Stage Driver Function Block

The StageDriver function block is used to control several devices such as pumps, Fans, boiler or chillers in an intelligent sequence. The function block can be configured with different strategies that allow the devices to be controlled in alternation or in the way that all devices will get a similar switch-on time. The function block determines which devices are switched on and off based on the active stages. If required, the function block will switch on several outputs at the same time. For example, if there are 5 pumps and 3 pumps are to run, then the function block determines which 3 of the 5 pumps will be switched on.

Figure 1: StageDriver Function Block

Figure 2: StageDriver Property Sheet

Inputs

Input Name

Description

N Stages Active

The input indicates how many individual outputs Stage1 - Stage30 are to be distributed to On/Off values. N Stages Active needs to be <= Maximum Stages. If, for example, N Stages Active = 5, then 5 outputs are also switched on; which ones these are, is decided by this function block.

Numeric: 32-Bit integer; Default = Null = All Outputs are Off, 0 = All Outputs are Off, 1 - 30 to switch Stage 1 - 30 according to the configured Lead Lag Strategy.

Run Time Reset

This input is only used if the configuration Lead Lag Strategy = Runtime Equalization for the lowest runtime. In the function block, the switch-on time in minutes is logged internally for each output as a floating point number. The maximum switch-on time is 16777216 min (31.92 years). The switch-on time is stored in a flash and reused when the controller is restarted.

This input resets the runtime of one output. The output number to be reset is written here. For example, to reset the runtime of output Stage 5, the value 5 is entered here. As long as a value of 1 - 30 is present, the runtime remains at 0 min; It means to activate the timer, the input must be changed to 0 = No reset.

Numeric: 32-Bit integer, Default = Null = No reset; 1 - 30 to reset the runtime of Output 1 - 30. 0 = No reset.

Table 1: Inputs of StageDriver Function

Outputs

Output Name

Description

Stage1

This output is typically connected via a Binary Output (relay, triac, ...) to the first device (pump 1 or fan 1). The output is turned on depending on the Lead Lag Strategy. By default, only Stage1 is shown on the wiresheet as output. More Stage outputs are visible by configuring MaximumStages to a higher value.

Binary: Value 0=Off, 1=On

Stage2

This output is connected to the second device (pump 2 or fan 2).

The slot is visible only if the parameter MaximumStage is >= 2.

Stage3 - Stage30

Same as the Stage2 description.

Table 2: Outputs of StageDriver Function

Parameters

Parameter Name

Description

Maximum Stages

This parameter configures the number of outputs Stage 1 - Stage30 = number of devices in the system (number of pumps or fans) controlled via this function block. By selecting a higher number than 1, more outputs are shown on the wiresheet.

Numeric: 32-Bit integer; 0 - 30 while 0 = All outputs are OFF, Default = 1

Lead Lag Strategy

The parameter selects the Lead Lag Strategy, which determines how the outputs are switched. For more details, refer to the below information. 0 = First On - Last Off 1 = First On - First Off (Rotation) 2 = Runtime Equalization for lowest runtime. Next On Stage has the lowest runtime, and next Off has the highest runtime.

With Runtime Equalization, when N Stages Active is changed, a decision is made as to which output is switched on or off depending on the runtime. If N Stages Active does not change, the outputs do not change either.

Numeric: 32-Bit integer; 0..2, Default = 0 = First On Last Off

Out Save

Stage1 - Stage30: For each stage output, the Out Save feature can be Enabled or Disabled. Enabled means that the last value at the stage output Stage1 - Stage30 is saved in case of a power loss and is set back to the saved value for one DDC cycle when the power returns.

Table 3: Parameters of StageDriver Function


Examples

0 on a white background means the stage is OFF and 1 on yellow background means the stage is ON.

Figure 3:Example - First On - Last Off with Maximum Stages = 3

0 on a white background means the stage is OFF and 1 on yellow background means the stage is ON.

Figure 4:Example - First On - First Off with Maximum Stages = 4

0 on a white background means the stage is OFF and 1 on yellow background means the stage is ON.

Figure 5:Example - Runtime Equalization with Maximum Stages = 4