How to write a sequence of operations

• The system: what equipment the sequence controls and which controller runs it.
• Modes: occupied, unoccupied, warm-up, cool-down, and how the system switches between them.
• Start and stop: schedules, interlocks, start-up order, proof of operation.
• Control loops: each setpoint, the sensor it reads and the device it drives.
• Alarms and safeties: freeze protection, smoke shutdown, high and low limits, what is hardwired and what is software.
• Adjustable values: which setpoints and timers the operator can change.

Specs ask that the sequences cross-reference the system point names. In practice: every point mentioned in the sequence exists in the points list under the same name, and every point in the list is used by a sequence or by monitoring. Checking the two against each other catches most review comments before they happen.

ASHRAE Guideline 36, High-Performance Sequences of Operation for HVAC Systems, first published in 2018 and updated since, gives standardized, detailed sequences for common systems such as multiple-zone VAV air handlers, terminal units and central plants. When the engineer specifies it, the contractor's job is to implement those sequences and document any deviation, not to rewrite them.

One system per section, short numbered statements, one action per statement, real point names and real setpoint values. The technician at startup should be able to test it line by line.