Making savings in commissioning
The Government’s energy white paper has set an aspiration to meet UK long-term reduction targets in the drive towards carbon neutral buildings. The decision the UK takes on energy policy is critical in meeting these targets. Under the umbrella of the Energy Performance of Buildings Directive (EPBD) Part L of the building regulations has already contributed to around 40% improvement in the energy efficiency of commercial and residential buildings.
Complying with Part L in order to produce an accurate and reliable HVAC system has had a profound effect on the market for building services as a core aspect of the energy efficiency of buildings. It is now vital that the mechanical services are considered as a key element, not only to protect the health of the occupants and preserve the structure of the building, but also to maintain a constant and comfortable working environment that is cost effective, carbon efficient and above all, easily sustainable. When designing a waterborne system, rigorous energy efficient criteria for compliance is required, of which architects, designers, contractors and developers need to be fully aware.
Two out of three buildings have indoor climate problems, with the majority stemming from hydronic imbalances. Unless accurately balanced the hydronic system will not function properly, leading to energy waste and poor quality indoor conditions for occupants. A fully functional and balanced HVAC system can cut energy consumption by up to 40%, as well as eliminating complaints and costly remedies that derive from the indoor climate.
Minimal operation throughout the night can save energy and cost for a business, but it is the return to full operation each morning that opens all the control valves, in which the balance can be tilted, a common design problem. In unbalanced plants the circuits with the lowest demand must wait for full flow until the temperature sensors in the favoured circuits signal that the set point has been reached. Meanwhile, occupants in the rooms supplied by unfavoured circuits do not receive the comfort they require. Many rooms only receive the desired temperature at midday, some not until late afternoon and others not at all.
The first reaction of occupants dealing with temperature fluctuations will be to complain – while staff or operatives lower the set point in cooling conditions and increase the set point in heating. All the while the boiler has to work on overtime to bring the warmth to the unfavoured circuit, which ultimately is not energy inefficient. This is what can be called the cost of discomfort – the cost of 1ºC lower than design conditions in cooling is 12-18%, and for the same in heating is between 6 and 11%, the result of loss of controllability in the system which can be prevented through the appropriate use of differential pressure controllers.
Tour & Andersson’s Total Hydronic Balancing is a set of means and methods for making waterborne systems readily controllable so they provide the intended indoor climate at minimum operating cost. Installing a variable flow system saves pump energy, particularly in cooling where pump energy is 6 – 12% of a chiller’s energy consumption in a cold water system.
In order to get the best out of a variable flow system the controllers must be able to do just that – control the system. However, this can only happen if design flows prevail in the plant when necessary.
In variable flow systems, the differential pressure is also variable. This may adversely affect working conditions for modulating control valves and wastes 15 – 25% of energy. The challenge faced by the system designer and building manager is that if the differential pressure varies too much it is necessary to stabilise it to prevent incorrect flow. Therefore being able to keep differential pressure constant will improve control, ensuring a comfortable indoor climate with less noise, shorter start-up times as well as reduced maintenance costs whilst providing an overall energy efficient operation.
New demands placed on designers and specifiers of shorter installation time frames, flexibility in design for the commercial and public sector, last-minute design changes as well as time and labour costs, contribute to forcing installers to find more cost-efficient solutions.
Systems such as the new TA-H.U.B. (Hydronic User-Friendly Balancing) is the latest technology for specifiers, offering time (and therefore cost) savings of at least 20% for installation, over 50% for commissioning, as well as significantly reducing maintenance time of waterborne systems.
As a completely bespoke solution, such systems use a central location approach, which means that instead of having to specify up to eight balancing valves, the whole process is combined into one specification. Commissioning is made easier by the installation requiring just one location for up to eight terminal units. The balancing of a building is easier when fewer locations need to be accessed. By installing this type of single unit valve arrangement you will cut down the access required by up to a factor of eight. This means that balancing will be easier and therefore more efficient as well as providing a balanced system to reduce running costs and increase occupant satisfaction.
Such innovations are suitable when there are several terminal units that need to be balanced, when the building demands high flexibility, for areas with difficult access such as apartments, office blocks, schools, and when there is restricted access for unauthorised personnel. With 80% of commercial buildings incurring last minute changes in design, an adaptable and accommodating system is required to provide quicker and cost effective re-balancing and fault finding.
Partnering with a supplier that is able to support products with sophisticated software that can size balancing valves, pipe work and aid in the selection of control valves and pumps, such as TA Select 3, will enable specifiers and installers to select a project and decide upon the correct valve and design, with the software forecasting the best results depending on the application.
Careful consideration is essential in choosing the correct waterborne system for a building. Taking into account the design and access of a building will determine the system used. Specifying a system that uses pre-assembled parts and is installed in one location will mean that access for commissioning and trouble-shooting is located in one place, eliminating the hassle of a restricted building. As well as time and cost savings, an accurate and reliable HVAC system will ensure a comfortable indoor climate with less noise and overall energy efficient operation – successfully fulfilling Part L.