Consulting-Specifying Engineer - May 2008 - (Page 54) Oversight Commissioning process Contractor Responsibility CxA Responsibility Complete Involvement Total Cx effort Figure 1: Commissioning provider involvement versus division of total costs determine who will perform this testing and to what level, based upon the level of assurance necessary. Possible conflict of interest issues need to be evaluated when determining roles and responsibilities. The criticality of the systems to be commissioned will be a primary factor in deciding who is best suited to perform the Cx tasks. For critical facilities, each entity should perform the work best suited to their strengths. Design engineers are very good at producing a set of construction documents to provide reality to the owner’s facility needs. Contractors are very good at providing labor and materials and constructing a facility in the most logical and economical manner to fit a schedule. CxA are very good at evaluating and testing systems to provide assurance the systems fulfill the requirements of the facility. A knowledgeable third party CxA provides an independent point of view in the installation and operation of the systems. Knowledge in the design combined with experience operating the equipment and systems provides a unique set of skills that the CxA must possess. The perceived disadvantage of the independent CxA is that there is significant extra cost associated with this option. As we will explain later, this is not the case. When selecting a Cx team, experience and diversity are a must. The requirements of the Cx team must be specific to ensure that the tests are written and witnessed by personnel with sufficient experience to verify that the systems will meet the OPR. Ensure that personnel have the appropriate level of experience required by each task in each process. This does not mean that a professional engineer with 20 years of experience needs to take a pitot tube duct traverse to ensure a restroom exhaust fan is delivering design flow. However, that level of expertise is required to verify all the required operating scenarios are included in the control sequences for the chiller plant of a data center. Due to the increased complexity of today’s critical facility systems, it is not possible for one person to be an expert in all commissioned systems. The complexity of the HVAC, building automation, electrical, fire and life safety, and security systems requires discipline specific specialists in each area. For example, the CxA may have an incredibly strong background in building automation systems with the ability to determine if a control loop is properly tuned, but may not be well-suited to identify the requirements of and be knowledgeable in testing generator paralleling gear with load shedding. It is necessary to pull together multiple experts in the various disciplines to perform the discipline specific Cx activities. The costs of commissioning When considering the total initial cost of the Cx effort, keep in mind all the work performed by all the team members is included in the total cost. The two key words are total and initial. Total cost includes time spent by the CxA, contractors, equipment suppliers, construction management, and the design team. Cx has cost implications far beyond the initial hours spent by the team members during the Cx process; however, we will only focus on the initial costs for this discussion. The total Cx costs can be divided into two primary groups; the CxA and the contractor. The contractor group includes the general contractor and/or construction manager, subcontractors, and equipment suppliers. The owner and design team also have costs directly related to the initial Cx effort, however, they are typically insignificant compared to the CxA and contractor group. The Cx approach greatly determines the total initial Cx cost and establishes how those costs are divided between the CxA and the contractor. Figure 1 illustrates the relationship between the CxA involvement in a project and how the total cost is divided between the CxA and contractor. The percentage of the total cost attributed to the contractor varies inversely with CxA involvement. The percentage of the total cost attributed to the CxA varies directly with CxA involvement. The Cx approach will dictate where on line A-B a project resides. For more discussion on Cx costs and how to hire a Cx provider, download the complete paper presented at the National Conference on Building Commissioning, April 21-24, at www.peci.org/ncbc. The complex, redundant nature of crucial facilities requires Cx processes and teams with commensurate breadth, depth, and experience. Owners need to decide early what level of assurance their facilities require for safe, reliable, and cost-effective operations. And then owners need to contract and empower an independent third-party Cx authority to see the job through. About the authors Prendergast and Whorton are project managers/commissioning providers for many of GBA/ViroCon’s commissioning projects with more than 11 and 14 years experience, respectively. Riley is the lead electrical engineer for all of GBA/ViroCon’s commissioning projects and has been providing electrical systems startup and commissioning services for more than 15 years. 54 Consulting-Specifying Engineer • MAY 2008 http://www.peci.org/ncbc
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