What distinguishes commissioning from recommissioning in HVAC controls?

• A. Commissioning and recommissioning are terms for equipment replacement.
• B. Commissioning verifies design intent and system performance at startup; recommissioning re-evaluates after changes or occupancy shifts.
• C. Commissioning is for existing buildings; recommissioning is for new buildings.
• D. Commissioning only focuses on energy efficiency; recommissioning only on comfort.

Answer: (B)

Understanding the difference between commissioning and recommissioning comes down to timing and purpose. Commissioning is the process of ensuring that a building’s HVAC controls deliver what was designed during initial startup. It involves validating the control logic, sequences of operation, sensor accuracy, setpoints, and how equipment coordinate together to meet both comfort and energy goals as the system first operates.

Recommissioning, on the other hand, happens after changes or shifts in how a space is used. When occupancy patterns change, new equipment or retrofits are added, or performance issues arise, recommissioning re-evaluates and tunes the controls to the current conditions. This helps restore or improve performance and energy efficiency in the existing building.

So the distinction is that commissioning verifies design intent at startup, while recommissioning re-evaluates and adjusts after changes or shifts in usage.