LeadLagRuntime provides lead-lag control of from 2 to 10 BooleanWritables based upon their accumulated runtimes (elapsed
active time). This object balances the active runtime of each of the devices. Only one of the controlled devices will be active
at a time based on runtime.
LeadLagRuntime is available in the HVAC folder of the kitControl palette, along with a similar LeadLagCycles object.
Setup of the object involves the following properties (also see Example 11), as follows:
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In
A StatusBoolean input that controls whether any control device should be on. If this input is true, one of the outputs will be active based on runtime.
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Number Outputs
Specifies the number of devices (outputs) that are controlled.
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Max Runtime
Specifies the maximum amount a given output will be true before switching to another output.
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Feedback
A StatusBoolean input, to provide positive feedback that a controlled device actually started. If the feedback value does not show true within the Feedback Delay time, the current controlled output will show alarm, and the LeadLagRuntime switches to the next controlled output. Setting this value to true (and not linking) disables this alarm feature.
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Feedback Delay Time
Specifies the delay time used to evaluate the feedback link (if any)
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Out A—J
StatusBoolean outputs, each typically linked to a BooleanWritable control point with a DiscreteTotalizerExt. Outputs are typically used to control loads of some type, such as 2 or more pumps.
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Runtime A—J
These are RelTime inputs that are used for runtime feedback for the corresponding Out A - J. These inputs will typically be linked to the ElapsedActiveTime property of the DiscreteTotalizerExt that is measuring the runtime of the corresponding Out A - J.
Example 11. LeadLagRuntime usage
A simple example LeadLagRuntime object controlling 3 pumps is shown in Figure 25 and Figure 26.
Note that in this example, each of the three BooleanWritable points has a DiscreteTotalizerExt, with its elapsedActiveTime slot exposed up in the composite of the parent point for link clarity. The “feedback” Or object simulates feedback, fed through a BooleanDelay object.