blockWSEOperation
Tower fan speed control when the waterside economizer is running alone
Information
Block that output cooling tower fan speed yTowSpe when only the
waterside economizer is running. This is implemented
according to ASHRAE Guideline 36-2021, section 5.20.12.2, item c.2.
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Fan speed shall be modulated to maintain chilled water supply temperature
TChiWatSup at setpoint TChiWatSupSet by a direct acting
PID loop that resets fan speed from minimum fanSpeMin at 0% loop output to
maximum at 100% loop output.
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If chilled water supply temperature
TChiWatSup drops below setpoint
and fans have been at minimum speed fanSpeMin for 5 minutes (cheCycOffTim),
fans shall cycle off for at least 3 minutes (minCycOffTim) and until
TChiWatSup rises above setpoint by 1 °F.
Parameters
| Type | Name | Default | Description |
|---|
| Integer | nChi | 2 | Total number of chillers |
| Real | fanSpeMin | 0.1 | Minimum tower fan speed |
| Real | fanSpeMax | 1 | Maximum tower fan speed |
| Chilled water controller |
| Buildings.Controls.OBC.CDL.Types.SimpleController | chiWatCon | 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 |
| Real | yMax | 1 | Upper limit of chilled water controller output |
| Real | yMin | 0 | Lower limit of chilled water controller output |
| Advanced |
| Real | cheCycOffTim | 300 | Threshold time for checking if fan should cycle off |
| Real | minCycOffTim | 180 | Minimum time of fan cycling off |
| Real | fanSpeChe | 0.05 | Lower threshold value to check fan speed |
Revisions
-
August 9, 2019, by Jianjun Hu:
First implementation.
