When providing commissioning services relative to HVAC, electrical, and plumbing, one issue that frequently comes up is the request that commissioning (functional performance testing) of these systems be completed during design peak demand. For HVAC systems, this means demonstrating heating system performance during the heating season and cooling during the air conditioning season.
If the commissioning engineer is brought on during the construction phase, it is very difficult to convince a contractor to defer the demonstration of one of these systems until the peak heating or air conditioning season. The contractor is anxious to close out the job on time and in budget. They do not want to have the owner acceptance be delayed four or six months while everyone waits for the correct outdoor air temperatures to arrive. The reasons can be many, but withholding final payment, owner sign-off for the project, and/or determining and designating the starting time for equipment warranty, are right up there at the top of the lists.