Maintenance: The key to BMS efficiency

Modern building management systems (BMS) deliver high levels of comfort and excellent energy efficiency – but only if they are properly maintained. Planning for proper maintenance starts at the specification stage, says Steve Loughney of Siemens Building Technologies.
There is no doubt that most newly installed BMS perform well. Whether they are still performing well after a year or two of operation is, however, a different question entirely. Any number of things can change. Perhaps the most common is that settings are altered to deal with a particular set of conditions and are never restored to their original values.

Manual overrides may be applied and forgotten and, of course, over a period of time, the components used in the installation are subject to wear which inevitably changes their operating characteristics. Maintenance is the key to addressing these issues but, if that maintenance is to be effective – and cost effective – the time to start thinking about it is not when problems arise, but at the specification stage.

Unfortunately, in the past, the cost of the initial installation frequently outweighed the need for on-going maintainability. This concentration on the lowest possible installation cost then puts the burden of increased running cost on the future owner/occupier of the building.

Recent changes to the Building Regulations are, however, doing a lot to improve this situation by encouraging those involved in a new building to think about energy usage from the outset. As a result, new BMS installations will start to be considerably easier and less costly to maintain than their older counterparts.

It is all very well making this statement, but what are the factors that contribute toward making a system maintainable? One of the most important is accessibility.

When designing a BMS for a hotel, for example, it may seem logical to put control components in the guest bedrooms. If work is needed on any of these components, however, access is likely to be difficult unless the room is taken out of use. And, if the room is taken out of use, the hotel stands to lose revenue.

These problems can be avoided by siting the control components in service cupboards accessed from the corridor, without the need to enter the guest rooms at all. Provided that this type of decision is taken at the specification stage, the extra installation cost involved is small or non-existent, but the savings during the lifetime of the system are likely to be significant.

Access problems are not, of course, confined to hotels. Another example is the ceiling-mounted heaters used in large factories and warehouses, which are sometimes supplied with the controls as an integral part of the heater.

If, as is often the case, the heaters are suspended 10 or 15 metres above floor level, this means that even the simplest maintenance task, such as adjusting start/stop time settings, becomes expensive and inconvenient because it can’t be carried out without erecting scaffolding. With a little forethought, the controls for these heaters can easily be centralised and fitted at ground level.

So far, we have focussed on how a little extra thought in design can make BMS installations a lot easier to maintain, but what about users of existing systems? What opportunities do they have for improving maintainability?

Perhaps the most important is that they and, indeed, all users of BMS installations should ensure that they make full and proper use of the facilities provided by the equipment they have installed. There is little point, for example, in having a sophisticated BMS installation if it has been set up so that heating or other systems simply operate continuously.

This situation is encountered surprisingly often. Not only does it lead to enormous energy wastage, it also has a big maintenance impact. It’s not hard to work out that if equipment which should run for around 12 hours a day is running for 24 hours, it will need maintaining twice as often. In addition, its overall working life will be halved leading to increased capital as well as operational expenditure.

Also, it’s not at all uncommon, particularly in older systems, to find that the controllers provide many potentially valuable options which have never been used.

They may, for example, log the running hours of key components in the installation, such as fans. This information can be invaluable in maintenance planning to ensure that the components are serviced sufficiently often to keep them working efficiently, without wasting money by servicing them when they don’t need it.

Some BMS controllers can do much more, logging all types of operational data. Properly analysed, this data is the key to saving money on both energy usage and maintenance.

It may reveal, for example, a slow decline in the efficiency of a boiler, which indicates that attention is necessary to halt energy wastage. It may equally show a sudden change in energy usage in a part of the building, perhaps indicating that settings have been changed inappropriately, or that some of the BMS functions have been manually overridden. These issues can then be investigated and corrective action taken.

An installation with good accessibility and where the BMS controls are used to their full potential provides the best possible foundation for effective maintenance, but there is another important factor – the organisation which carries out the maintenance work. The essential requirement is to make sure that the organisation chosen is fully conversant with the equipment in use.

In practice, this is most easily achieved by selecting a maintenance provider that is a member of an approved partner scheme operated by the equipment manufacturer. This will ensure that the organisation has properly trained staff, and has full access to the latest product data and maintenance instructions.

Other considerations may include the size of the maintenance provider. Building owners with premises around the country may well find it convenient to have a provider that operates on a national scale.

Another factor worth taking into account is the maintenance provider’s ability to offer remote monitoring services. Most modern BMS installations have the facilities needed to send data, usually via a telephone line or broadband link, to a remote location. Maintenance providers with facilities for monitoring and using this data are in a position to offer valuable extra services.

They can, for example, analyse the data to ensure that maintenance is properly scheduled. Should a fault occur, the remote monitoring system will often make them aware of it before the building occupier even realises that there is a problem. In some cases, they may be able to send instructions to the BMS, via the same link as is used for monitoring, to correct or at least to temporarily bypass the fault.

If a site visit is unavoidable, remote diagnostics implemented via the monitoring link will usually indicate the type of problem and its probable cause. The maintenance provider can then be sure of bringing the correct replacement components to site on the first trip, eliminating the delays and costs associated with repeat visits.

As we have seen, the first step toward efficient maintenance is to take maintainability into account at the system specification stage, considering particularly accessibility of equipment, and the likelihood of its continuing availability. The next step is to make full use of the facilities offered by the equipment and, in particular, to take advantage of any data it produces which can help in forecasting and planning maintenance requirements.

Finally, it’s important to choose the right maintenance provider: appropriate know-how is essential, and the ability to provide on-line monitoring is a decided advantage. Following these steps is the route to operating a BMS which offers good performance throughout its life, and which always ensures that energy usage is optimised.