What is HVAC Commissioning?

Several activities take place before the Commissioning team becomes site-based. Design preparation and pre-construction phases center around planning, investigation, and prevention. This is where thorough and methodical planning is carried out. We call this a Commissioning Plan more commonly known in New Zealand as a Cx Plan.

The key objective of the planning is to assess the construction documentation to identify any potential commissioning-related issues before they are built, allowing the mechanical installation team time to resolve any system deficiencies ahead of the programme. This assessment is also where the sequence of activities is defined for the construction milestones.
The Cx Plan is an important document that provides all of the project planning details specific to the mechanical installations.

The plan should be reviewed and approved by the Design Engineer/ICA before setting to work. This document should be adhered to by all parties involved in the commissioning process. From here, the construction programme should be reviewed to generate a commissioning programme for the services commissioning trades.

Pre-commissioning is a very important part of the commissioning process. The Pre-commissioning Phase commences once the mechanical installation work is complete and quality assurance has been submitted to the main contractor, by the mechanical team. Pre-commissioning is the construction procedure by which the working parts of a system are tested for functionality, operation, and safety.

Pre-commissioning activities will vary depending on the equipment that is installed. In HVAC, the two key sub-systems are Mechanical & Electrical for Mechanical (E4M) - some examples would be, but are not limited to:

• duct leakage testing
• pipework flushing
• removal of travel mounts from fans/pumps/compressors
• opening of all manual & motorised balancing dampers
• stroke testing motorised dampers from fully closed positions
• confirming smoke fire dampers are powered open
• fire dampers drop-tested and reset
• verification of local isolators to plant items
• variable speed drives configured to pump/fan motors
• motors rotation checked
• strainers installed and clean of debris
• water treatment dosing complete on hydraulic systems
• flushing/reverse return loops closed and IR/PICV valves open and preset
• controls point-to-point testing complete
• protective plastic removed from ductwork/grilles/louvres
• final filters installed
• building envelope complete, including door hardware & undercuts
• condensate to waste pipework installed
• pipework insulation complete
• motorised actuators installed and tested for correct orientation
• temperature/air quality sensors installed and in the correct locations

Who is responsible for carrying out pre-commissioning?

This is dependent on what has been agreed at the start of a project. Generally, this process is carried out by the mechanical contractor but can be carried out by AirRated.

Our AirRated®  commissioning engineers can provide the Testing, Adjusting, & Balancing (TAB) of all different types of HVAC equipment. We have commissioning experience in a variety of commercial buildings such as hospitals, laboratories, schools, museums, office buildings, multi-story high rise buildings, quarantine facilities, and shopping centers & stadiums - to name a few. All our equipment is externally calibrated and maintained to a high standard to ensure accurate test results are provided to our clients.

Duct leakage testing is carried out using a calibrated diagnostics tool that measures the airtightness of the HVAC system under specified static test pressure. Duct leakage testing can be carried out in new and existing HVAC systems depending on contract requirements.

Duct leakage testing more commonly occurs at the end of a job during airside commissioning on handover of the building. Why so late? Because during airside commissioning we may find that the fan total volume traverse is much higher than the terminal readings, proving leakage in the system. The terminal load may not be achieving the specified terminal duties, and the fan is running at full speed due to excess leakage. In some cases, it is found that the installation contractor does not think the testing is required as it operates under low static pressure. This theory is good until the numbers don't stack up during commissioning, hence it is always recommended to test a selection of systems to prove the quality of the manufacture & installation.

Duct leakage testing is often specified in commercial buildings as the systems operate at the mid-high static pressure classes. Leakage testing is carried out on the completion of the first fix. Over the years of pressure testing HVAC systems, we have found a lot of causes of excessive leakage come from lack of sealant on the longitude/latitude joints, Mezz flanges, and around dampers. All ductwork should be sealed in the factory before they arrive on-site, hence it is important that the mechanical contractor checks all joints when the ductwork is delivered to the site. As always, thorough QA can make all the difference to whether your system ends up with minimal leakage.

Risers also require testing, as they may be fire-rated cells that cannot be accessed once the ductwork is installed. Critical rooms such as operating theatres and isolation rooms are often tested as the ductwork is behind solid ceilings which cannot be accessed easily once installed.

A smoke test is a common test method used to identify leaks within the ductwork. The amount of remedial work that may be required upon a failed test is entirely dependent on the quality of the duct manufacture and installation. There could be a few flange leaks (lack of cleats or foam seals), or a magnitude of tiny leaks that are hard to see even with a smoke test. All leaks are significant, so it is in the contractors' best interest to ensure quality ductwork is installed.

Testing in New Zealand is often carried out to DW143 or SMACNA procedural standards. AirRated has the diagnostic equipment to test systems to meet the test criteria set out by the Design Engineer or client.

Temperature, humidity, and CO2 data logging are often carried out on completion of HVAC commissioning to ensure the control system is operating within design parameters. We employ independent data loggers to trend the air quality of the room at the same locations as the installed temp/RH/CO2 sensor locations. Using this recorded data, we can analyse the trends against the BMS to see if dead bands require fine-tuning. Carrying out independent data logging provides reassurance that the installed sensors are working correctly. Alternatively, the trends may prove that there is an overlooked mechanical issue, such as control valves not seated correctly to the valve body, which as a result, provides poor off coil temperature. Data logging is an important process to final commissioning on-site as it proves the controls system is operating as intended.

Re-commissioning (RCx) HVAC systems is essentially the same process as Commissioning except the building/systems are existing. Systems often require re-commissioning when a new tenant has moved into a building, or when the owner wants to renovate/upgrade their mechanical systems. RCx ensures systems are operating optimally to meet occupant needs.

Post-completion testing occurs after the project has been completed and the building has been handed over to the client. The duration of the building tuning process will be as per the specification requirements (often 24 months from being occupied). This tuning process commences once all commissioning has been completed and system deficiencies have been rectified.

Quarterly tuning and reporting are often carried out by the main contractor who analyses the building controls, energy metering, indoor air quality, plant staging, and system performances. The final re-commissioning (fine-tuning) of these systems may be carried out in the last quarter of the building tuning process. AirRated may be engaged to provide fine-tuning of air & water systems, depending on the requirements detailed in the building tuning reporting.

A Commissioning Management specialist oversees the entire commissioning process from design review to implementing a site-specific commissioning plan with systematic methodologies and strategies for testing, quality assurance, & pre-commissioning, then right through to the on-site commissioning.

It is the Commissioning Manager's responsibility to ensure that the entire commissioning process is methodically planned and executed well to make sure that the main contractor can deliver their project on time. During the planning stages, acceptance criteria and test methodologies should be reviewed by the Commissioning Manager and the design team to ensure clarity over the test procedures being used.

The Commissioning Manager will liaise with the incumbent Controls Contractor during the planning phase, and verify their prerequisites to Controls Commissioning. The Commissioning Manager will chair regular site meetings with the Controls, Electrical & Mechanical Contractor to ensure sequencing of commissioning falls in line with the commissioning programme. Construction conflict occurs all of the time, hence it is important that the Commissioning Manager can adapt to any unforeseen issues that may arise in the lead up to on-site testing.

Static checks of the testing and balancing should be carried out by the Commissioning Manager to ensure inter-operator commissioning engineers are providing consistent test results. Reporting must be reviewed and submitted by the Commissioning Manager to the client.

Our experienced engineers work collaboratively with the stakeholders, design team, and installation contractors to ensure optimum performance and maximum energy efficiencies are achieved.