Chapter 4 — Control Principles

Chapter 4Control Principles

Control System Components • Sensors • Controllers • Controlled Devices • Control Agents • Control Functions • Control System Characteristics • Closed Loop Control •

Open Loop Control • ON/OFF Control • Proportional Control • Control System Requirements

Chapter 4 — Control Principles

CompetenciesList and describe common HVAC control system

components.

Compare common control system components found in heating, cooling, humidification, and ventilation systems.

List and describe common methods used to control temperature, humidity, and pressure.

Identify common control system characteristics.

Describe common control system arrangements.

Identify common control system requirements.

Chapter 4 — Control Principles

HVAC control system components

sensorcontrollercontrolled devicecontrol agent

Chapter 4 — Control Principles

Comparison of HVAC control system components

Heating systemshot water, steam, electric heating

elements, or combustionCooling systems

chilled water, direct expansion cooling or outside air

Humidificationlow-pressure steam, hot water vapor

Chapter 4 — Control Principles

Controlling temperature, pressure, and humidity

room controller or thermostatreturn air sensor or controllersafety controlshumidity sensor or controllerpressure sensor

Chapter 4 — Control Principles

Control system characteristics

setpointcontrol pointoffsetfeedback

Chapter 4 — Control Principles

Control system arrangementsclosed loopopen loopON/OFFproportional

(analog)

Chapter 4 — Control Principles

Control system requirementsprovides safe, automatic and accurate

regulation of environmental conditionsposes no immediate risk to building

occupant healthoperates automaticallyaccuracy is measured and provided to

the customer

Chapter 4 — Control Principles

Chapter 4 Review

What is the function of a controller?to compare a signal to a setpoint value and send an

appropriate output signal

What is open loop control?no feedback occurring between the controller, sensor,

and controlled device