blockSystemRequests

Information

This sequence outputs the system reset requests, i.e.,

• the cooling supply air temperature reset requests yZonTemResReq,
• the static pressure reset requests yZonPreResReq,
• the hot water reset requests yHeaValResReq, and
• the boiler plant reset requests yHeaPlaReq.

The calculations are according to ASHRAE Guideline 36 (G36), PART 5.E.9, in the steps shown below.

a. Cooling SAT reset requests yZonTemResReq

1. If the zone temperature TZon exceeds the zone cooling setpoint TZonCooSet by 2.8 °C (5 °F)) for 2 minutes and after suppression period due to setpoint change per G36 Part 5.A.20, send 3 requests (yZonTemResReq=3).
2. Else if the zone temperature TZon exceeds the zone cooling setpoint TZonCooSet by 1.7 °C (3 °F) for 2 minutes and after suppression period due to setpoint change per G36 Part 5.A.20, send 2 requests (yZonTemResReq=3).
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).

b. Static pressure reset requests yZonPreResReq

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

c. If there is a hot water coil (have_heaWatCoi=true), hot water reset requests yHeaValResReq

1. If the discharge air temperature TDis is 17 °C (30 °F) less than the setpoint TDisHeaSet for 5 minutes, send 3 requests (yHeaValResReq=3).
2. Else if the discharge air temperature TDis is 8.3 °C (15 °F) less than the setpoint TDisHeaSet for 5 minutes, send 2 requests (yHeaValResReq=2).
3. Else if the hot water valve position uHeaVal is greater than 95%, send 1 request (yHeaValResReq=1) until uHeaVal is less than 85%.
4. Else if uHeaVal is less than 95%, send 0 request (yHeaValResReq=0).

d. If there is hot water coil (have_heaWatCoi=true) and a boiler plant (have_boiPla=true), send the boiler plant that serves the zone a boiler plant requests yHeaPlaReq as follows:

1. If the hot water valve position uHeaVal is greater than 95%, send 1 request (yHeaPlaReq=1) until uHeaVal is less than 10%.
2. Else if uHeaVal is less than 95%, send 0 request (yHeaPlaReq=0).

Implementation

Some input signals are time sampled, because the output that is generated from these inputs are used in the trim and respond logic, which is also time sampled. However, signals that use a delay are not sampled, as sampling were to change the dynamic response.

Parameters

Connectors

Components

Revisions

• June 26, 2024, by Antoine Gautier:
  Replaced hold with pre to break the algebraic loop involving the latch component. This is for #3915.
• March 1, 2023, by Michael Wetter:
  Changed constants from 0 to 0.0 and 1 to 1.0.
  This is for #3267.
• September 13, 2017, by Jianjun Hu:
  First implementation.