.Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Controller

Information

Controller for terminal box of VAV system with reheat according to Section 5.6 of ASHRAE Guideline 36, May 2020. It outputs discharge airflow setpoint VSet_flow, damper position setpoint yDam, hot water valve position setpoint yVal, AHU cooling supply temperature setpoint reset request yZonTemResReq, and static pressure setpoint reset request yZonPreResReq, hot water reset request yHeaValResReq and yHotWatPlaReq. It also outputs the alarms about the low airflow yLowFloAla, low discharge temperature yLowTemAla, leaking damper yLeaDamAla and valve yLeaValAla, and airflow sensor calibration alarm yFloSenAla.

The sequence consists of following 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 THeaSet and TCooSet 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 5.6.4. Depending on operation modes uOpeMod, it sets the airflow rate limits for cooling and heating supply. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.ActiveAirFlow.

c. Damper and valve control

This sequence sets the damper and valve position setpoints for VAV reheat terminal unit. The implementation is according to Section 5.6.5. According to heating and cooling control loop signal, it calculates the discharge air temperature setpoint TDisSet. Along with the active maximum and minimum airflow setpoint, measured zone temperature, the sequence outputs yDam, yVal, TDisSet and discharge airflow rate setpoint VDisSet_flow. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.DamperValves.

d. System reset requests generation

According to Section 5.6.8, this sequence outputs the system reset requests, i.e. cooling supply air temperature reset requests yZonTemResReq, static pressure reset requests yZonPreResReq, hot water reset requests yHeaValResReq, and the hot water plant reset requests yHotWatPlaReq. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.SystemRequests.

e. Alarms

According to Section 5.6.6, this sequence outputs the alarms of low discharge flow, low discharge temperature, leaking damper, leaking valve, and airflow sensor calibration alarm. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.Alarms.

f. Testing and commissioning overrides

According to Section 5.6.7, this sequence allows the override the aiflow setpoints, damper and valve position setpoints. See Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.Overrides.

Revisions

• January 12, 2023, by Jianjun Hu:
  Removed the parameter have_preIndDam to exclude the option of using pressure independant damper.
  This is for issue 3139.
• August 1, 2020, by Jianjun Hu:
  First implementation.