blockIntegratedOperation
Tower fan speed control when the waterside economizer is enabled and the chillers are running
Information
Block that outputs cooling tower fan speed ySpeSet when both waterside
economizer and chillers are enabled, i.e., integrated operation. This is implemented
according to ASHRAE Guideline 36-2021, section 5.20.12.2, item c.1.
When the waterside economizer is enabled (uWse=true) and chillers
are running (uChi=true):
- Fan speed shall be equal to the waterside economizer tower maximum speed.
-
The waterside economizer tower maximum speed shall be reset by a direct acting PID
loop maintaining the chiller load at 110% of the sum of the minimum cycling load for
the operating chillers. Map the tower maximum speed from the minimum speed
fanSpeMinat 0% loop output to 100% speed at 100% loop output. Bias the loop to launch from 100% output. -
When starting integrated operation after previously operating with only the waterside
economizer, hold the tower maximum speed at 100% for 10 minutes (
intModTim) to give the chiller time to get up to speed and produce at least the minimum cycling load, then enable the loop.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nChi | 2 | Total number of chillers |
| Real[nChi] | chiMinCap | {1e4, 1e4} | Minimum cyclining load below which chiller will begin cycling |
| Real | fanSpeMin | 0.1 | Minimum cooling tower fan speed |
| Load controller | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | conTyp | 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 load controller output |
| Real | yMin | 0 | Lower limit of load controller output |
| Advanced | |||
| Real | intModTim | 600 | Threshold time after switching from WSE-only mode to integrated mode |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nChi] | uChi | Vector of chillers proven on status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uChiLoa | Current cooling load | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uWse | Waterside economizer enabling status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | ySpeSet | Tower fan speed setpoint when WSE is enabled and there is any chiller running |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Reals.Switch | fanSpe | Switch from the holding maximum speed to regulated speed |
Revisions
-
August 9, 2019, by Jianjun Hu:
First implementation.