Installation, Commissioning, and Testing
What you must know
The commissioning sequence: visual inspection, tightness test, purge, operating pressure check, combustion analysis (where applicable), and recording results. Understand tightness testing methods (e.g. let-by and stabilisation, test duration by volume) and that a test must be done before purging and after any work. Know how to set appliance burner pressures and gas rates, check flame picture, and confirm safe operation. Commissioning includes checking ventilation, flue flow, and safety devices. Records must be completed and the user instructed.
Traps in questions
- Skipping the tightness test or doing it after purge - order matters.
- Confusing let-by test (valve integrity) with tightness test (pipework integrity).
- Forgetting to record test results and instruct the user.
- Assuming combustion analysis is optional on all appliances - it is required where specified.
Worked example / rule of thumb
Rule of thumb: Inspect → test tight → purge → set pressures/rates → analyse → record → instruct. If a stem jumps to "set the burner pressure" without mentioning the tightness test, the correct answer usually restores the missing step first.
Key exam behaviours
Sequence questions reward knowing the correct order. Watch for answers that omit purge, omit recording, or test after commissioning rather than before.