A Sequence of Operations is a detailed written description of how an HVAC system responds to various operating conditions and control inputs throughout the day. It defines the logical progression of equipment startup, operation, and shutdown based on temperature, occupancy, and other sensors.
Technical Specifications
The sequence outlines setpoint temperatures (typically 72°F heating, 76°F cooling), deadband ranges (usually 2-4 degrees), and timing delays in seconds. It specifies which equipment stages activate at specific outdoor temperatures, occupancy conditions, or demand levels. The sequence includes emergency modes, night setback procedures, and seasonal changeover logic. Control system response times and sensor thresholds are explicitly defined.
Control System Design
Sequences form the basis for building automation system programming and contractor commissioning work. They ensure consistent comfort conditions while minimizing energy consumption. A clear sequence prevents equipment hunting, reduces wear cycles, and enables technicians to verify proper operation during commissioning. Changes to sequences require documentation and retesting to maintain system performance.