What Checks Are Done During Pre-Commissioning? A System-by-System Guide for Building & MEP Commissioning

This article covers what checks are done during pre-commissioning specifically in the building and MEP context – walking through every category of check, in the order they happen, then system by system. If you want a broader definition of the phase itself first, start with our article What Is Pre-Commissioning?

What Pre-Commissioning Actually Covers

Pre-commissioning in building and MEP commissioning covers the checks performed between mechanical completion and functional performance testing – verifying that systems are correctly installed, connected, and ready to be energised. Per ASHRAE Guideline 0, this is the construction verification phase; ASHRAE Guideline 1.1 sets the HVAC&R technical requirements. Checks are grouped into four categories:

• Documentation verification,
• Installation inspection,
• Pre-functional checks (PFCs), and
• Static testing.

The Main Categories of Pre-Commissioning Checks

Pre-commissioning activities in building projects fall into four sequential categories. Each category must be substantially addressed before the next begins, and each produces its own documentation. This is not a free-for-all run through a checklist the morning before startup [a common mistake on compressed programmes].

Category 1 – Documentation and Submittal Verification

Before anyone walks a system, the paperwork has to be in order. Are the approved shop drawings on file and current? Have the technical / material submissions been reviewed and approved by the designer? Has the commissioning specification been reviewed? Are the project specifications available for inspection and review?

Category 2 – Delivery and Installation Checks

With documentation confirmed, the physical inspection begins. Is equipment correctly positioned and mounted to the manufacturer’s base frame requirements? Maintenance space is inline with the manufacturers requirements? Are pipework and ductwork connections made per the design drawings? All ancillaries installed in the correct positions? Is electrical wiring complete and terminated? Are labels, tags, and equipment identification fitted? This category produces the installation section of the pre-functional checklist, completed by the installing contractor.

Category 3 – Pre-Functional Inspection

This is the core of the pre-commissioning activities list – static checks performed before equipment is energised under operational load. Belt tensions set to specification. Oil and fluid levels confirmed. Strainers cleaned before and after flush. Safety devices wired and in the correct position. Isolation valves tagged and set to normal operating position. Sensor mounting locations confirmed against the instrumentation schedule. The formal output is the Pre-Functional Checklist [PFC] – a document signed by the contractor and witnessed by the commissioning engineer [CxP], confirming each item has been physically checked.

Category 4 – Static Testing

Static testing runs in parallel with or immediately after the pre-functional inspection, depending on programme, and covers a broad range of disciplines. On the electrical side, insulation resistance [megger] testing is completed on all cables before energisation, continuity checks are verified, earth bonding is confirmed, and protective devices are checked against the protection coordination study. Mechanical static tests include pressure testing of pipework systems [hydraulic or pneumatic, depending on the medium], flushing and cleaning verification, and confirmation that chemical dosing is complete on closed systems. Controls and BAS static testing verifies that control sequences are loaded into the DDC controllers, every field device is confirmed at the controller and the BMS front end against the I/O schedule, actuator stroke tests are completed, alarm set-points are loaded, and fail-safe positions are verified. The output is a set of static test records and verification sheets covering each discipline, signed by the relevant contractor and reviewed by the commissioning engineer [CxP].

Pre-Commissioning Checks by System – What Actually Gets Inspected

The four categories above apply to every system on the project. The specific checks within each category vary by system type. Below is a practical overview of what actually gets verified on site.

HVAC Systems

Air handling units, chillers, boilers, pumps, VAV boxes, fan coil units, ductwork, pipework, water tanks, and associated ancillaries – each has its own pre-functional checklist, and the pre-commissioning HVAC scope is typically the largest volume of work on a building project.

For an AHU, typical checks include: base frame fixing and vibration isolator compression within the manufacturer’s tolerances; ductwork supply and return connections made and sealed; belt tension and drive alignment confirmed [this is one of the most common items that gets missed]; motor rotation direction verified dry before fluid systems are energised; control dampers operable through full stroke; sensor mounting positions confirmed against design; thermal insulation complete on all surfaces including flanges and connections. For chillers and boilers, the manufacturer startup procedure kicks in at the boundary between pre-commissioning and commissioning proper, so the pre-functional checks focus on confirming that all preconditions for that startup are met – water connections, refrigerant charge status [for chillers], flue connections, safety interlocks, and BMS points wired and mapped etc.

Electrical Systems

Pre-commissioning electrical checks cover switchgear and distribution boards, generators, UPS systems, lighting control panels, containment systems, final sub-circuits, and associated cabling. Cable terminations must be complete and confirmed against the single-line drawings. Cable identification labels are fitted per the project’s labelling schedule. Protective devices [MCBs, MCCBs, fuses] are installed and rated correctly against the protection coordination study. Insulation resistance testing [megger tests] is conducted on cables before energisation – this is a critical safety check. Earth bonding is confirmed. Arc flash labels are fitted where required. Interlocks between interdependent systems [e.g. generator and mains incoming, AHU and fire alarm] are wired and documented before any energisation.

BMS / Controls

BMS/controls pre-commissioning covers DDC controllers, field devices, sensors, actuators, cabling, network infrastructure, and the BMS front end. Controllers are powered and communicating on the network. Control software sequences of operation are loaded and version-confirmed against the approved submittal. Point-to-point verification runs against the I/O schedule – every field device is confirmed at the controller and at the BMS front end. Actuator stroke tests confirm dampers and valves are moving in the correct direction and over the correct range. Sensor calibration is confirmed against certificates [not just assumed from a commissioning certificate]. Alarm set-points and priorities are loaded and confirmed. Fail-safe positions are verified for dampers and valves.

Plumbing and Drainage

Plumbing and drainage pre-commissioning covers domestic hot and cold water pipework, cold water storage tanks, booster sets, above-ground drainage, below-ground drainage connections, and associated valves and fittings. Domestic hot and cold water pipework is pressure tested and, for new systems, flushed and disinfected in accordance with the applicable standard [in the UK, this is BSRIA BG 29; in the US, AWWA C651 or equivalent local health authority requirements apply]. Water treatment dosing is confirmed for closed heating and chilled water systems. Isolation valves are tagged and set. Pipe insulation is complete, including trace heating on cold water pipework in frost-exposed areas. Drainage fall and trap depth are verified before fit-out covers access.

Who Carries Out Pre-Commissioning Checks?

The most consistent source of confusion we see on site is the assumption that the commissioning team [CxP] carries out pre-commissioning. They do not – at least not in terms of executing the checks. The installing contractor carries out the physical work; the commissioning team witnesses, records, and signs off.

The PFC documents are prepared by the CxP, per ASHRAE Guideline 0, PFC templates are developed during the pre-design phase [typically Schematic Design through Construction Documents] so they are ready for contractor use the moment mechanical completion is achieved. The commissioning team [CxP] owns the document, defines what needs to be checked, and sets the standard.

The installing contractor or specialist subcontractor then works through the PFC item by item, completing each check and recording the result. They sign the completed PFC to confirm their work is done.

The Commissioning Provider [CxP] witnesses the checks, verifies the outcomes, and signs the completed PFC. Never take someone’s word that a system is ready [Trust but Verify] – the CxP’s job is to physically verify that the PFC has been worked through correctly, not to accept a contractor’s verbal assurance. For a detailed breakdown of how responsibility for commissioning is allocated across the project team, that is covered separately.

On larger projects, the Commissioning Manager [CxM] from the CxP reviews the completed PFC package and issues the formal proceed-to-test authorisation before functional testing begins. No system moves to functional testing until the CxM has confirmed pre-commissioning is complete and the punch list is at acceptable status.

What Documents Does Pre-Commissioning Produce?

Pre-commissioning is a documentation phase as much as a physical inspection phase. The formal outputs are what give the commissioning programme its audit trail and allow the CxM to make a sign-off decision.

The key documents produced are:

• Completed Pre-Functional Checklists [one per system or equipment item] – signed by the contractor and countersigned by the commissioning engineer. These confirm that each physical check has been carried out and the result recorded.
• The Pre-Commissioning Punch List – a deficiency log capturing every item found during pre-commissioning that requires action before functional testing can proceed, with the responsible party and a close-out date assigned to each item. For a full explanation of how the punch list is structured and managed, see What Is a Pre-Commissioning Punch List?
• Startup Records – manufacturer’s startup report forms completed by the manufacturer’s engineer or a qualified specialist, with first-energisation data recorded. These are particularly relevant for chillers, boilers, and generators.
• The Pre-Commissioning Sign-Off Sheet – issued by the CxM or CxP, confirming that pre-functional checks are complete, the punch list is at agreed status, and the system is authorised to progress to functional performance testing. This document is a formal gate. It sits in the commissioning record alongside the completed PFCs and forms part of the documentation that ultimately supports the commissioning completion report required under ASHRAE Guideline 0.

How Pre-Commissioning Differs from Commissioning

The terms are used interchangeably on some projects, but they are not the same thing. Pre-commissioning and commissioning [functional performance testing] are sequential phases with different objectives, different equipment states, and different lead responsibilities, commissioning starts once the pre-commissioning has been completed and signed off.

The practical implication: you cannot safely run functional performance testing on a system that has not passed pre-functional inspection. Attempting to do so – which happens on compressed programmes – means functional testing time is spent catching installation deficiencies that should have been caught earlier, at a much higher cost in both remedial work and programme delay [the $1:$10:$100 cost escalation rule applies here directly].