blockDisableChiller
Sequence for disabling chiller in stage-down process
Information
Block that controlls chiller when there is a staging down command uStaDow=true.
This implementation is based on ASHRAE Guideline 36-2021, section 5.20.4.17,
items a.5 and a.6. These two sections specify how to start the smaller chiller and shut
off larger chiller when the stage change requires large chiller off and small chiller on.
In other stage change, when it does not require chiller on/off, the chiller will then
be shut off as specified in section 5.20.4.17, item b.
When the stage-down process requires a smaller chiller to be staged on and a larger chiller to be staged off:
-
Start the smaller chiller after its chilled water isolation valve is fully open (
uEnaChiWatIsoValbecomes true). -
Wait 5 minutes (
proOnTim) for the newly enabled chiller to prove that it is operating correctly, then shut off the larger chiller and release the demand limit.
If it stages down from any other stage that does not require one chiller to be off and another chiller to be on, then shut off the last stage chiller.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nChi | 2 | Total number of chillers |
| Real | proOnTim | 300 | Enabled chiller operation time to indicate if it is proven on |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | nexEnaChi | Index of next enabling chiller | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uStaDow | Stage-down command | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uEnaChiWatIsoVal | Status of chiller chilled water isolation valve control: true=enabled valve is fully open | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nChi] | uChi | Chiller status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | nexDisChi | Next disabling chiller when there is any stage up that need one chiller on and another off | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uOnOff | Indicate if the stage require one chiller to be enabled while another is disabled | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput[nChi] | yChi | Chiller enabling status | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yRelDemLim | Release demand limit |
Revisions
-
September 15, 2019, by Jianjun Hu:
First implementation.