The Building Automation System (BAS) could be considered the heart of the building. The automation of HVAC equipment is what keeps occupants and tenants comfortable and this is one of the factors that has a direct effect on productivity and performance. Having dealt with many different types of buildings in the Dimax portfolio, which includes multi-unit residential buildings, commercial office buildings, data centers, hospitals, universities and others, we have found this to be the case. Once a BAS is specified, installed and commissioned by various parties, it is up to the building operations team to make sure that the heart of the building doesn't skip a beat. Dimax works with the building operations team and uses live BAS data to ensure the buildings perform as efficiently as possible. Here are some of the most common operational issues that we see:
1. Uncalibrated sensors showing incorrect readings
Sensors need to be calibrated at installation to be no more than 1% of the sensor’s measurement range. Depending on the purpose and application, some sensors might need to be calibrated to 0.1% of their measurement range. New sensors are normally factory calibrated so there aren't any major issues unless the product is defective. As sensors get old, some will lose their accuracy if not calibrated regularly. It is standard industry convention for maintenance contractors to calibrate sensors annually. If a sensor is showing an incorrect reading, if it is too high or too low, it may run equipment harder or longer than required. Or it may not run equipment at all which may result in alarms and/or complaints from occupants.
2. Faulty actuators, valves, dampers
Valves and dampers control the flow of water and air, the two heat exchanging mediums. In order for there to be efficient utilization or rejection of heat, it is essential that the actuators for the valves and dampers operate properly. An actuator that is jammed, out of alignment or failed will affect the transfer of heating or cooling which will result in loss of efficiency and potentially damage to the HVAC equipment and/or occupant discomfort. For larger AHUs, there are some applications of multiple dampers being connected through linkages in order to direct airflow with one incoming command signal that controls all the damper actuators. Sometimes, the actuators might not have an issue but the linkages might become loose, disconnected, or even brok
en which will restrict or prevent air flow. Actuators need calibration as well. We have found many instances of the correct voltage being sent to the actuator from the BAS and the actuator opening too little or too much due to lack of calibration.
3. Loss of connection with the BAS
In the event of communication failure with the BAS or the BAS crashing, most of the equipment could begin operating in its fail-safe mode. The operators are then required to run the equipment in manual mode until the controller comes back online or is replaced. Once the BAS controller is replaced, the building operator has to remember to put all equipment back into automatic with all the same settings as before in order for the equipment to operate properly and as efficiently as it was before.
4. Equipment in manual mode
BAS technology has come a long way and is constantly improving with new features. It is interesting to note that there are still many building operators who operate HVAC equipment
manually and do not trust the BAS. Whether this is due to lack of understanding or the BAS simply not being configured properly by the installation contractors, there are far too many buildings with perfectly capable BASs that have their equipment being run manually by the building operators. As we mentioned in our previous blog, “The Changing Role of the Building Operator”, the average age of a building operator is 55 years. Some of these building operators are not entirely comfortable with new technology and get overwhelmed with complications in the initial set up of the BAS. On more than one occasion, we have found that the building operator will simply prefer to run the equipment in manual mode instead of fixing a glitch or programming error in the BAS. Running equipment in manual mode can waste a lot of energy as it might keep equipment on after hours. Equipment that has the capability to modulate (boilers, chillers, fans and pumps with VFDs) might keep running at 100% even though the building requirement might be much less. In short, running equipment in manual mode might be necessary during repairs and maintenance, but it certainly wastes energy if it is being done all or most of the time.
5. Faulty connections
When the mechanical and controls consultants prepare complete engineering specifications and drawings, the job of the installation contractor is straightforward. Equipment and sensors are installed as per the drawings and the BAS is programmed according to specifications. However in reality, this is sometimes not the case. The construction and controls industry is full of examples where equipment was installed ‘on the fly’, without any drawings or specifications. This could be hard to fathom for an outsider, but it is common practice for contractors to ‘wing’ the installation and wiring in order to meet tough deadlines and/or extremely tight budgets and/or compensate for their own or someone else’s lack of due diligence. Even in the presence of complete specifications and drawings, sometimes changes need to be made due to limitations on site or environmental factors that could not be foreseen by the design team. These changes could be for better or worse. For example, we have found many cases of sensors and equipment being wired to the wrong terminals on the BAS controllers. Simple errors like connecting the supply water temperature sensor to the terminal of the return water temperature and vice versa, can alter the operation of a chiller or boiler, forcing it to work harder or go into alarm.
