Thermostats, sensors, actuators, control valves, VFDs, sequences of operation, DDC, and Building Automation Systems — how a system actually decides what to do, not just what it's made of.
Every earlier module in this program covers what HVAC equipment is and how to size it. This module covers what makes that equipment actually do the right thing at the right time: how sensors and actuators translate a physical condition into a control signal and back again, why a spring-return actuator fails to a safe position on a power loss, and why a two-way valve and a three-way valve behave completely differently on a variable-flow hydronic loop even though both just look like a valve on a drawing.
The real subject, though, is the sequence of operation — the plain-language description of what starts what, under what conditions, and what every fault does to the sequence — and how that judgment gets carried up into a full Building Automation System over BACnet or Modbus. Module 9's drawings build directly on this module's control diagrams and points lists.