.Buildings.Controls.OBC.ASHRAE.G36.TerminalUnits.Reheat.Subsequences.SystemRequests

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

1. 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).
2. 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).
3. Else if the cooling loop uCoo is greater than 95%, send 1 request (yZonTemResReq=1) until uCoo is less than 85%.
4. Else if uCoo is less than 95%, send 0 request (yZonTemResReq=0).

Static pressure reset requests yZonPreResReq

1. 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).
2. 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).
3. Else if the damper position uDam is greater than 95%, send 1 request (yZonPreResReq=1) until uDam is less than 85%.
4. 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

1. If the discharging air temperature TDis is 17 °C (30 °F) thrTDis_1 less than the setpoint TDisSet for 5 minutes, send 3 requests.
2. 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.
3. 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%.
4. 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:

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

Revisions

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