blockSpeed_primary_localDp
Pump speed control for primary-only plants where the remote DP sensor(s) is not hardwired to the plant controller, but a local DP sensor is hardwired
Information
Block that controls speed of enabled chilled water pumps for primary-only plants where
the remote pressure differential (DP) sensor(s) is not hardwired to the plant controller,
but a local DP sensor is hardwired to the plant controller,
according to ASHRAE Guideline 36-2021,
section 5.20.6 Primary chilled water pumps, part 5.20.6.10, 5.20.6.11, and 5.20.6.12.
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Remote DP shall be maintained at setpoint
dpChiWatSet by a reverse-acting
PID loop running in the controller to which the remote sensor is wired.
The loop output shall be a DP setpoint for the local primary loop DP sensor
hardwired to the plant controller. Reset local DP from minLocDp,
e.g., 5 psi (34473.8 Pa), at 0% loop output to maxLocDp at 100%
loop output.
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When any pump is proven on, pump speed shall be controlled by a reverse-acting
PID loop, maintaining the local primary DP signal at the DP setpoint output
from the remote sensor control loop. All pumps receive the same speed signal.
PID loop output shall be mapped from the minimum pump speed (
minPumSpe)
at 0% to the maximum pump speed (maxPumSpe) at 100%.
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Where multiple remote DP sensors exist, a PID loop shall run for each sensor.
The DP setpoint for the local DP sensor shall be the highest DP setpoint output
from each of the remote loops.
Parameters
| Type | Name | Default | Description |
|---|
| Integer | nPum | 2 | Total number of chilled water pumps |
| Real | minPumSpe | 0.1 | Minimum pump speed |
| Real | maxPumSpe | 1 | Maximum pump speed |
| Speed controller |
| Buildings.Controls.OBC.CDL.Types.SimpleController | controllerType | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | k | 1 | Gain of controller |
| Real | Ti | 0.5 | Time constant of integrator block |
| Real | Td | 0.1 | Time constant of derivative block |
Revisions
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August 1, 2019, by Jianjun Hu:
First implementation.
