Common deficiencies found during commissioning

Every commissioning project produces an issues log, and after enough projects the same entries keep appearing. A sensor installed in the wrong place, a damper actuator wired backwards, a sequence that cannot work as written, a pump that was never balanced. None of these are exotic. They are the predictable results of complex systems being designed, built and programmed by many people under schedule pressure.

Knowing which deficiencies are most common helps everyone. Designers can address them on the drawings, contractors can check for them before inviting the commissioning provider to witness tests, and owners can understand why commissioning time and budget are well spent. This guide groups typical findings by category and explains how to prevent them.

Design-stage deficiencies

Many problems found in the field were built into the design documents. Commissioning design reviews aim to catch them early.

• Incomplete or ambiguous sequences of operation. Sequences that omit modes such as warm-up, failure response or alarm handling leave programmers to guess. See writing clear sequences of operation.
• Missing access. Valves, dampers, actuators, filters and coils located above hard ceilings or behind other equipment without access panels.
• No provision for measurement. Missing test ports, flow measuring stations or balancing valves needed for TAB and verification.
• Mismatch with the OPR. Design conditions, redundancy or operating hours that differ from what the owner requested.
• Points list does not support the sequence. A sequence calls for a reset based on valve position or airflow, but the necessary points are not included.
• Equipment selections without turndown. Boilers, chillers or fans that cannot operate stably at the low loads that occur most of the year.

Installation deficiencies

Air systems

• Fire, smoke and volume dampers left closed after construction.
• Ductwork leakage at joints, access doors and connections.
• Flexible duct that is too long, kinked or crushed.
• Filters missing, installed with bypass gaps or in the wrong direction.
• Fans rotating in reverse or with incorrect drives.
• VAV box airflow sensors installed with insufficient straight duct upstream, producing unstable readings.
• Outdoor air intakes too close to exhaust outlets or plumbing vents.

Hydronic systems

• Strainers not cleaned after flushing.
• Air trapped in piping because automatic air vents were not installed at high points.
• Control valves installed backwards or in the wrong pipe.
• Balancing valves missing or installed where flow cannot be measured accurately.
• Pumps with incorrect impellers or rotation.
• Glycol concentration different from design.

Controls

• Sensors installed in poor locations, such as space sensors on exterior walls or in direct sunlight, or duct sensors too close to coils. See sensor selection, location and calibration.
• Averaging temperature sensors installed as single-point sensors, or not serpentined across the duct.
• Actuators wired to open when they should close, or with the wrong fail position.
• Points mapped to the wrong equipment, so the BAS graphic shows one unit while controlling another.
• Sensors not calibrated, or with incorrect scaling in the controller.
• Missing or wrong network addresses causing communication failures.

Programming and sequence deficiencies

Controls programming generates more commissioning issues than any other area on most projects.

Economizers deserve particular mention because they fail so often. See economizers: types, controls and common failures.

Testing and balancing deficiencies

• Air or water flows not meeting design, with no explanation in the TAB report.
• Outdoor air quantity not measured.
• VAV box flow calibration not completed, so the BAS reports airflows that differ from measured values.
• Duct static pressure or pump differential pressure setpoints set higher than necessary.
• Reports with values that do not match spot-check measurements.

Documentation and turnover deficiencies

• Operations and maintenance manuals that are generic catalogues rather than project-specific information.
• As-built drawings that do not reflect field changes.
• Controls drawings and sequences that differ from what was programmed.
• Training delivered in a single short session without hands-on content, or not recorded.
• Missing warranty information and spare parts lists.

Why these deficiencies keep happening

The root causes are remarkably consistent:

1. Compressed schedules. When construction runs late, start-up, controls checkout and TAB are squeezed into the final weeks.
2. Poor coordination between trades. Mechanical, electrical, controls and fire alarm contractors each assume another is responsible for an interface.
3. Contractor self-testing skipped. Systems are presented for witnessed testing before the contractor has checked them.
4. Unclear documents. Ambiguous sequences and incomplete points lists invite interpretation.
5. Changes not communicated. Field changes and substitutions that are not reflected in sequences or drawings.

How to prevent them

• Start commissioning in design and include sequence reviews at every milestone.
• Require contractors to complete construction checklists and controls point-to-point checkout before functional testing.
• Hold coordination meetings focused on interfaces: fire alarm and HVAC, electrical and mechanical, BAS and packaged equipment controls.
• Protect time for start-up, TAB and testing in the construction schedule.
• Use trend data after occupancy to catch issues that do not appear during short tests.
• Track issues in a shared log with clear responsibility and due dates.

Frequently asked questions

Are deficiencies a sign of a bad contractor?

Not necessarily. Some deficiencies occur on nearly every project because of the complexity involved. What matters is whether they are found and corrected before the owner takes over.

Who pays to fix deficiencies?

Installation and programming deficiencies are generally the responsibility of the contractor under the contract documents. Design deficiencies are resolved through the design team and may involve change orders. The commissioning provider documents the issue; the contract determines who pays.

Key takeaways

• The same categories of deficiencies appear on most projects: design gaps, installation errors, programming problems, TAB issues and weak documentation.
• Controls programming and sequences generate a large share of commissioning issues.
• Root causes are compressed schedules, poor trade coordination and skipped self-testing.
• Early design review, contractor checklists and protected testing time prevent many deficiencies.
• Post-occupancy trend review catches what short-term tests miss. Our building commissioning process is built around catching these issues early.