Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences

Chilled water pump control sequences

Information

This package contains subsequences for chilled water pumps control for plants with parallel chillers.

Package Content

Name	Description
EnableLag_primary_dP	Sequences for enabling and disabling lag pumps for primary-only plants using differential pressure pump speed control
EnableLead_dedicated	Sequence to enable or disable the lead pump of plants with dedicated primary chilled water pumps
EnableLead_headered	Sequence to enable or disable the lead pump of plants with headered primary chilled water pumps
LocalDp_setpoint	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
Speed_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
Speed_primary_remoteDp	Pump speed control for primary-only plants where the remote DP sensor(s) is hardwired to the plant controller
Validation	Collection of validation models

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.EnableLag_primary_dP

Sequences for enabling and disabling lag pumps for primary-only plants using differential pressure pump speed control

Information

Block that enables and disables lag primary chilled water pump, for plants with headered primary chilled water pumps, according to ASHRAE Guideline 36-2021, section 5.20.6 Primary chilled water pumps, part 5.20.6.6.

Chilled water pump shall be staged as a function of chilled water flow ratio (CHWFR), i.e., the ratio of current chilled water flow VChiWat_flow to design flow VChiWat_flow_nominal, and the number of pumps num_nominal that operate at design conditions. Pumps are assumed to be equally sized.

                  VChiWat_flow
     CHWFR = ----------------------
              VChiWat_flow_nominal

1. Start the next lag pump yNexLagPum whenever the following is true for 10 minutes:

              Number_of_operating_pumps
     CHWFR > ---------------------------  - 0.03
                       num_nominal

2. Shut off the last lag pump whenever the following is true for 10 minutes:

              Number_of_operating_pumps - 1
     CHWFR ≤ -------------------------------  - 0.03
                       num_nominal

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.EnableLead_dedicated

Sequence to enable or disable the lead pump of plants with dedicated primary chilled water pumps

Information

Block that enables and disables the leading primary chilled water pump, for plants with dedicated primary chilled water pumps and parallel chillers, according to ASHRAE Guideline 36-2021, section 5.20.6.6.

The lead primary chilled water pump should be enabled when the plant is enabled (uPla = true). It should be disabled when the lead chiller is disabled (uLeaChiEna = false) and either the lead chiller has been proven off (uLeaChiSta = false) for 3 minutes or is not requesting chilled water flow (uLeaChiWatReq = false).

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.EnableLead_headered

Sequence to enable or disable the lead pump of plants with headered primary chilled water pumps

Information

Block that enables and disables the leading primary chilled water pump, for plants with headered primary chilled water pumps and parallel chillers, according to ASHRAE Guideline 36-2021, section 5.20.6 Primary chilled water pumps, part 1, 2, and 3.

1. Primary chilled water pumps shall be lead-lag. Note that the lead-lag control is implemented in a separate sequence.
2. Enable lead primary chilled water pump when any chiller CHW isolation valve uChiIsoVal is commanded open. Disable the lead primary chilled water pump when all chiller CHW isolation valves are commanded closed.
3. Or if the plant has the waterside economizer, enable lead primary CHW pump when any chiller CHW isolation valve is commanded open or waterside economizer is enabled. Disable the lead primary CHW pump when all chiller CHW isolation valves are commanded closed and WSE is disabled.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.LocalDp_setpoint

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 calculates the local DP setpoint for the local primary loop DP sensor hardwired to the plant controller. It is applicable for the primary-only plants where the remote pressure differential (DP) sensor(s) are 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.

1. 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.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.Speed_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.

1. 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.
2. 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%.
3. 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

Connectors

Modelica definition

Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.ChilledWater.Subsequences.Speed_primary_remoteDp

Pump speed control for primary-only plants where the remote DP sensor(s) is hardwired to the plant controller

Information

Block that outputs chilled water pump speed setpoint for primary-only plants where the remote pressure differential sensor is hardwired to the plant controller, according to ASHRAE Guideline 36-2021, section 5.20.6 Primary chilled water pumps, part 5.20.6.7 and 5.20.6.8.

1. When any chilled water pump is proven on, uChiWatPum = true, the pump speed will be controlled by a reverse-acting PID loop, maintaining the differential pressure signal at a setpoint dpChiWatSet. 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%.
2. Where multiple differential pressure sensors exist, a PID loop shall run for each sensor. Chilled water pumps shall be controlled to the maximum signal output of all DP sensor loops.

Parameters

Connectors

Modelica definition