Course: HET 273 - Pneumatic, Electric and DDC Automation - Spring 2015

Unit 3 Outline

Unit 3 Outline
Unit 3 Outline

Control Principals

Objectives

This week’s assignments will support the HVAC Learner to:

- Understand the functions of controls
- Understand sensors
- Understand controllers
- Understand controlled devices
- Understand control agents
- Describe control system characteristics
- Distinguish between open and closed loop systems

Introduction

The understanding of control principals are critical for the technician to properly troubleshoot and operate HVAC/R systems. Specifically, the understanding of each type of control and how they work together to operate systems in a safe and economical manner. This knowledge will help the technician as problems can arise at any point in the system.

This Week’s Learning Objectives

1. Control Components
  1. Sensors
  2. Controllers
  3. Controlled devices
  4. Control agents

1. Control System Characteristics
  1. Control point
  2. Set point
  3. Offset
  4. Feedback

1. Control Loops
  1. Closed loop
  2. Open loop
  3. On/off control
  4. Proportional control

Summary

- On/off is when the controller produces 0% or 100%
- Closed loop is control where feedback occurs between controller, sensor and controlled device
- The arrangement of a sensor, controller, and controlled device to maintain a specific controlled variable. Describes a control system
- The HVAC/R technician must understand the control system relationship in order to troubleshoot systems
- Control system components work to maintain building comfort. The sensor measures a variable and reports to a controller. A controller receives the measurement and sends a signal to a controlled device. The controlled device regulates the flow to provide the proper cooling, heating, and ventilation.

Review the vocabulary terms listed below and look up their definitions / descriptions before taking the Vocabulary Quiz.

Vocabulary

- Offset
- Proportional Band
- Feedback
- Closed Loop
- Controlled Device
- Control Agents
- Controller
- Sensor
- Set Point
- Proportional Control