blockDown

Generates a stage down signal

Information

Outputs a boolean stage down signal y when:

Operating uOpeDow part load ratio of the next available stage down is below its staging uStaDow part load ratio for at least parLoaRatDelay, and
Failsafe condition is not true.

If the plant has a WSE, staging from the lowest available chiller stage to WSE stage occurs when:

WSE is enabled, and
The predicted WSE return temperature TWsePre is sufficently under the chilled water supply temperature setpoint TChiWatSupSet for defined periods of time, and
Maximum cooling tower fan speed uTowFanSpeMax is below 100%

The implementation is according to ASHRAE Guideline 36-2021, section 5.20.4.15. and can be used for both primary-only plants with and without a WSE.

Type	Name	Default	Description
Boolean	have_WSE	true	true = plant has a WSE, false = plant does not have WSE
Boolean	have_serChi	false	true = series chillers plant; false = parallel chillers plant
Boolean	have_senDpChiWatRemWir	true	True=remote DP sensor hardwired to controller
Integer	nRemSen	2	Total number of remote differential pressure sensors
Real	parLoaRatDelay	900	Enable delay for operating and staging part load ratio condition
Real	faiSafTruDelay	900	Enable delay for failsafe condition
Real	faiSafTDif	1	Offset between the chilled water supply temperature and its setpoint for the failsafe condition
Real	TDif	1	Offset between the chilled water supply temperature and its setpoint
Real	TDifHys	1	Hysteresis deadband for temperature
Real	faiSafDpDif	2*6895	Offset between the chilled water pump differential static pressure and its setpoint

Type	Name	Description
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	uWseSta	WSE status
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput	u	Chiller stage
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uOpeDow	Next available stage down operating part load ratio (OPLR)
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uStaDow	Next available stage down staging part load ratio (SPLR)
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TChiWatSupSet	Chilled water supply temperature setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TChiWatSup	Chilled water supply temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	dpChiWatSet_local	Chilled water local differential static pressure setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	dpChiWat_local	Chilled water pump differential static pressure from local sensor
Buildings.Controls.OBC.CDL.Interfaces.RealInput[nRemSen]	dpChiWatSet_remote	Chilled water remote differential pressure setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput[nRemSen]	dpChiWat_remote	Chilled water differential pressure from remote sensor
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TWsePre	Predicted waterside economizer outlet temperaturePredicted WSE outlet temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uTowFanSpeMax	Maximum cooling tower fan speed
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput	y	Stage down signal