What Are Pid Loops - Trane Tracer MP501 Installation, Operation And Maintenance Manual

PID Control
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For more details about PID loops, refer to the PID Control in Tracer Multi-Purpose Controllers
Applications Guide, (BAS-APG002).

What Are PID Loops?

A PID loop automatically controls an output to maintain a measured value at its setpoint by
monitoring the error (the difference between the measured value and the setpoint). The loop
performs proportional, integral, and derivative calculations to determine how aggressively to
change the output.
The goal of PID control is to reach the setpoint as quickly as possible without overshooting the
setpoint or destabilizing the system, while maintaining the setpoint consistently over time. If the
system is too aggressive, it overshoots the setpoint as shown in
enough, the time to reach the setpoint is unacceptably slow.
Figure 13. The effects of PID aggressiveness
In the heating, ventilating, and air-conditioning (HVAC) industry, PID loops are used to control
devices such as valves and dampers. Some common PID applications include:
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What are PID loops?
PID calculations
Throttling range and gain
Calculating gain
Sampling frequency
Calculaing sampling frequency
PID loop action
Error deadband
Other PID settings
Troubleshooting procedure
Tips for specific problems
Too aggressive (overshoot)
Setpoint
Ideal response
Initial point
Temperature control
Humidity control
Duct static pressure control
Staging applications
Too slow
Time
Figure 13. If it is not aggressive
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