blockEnableChiller

Sequence for enabling chiller

Information

Block that controlls chiller when there is a staging up command uStaUp=true. This implementation is based on ASHRAE Guideline 36-2021, section 5.20.4.16, item f and item g.1. These sections specify when the next chiller should be enabled and when the running smaller chiller should be disabled.

When the stage-up process does not require a smaller chiller being staged off and a larger chiller being staged on (uOnOff=false):

Start the next stage chiller after the chilled water isolation valve is fully open uEnaChiWatIsoVal=true.

For any stage change during which a smaller chiller is disabled and a larger chiller is enabled (uOnOff=true):

Wait 5 minutes (proOnTim) for the newly enabled chiller to prove that is operating correctly yNewChiEna=true, then shut off the smaller 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	Description
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput	nexEnaChi	Index of next enabling chiller
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	uStaUp	Stage-up command
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	uEnaChiWatIsoVal	Status of 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.BooleanInput	uOnOff	Indicate if the stage require one chiller to be enabled while another is disabled
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.BooleanOutput[nChi]	yChi	Chiller enabling status
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput	yNewChiEna	Newly enabled chiller has been proven on by more than 5 minutes

Revisions

September 15, 2019, by Jianjun Hu:
First implementation.