blockFailsafeCondition

Evaluate failsafe stage up condition

Information

For heating applications with primary-secondary distribution: The failsafe stage up condition evaluates to true if either of the following is true.

Secondary HW supply temperature < primary HW supply temperature - dT for a period of dtSec and secondary HW supply temperature < setpoint – dT for dtSec.
Primary HW supply temperature < setpoint - dT for dtPri.

For heating applications with primary-only distribution: The failsafe stage up condition evaluates to true if the following is true.

Primary HW supply temperature < setpoint - dT for dtPri.

For cooling applications with primary-secondary distribution: The failsafe stage up condition evaluates to true if either of the following is true.

Secondary CHW supply temperature > primary CHW supply temperature + dT for a period of dtSec and secondary CHW supply temperature < setpoint + dT for dtSec.
Primary CHW supply temperature > setpoint + dT for dtPri.

For cooling applications with primary-only distribution: The failsafe stage up condition evaluates to true if the following is true.

Primary CHW supply temperature > setpoint + dT for dtPri.

Parameters

Type	Name	Default	Description
Buildings.Templates.Plants.Controls.Types.Application	typ		Type of application
Boolean	have_pumSec		Set to true for primary-secondary distribution, false for primary-only
Real	dT		Delta-T triggering stage up command (>0)
Real	dtPri	900	Runtime with high primary-setpoint Delta-T before staging up
Real	dtSec	600	Runtime with high secondary-primary and secondary-setpoint Delta-T before staging up

Components

Type	Name	Description
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TSecSup	Secondary supply temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TPriSup	Primary supply temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TSupSet	Supply temperature setpoint
Buildings.Controls.OBC.CDL.Reals.Subtract	dTSecPri	Secondary-primary ∆T
Buildings.Controls.OBC.CDL.Reals.Subtract	dTPriSet	Primary-setpoint ∆T
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter	polHeaCoo	Polarity depending on heating or cooling application
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter	polHeaCoo1	Polarity depending on heating or cooling application
Buildings.Controls.OBC.CDL.Reals.LessThreshold	lesPriSet	True if Delta-T less than threshold
Buildings.Controls.OBC.CDL.Reals.LessThreshold	lesSecPri	True if Delta-T less than threshold
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	reset	Reset timers to zero at completion of stage change
Utilities.TimerWithReset	timPriSet	Timer
Utilities.TimerWithReset	timSecPri	Timer
Buildings.Controls.OBC.CDL.Logical.Or	any	Any criterion met
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput	y1	Failsafe stage up condition met
Utilities.PlaceholderLogical	ph	Placeholder signal
Buildings.Controls.OBC.CDL.Reals.Subtract	dTSecSet	Secondary-setpoint ∆T
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter	polHeaCoo2	Polarity depending on heating or cooling application
Buildings.Controls.OBC.CDL.Reals.LessThreshold	lesSecSet	True if Delta-T less than threshold
Utilities.TimerWithReset	timSecSet	Timer
Buildings.Controls.OBC.CDL.Logical.And	allSec	All criteria on secondary temperature met

Revisions

May 31, 2024, by Antoine Gautier:
First implementation.