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Commissioning: Warranty Period

The comprehensive definitions of commissioning, as it applies to building systems, state that the commissioning process starts during the early design phases and continues through the first year of building occupancy of a new or renovated facility. Warranty period commissioning activities vary widely from project-to-project, depending primarily on the priorities, past experiences, and budget of the building owner.

Commissioning tasks, leading up to and including final verification tests and training, minimize system operational problems during the first year of occupancy (and through the life of the building). Ideally, the only problems which should arise during the warranty period are equipment problems, i.e., motors that burn out, valves that leak, pump seals that fail, etc. Correcting system performance problems, i.e., sequences of operation which don’t function as specified, systems which don’t “talk” to each other, etc., should be taken care of during the verification testing and deficiency correction at the end of construction.

However, many building owners choose to retain the services of the commissioning consultant for one more year as a smooth transition period between construction and full-fledged operation by the owner’s operations & maintenance (O&M) staff. The commissioning consultant becomes an advisor to the O&M staff as they start running the building in “real life.” The consultant is available for questions, clarifications, and troubleshooting - providing an on-call, on-the-job training service.

Deferred Testing

At a minimum commissioning extends into the warranty period as necessary to perform “opposite season” verification tests. These are system performance tests which could not be conducted immediately after the systems were installed, usually because the equipment could not be operated or adequately exercised due to weather conditions.

Most deferred testing is of HVAC systems, as they are most likely to be seasonal in nature. For example, some chiller/cooling tower combinations are not intended to be operated in the winter, some buildings may not be provided with high pressure steam in the summer, etc. In addition, when testing system capacities, it may be detrimental to a building to create summer conditions (i.e., hot and humid) in the middle of the winter in order to test a cooling system’s capacity. Similarly, it may be virtually impossible to simulate design winter conditions in the middle of the summer.

Therefore, some of the verification testing must be performed during the warranty period. The commissioning specification should be clear about exactly which tests, or portions of tests, fall in this category so that the contractors understand their responsibilities to return to the building for these opposite season testing. A mechanism for holding payment for the cost of these tests should also be included in the contract documents. Even with financial leverage, it can be very challenging to pull the team of contractors together 4-6 months after substantial completion.

10 Month Checkup

Another popular feature of warranty period commissioning is the 10 Month Checkup. The commissioning consultant returns to the building 10 months into the 12 month warranty period to formally visit with the O&M staff, building occupants, and other interested people. This is an opportunity for the O&M staff to discuss system features that have worked well, things that haven’t lived up to their expectations, and features they wish they had thought about during design.

The commissioning consultant takes this information and develops two courses of action. First, any system deficiencies which should be corrected by the contractors because they were part of the original construction scope of work are documented and submitted to the contractors for correction. Second, system modifications which are desired but outside of the original scope of work are also documented and submitted to the building owner. Although the contractors are not responsible for addressing this latter “wish list,” the commissioning consultant can give the building owners some ideas on how the building owners might implement the system modifications as time and budget allow.

Performance Monitoring

Other commissioning tasks considered for the warranty period include “realtime” monitoring of system performance via trend logs and maintenance work orders. HVAC systems with direct digital control (DDC) are relatively easy to monitor through carefully set up point trend logs programmed into the DDC software. The O&M staff can print out graphical representations of the trend information and send them to the commissioning consultant, or the commissioning consultant can be provided with modem communication directly into the building’s DDC system.

By evaluating the trend logs, the commissioning consultant can discover system performance anomalies and often save energy consumption and improve indoor environmental conditions by seeing that the problems are corrected in a timely fashion. Also, in reporting back to the O&M department, the commissioning consultant teaches the O&M staff how to read and interpret the trend logs on their own – a skill which will prove valuable throughout the life of the systems.

Finally, some building owners request their commissioning consultants to receive copies of all maintenance work orders related to the commissioned systems. The consultant then evaluates the work orders in light of possible recurring or systemic problems which need to be corrected by the contractors prior to the end of the warranty period.


Commissioning: Getting It Right

Engineered Systems, May, 1998

Rebecca Ellis, PE, LEED AP, CCP, CxA
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318