Two years ago, the Building Services Research and Information Association (BSRIA) identified these problems, and others, in The effective bms: a guide to improving system performance. The guide sought to establish an assessment method that would help facilities managers and maintenance staff improve the performance of their systems.
BSRIA's manager for the project was Kevin Pennycook, now technical knowledge manager at the association. He explains: "The fact is that, over the years, we've done lots of projects that relate to building management systems and many don't work particularly well."
There are three primary reasons to install a bms: to save energy; to ensure that plant operates properly; and to keep the occupants of the building comfortable. Energy saving tends to take priority, but a poorly performing bms will fall well short of its energy-saving targets.
However, excess energy use is rarely the reason for a complaint about a bms. "What's flagged up is thermal comfort," says Pennycook. "If you have staff in an office, a bank in the City for example, and they all start shouting that it is too hot, cold or stuffy, people take notice."
So why do building management systems so frequently fail to live up to expectations? At all stages in the life of a bms – specification, installation, commissioning, day-to-day use and maintenance – there is a chance that its performance could be compromised.
Without a detailed and complete specification, the bms that is installed is unlikely to meet the client's needs, and disputes are more likely to arise in a lengthy contractual chain that includes the client, main contractor, a mechanical or m&e contractor, and, finally, the controls supplier and commissioning engineer.
In particular, commissioning engineers should be consulted as early as possible. "If you speak to a commissioning engineer," says Pennycook, "their main complaint will be a lack of liaison."
Doug Robins is project director at AES Control Systems in Northampton. He stresses that direct access to the client can be vital: "When you get access to the client directly, things run a lot more smoothly."
But installation and commissioning are where most of the problems occur. CIBSE Commissioning code C: automatic controls, written by Pennycook and also published in 2001, highlights the problems of compressed schedules for commissioning.
Any activity that takes place towards the end of a project can be pushed for time because of earlier delays, and engineers who commission building management systems tend to feel the squeeze. Commissioning engineers depend on m&e contractors to finish their work before they can start their own.
"Programmes get constrained," says Robins, "and commissioning time can be cut drastically." He says it is not unusual for a schedule to be cut from four weeks to two. "It puts a lot of pressure on contractors like ourselves," he adds, "and often we're still commissioning when the job is finished. You do your best at the end of the day."
Inadequate specification and rushed commissioning have a knock-on effect on maintenance. There may be no documents describing the system or its operation, other than manufacturers' product manuals and data sheets.
Unfortunately, rushed commissioning may also increase the need for maintenance of both the control system and the plant that it controls. Any unnecessary switching of plant will shorten not only the interval between breakdowns, but also the working life of the equipment.
At the end of a project, the main contractor will be looking for ways to cut costs and may downgrade the bms by, for example, removing local controls for use by the building's occupants. Such actions will inevitably increase the number of complaints about discomfort when the building is occupied.
Even after the bms is installed and commissioned, it will not work effectively unless its operators are well trained. Pennycook says: "Often, the people who operate them are not effectively trained, not in the sense that they don't know which icons to click on in the software, but they need to understand how the plant operates and how to interpret the data."
For this reason, bms operators must understand hvac systems and components and have a detailed knowledge of the buildings in which they are working.
Some operators may not be trained at all. "What tends to happen is that you arrange days for training and often people don't turn up," says Robins, "or the people that do come are not the ones who will be dealing with the system, so they are not interested."
Solving potential problems
Installation and commissioning problems demand practical solutions. For example, technology may come to the rescue of hard-pressed commissioning engineers. "People have developed quite sophisticated algorithms, which you can fine-tune for a particular building," says Pennycook. But those algorithms are currently difficult to transfer from one building to another.
A development engineer from one controls manufacturer says: "We're providing more facilities to see and interface with the control strategy and the plant during commissioning...but I wouldn't say we've reached the perfect solution yet."
Trend Control Systems already has its Loop Tuner, which takes some of the drudgery out of tuning control loops, both during commissioning and maintenance. Other software tools can rapidly scan system sensors and outputs.
In its Commissioning code C, CIBSE describes two possible approaches to shortening timescales, although it recommends neither. The first is to throw more manpower at the problem, either by extending working hours or hiring more engineers.
This approach has its disadvantages. There may be health and safety implications and there are rarely enough skilled staff available for commissioning anyway.
The second approach is to do as Robins has suggested: finish the commissioning after the building is occupied. In general, says CIBSE, commissioning activities can be divided into two groups: those that must be done before the building is occupied and those that can be carried out in the early stages of occupation.
Those in the first category include commissioning control panels, the communications network, sensors and actuators, and the operator workstation for the bms. Those in the second include functions that can operate under simple manual control, sensors for non-critical monitoring, low priority alarms and completing the documentation.
Pre-commissioning is another possibility. Although wiring, connecting the communication bus and installing sensor and actuators must, by definition, be done on site, other tasks can be done elsewhere. Initial configuration of control panel software, user interface software and control panels can be started off site.
Maintenance is an ongoing cost that is rarely budgeted for during the specification and tender stages of a project. As a result, it is often neglected and the performance of the bms steadily deteriorates. If maintenance is considered from the start, and bms performance checks are included in the contract, the bms should perform well.
BSRIA says that training should be incorporated in any system specification, and that operators should, if possible, be present while the bms is commissioned to gain an insight into its configuration.
The most difficult bms problems to tackle, however, are contractual. Ideally, commissioning engineers would be involved in all aspects of the project and have direct access to the client. This, however, will be difficult to achieve as long as the bms vendor and commissioning engineer remain, as BSRIA says, "at the end of the contractual chain".
Source
Electrical and Mechanical Contractor
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