blockChilledWaterPlantReset
Sequences to generate chilled water plant reset
Information
Block that output chilled water plant reset yChiWatPlaRes according
to ASHRAE Guideline 36-2021, section 5.20.5.2.
Following implementation is for plants with primary-only and primary-secondary systems serving differential pressure controlled pumps.
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Chilled water plant reset
yChiWatPlaResshall be reset using trim-respond logic with the following parameters:
| Variable | Value | Definition |
|---|---|---|
| Device | Any chilled water pump | Associated device |
| SP0 | iniSet | Initial setpoint |
| SPmin | minSet | Minimum setpoint |
| SPmax | maxSet | Maximum setpoint |
| Td | delTim | Delay timer |
| T | samplePeriod | Time step |
| I | numIgnReq | Number of ignored requests |
| R | TChiWatSupResReq | Number of requests |
| SPtrim | triAmo | Trim amount |
| SPres | resAmo | Respond amount |
| SPres_max | maxRes | Maximum response per time interval |
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Plant reset loop shall be enabled when the plant is enabled (any chilled water
pump is enabled,
uChiWatPum= true) and disabled when the plant is disabled (all chilled water pumps are disabled,uChiWatPum= false).
-
When the plant stage change is initiated (
uStaCha=true), the plant resetyChiWatPlaResshall be disabled and the value fixed at its last value for the longer ofholTimand the time it takes for the plant to successfully stage.
For primary-secondary plants serving more than one set of differential pressure controlled pumps, a unique instance of the reset shall be used for each set of differential pressure controlled secondary pumps.
- Chilled water reset requests from all loads served by a set of pumps shall be directed to those pumps reset loop only.
- The differential pressure setpoint output from each reset shall be used in the pressure control loop for the associated set of pumps only.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nPum | 2 | Total number of chilled water pumps |
| Real | holTim | 900 | Time to fix plant reset value |
| Trim and respond parameters | |||
| Real | iniSet | 1 | Initial setpoint |
| Real | minSet | 0 | Minimum setpoint |
| Real | maxSet | 1 | Maximum setpoint |
| Real | delTim | 900 | Delay time after which trim and respond is activated |
| Real | samplePeriod | 300 | Sample period time |
| Integer | numIgnReq | 2 | Number of ignored requests |
| Real | triAmo | -0.02 | Trim amount |
| Real | resAmo | 0.03 | Respond amount (must be opposite in to triAmo) |
| Real | maxRes | 0.07 | Maximum response per time interval (same sign as resAmo) |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | TChiWatSupResReq | Chilled water supply temperature setpoint reset request | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | chaPro | Plant staging status that indicates if the plant is in the staging process | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nPum] | uChiWatPum | Chilled water pump status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yChiWatPlaRes | Chilled water plant reset |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.ASHRAE.G36.Generic.TrimAndRespond | triRes | Calculate chilled water plant reset |
Revisions
-
April 15, 2019, by Jianjun Hu:
First implementation.