blockSystemRequests

Output system requests for VAV terminal unit with reheat

Information

This sequence outputs the system reset requests for terminal unit with reheat. The implementation is according to the Section 5.6.8 of ASHRAE Guideline 36, May 2020.

Cooling SAT reset requests `yZonTemResReq`

If the zone temperature TZon exceeds the zone cooling setpoint TCooSet by 3 °C (5 °F)) for 2 minutes and after suppression period (uAftSup=true) due to setpoint change per G36 Part 5.1.20, send 3 requests (yZonTemResReq=3).
Else if the zone temperature TZon exceeds the zone cooling setpoint TCooSet by 2 °C (3 °F) for 2 minutes and after suppression period (uAftSup=true) due to setpoint change per G36 Part 5.1.20, send 2 requests (yZonTemResReq=2).
Else if the cooling loop uCoo is greater than 95%, send 1 request (yZonTemResReq=1) until uCoo is less than 85%.
Else if uCoo is less than 95%, send 0 request (yZonTemResReq=0).

Static pressure reset requests `yZonPreResReq`

If the measured airflow VDis_flow is less than 50% of setpoint VSet_flow while the setpoint is greater than zero and the damper position uDam is greater than 95% for 1 minute, send 3 requests (yZonPreResReq=3).
Else if the measured airflow VDis_flow is less than 70% of setpoint VSet_flow while the setpoint is greater than zero and the damper position uDam is greater than 95% for 1 minute, send 2 requests (yZonPreResReq=2).
Else if the damper position uDam is greater than 95%, send 1 request (yZonPreResReq=1) until uDam is less than 85%.
Else if the damper position uDam is less than 95%, send 0 request (yZonPreResReq=0).

If there is a hot-water coil, hot-water reset requests `yHeaValResReq`

If the discharging air temperature TDis is 17 °C (30 °F) thrTDis_1 less than the setpoint TDisSet for 5 minutes, send 3 requests.
Else ff the discharging air temperature TDis is 8 °C (15 °F) thrTDis_1 less than the setpoint TDisSet for 5 minutes, send 2 requests.
Else if the hot water valve position uVal is greater than 95%, send 1 request until the hot water valve position is less than 85%.
Else if the hot water valve position uVal is less than 95%, send 0 request.

If there is a hot-water coil and heating hot-water plant, heating hot-water plant reqeusts. Send the heating hot-water plant that serves the zone a heating hot-water plant request as follows:

If the hot water valve position uVal is greater than 95%, send 1 request until the hot water valve position is less than 10%.
If the hot water valve position uVal is less than 95%, send 0 requests.

Parameters

Type	Name	Default	Description
Buildings.Controls.OBC.ASHRAE.G36.Types.HeatingCoil	heaCoi	Buildings.Controls.OBC.ASHRAE.G36.Types.HeatingCoil.WaterBased	Heating coil type
Real	thrTemDif	3	Threshold difference between zone temperature and cooling setpoint for generating 3 cooling SAT reset requests
Real	twoTemDif	2	Threshold difference between zone temperature and cooling setpoint for generating 2 cooling SAT reset requests
Real	thrTDis_1	17	Threshold difference between discharge air temperature and its setpoint for generating 3 hot water reset requests
Real	thrTDis_2	8	Threshold difference between discharge air temperature and its setpoint for generating 2 hot water reset requests
Duration times
Real	durTimTem	120	Duration time of zone temperature exceeds setpoint
Real	durTimFlo	60	Duration time of airflow rate less than setpoint
Real	durTimDisAir	300	Duration time of discharge air temperature less than setpoint
Advanced
Real	dTHys	0.25	Near zero temperature difference, below which the difference will be seen as zero
Real	floHys		Near zero flow rate, below which the flow rate or difference will be seen as zero
Real	looHys		Loop output hysteresis below which the output will be seen as zero
Real	damPosHys		Near zero damper position, below which the damper will be seen as closed
Real	valPosHys		Near zero valve position, below which the valve will be seen as closed
Real	samplePeriod	120	Sample period of component, set to the same value as the trim and respond that process yPreSetReq

Connectors

Type	Name	Description
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	uAftSup	After suppression period due to the setpoint change
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TCooSet	Zone cooling setpoint temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TZon	Zone temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uCoo	Cooling loop signal
Buildings.Controls.OBC.CDL.Interfaces.RealInput	VSet_flow	Discharge airflow rate setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	VDis_flow	Measured discharge airflow rate
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uDam	Damper position setpoint
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TDisSet	Discharge airflow setpoint temperature for heating
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TDis	Measured discharge airflow temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInput	uVal	Hot water valve position setpoint
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput	yZonTemResReq	Zone cooling supply air temperature reset request
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput	yZonPreResReq	Zone static pressure reset requests
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput	yHeaValResReq	Hot water reset requests
Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput	yHotWatPlaReq	Request to heating hot-water plant

Revisions

August 1, 2020, by Jianjun Hu:
First implementation.