Guide to Witness Testing

Witness testing is a critical stage in the commissioning process of Building Energy Management Systems (BEMS). This process validates that the system operates as intended, meets design specifications, and satisfies all stakeholder requirements. By systematically involving key parties, witness testing ensures confidence in the system’s functionality and prepares it for handover. Below is our recommended approach to witness testing, structured for clarity and ease of use.

 

The Importance of Witness Testing

 

Witness testing is the final step in ensuring the BEMS is ready for operation. It provides measurable assurance to all stakeholders that the system:

 

• Meets the agreed design intent and performance criteria.
• Resolves any outstanding issues identified during commissioning.
• Demonstrates its reliability and functionality under real world conditions.
• Fosters trust and confidence in the system’s capabilities among all stakeholders.

 

Our Recommended Approach

 

There are no official guidelines for witness testing and the process is usually dictated by the client or their consultant. But we recommend a phased witness testing process, progressing from detailed internal checks to final client approval. This approach ensures all issues are addressed methodically while engaging stakeholders at the right time.

 

Phase 1: Internal Witness Testing

The initial phase involves the BEMS contractor and mechanical contractor testing approximately 30-40% of the system. This sample is chosen to represent critical components and control sequences, ensuring the system operates as expected and that early issues are resolved.

 

Phase 2: Consultant Witness Testing

In the second phase, the BEMS contractor, mechanical contractor, and consultant review 10% of the system. This focused phase validates that critical elements meet the design intent and ensures alignment with project specifications.

 

Phase 3: Final Client Witness Testing

The final phase engages the client alongside the BEMS contractor, mechanical contractor, and consultant. Testing a smaller sample (2-3%) emphasizes user specific priorities and critical operations, demonstrating readiness for handover and addressing any remaining concerns.

 

Conducting Witness Testing

 

The witness testing process begins with a system overview to align all parties on the system’s design, control strategies, and key features. Testing then proceeds systematically, verifying components and sequences against the agreed performance criteria.

 

During the testing, parameters such as setpoints and schedules are adjusted to demonstrate system responsiveness. Simulated alarms and faults test the system’s ability to detect and log issues, ensuring reliability.

 

Special attention is given to specific areas:

• Sensors and actuators are tested for accuracy and functionality.
• Control sequences like optimum start/stop and seasonal setpoint adjustments are validated.
• Integration with external systems, such as HVAC or lighting, is confirmed.
• The user interface is reviewed for accuracy and ease of use.

 

Stakeholder Benefits

 

• For the BEMS Contractor: Witness testing showcases system functionality and resolves any remaining issues from commissioning, demonstrating quality workmanship.
• For the Mechanical Contractor: It verifies the correct interaction between mechanical systems and the BEMS, highlighting areas for improvement where necessary.
• For the Consultant: Witness testing ensures the design intent has been met and that all specified performance criteria are achieved.
• For the Client: This final step builds confidence in the system’s reliability and ensures their requirements have been addressed, preparing them for system operation.

 

Documentation and Reporting

 

Accurate and comprehensive documentation is essential throughout the testing process. Key records include:

 

• Test results, noting any deviations from expected performance.
• Trend logs and screenshots from the BEMS to visually demonstrate functionality.

 

The final report should summarize the outcomes, provide a detailed checklist of items tested, and include recommendations for addressing any unresolved issues. A sign-off section ensures all stakeholders acknowledge and accept the system’s performance.

 

Post-Testing and Handover

 

Once all testing phases are complete, the system is demonstrated to the client, focusing on key features and addressing any final questions. Updated documentation, including the test report, as-built drawings, and an Operation and Maintenance (O&M) manual, is handed over to the client for ongoing reference.

 

Best Practices

 

Successful witness testing relies on thorough preparation and transparent communication. Ensure all commissioning activities are complete before testing begins, and actively engage stakeholders in each phase. Transparency about identified issues and proposed solutions fosters trust and confidence in the process. Finally, focus the testing on client-specific priorities and operational goals to demonstrate the system’s value.

 

Conclusion

 

Witness testing is a vital step in delivering a reliable and functional BEMS. A phased approach, involving all key stakeholders at the appropriate stages, ensures that issues are addressed early, system performance is validated, and client confidence is secured. This methodical process prepares the system for successful operation and builds trust among all parties involved.