Last month, Part I of this series, I defined the lead lag control strategy as it applies to parallel pump operation and discussed the need for identifying the designer's intent as to whether or not it's appropriate.
Defining set point names within the sequence makes it easier for building operators to compare the sequence to point labels on BAS graphic.
This provides the temperature controls contractor the chance to start in the ballpark as he or she works out the kinks of getting the automation of the system zeroed in.
Lag Pump Stage Off Set Point ) should be updated in the as-built sequence of operation to ensure the appropriate set points are sustained well into the phase of the building..
The lack of cooling dehumidifying at AHUs was result of too low of differential pressure set point in the water system.
The conventional approach of specifying 95% instead of 100% for Lag Pump Stage On Set Point is that engineers do not want to wait until the pump is maxed out failing to meet CHW dP Set Point prior to enabling the lag pump.
what is often not programmed is provisions to prevent Lag Pump Stage Off Set Point from being adjusted to value too close to, or above, Lag Pump Stage On Set Point.
For example, the result would be situation where the lag pump is cycled on and off.
Paragraph 1.e.i has the pumps rotating lead designation on day and time when it's expected someone will be on-site to assist if something goes wrong or improves the chances of mechanical service provider arriving within business hours to prevent the owner from paying increased labor rates.
This column, the second of three-part series, aimed to deeper into the lead lag control sequence for variable-speed distribution pumps, provide some best practices, and offer few items to be aware of.
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