This quick read comes from James Piper, a contributing editor for Building Operating Management. Facility managers too often overlook the importance of retrocommissioning the BAS. Building automation systems are not install-and-forget systems. They require regular maintenance if they are to operate effectively. Even with good operating and maintenance practices, however, wear and tear take their toll on system components, from temperature sensors to valves and dampers. And while the HVAC equipment will most likely keep operating, it will not be operating at peak efficiency. If facility managers are to maximize the potential of the BAS, they must confirm that the information being gathered by the system is correct and accurate, and that all functions carried out by the system are carried out as intended.
The only way to confirm that things are as they should be is through retrocommissioning. Retrocommissioning, like its cousin, commissioning, verifies the readings of all sensors and the operation of all control devices in the system.
Start by interviewing the system operators. What problems are they aware of, and what has been attempted to correct them? The reading of every sensor in the system will have to be verified. All devices connected to the system must be cycled and witnessed to confirm they are being operated properly. Failing to do this will allow error creep to slowly rob the system of performance and reliability. How often retrocommissioning should be repeated depends on the complexity of the system; in general, it is recommended that retrocommissioning be conducted at least once every two years.
Retrocommissioning can also help to identify changes that have taken place within the facility but have not yet been addressed by the system. Facilities are always in a state of flux. Functions change. Occupancy changes. As a result, HVAC system needs change. To keep up with these changes, existing HVAC systems are modified or replaced. While the connections from those systems to the BAS should be updated at the time of the occupancy change, not all are. Retrocommissioning is one way to ensure that all systems and their interface with the BAS are current.
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