Applications Guide Tracer Graphical Programming - Trane

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Writing the discharge air control program
Figure 171: Modulate or open the cooling valve?
As in Chapter 7, when the cooling valve is enabled, a PID loop controls
the discharge air temperature. And if dehumidification is also active, a
second PID loop calculates the cooling valve position based on the space
relative humidity. Control the valve to the greater of the two calculated
valve positions.
If pre-cool mode is active and economizing is not allowed, use a Switch
block to bypass the PID outputs and open the valve completely
(Figure 172 on page 208).
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