CVAHU PID

Description

CVAHU application PID settings.

Purpose

Adjust PID (Proportional Integral Derivative) control parameters for the CVAHU.

Mode

Off-line or On-line

CAUTION

Equipment Damage Possible.

Can cause short cycling of compressors or wide swings in space temperature and excessive overdriving of modulating outputs.
If large or frequent change to PID control parameters is made, it is possible to cause equipment problems such as short cycling compressors (if the stage minimum run times were disabled). Other problems that can occur include wide swings in space temperature and excessive overdriving of modulating outputs.
The default values provide proper control for most applications. If the PID parameters require adjustment away from these values, use caution to ensure that equipment problems do not arise. If any change to PID control parameters is made, the adjustments should be gradual. After each change, allow the system to stabilize so the effects are accurately observed. Make further refinements as needed until the system is operating as desired.

If the default values are changed and you want to reset them, add a second CVAHU Controller to the subnet, record then re-enter the default PID values to the first CVAHU.

Procedure

  1. Click the PID button on the left pane to open the PID Configuration page.
  2. Enter information into available fields.
  3. Click Commit to save the settings or Reset to revert to the last saved settings.
  4. Click Next to display the Custom Wiring page or Back to display the Miscellaneous Parameters Configuration page.

CAUTION

Equipment Damage Possible.

Setting Control Band too low may cause large over or undershooting of setpoint.

The smaller the Control Band, the more responsive the control output. Be careful not to set the Control Band (heating, cooling, or econ) too low. This can happen if the space or discharge sensors or wiring are in noisy environments and the value reported to the controller is not stable (such that it bounces). The Control Band is used only in modulating control, and has no purpose when staged control is configured.

Fields           

Name Definition
Cooling Proportional Gain Enter the range in degrees 2 – 30 DDF (1.1 – 16.7 DDK).
Cooling Integral Gain Enter the range in seconds (0 – 5,000).
Cooling Derivative Time Enter the range in seconds (0 – 9,000).
Heating Proportional Gain Enter the range in degrees 2 - 30 DDF (1.1 - 16.7 DDK).
Heating Integral Gain Enter the range in seconds (0 – 5,000).
Heating Derivative Time Enter the range in seconds (0 – 9,000).
DA Heating Control Band Enter the range in degrees 5 - 30 DDF (2.8 - 16.7 DDK).
DA Cooling Control Band Enter the range in degrees 5 - 30 DDF (2.8 - 16.7 DDK)
Econ Control Band Enter the range in degrees 5 - 30 DDF (2.8 - 16.7 DDK).

 Note:

Throttling Range or Proportional Gain

Determines what impact the error has on the output signal. Decreasing the Throttling Range amplifies the effect on the error, that is, for a given error (the difference between the measured space temperature and the current actual space temperature setpoint), a small Throttling Range causes a higher output signal value.

Integral Time

Determines what impact the error-over-time has on the output signal. Error-over-time has two components that make up its value: the amount of time the error exists and the size of the error. The higher the integral time, the slower the control response. In other words, a decrease in Integral Time causes a more rapid response in the output signal.

Derivative Time or Gain

Determines what impact the error rate has on the output signal. The error rate is how fast the error value is changing. It can also be the direction space temperature is going, either towards or away from the setpoint and its speed - quickly or slowly. A decrease in Derivative Time causes a given error rate to have a larger effect on the output signal.

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