In Austria, the Heizkostenverordnung<\/strong> (Heating Cost Ordinance) and provincial building codes in Vorarlberg, Tirol, Steiermark, and Wien explicitly require commissioning documentation that includes hydraulic balancing verification.<\/p>\nIn Germany, the Geb\u00e4udeenergiegesetz (GEG)<\/strong> requires that new heating system installations demonstrate efficient operation. Hydraulic imbalance is a direct violation of this requirement.<\/p>\nFor installations receiving federal subsidies<\/strong> \u2014 including Austria’s Raus aus \u00d6l und Gas<\/em> programme, Germany’s Bundesf\u00f6rderung f\u00fcr effiziente Geb\u00e4ude (BEG)<\/em>, and Switzerland’s cantonal energy incentive schemes \u2014 documented hydraulic balancing is a mandatory condition for receiving grant payments.<\/p>\n<\/span>Key Features of Hydraulic Balancing<\/span><\/h2>\nHydraulic balancing is not a single action. It is a system-level calibration process consisting of five core technical features:<\/p>\n
\n- Flow Rate Calculation<\/strong><\/li>\n
- Differential Pressure Control<\/strong><\/li>\n
- Presetting of Balancing Valves<\/strong><\/li>\n
- Pump Optimisation<\/strong><\/li>\n
- Commissioning Documentation<\/strong><\/li>\n<\/ol>\n
<\/span>Detailed Explanation of Features<\/span><\/h2>\nFeature 1: Flow Rate Calculation<\/h3>\n
Definition:<\/strong> Flow rate calculation determines the required volumetric flow (in litres per hour, l\/h) for each individual circuit in the heating system.<\/p>\nPurpose:<\/strong> It establishes the target values that balancing valves and pump settings must achieve.<\/p>\nHow it works:<\/strong><\/p>\nThe required flow rate for each emitter is calculated using the fundamental heat transfer equation:<\/p>\n
\nQ = \u1e41 \u00d7 c \u00d7 \u0394T<\/strong><\/p>\n<\/blockquote>\nWhere:<\/p>\n
\n- Q<\/strong> = Required heat output of the emitter (W)<\/li>\n
- \u1e41<\/strong> = Mass flow rate (kg\/s)<\/li>\n
- c<\/strong> = Specific heat capacity of water (4,182 J\/kg\u00b7K)<\/li>\n
- \u0394T<\/strong> = Temperature differential between flow and return (K)<\/li>\n<\/ul>\n
Practical example:<\/strong><\/p>\nA radiator with a design heat output of 1,000 W, operating at a flow temperature of 45 \u00b0C and a return temperature of 35 \u00b0C, requires:<\/p>\n
\u1e41 = Q \u00f7 (c \u00d7 \u0394T) = 1,000 \u00f7 (4,182 \u00d7 10) = 0.024 kg\/s \u2248 86 l\/h<\/p>\n
This value becomes the target for the balancing valve on that circuit.<\/p>\n
Benefits:<\/strong><\/p>\n\n- Eliminates guesswork from system commissioning<\/li>\n
- Creates a verifiable performance baseline<\/li>\n
- Enables repeatable recalibration after system changes<\/li>\n<\/ul>\n
Practical application:<\/strong> Flow rate calculations are performed during the heat load calculation phase (EN ISO 12831) and documented in the hydraulic schematic. iDM heat pump controllers use these values to configure flow-based control algorithms.<\/p>\nFeature 2: Differential Pressure Control<\/h3>\n
Definition:<\/strong> Differential pressure control maintains a stable pressure difference across each balancing point, regardless of which thermostat valves are open or closed.<\/p>\nPurpose:<\/strong> It prevents flow redistribution when individual room thermostats modulate. Without pressure control, closing one valve increases pressure and flow in all other circuits.<\/p>\nHow it works:<\/strong><\/p>\nTwo devices manage differential pressure:<\/p>\n
Differential pressure controllers (DPC \/ Differenzdruckregler):<\/strong> These are automatic valves installed at the branch or riser level. They maintain a fixed pressure differential across their section of the network. When thermostat valves close and system pressure rises, the DPC opens to bypass excess pressure. When valves open, the DPC closes to maintain the set point.<\/p>\nPressure-independent control valves (PICV):<\/strong> These combine flow limitation and differential pressure control in a single valve body. They maintain rated flow regardless of pressure fluctuations in the network.<\/p>\nBenefits:<\/strong><\/p>\n\n- Eliminates noise from thermostatic valves (whistling, water hammer)<\/li>\n
- Prevents circulation pump hunting<\/li>\n
- Allows low-temperature operation without pressure-induced flow surges<\/li>\n<\/ul>\n
Regulatory note:<\/strong> DIN EN 215 governs thermostatic radiator valve performance. Stable differential pressure is a precondition for thermostatic valves operating within their rated range.<\/p>\nPractical application:<\/strong> In multi-storey residential buildings, DPCs are installed at each floor manifold. This allows each floor to be balanced independently, simplifying commissioning and troubleshooting.<\/p>\nFeature 3: Presetting of Balancing Valves<\/h3>\n
Definition:<\/strong> Presetting is the mechanical pre-configuration of a balancing valve to a specific flow-limiting position before the system is activated.<\/p>\nPurpose:<\/strong> It imposes a hydraulic resistance on each circuit that corresponds to the calculated pressure drop needed to achieve design flow.<\/p>\nHow it works:<\/strong><\/p>\nBalancing valves are installed in series with each emitter circuit. Each valve has a graduated scale (expressed in pre-setting values, Kv values, or flow units depending on the manufacturer). The installer calculates the required pressure drop for each circuit, converts it to a valve setting, and mechanically sets the valve before system startup.<\/p>\n
Types of balancing valves used:<\/strong><\/p>\n<\/div>\n\n
\n\n\n| Valve Type<\/th>\n | Function<\/th>\n | Application<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| Static balancing valve (e.g., IMI TA-STAD, Oventrop Hydrocontrol)<\/td>\n | Fixed flow restriction<\/td>\n | Radiator and circuit branches<\/td>\n<\/tr>\n |
\n| Dynamic balancing valve (PICV)<\/td>\n | Pressure-independent flow control<\/td>\n | Variable flow systems<\/td>\n<\/tr>\n |
\n| Thermostatic balancing valve<\/td>\n | Integrated temperature and flow control<\/td>\n | Individual radiator circuits<\/td>\n<\/tr>\n |
\n| Manifold flow setter<\/td>\n | Multi-circuit flow balancing<\/td>\n | Underfloor heating manifolds<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\nBenefits:<\/strong><\/p>\n\n- Prevents over-supply to favourable circuits<\/li>\n
- Reduces commissioning time by setting values before water is introduced<\/li>\n
- Provides a physical record of intended system configuration<\/li>\n<\/ul>\n
Practical application:<\/strong> On underfloor heating manifolds, flow meters with integrated adjustment knobs allow the installer to observe actual flow in l\/h while turning the valve. Each loop is adjusted until the display matches the calculated design flow.<\/p>\nFeature 4: Pump Optimisation<\/h3>\nDefinition:<\/strong> Pump optimisation is the selection and configuration of the circulation pump to deliver total system flow at the lowest possible electrical consumption.<\/p>\nPurpose:<\/strong> It ensures the pump operates at its efficiency point (BEP \u2014 Best Efficiency Point) rather than over-sizing or under-sizing relative to system demand.<\/p>\nHow it works:<\/strong><\/p>\nAfter balancing valves are set, the system’s hydraulic resistance curve is defined. The pump must be matched to this curve. Modern high-efficiency electronically commutated (EC) pumps \u2014 such as the Grundfos Alpha series or Wilo Stratos \u2014 offer automatic control modes:<\/p>\n Control modes relevant to balanced heat pump systems:<\/strong><\/p>\n\n- Constant pressure (\u0394p-c):<\/strong> Maintains fixed differential pressure. Used in systems with minimal thermostatic valve activity.<\/li>\n
- Proportional pressure (\u0394p-v):<\/strong> Reduces pressure setpoint as flow decreases. Recommended for systems with thermostatic radiator valves.<\/li>\n
- Constant flow:<\/strong> Maintains fixed volumetric flow. Used in primary heat pump circuits.<\/li>\n
- Variable speed with temperature control:<\/strong> Adjusts pump speed based on return temperature differential. Used in advanced heat pump integration.<\/li>\n<\/ul>\n
Benefits:<\/strong><\/p>\n\n- EC pumps consume up to 80% less electricity than unregulated pumps<\/li>\n
- Correct pump sizing prevents noise, cavitation, and premature bearing failure<\/li>\n
- Variable speed operation extends pump service life<\/li>\n<\/ul>\n
Regulatory note:<\/strong> EU Regulation No. 641\/2009 and its amendment 622\/2012 mandate that circulation pumps in heating systems meet Minimum Efficiency Index (MEI) \u2265 0.4. Hydraulic balancing is required to allow the pump to operate at this efficiency level.<\/p>\nPractical application:<\/strong> iDM heat pump systems include integrated primary circuit pumps controlled by the iDM Navigator controller. Secondary distribution pumps are configured during system commissioning to match the hydraulic resistance of the balanced distribution network.<\/p>\nFeature 5: Commissioning Documentation<\/h3>\nDefinition:<\/strong> Commissioning documentation is the formal record of all measured and set hydraulic parameters produced at system startup.<\/p>\nPurpose:<\/strong> It provides regulatory compliance evidence, a baseline for future maintenance, and a diagnostic reference for fault finding.<\/p>\nWhat commissioning documentation includes:<\/strong><\/p>\n\n- As-built hydraulic schematic<\/li>\n
- Heat load calculation per room (EN ISO 12831)<\/li>\n
- Required and measured flow rates for each circuit<\/li>\n
- Balancing valve settings (pre-set values and measured Kv values)<\/li>\n
- Differential pressure controller settings<\/li>\n
- Pump operating point (head, flow, speed, power consumption)<\/li>\n
- Flow and return temperatures at design conditions<\/li>\n
- System water volume and inhibitor concentration<\/li>\n
- Installer declaration and date<\/li>\n<\/ul>\n
Benefits:<\/strong><\/p>\n\n- Required for subsidy approval (BEG, Austria Raus aus \u00d6l und Gas, Swiss cantonal schemes)<\/li>\n
- Enables fast fault diagnosis \u2014 deviations from documented values identify the problem circuit<\/li>\n
- Supports warranty claims with the heat pump manufacturer<\/li>\n<\/ul>\n
Practical application:<\/strong> iDM Energiesysteme provides commissioning checklists aligned with \u00d6NORM H 5151 and EN 14336. The iDM Navigator controller stores operating data that can be compared against commissioning records during service visits.<\/p>\n<\/span>Types of Hydraulic Balancing Methods<\/span><\/h2>\nThere are three primary approaches to hydraulic balancing. Each suits different system types and installation contexts.<\/p>\n Method 1: Static Hydraulic Balancing<\/h3>\nDefinition:<\/strong> Static balancing is performed at fixed, design-point conditions. Balancing valves are set to achieve design flow at the design pump head, assuming all thermostat valves are fully open.<\/p>\nHow to perform static balancing \u2014 step by step:<\/strong><\/p>\n\n- Complete the heat load calculation for every room (EN ISO 12831)<\/li>\n
- Calculate design flow rate for each emitter circuit (Q = \u1e41 \u00d7 c \u00d7 \u0394T)<\/li>\n
- Perform hydraulic network calculation \u2014 determine pipe pressure drops for each circuit<\/li>\n
- Calculate required resistance to be imposed by each balancing valve<\/li>\n
- Convert resistance to valve pre-setting value using valve Kv data<\/li>\n
- Set each valve to its calculated pre-setting<\/li>\n
- Start system and verify actual flow using flow meters or measuring instruments<\/li>\n
- Adjust settings iteratively until measured flow matches design flow within \u00b110%<\/li>\n
- Record all settings and measurements in the commissioning document<\/li>\n<\/ol>\n
Best for:<\/strong><\/p>\n\n- New construction<\/li>\n
- Systems with thermostatic radiator valves<\/li>\n
- Underfloor heating with manifold flow setters<\/li>\n
- Heat pump systems with weather-compensated control<\/li>\n<\/ul>\n
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