Modern Building Services

MODERN BUILDING SERVICES MARCH 2023 19 FEATURE WORKING BUILDINGS of a required filter change, but there is then a time-lag before replacement while the filters are operating inefficiently. A stand alone AHU monitoring system communicating to the cloud via a 4G gateway can be provided so that both the filter status and AHU run-time can be monitored remotely. Attendance on site to change the filters is therefore only required when the filter has reached the point where it’s dust loading and pressure-drop makes it more economical to change. This brings savings in material use, labour costs and energy. Reduced occupancy in buildings is the newnormal It is no longer appropriate to use the same filter change intervals as it was three years ago, and it is more important than ever to know the quality of the air and the amount of it that is being brought into the building. By measuring the air flow through the filters and correlating that with the outdoor air quality at the time, it is possible to model the dust loading of the filter so they can be scheduled to be changed at an appropriate time. In a building with demand controlled ventilation where the workers are now running a hybrid working strategy, filters that were previously changed every three months could potentially go six to nine months without replacement. Doing away with routine planned maintenance for filters only provides minimal labour savings when the FM teams still need to regularly inspect the belts on the fans in the air handling units. By simultaneously changing to direct drive fans, the need to regularly replace fan belts is removed. Modern fan motors can measure and report their status in terms of torque, power consumption, vibration etc to either a BMS or to a remote software platform via a 4G gateway. While we would recommend using 4G gateways to transport the data to the cloud, all of these monitoring systems can be directly connected to the building management system if data concerns exist at critical sites. Older style centrifugal fans may have been optimised for delivering high pressure with forward curved blades. Modern backward curved fans aremore efficient and quieter, and themotors that drive themhave come a long way in just the past ten years with far more efficient systems now available. Mixed flow fans combined with a replacement fan wall will offer the biggest energy savings in certain situations. The choice of which style of fan to use is dependent on how the building is to be operated. EC fans are highly efficient at their design duty, but do not give the same energy savings at lower speeds as the latest switched reluctance motors. Because of this, it is important to understand whether the ventilation system is demand controlled or operates at reduced fans speeds for large portions of the time, or if the system is typically running at a constant ventilation rate. This will help define which style of fan upgrade is most appropriate. This step change in maintenance requirements can be demonstrated via a return-on-investment calculation that takes into account both reduced energy frommore efficient fans and filters plus the reduced site labour costs. ROI when changing to a cloud-based maintenance and operation strategy is significantly shortened where travel times are longer or there is a high level of security at the site causing access challenges. Further considerations To derive real value from an AHU upgrade, it’s important to consider all aspects of the refurbishment. Such as If replacing coils or fitting UVGI systems on the downstream side of the cooling coil will keep the coil surface and drain pans free from biofilm build-up will further reduce the need to regularly inspect coils and drain pans. Further energy savings are realised by reducing biofilm build-up, as this keeps the cooling coil working optimally by ensuring efficient heat-transfer. Combining upgrades to air handling units in combination with adding in-room, or in-duct indoor air quality monitoring sensors allows for further enhancement opportunities. The addition of IAQ monitoring allows for air quality improvements to be made without wasting energy, as the ventilation rates can be altered according to both CO2 and other indoor pollutant concentrations. Source 1 https://tinyurl.com/59fh8pez More information can be found at www.arm-environments.com Table 2 Compact filter comparison – 2” panel and E rated 535mm ePM1 60% 8 pocket bag vs. 2” panel and A+ rated ePM1 60% compact filter. Product Basic Design Nominal Airflow Rate [m£/h] Energy Class Annual Energy Consumption [kWh] Total Energy Cost [GBP] PM1, m Load in t Op [µg/m£] Initial Pressure Drop [Pa] Stage 1 ePM10 80% Panel 0.944 E >1400 3360 71 60 Stage 2 ePM1 60% 8P Bag 0.944 E >2050 4920 41 145 Stage 1 COARSE 80% Panel 0.944 N/A 1832 4397 71 60 Stage 2 ePM1 60% V-Type 0.944 A+ 808 1939 68 65