provided by: Plant EngineeringHow long has your plant been operating since it was built? Is your maintenance thorough and up-to-date? Has there been an unexplained increase in energy usage? Have changes been made to the building systems? The answers to these questions and more may indicate that your plant needs recommissioning.
Recommissioning, or ?retrocommissioning,? is much like new building commissioning. It is a process where a detailed evaluation is performed for an existing facility to improve and optimize the building?s system operation, reduce energy usage and reduce maintenance downtime. When the evaluation is complete, the systems are adjusted, modified or repaired to implement the recommendations.
Recommissioning will identify problems with the operation or control of the building systems. From this, the equipment can be readjusted to operate more efficiently so it is less wasteful of energy. The additional benefits from recommissioning are that it can document these systems, providing the necessary information to troubleshoot problems or to track when the systems become unbalanced in the future. This will lead to systems with extended equipment life that will operate as the design intended, leaving a better controlled environment for the occupants and processes.
Recommissioning controls
Where initial cost is often the primary driver for building construction, many buildings are built without energy efficiency as the primary ? or even secondary ? focus of the building. Oftentimes, the control systems are ?value engineered? during construction to reduce first cost. Control systems, once programmed for their original configuration, very often are not properly modified when new systems are added to the building. Older control systems are not updated and have failures that are not properly repaired.
Large energy-using systems rely on the control system to do its job. When an economizer has been disabled, a variable-frequency drive is permanently moved to bypass or a lighting controller does not shut down the lights at the appropriate time, the result is wasted energy.
Savings and costs
A thorough recommissioning effort, including implementation of the recommendations, can result in overall energy savings between 5% and 15%, depending on age, condition, number of affected systems and complexity of the building.
Costs for the recommissioning process will also depend on these factors, as well as the type of facility involved. Typical costs for recommissioning can range from $0.50 per square foot to $2.50 per square foot or more. Proper planning ahead of time can lower costs. Plant managers and others involved should plan out goals, expectations and commitments of all shareholders before starting any recommissioning effort.
When considering recommissioning, evaluate the equipment life of the building. Equipment that is currently scheduled to be replaced due to age, condition or obsolescence should not be investigated during the recommissioning effort. Newer equipment offers the best opportunities to benefit from recommissioning efforts. The money saved due to energy savings can be used to pay for capital improvements, such as replacement of older equipment.
Where to start
Some power companies offer recommissioning programs and assistance such as trend information, building analysis or rebates. These can help reduce the costs of recommissioning. State energy offices are another resource. Local chapters of the Association of Energy Engineers, the Building Commissioning Association or ASHRAE are also good sources for finding recommissioning professionals.
All facilities change over time, but the commissioning process can be used to reduce energy costs on an ongoing basis. With rising energy rates, constrained budgets and renewed interest in conservation, performing and documenting the results of recommissioning can assist in achieving multiple objectives.
Michael Loftus, PE, CEM, LEED AP, manages the mechanical engineering department of CH2M HILL?s Dallas office. He has 14 years of energy management and sustainable design experience as well as mechanical engineering experience for industrial and manufacturing facilities.
author: By Michael Loftus, CH2M HILL
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