.Buildings.Templates.Plants.Controls.Pumps.Generic.ResetLocalDifferentialPressure

Information

For plants where the remote DP sensor(s) is not hardwired to the plant controller, but a local DP sensor is hardwired to the plant controller, remote DP is maintained at setpoint by a reverse acting PI loop running in the controller to which the remote sensor is wired.

The loop output is a DP setpoint for the local primary loop DP sensor hardwired to the plant controller.

The local DP setpoint is reset from dpLocSet_min at 0 % loop output to dpLocSet_max at 100 % loop output.

The minimum local differential pressure setpoint dpLocSet_min is dictated by minimum flow control in primary-only plants but has no lower limit in primary-secondary plants. In primary-only plants, the minimum setpoint needs to be high enough to drive design minimum flow for the largest equipment through the minimum flow bypass valve.

Details

This logic is prescribed in ASHRAE, 2021 for:

• variable speed primary pumps in primary-only chiller and boiler plants where the remote DP sensor(s) is not hardwired to the plant controller, but a local DP sensor is hardwired to the plant controller,
• variable speed secondary pumps in primary-secondary chiller and boiler plants where a remote DP sensor is not hardwired to the secondary pump controller, but a local DP sensor is hardwired to the secondary pump controller.

References

• ASHRAE, 2021. Guideline 36-2021, High-Performance Sequences of Operation for HVAC Systems. Atlanta, GA.

Revisions

• March 29, 2024, by Antoine Gautier:
  First implementation.