office buildingIt is an alarming fact that many building energy management systems (BEMS) have either never been serviced or have received little or no maintenance in years. Some will not even have been reset to compensate for changes to a building’s layout or occupancy patterns. To enable users of its systems to address this potentially costly problem, a comprehensive BEMS audit should be carried out.

By reducing energy and maintenance costs, audits should generally pay for themselves within a year — sometimes far sooner. Moreover, they will usually lead to improved comfort conditions for a building’s occupants. If the BEMS controls cooling towers or a hot water system, it could also help ensure that the risk of legionellosis continues to be effectively combated. Invariably, the service will increase end-user confidence in the building energy management system.

What Happens During a BEMS Audit?

A BEMS audit begins with a field service engineer making an initial appraisal of what needs to be done — having first talked to the end-user. The engineer then reports back with detailed recommendations. The audit will always include an integrity scan of the system, plus a thorough check of its functionality to confirm it is controlling the services as intended and has not been overridden or subjected to unauthorized changes.

It may also be necessary to recalibrate sensors (or possibly replace them) and retune control loops. A small measure like loop tuning, which might be required to prevent space temperature overshoot, can result in significant energy savings.

Controller and supervisor files will be backed up as a matter of course as a safeguard against loss or corruption of data. If the supervisory software was not the latest version, an upgrade would be installed. It is expected that in many instances there will also be a need to supply new system documentation, comprising control strategy diagrams and a full description of what the controls do. This will be a particular requirement on older systems, where the original documentation may have been lost or be in need of updating.

As part of the audit, the engineer should look to identify ways of further cutting costs through development of the control strategies. Small enhancements, such as adding automatic changeover of boilers and pumps, could generally be implemented immediately. Systems in air conditioned buildings often offer the most scope for improvement, especially if the original control specification made no provision for use of free cooling or coordinated control of the heating and cooling plant.

Publication date: 11/17/2014

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