Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly
Sequences for VAV cooling only terminal unit
Information
This package contains sequences for VAV cooling only terminal unit. They are created according to Section 5.5 of ASHRAE Guideline 36, May 2020.
Package Content
Name | Description |
---|---|
Controller | Controller for cooling only VAV box |
Subsequences | Package of subsequences for cooling only box control |
Validation | Collection of validation models |
Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Controller
Controller for cooling only VAV box
Information
Controller for cooling only terminal box according to Section 5.5 of ASHRAE
Guideline 36, May 2020. It outputs discharge airflow setpoint VSet_flow
,
damper position setpoint yDam
, AHU cooling supply temperature
setpoint reset request yZonTemResReq
, and static pressure setpoint
reset request yZonPreResReq
. It also outputs the alarms about the low airflow
yLowFloAla
, leaking damper yLeaDamAla
, and
airflow sensor calibration alarm yFloSenAla
.
The sequence consists of six subsequences.
a. Heating and cooling control loop
The subsequence is implementd according to Section 5.3.4. The measured zone
temperature TZon
, zone setpoints temperatures TZonHeaSet
and
TZonCooSet
are inputs to the instance of class
Buildings.Controls.OBC.ASHRAE.G36.ThermalZones.ZoneStates to generate the
heating and cooling control loop signal.
b. Active airflow setpoint calculation
This sequence sets the active maximum and minimum airflow according to
Section 5.5.4. Depending on operation modes uOpeMod
, it sets the
airflow rate limits for cooling supply.
See
Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.ActiveAirFlow.
c. Damper control
This sequence sets the damper position setpoints for the terminal unit. The implementation is according to Section 5.5.5. According to heating and cooling control loop signal, along with the active maximum and minimum airflow setpoint, measured zone temperature, the sequence outputs damper position setpoint, and active airflow rate setpoint. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.Dampers.
d. System reset requests generation
According to Section 5.5.8, this sequence outputs the system reset requests, i.e.
cooling supply air temperature reset requests yZonTemResReq
,
static pressure reset requests yZonPreResReq
.
See
Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.SystemRequests.
e. Alarms
According to Section 5.5.6, this sequence outputs the alarms of low discharge flow, leaking damper and airflow sensor calibration alarm. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.Alarms.
f. Testing and commissioning overrides
According to Section 5.5.7, this sequence allows the override the aiflow setpoints, damper position setpoints. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.CoolingOnly.Subsequences.Dampers.
Parameters
Type | Name | Default | Description |
---|---|---|---|
VentilationStandard | venStd | Ventilation standard, ASHRAE 62.1 or Title 24 | |
Boolean | have_winSen | true | True: the zone has window sensor |
Boolean | have_occSen | true | True: the zone has occupancy sensor |
Boolean | have_CO2Sen | true | True: the zone has CO2 sensor |
Boolean | permit_occStandby | true | True: occupied-standby mode is permitted |
Real | VOccMin_flow | Zone minimum outdoor airflow for occupants [m3/s] | |
Real | VAreMin_flow | Zone minimum outdoor airflow for building area [m3/s] | |
Design conditions | |||
Real | VAreBreZon_flow | Design area component of the breathing zone outdoor airflow [m3/s] | |
Real | VPopBreZon_flow | Design population component of the breathing zone outdoor airflow [m3/s] | |
Real | VMin_flow | Design zone minimum airflow setpoint [m3/s] | |
Real | VCooMax_flow | Design zone cooling maximum airflow rate [m3/s] | |
Control loops | |||
Cooling | |||
Real | kCooCon | 0.1 | Gain of controller for cooling control loop |
Real | TiCooCon | 900 | Time constant of integrator block for cooling control loop [s] |
Heating | |||
Real | kHeaCon | 0.1 | Gain of controller for heating control loop |
Real | TiHeaCon | 900 | Time constant of integrator block for heating control loop [s] |
Damper control | |||
Controller | |||
SimpleController | damCon | Buildings.Controls.OBC.CDL.T... | Type of controller |
Real | kDam | 0.5 | Gain of controller for damper control |
Real | TiDam | 300 | Time constant of integrator block for damper control [s] |
Real | TdDam | 0.1 | Time constant of derivative block for damper control [s] |
System requests | |||
Real | thrTemDif | 3 | Threshold difference between zone temperature and cooling setpoint for generating 3 cooling SAT reset requests [K] |
Real | twoTemDif | 2 | Threshold difference between zone temperature and cooling setpoint for generating 2 cooling SAT reset requests [K] |
Duration time | |||
Real | durTimTem | 120 | Duration time of zone temperature exceeds setpoint [s] |
Real | durTimFlo | 60 | Duration time of airflow rate less than setpoint [s] |
Alarms | |||
Real | staPreMul | 1 | Importance multiplier for the zone static pressure reset control loop |
Real | lowFloTim | 300 | Threshold time to check low flow rate [s] |
Real | fanOffTim | 600 | Threshold time to check fan off [s] |
Real | leaFloTim | 600 | Threshold time to check damper leaking airflow [s] |
Time-based suppresion | |||
Real | samplePeriod | 120 | Sample period of component, set to the same value as the trim and respond that process static pressure reset [s] |
Real | chaRat | 540 | Gain factor to calculate suppression time based on the change of the setpoint, second per degC |
Real | maxSupTim | 1800 | Maximum suppression time [s] |
Advanced | |||
Real | dTHys | 0.25 | Near zero temperature difference, below which the difference will be seen as zero [K] |
Real | floHys | 0.01*VMin_flow | Near zero flow rate, below which the flow rate or difference will be seen as zero [m3/s] |
Real | looHys | 0.01 | Loop output hysteresis below which the output will be seen as zero [1] |
Real | damPosHys | 0.005 | Near zero damper position, below which the damper will be seen as closed [1] |
Real | staTim | 1800 | Delay triggering alarms after enabling AHU supply fan [s] |
Real | iniDam | 0.01 | Initial damper position when the damper control is enabled [1] |
Control loops | |||
Real | timChe | 30 | Threshold time to check the zone temperature status [s] |
Distribution effectiveness | |||
Real | zonDisEff_cool | 1.0 | Zone cooling air distribution effectiveness [1] |
Real | zonDisEff_heat | 0.8 | Zone heating air distribution effectiveness [1] |
Connectors
Type | Name | Description |
---|---|---|
input RealInput | TZon | Measured room temperature [K] |
input RealInput | TCooSet | Zone cooling setpoint temperature [K] |
input RealInput | THeaSet | Zone heating setpoint temperature [K] |
input BooleanInput | u1Win | Window status, normally closed (true), when windows open, it becomes false |
input BooleanInput | u1Occ | True: the zone is populated |
input IntegerInput | uOpeMod | Zone operation mode |
input RealInput | ppmCO2Set | CO2 concentration setpoint |
input RealInput | ppmCO2 | Detected CO2 concentration |
input RealInput | TDis | Measured discharge air temperature [K] |
input RealInput | TSup | Temperature of the air supplied from central air handler [K] |
input RealInput | VDis_flow | Measured primary discharge airflow rate [m3/s] |
input IntegerInput | oveFloSet | Index of overriding flow setpoint, 1: set to zero; 2: set to cooling maximum; 3: set to minimum flow; 4: set to heating maximum |
input IntegerInput | oveDamPos | Index of overriding damper position, 1: set to close; 2: set to open |
input BooleanInput | u1Fan | AHU supply fan status |
output RealOutput | VSet_flow | Discharge airflow setpoint after considering override [m3/s] |
output RealOutput | yDam | Damper commanded position, or commanded flow rate ratio [1] |
output RealOutput | VAdjPopBreZon_flow | Adjusted population component breathing zone flow rate [m3/s] |
output RealOutput | VAdjAreBreZon_flow | Adjusted area component breathing zone flow rate [m3/s] |
output RealOutput | VMinOA_flow | Minimum outdoor airflow setpoint [m3/s] |
output RealOutput | VZonAbsMin_flow | Zone absolute minimum outdoor airflow setpoint [m3/s] |
output RealOutput | VZonDesMin_flow | Zone design minimum outdoor airflow setpoint [m3/s] |
output RealOutput | yCO2 | CO2 control loop signal [1] |
output IntegerOutput | yZonTemResReq | Zone cooling supply air temperature reset request |
output IntegerOutput | yZonPreResReq | Zone static pressure reset requests |
output IntegerOutput | yLowFloAla | Low airflow alarms |
output IntegerOutput | yFloSenAla | Airflow sensor calibration alarm |
output IntegerOutput | yLeaDamAla | Leaking damper alarm |