HEATING AND COOLING SYSTEMS CIRCUIT BALANCING


For every single degree temperature above 20°C, there is an 8% increase in heating costs


HVAC system fl ows are dynamic, changing throughout a typical 24-hour period. Because of heat gain from the sun and changes in building occupancy, the demand for heating and cooling varies, not only throughout the day and night, but also by building sector. An effective and effi cient HVAC system must provide correct energy output when and where required, and proper hydronic balancing is the key to proper performance in the most cost-effective way. Circuit balancing is essential to ensuring that heating and chilled-water systems deliver correct fl ows to all terminal units in an HVAC circuit. In an unbalanced system, sectors of a building have underfl ow or overfl ow conditions that impact control-valve authority and, therefore, indoor climate. For instance, areas closest to an energy production and delivery source could receive excess fl ow, resulting in excessive heating or cooling. On the other hand, areas furthest from an energy production and delivery source could receive insuffi cient fl ow, causing inadequate heating or cooling. For every single degree temperature


Balancing Valve ∆H Coil Figure 1: Coil-CW/HW schematic drawing


above 20°C there is an 8% increase in heating costs, while each and every degree of cooling below 23°C adds 15% to costs. By properly applying circuit balancing techniques to each balancing valve it is possible to achieve proper balance throughout a system, so that all circuits receive specifi ed design fl ows for optimal performance. When pumps, chillers and other components operate at the lowest possible load, owners benefi t from less wear and tear, longer equipment life and lower energy and maintenance costs.


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Isolating system trouble spots An improperly adjusted balancing valve, clogged strainer/coil or other system issue that changes the specifi ed fl ow rate through a coil or air handling unit (AHU), typically causes insuffi cient or excessive heating or cooling. Diagnostic analysis can be performed readily by checking the rate of fl ow through a balancing valve. Moreover, issues can be identifi ed during building commissioning and before tenant move-in. In addition to providing a comprehensive


record of specifi ed and actual fl ows, circuit balancing helps simplify the setup and monitoring of control equipment. This reduces capital costs, as well as the time needed for commissioning.


Conclusion Far too many buildings are plagued by temperature variations that can lead to tenant complaints, high energy consumption and increased operating expenses. In most cases, these faults can be easily resolved through proper balancing of the heating or cooling system in conformance with original design performance specifi cations. In addition to ensuring occupant comfort


and minimising energy and operating costs, effective circuit balancing can help determine the causes of improper heating and cooling. Therefore, a comprehensive circuit balancing programme should be integrated into any commissioning to save time and energy and to improve the long- term value of the building. CJ


DAVID L HUDSON is a senior product engineer for Victaulic. He is a practising mechanical engineer with more than 26 years of experience.


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