating valve in the same manner you incorporated pre-cool for the cooling valve. Minor changes to the sequence of operation relative to the sequence in Chapter 7 are shown below in italics. 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. Or when both of the following are true: • The supply fan is on. • Dehumidification is enabled. Open the heating valve completely when both ofthefollowingaretrue: • The supply fan is off. • The outdoor air temperature falls below the adjustable freeze avoidance setpoint. 208 CNT-APG001-EN

® Writing the discharge air control program Figure 173: Controlling the heating valve Or when all ofthefollowingaretrue: • The supply fan is on. • The air handler is in heating mode. • The warm-up mode is active. Close the heating valve when any of the following is true: • The air handler is in cooling mode, and dehumidification is disabled. • The supply fan is off. • The discharge air temperature sensor is failed. Adding consideration of warm-up mode to the program increases the complexity of the logic. Similar to control of the cooling valve, use a Switch block to bypass the PID output and open the valve completely when warm-up mode is active (Figure 173). After you complete changes to the discharge air control program (Figure 174 on page 210), compile and download it to the controller. CNT-APG001-EN 209

®<br />

Writing the discharge air control program<br />

Figure 173: Controlling the heating valve<br />

Or when all ofthefollowingaretrue:<br />

• The supply fan is on.<br />

• The air handler is in heating mode.<br />

• The warm-up mode is active.<br />

Close the heating valve when any of the following is true:<br />

• The air handler is in cooling mode, and dehumidification is disabled.<br />

• The supply fan is off.<br />

• The discharge air temperature sensor is failed.<br />

Adding consideration of warm-up mode to the program increases the complexity<br />

of the logic. Similar to control of the cooling valve, use a Switch<br />

block to bypass the PID output and open the valve completely when<br />

warm-up mode is active (Figure 173).<br />

After you complete changes to the discharge air control program<br />

(Figure 174 on page 210), compile and download it to the controller.<br />

CNT-APG001-EN 209

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