Functional performance testing
Running an installed system through its documented control sequence and checking that occupied and unoccupied modes, staging, lockouts, and safety interlocks each perform as specified. It checks control logic, which is distinct from testing, adjusting, and balancing, which checks flow rates.
Also called FPT
What is functional performance testing in HVAC commissioning?
Functional performance testing runs an installed system through its actual sequence of operations, checking that every mode, stage, and safety interlock behaves as specified. It verifies control logic, not flow rates, which is a separate check.
Functional performance testing: how it works
A written sequence of operations names the states a system can be in and the exact condition that triggers each one. Functional performance testing forces those conditions on the installed system and confirms the response matches the specification, covering transitions, staging delays, lockouts, and failure conditions a static flow measurement never exercises.
Where you meet the term
- In ASHRAE Guideline 0's commissioning process, as the step that verifies control sequences rather than static conditions.
- In a commissioning report's issues log, where a deficiency found during testing is documented and tracked to a verified correction.
- In a system that balances correctly but still fails to enter a mode correctly, which functional testing catches and a flow measurement alone would miss.
How to check it
- Confirm the sequence of operations is specific enough to test. Functional performance testing needs a stated trigger condition to force and a stated output to verify. A narrative sequence without those specifics gives the tester nothing concrete to check. Technician
- Record the measured response, not a pass or fail alone. A useful test result states what was forced and what the system actually did, so a deficiency is traceable back to the exact condition that produced it. Technician
Functional performance testing: what it is not
- A system that passes flow balancing has not automatically passed functional performance testing. The two check different things and neither substitutes for the other.
- A completed punch list or a signed installer checklist is not evidence of functional performance testing. Evidence is the measured response recorded against the specified trigger.
Functional performance testing questions
Who typically performs functional performance testing?
A named commissioning authority carries this responsibility on most projects, held apart from the installing contractor for the plain reason that a party checking work should not be the same party who did it.
Can functional performance testing happen before construction finishes?
Portions of it can be planned and staged during construction, though full testing of an installed system's actual operating modes waits until the system is complete enough to run through its full sequence.
What happens when a functional test reveals a deficiency?
It is recorded in a documented issues log, tracked, and closed only against evidence of a re-test showing the correction, rather than resolved informally and left unrecorded.
Where this definition comes from
Written from standards body publication material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
- Guideline 0, The Commissioning ProcessASHRAE guideline defining commissioning as a quality process running from owner requirements through design review, construction checks, functional performance testing, and documented issue resolution, with verification carried out against the documented control sequences rather than against installer judgement.