blockBypassValve
Information
Waterside economizer valves control when the chilled water flow through the economizer is controlled using a modulating heat exchanger bypass valve. It is implemented according to ASHRAE Guideline 36-2021, section 5.20.3.4-6.
When economizer is enabled, start next condenser pump and (or) adjust the pump speed
(see
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.CondenserWater.Controller),
open the condenser water isolation valve to the heat exchanger (yConWatIsoVal=true),
and enable the economizer in-line chilled water return line valve.
When the in-line chilled water return valve is enabled, it shall be modulated by a direct-acting PID
loop to maintain the static pressure difference across the chilled water side
of the heat exchanger at the design value (dpDes). Map the loop output from 0% open
at 0% output to 100% open at 100% output. Bias the loop to launch from 100%
output. The valve shall be fully open when the loop is disabled.
When the economizer is disabled, the economizer in-line chilled water return line
valve shall be disabled (fully open), the heat exchanger condensing water isolation
valve fully closed (yConWatIsoVal=0), and the last lag condenser water
pump disabled and (or) change the pump speed
(see
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.CondenserWater.Controller).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | dpDes | 6000 | Design pressure difference across the chilled water side economizer |
| Valve controller | |||
| CDL.Types.SimpleController | controllerType | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | k | 0.1 | Gain of controller |
| Real | Ti | 0.5 | Time constant of integrator block |
| Real | Td | 0.1 | Time constant of derivative block |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uPla | Plant enable signal | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uWSE | True: waterside economizer is enabled | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | dpChiWat | Differential static pressure across economizer in the chilled water side | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yConWatIsoVal | Economizer condenser water isolation valve commanded status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yRetVal | WSE in-line CHW return line valve position |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.Utilities.PIDWithEnable | conPID | Chilled water return line valve controller | |
| Buildings.Controls.OBC.CDL.Reals.Sources.Constant | con | Constant one | |
| Buildings.Controls.OBC.CDL.Reals.Sources.Constant | con1 | Design static pressure difference across waterside economizer in chilled water side | |
| Buildings.Controls.OBC.CDL.Reals.Divide | div1 | Normalize the measured value | |
| Buildings.Controls.OBC.CDL.Reals.Switch | swi | Return line valve position | |
| Buildings.Controls.OBC.CDL.Logical.And | and1 | Waterside economizer commanded on | |
| Buildings.Controls.OBC.CDL.Logical.Not | disWse | Disabled economizer | |
| Buildings.Controls.OBC.CDL.Logical.TrueDelay | truDel | Delay disable | |
| Buildings.Controls.OBC.CDL.Logical.Not | enaWse | Economizer is enabled |
Revisions
-
July 14, 2022, by Jianjun Hu:
First implementation.