modelClosedLoop

Information

System Configuration

This example demonstrates the implementation of a primary-only chiller plant with two identical chillers, two headed variable speed chilled water pumps, and two headed constant speed condenser water pumps. The system schematics is as shown below.

The model makes following assumptions:

• The room supply air flow rate equals the nominal air flow rate mAir_flow_nominal.
• The air flow returns to the cooling coil includes 70% of the return room air and 30% of the outdoor air.
• The room air supply temperature setpoint is 18 °C.
• The return room air temperature is 28 °C.
• The room air supply temperature is controlled by a direct acting PID controller. It modulates the valve that controls the chilled water flow into the cooling coil.
• The chilled water reset request is generated as below:
  1. If the air supply temperature is 3 °C higher than its setpoint by more than 2 minutes, it generates 3 requests.
  2. If the air supply temperature is 2 °C higher than its setpoint by more than 2 minutes, it generates 2 requests.
  3. If the output of the PID controller that controls the supply air temperature is greater than 0.95, it generates 1 request. When it becomes less than 0.85, it generates 0 request.
• For the chiller plant request, if the output of the PID controller that controls the supply air temperature is greater than 0.95, it generates 1 request. When it becomes less than 0.1, it generates 0 request.

The chiller plant is controlled based on the ASHRAE Guideline 36, and implemented using the sequence Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Controller.

Parameters

Connectors

Components

Contents

Name	Description
MediumW
MediumA

Revisions

• March 12, 2024, by Jianjun Hu:
  First implementation.