Danfoss ASV Automatic Balancing Valves

Introduction and Application

The ASV balancing valves are used for dynamic hydraulic balancing in two-pipe radiator heating and cooling systems. Dynamic balancing ensures constant, automatic balancing from 0 to 100% load by regulating differential pressure in variable flow systems. This prevents issues like insufficient flow in distant radiators and excessive flow in radiators near the pump.

Using ASV valves eliminates complex commissioning and hydraulic balancing methods, saving time and energy while improving comfort.

Flow Limitation

When combined with ASV differential pressure regulators and pre-setting valves on terminal units (radiators), flow limitation is achieved for each terminal, preventing uneven flow distribution.

Low Noise Emission

Differential pressure limitation ensures that pressure across the regulating valve does not increase during partial loads, which reduces noise emission. This is a requirement specified by DIN 18380 for differential pressure control at partial system loads.

No Need for Classic Balancing

Flow limitation is achieved by setting each hydraulic circuit individually, preventing mutual influence between different circuits. Once an ASV valve is set for a specific vertical, it does not require re-balancing regardless of changes elsewhere in the system.

Authority of Regulating Valve

Differential pressure regulation through the valve ensures high authority, enabling precise and stable regulation and energy savings.

Zone Balancing

ASV sets allow hydraulic systems to be divided into pressure-independent zones. This facilitates phased connection of zones in new or renovated buildings without the need for extensive re-balancing. Automatic hydraulic balancing occurs as system changes are made.

ASV-P valves have a fixed setting of 10 kPa, which can be increased to 20 or 30 kPa by replacing the spring. This feature is useful for troubleshooting and ensures predicted flow even if calculations differ from the actual installation.

ASV-PV valves can be adjusted for different pressure ranges:

• 5-25 kPa: Primarily for radiator heating.
• 20-40 kPa: For radiators, fan coil units, chilled beams, and substations.
• 35-75 kPa: For substations, fan coil units, and chilled beams.
• 60-100 kPa: For large terminals (air handling units, fan coil units, etc.).

ASV valves optimize pump performance, and independent pressure zones maintain high valve authority at terminal units.

Valve Features and Applications

ASV valves are constructed for high-quality automatic balancing, featuring a pressure-unloaded cone, diaphragms adapted to each valve size for consistent performance, and springs with linear characteristics for easy differential pressure adjustment. The 90° angle for all service functions (shut-off, draining, adjustment, measurement) allows for simple installation in any mounting position. Their compact, integrated dimensions facilitate easy mounting even in confined spaces.

ASV valves regulate pressure at both design conditions (100% load) and partial loads, meeting DIN 18380 requirements. By regulating pressure at partial loads, they prevent noise issues often associated with thermostatic radiator valves in unbalanced systems.

ASV valves are supplied in EPS styrofoam packaging, suitable for insulation up to 80°C. Optional insulation covers are available for temperatures up to 120°C.

ASV valves are available with internal or external threads (DN 15-40), external threads only (DN 50), or as flanged valves (DN 65-100). They include built-in service functions like shut-off and draining.

ASV-PV valves can be equipped with flow measurement ports, which must be ordered separately and installed on the drain valve (DN 15-50) or the flange connection (DN 65-100).

ASV-PV valves should be installed in the return line, paired with partner valves (ASV-M/I/BD, MSV-F2) in the supply line. ASV-M/I/BD are recommended for DN 15-50, and MSV-F2 for DN 65-100.

Partner Valve Configurations

Two main configurations exist when using partner valves (ASV-BD, ASV-I, ASV-M, MSV-F2):

1. Partner valve outside the control loop (Fig. 1): This is the recommended configuration, providing optimal performance as the full differential pressure range is available for the vertical. Flow limitation is performed at each terminal unit (e.g., RA-N radiator valves with presetting). For DN 15-50, use ASV-M or ASV-BD. For DN 65-100, use MSV-F2, connecting the impulse pipe to the lower measuring port.
2. Partner valve inside the control loop (Fig. 2): This configuration limits flow at the outlet but uses part of the controlled pressure range for the pressure drop across the partner valve (Δpᵢ). It is recommended when flow limitation cannot be achieved at all terminal units. For DN 15-50, use ASV-I or ASV-BD. For DN 65-100, use MSV-F2, connecting the impulse pipe to the upper measuring port.

ASV-BD can be used inside or outside the control loop, depending on which measuring port is open. For external use, the blue measuring port should be open. For internal use, the red measuring port should be open. Flow checks are possible in both configurations.

Applications in Heating Systems

ASV valves are used in two-pipe radiator heating systems to regulate differential pressure in verticals. To limit flow per radiator (hydronic balancing), radiator valves with double regulation should be installed on the radiators.

Alternatively, flow in the vertical can be limited using the presetting function of the ASV-I valve. Regulating differential pressure across the vertical ensures high authority for thermostatic radiator valves, leading to precise and stable temperature regulation and energy savings.

ASV valves are also suitable for underfloor heating systems. To limit flow for each underfloor heating circuit, use valves with presetting and flow limitation functions. The constant differential pressure maintained by ASV-PV, combined with the set valve in the heating circuit, results in a limited maximum flow rate for the regulated circuit. Alternatively, system flow can be limited using ASV-I or ASV-BD presetting functions.

ASV-PV valves can maintain differential pressure across several ranges as needed. Their small dimensions allow for easy installation in wall boxes for underfloor heating pipework.

ASV valves can be used with fan coil units, induction units, and air heaters to provide automatic hydraulic balancing by regulating differential pressure in branches or at each unit. Constant differential pressure, combined with preset regulating valves like ASV-I or ASV-BD, limits flow.

ASV valves are also applicable in other scenarios, such as preventing noise issues with thermostatic radiator valves in small systems by regulating differential pressure. They are suitable for any application requiring a small differential pressure regulator, like in underfloor heating pipework or flat stations. In buildings with flat stations, ASV valves ensure reliable automatic balancing by regulating differential pressure in verticals/zones.

In flat stations, pressure conditions change when heating domestic hot water compared to space heating. ASV-PV valves maintain differential pressure in these conditions as well. Constant differential pressure, combined with preset regulating valves (ASV-I or ASV-BD), limits flow.

Dimensioning and Selection

Figure 7 provides a diagram for dimensioning ASV-P/PV valves. The maximum flow rates shown are based on a 10 kPa differential pressure across the thermostatic radiator valve, ensuring good regulation and energy savings.

When selecting the size for ASV-P/PV, choose the same size for the partner valve (ASV-BD/ASV-I/ASV-M/MSV-F2).

Valve Size vs. Pipe Size

The Kv values for each dimension are designed to cover the flow range according to VDI 2073, with water velocities up to 0.8 m/s at a 10 kPa differential pressure across the valve. If the water velocity in the pipe is between 0.3 and 0.8 m/s, the valve size should match the pipe size.

Example: For a flow of 200 l/h in a DN 15 pipe, the horizontal line intersects the DN 15 valve line, indicating suitability.

Detailed examples and dimensioning diagrams are available on pages 12-13 and in Addendum A.

Ordering Information

The catalog provides detailed tables for ordering ASV valves, including:

• ASV-P Valves: Specifications for balancing valves, including impulse pipe (1.5m) and drain valve. Constant differential pressure of 10 kPa, upgradeable to 20 or 30 kPa. Tables list DN, Kvs, internal thread (ISO 7/1), external thread (ISO 228/1), and corresponding code numbers.
• ASV-PV Valves: Similar to ASV-P, with options for impulse pipe length (1.5m or 2.5m) and connection types. Tables detail DN, Kvs, connection type, adjustable differential pressure ranges (5-25, 20-40, 35-75, 60-100 kPa), and code numbers. Specific tables are provided for DN 15-50 and DN 65-100.
• ASV-BD Valves: Shut-off and multi-functional partner valves. Tables list DN, Kvs, internal thread, and code numbers.
• ASV-M Valves: Shut-off valves without measuring ports. Tables list DN, Kvs, internal thread, and code numbers.
• ASV-I Valves: Preset valves with two measuring ports. Tables list DN, Kvs, internal thread, and code numbers.
• Accessories and Spare Parts: A comprehensive list of available accessories such as handles, adapters, drain valves, impulse pipes, springs, and seals, with their respective code numbers.

Technical Data and Construction

Technical Specifications: A table details the technical data for ASV-I/M/P/PV and ASV-BD valves, including nominal diameter, maximum pressure, test pressure, differential pressure range, operating temperature, and materials for wetted parts (valve body, cone, ball), diaphragm/seals, and springs.

Construction: Diagrams illustrate the internal construction of ASV-P, ASV-PV (DN 15-40, DN 50, DN 65-100), ASV-BD, ASV-M, and ASV-I valves. The operation of ASV-P and ASV-PV is explained, detailing how they maintain constant differential pressure using diaphragm and spring mechanisms. Adjustment procedures for ASV-PV valves are provided, including tables showing the relationship between spindle turns and differential pressure settings for various ranges.

Partner Valve Integration: The role of partner valves (ASV-BD/I/M) in conjunction with ASV-PV/P for vertical differential pressure regulation is described. ASV-BD is highlighted for its unique features, including high Kv values, low pressure drops, and easy installation. Procedures for flow limitation, flow checking, and draining are detailed for ASV-BD.

Impulse Pipe Connection: Proper connection of the impulse pipe between the partner valve and the ASV-P/PV is crucial. Configurations for impulse pipe connection (inside/outside control loop) are explained, along with notes on flow measurement and ensuring correct pressure balance during installation and commissioning.

Dimensioning Examples

The catalog includes practical dimensioning examples to guide users:

• Example 1: Sizing for a radiator system with presetting thermostatic valves, determining the appropriate ASV-M and ASV-PV combination and their settings based on system pressure and flow requirements.
• Example 2: Adjusting the flow rate by modifying the ASV-PV differential pressure setting to achieve a desired increase in flow.
• Example 3: Limiting flow in a branch circuit using an ASV-I valve, calculating the required Kv value and setting based on system pressure drop.
• Example 4: Sizing for a flat station application, considering multiple stations, heating loads, and domestic hot water usage to determine the correct ASV-PV valve size and setting based on available vertical pressure.

These examples utilize diagrams from Addendum A (Figs. A, B, C, D, E) for flow and pressure drop calculations.

Addendum A: Dimensioning Diagrams

Addendum A provides essential graphical tools for valve selection and dimensioning:

• Fig. A: Dimensioning diagram for ASV-P/PV valves, DN 15-40.
• Fig. B: Dimensioning diagram for ASV-PV valves, DN 50-100.
• Fig. C: Dimensioning diagram for ASV-BD valves, DN 15-50.
• Fig. D: Dimensioning diagram for ASV-I valves, DN 15-50.
• Fig. E: Pressure drop chart for ASV-M valves, DN 15-50.

These diagrams help users determine the correct valve size and settings based on flow rate, differential pressure, and Kv values.

Insulation and Connections

Insulation: ASV valves are supplied with EPS styrofoam packaging, which can also serve as insulation for systems operating up to 80°C. EPP insulation covers are available for ASV-BD valves, suitable for temperatures up to 120°C. Both materials meet fire resistance standards (B2, DIN 4102).

Connections: Danfoss offers threaded or weld-on connections as accessories for valves with external threads. These are available in brass and steel.

Ordering Accessories: Tables list EPP insulation covers for ASV and ASV-BD valves, along with code numbers. Various threaded and welded connections for different pipe sizes and valve types are also detailed with their respective code numbers.

Technical Data for ASV-PV

Key technical requirements for ASV-PV valves are outlined:

• Availability in DN 10-100 range.
• Differential pressure regulation based on an integrated diaphragm element.
• Adjustable differential pressure ranges: 5-25 kPa or 20-40 kPa for DN 15-40; 20-40 kPa, 35-75 kPa, or 60-100 kPa for DN 50-100.
• Protection against accidental changes in pressure settings.
• Linear pressure setting (1 turn per 1 kPa or 2 kPa depending on size).
• Interchangeable pressure setting range via spring replacement (DN 15-40) without system draining.
• Shut-off function operable via handle.
• Draining function required for DN 15-50.
• Operating temperature range: -20 to +120°C (DN 15-40) and -10 to +120°C (DN 50-100).
• Nominal pressure: 16 bar, test pressure: 25 bar.
• ASV-PV kits (DN 15-40) include a minimum 1.5m impulse pipe and EPS insulation up to 80°C.

Contact information for Danfoss d.o.o. is provided.