Functional Performance Testing (FPT) for HVAC
Functional Performance Testing verifies that HVAC systems and their controls operate according to the design intent and sequences of operation. FPT goes beyond point-to-point checkout to test integrated system behavior under various operating conditions.
What is Functional Performance Testing?
FPT validates that:
- Control sequences execute as designed
- Systems respond correctly to load conditions
- Setpoints are maintained within tolerance
- Safety interlocks function properly
- Energy efficiency measures work as intended
FPT vs. Other Testing
| Test Type | Purpose | When |
|---|
| Pre-functional | Verify installation complete | Before startup |
| Point-to-Point | Verify I/O wiring and addressing | During startup |
| FPT | Verify sequence operation | After P2P complete |
| Seasonal | Verify heating/cooling modes | Ongoing |
FPT Process Overview
Phase 1: Preparation
- Verify pre-functional checklists complete
- Confirm P2P checkout passed
- Review sequences of operation
- Develop test procedures
- Schedule with building operations
Phase 2: Test Execution
- Execute tests per procedures
- Document all results
- Identify deficiencies
- Coordinate corrections
Phase 3: Verification
- Retest corrected deficiencies
- Document final results
- Issue commissioning report
Developing Test Procedures
Test Procedure Components
Each FPT procedure should include:
- Objective: What is being verified
- Prerequisites: Required conditions before testing
- Test steps: Specific actions in sequence
- Expected results: What should happen
- Acceptance criteria: Pass/fail thresholds
- Data recording: What to document
Sample Test Procedure Format
Test ID: AHU-01-FPT-003
System: Air Handling Unit 1
Test: Economizer Operation
Objective: Verify economizer sequence per SOO section 3.2
Prerequisites:
- AHU in occupied mode
- OA damper operational
- All temperature sensors calibrated
Procedure:
1. Record outside air temperature (OAT)
2. Simulate OAT below economizer enable (55°F)
3. Verify OA damper modulates to maintain MAT setpoint
4. Simulate OAT above high limit (75°F)
5. Verify OA damper returns to minimum position
6. Simulate OAT between limits
7. Verify integrated economizer/mechanical cooling
Expected Result: Economizer enables when OAT < 55°F,
disables when OAT > 75°F, modulates to maintain 55°F MAT
Acceptance: MAT within ±2°F of setpoint during economizer mode
Common FPT Tests
Air Handling Unit Tests
Startup/Shutdown Sequence
- Verify proper equipment staging
- Confirm interlock operation
- Test safety shutdown response
- Verify status feedback
Supply Air Temperature Control
- Test heating mode operation
- Test cooling mode operation
- Verify reset schedules
- Test mode changeover
Static Pressure Control
- Verify setpoint maintenance
- Test reset based on VAV demand
- Confirm high-limit shutdown
- Test duct pressure sensor accuracy
Economizer Operation
- Test enable/disable based on OAT
- Verify enthalpy comparison (if applicable)
- Test damper minimum position
- Confirm integrated operation with cooling
VAV Box Tests
Cooling Mode
- Verify airflow modulation with load
- Test minimum flow operation
- Confirm maximum flow limiting
- Test reheat lockout during cooling
Heating Mode
- Verify reheat staging
- Test airflow increase with heating
- Confirm heating setpoint operation
- Test unoccupied heating mode
Occupancy Response
- Test occupied/unoccupied transitions
- Verify schedule operation
- Test override functionality
- Confirm setback recovery
Chilled Water System Tests
Chiller Staging
- Test lead/lag rotation
- Verify staging based on load
- Test staging delays
- Confirm emergency shutdown
Chilled Water Temperature Reset
- Verify reset based on valve position
- Test load-based reset
- Confirm high limit protection
Pump Operation
- Test variable speed control
- Verify differential pressure control
- Test pump alternation
- Confirm minimum flow protection
Hot Water/Steam System Tests
Boiler Staging
- Test firing rate modulation
- Verify lead/lag operation
- Test low-limit protection
- Confirm safety interlock operation
Hot Water Reset
- Verify OA reset operation
- Test high limit protection
- Confirm setpoint maintenance
Test Methods
Simulating Conditions
When real conditions aren't available:
Temperature Simulation
- Use heat gun/ice for local sensors
- Override sensor values in BAS (document!)
- Wait for natural condition changes
Load Simulation
- Override setpoints to create demand
- Use portable heating/cooling equipment
- Test during appropriate seasons
Failure Simulation
- Disconnect sensors (safely)
- Override status inputs
- Test communication failures
Override Best Practices
- Document all overrides before applying
- Use BAS override tracking features
- Clear all overrides after testing
- Verify normal operation restored
Documentation Requirements
Test Records
For each test, document:
- Test ID and description
- Date, time, and personnel
- Initial conditions
- Step-by-step results
- Deviations from expected
- Pass/fail determination
- Corrective actions (if needed)
Trend Data
Collect and archive:
- Temperature trends during tests
- Pressure trends during tests
- Actuator position trends
- Energy consumption data
Deficiency Log
Track all issues found:
- Deficiency ID and description
- System affected
- Severity (critical/major/minor)
- Responsible party
- Resolution and retest date
Acceptance Criteria Guidelines
Temperature Control
| Parameter | Typical Tolerance |
|---|
| Space temperature | ±1°F of setpoint |
| Supply air temperature | ±2°F of setpoint |
| Chilled water temperature | ±1°F of setpoint |
| Hot water temperature | ±2°F of setpoint |
Pressure Control
| Parameter | Typical Tolerance |
|---|
| Duct static pressure | ±0.1" w.c. |
| Building pressure | ±0.01" w.c. |
| Differential pressure | ±5% of setpoint |
Timing
| Parameter | Typical Tolerance |
|---|
| Startup delays | ±30 seconds |
| Stage delays | ±60 seconds |
| Schedule accuracy | ±1 minute |
Seasonal Testing
Deferred Testing
Some tests require specific conditions:
- Heating mode: Cold weather
- Economizer high limit: Hot weather
- Peak cooling: Design day conditions
- Humidity control: High humidity
Planning for Seasonal Tests
- Identify tests requiring specific conditions
- Define trigger conditions for notification
- Assign responsibility for execution
- Include in ongoing commissioning plan
References
- ASHRAE Guideline 0: The Commissioning Process
- ASHRAE Guideline 1.1: HVAC&R Technical Requirements for Commissioning
- Building Commissioning Association (BCA) Best Practices
- PECI Functional Testing Guide
FPT is where you prove the system actually works, not just that it's installed. Take time to develop thorough procedures and don't skip tests when conditions aren't ideal—schedule seasonal testing instead.