The key states are described below. If the Heating Mode is Shutdown, the Heating Percent Cmd is set to 0%, and the state is not allowed to enter Control Heating. Otherwise, the Cooling Mode is Control and the Zone Temperature is reliable. A two-state FSM determines whether heating or cooling should be active.
Cooling Mode
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Control: Modulates the zone damper to control the Process Variable at the Effective Setpoint. If the Process Variable is unreliable, the Damper Percent Cmd is set is based on the Unreliable output input.
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Shutdown: Sets the Damper Percent Cmd based on the Shutdown Option input. If the input PID Tuning Reset is Normal, the Reset Tuning input to the PID is set to true causing the PID to recalculate its tuning parameters.
Heating Mode
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Control: Cycles the staged heating to control the Process Variable at the Effective Setpoint. If the Process Variable is unreliable, the Heating Percent Cmd is set based on the Unreliable Option input. If the input PID Tuning Reset is not Normal, the Reset Tuning input to the PID is set to true causing the PID to recalculate its tuning parameters.
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Shutdown: Sets the Heating Percent Cmd based on the Shutdown Option input.
Cooling Mode |
Heating Mode |
Shutdown Option |
Unreliable Option |
ZN-T Reliable |
FSM State |
PID Tuning Reset |
State |
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Hold |
* |
Reset 1st PID |
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Hold |
Reset 2nd PID |
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Hold |
* |
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* |
Hold |
Reset 1st PID |
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* |
Hold |
Reset 2nd PID |
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* |
Hold |
* |
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Shutdown |
Not (Control) |
Open (Cooling) |
* |
* |
* |
Open (Cooling) |
|
Close (Heating) |
* |
* |
* |
Close (Heating) |
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Hold Damper |
* |
* |
* |
Hold Damper |
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Control |
* |
* |
TRUE |
* |
Control Heating |
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Open (Cooling) |
FALSE |
* |
Open (Cooling) |
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Close (Heating) |
* |
Close (Heating) |
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Hold Damper |
* |
Hold Damper |
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Not (Shutdown) |
* |
* |
* |
TRUE |
Cooling |
Control Cooling |
|
Heating |
Control Heating |
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Open (Cooling) |
FALSE |
* |
Open (Cooling) |
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Close (Heating) |
* |
Close (Heating) |
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Hold Damper |
* |
Hold Damper |