Getting the balance right
Ensuring that office heating operates effectively and efficiently is not simply a case of setting thermostats. The entire HVAC system must be designed and balanced to control heating throughout a building. Greg Tracy explains how this can be achieved.
Good business sense
We all know how the interior climate in a workplace can affect overall mood and efficiency. A hot and stuffy atmosphere tends to make employees lethargic, which will obviously have a negative impact on their productivity and creativity levels. It’s not surprising, therefore, that optimising indoor comfort is not only good for the wellbeing of building occupants but also makes good business sense. By investing in the right balancing and control solutions you can create a comfortable and more productive working environment.
On top of these important benefits, achieving more precise control over temperatures throughout a building will avoid over heating some areas and wasting energy by heating unoccupied spaces. Correct hydronic balance within the heating system will cut energy consumption, resulting in lower energy bills, and help reduce the building’s carbon footprint. All this can increase the sales value, or rental potential, of an office building – so there is a lot at stake.
Hydronic balance and control
As any HVAC professional knows, the indoor climate in the average office building is subject to constant changes in demand. Heat loads will vary depending on the occupants, lighting, office equipment and the outdoor weather conditions. Problems with under- or over-heating due to system imbalance are a common cause for complaint in office environments. If, for example, the fan coil units serving one part of a building experience excessive demand, the units serving the rest of the building will be starved of their hot water supply. However, if the system is perfectly balanced it will perform as designed under all system conditions (full and partial load) and provide even heat distribution throughout the building, with no costly overflows or wasted energy.
Traditionally, balancing valves have played a key role in HVAC system design and hydronic balance. Perhaps the most notable development in this field has been the Pressure independent balancing and control Valve (PICV). The PICV has become a standard in lots of heating (and cooling) installations, particularly larger-sized systems in public and commercial buildings.
This versatile solution combines the control function, pressure independency and flow limitation all in one valve, reducing installation cost and time. This is because the previously complicated and time-consuming commissioning of a system is replaced by simple flow setting. Generally speaking, system designers no longer need to make Kv calculations for each single valve in the system. They can simply stop calculating once the design flow is determined because the PICV is selected on the necessary flow.
To take full advantage of its combined balancing and control features, a PICV needs to be equipped with an actuator, controlled by a room thermostat or building management system (BMS). The best results as far as indoor climate are concerned will depend, primarily, on the speed and accuracy with which the actuator responds to the control signal. The relatively recent development of digital actuators, is taking the balancing and control of commercial HVAC installations to new levels of ease, efficiency and accuracy.
We are living in a digital world so it is not surprising that this modern technology now offers a highly efficient replacement for standard on/off actuators and traditional installation and commissioning methods, which are both time-consuming and labour intensive.
Another benefit of going digital is the ability of the actuator to provide fully integrated BMS connectivity from head-end out to field devices. A digital actuator makes it possible to connect a HVAC system to the BMS via the BACnet communications protocol. It also offers remote commissioning of the system via the BMS, so hundreds of valves could be balanced with a single mouse click. As a result, valuable time is saved on site and much greater accuracy is achieved compared with using manual techniques.
Additionally, in the age of ‘big-data’ the ability of a digital actuator to collect and store performance data, on individual terminal valves, is a major advantage during installation, commissioning and ongoing maintenance. Faults, such as a jammed valve due to the build-up of particles, can be identified remotely and resolved more quickly, reducing disruption to building owners and occupants.
It is widely acknowledged that HVAC systems account for most of the energy use in a typical office building. Hydronic balance is the only way to ensure the installation delivers the intended indoor comfort at optimum efficiency and operating cost. A combination of multi-tasking PICV and the latest digital actuators is now helping to make this essential process faster, simpler and more accurate – and with the invaluable added benefits of ongoing system monitoring and feedback.
Greg Tracy is business development manager of Danfoss