Two- or four-pipe heating and/or cooling systems are characterized by changing conditions due to valves opening and closing depending on the need for heating or cooling. This continuously causes flow and differential pressure changes.
Without proper measurements, such systems suffer from uneven heat distribution, poor energy inefficiency and are very difficult to commission.
By adding an actuator, the valves function as flow-limited control valves, automatically balancing the system and providing the best possible indoor comfort and energy efficiency. The commissioning of the system is a lot easier, all valves only need to be set to the design flow before the actuators are mounted.
Danfoss offers a broad range of pressure-independent balancing and control valves and matching actuators.
Features and benefits
1. Stable room temperature.
Eliminating the overflow situations at partial load conditions has a significant effect on the stability of the room temperature
2. Improved indoor comfort.F
With the stable room temperature, the indoor comfort increases. Required temperatures are accurately met, increasing the productivity of office employees or benefitting the experience of hotel guests.
3. Energy savings.
The perfectly balanced system, under all conditions, increases the energy efficiency and leads to savings on energy costs.
4. Reduced maintenance costs.
As the pressure-independent valves ensure perfect working conditions, the actuators mounted on them require fewer movements to keep the temperature stable. This increases the lifetime value of the actuators and reduces the maintenance costs.
Pressure independent balancing and control valve AB‑QM DN 10-250
The precise flow control performance of the AB-QM with a Danfoss actuator provides increased comfort and lower Total Cost of Ownership because of savings made on:
• Efficient energy transfer and minimal pumping costs since there are no overflows at partial loads because of the exact pressure independent flow limitation.
• Smaller pump investments and lower energy consumption as the pump head needed is lower than in the traditional setup. With the built in test plugs it is easy to troubleshoot and find the optimal setpoint for the pump.
• Reduced movements of the actuator since the built-in differential pressure controller ensure the pressure fluctuations do not influence the room temperature.
• Achieving a stable temperature in a room leading to a lower average temperature at the same comfort level.
• Minimal flow complaints, as the valve performs as designed.
• Minimal blockage complains, as the membrane design makes AB-QM less susceptible to blockage than a cartridge type construction.
• Trouble-free segmentation of the building project. When sections of a project are finished they can normally not be handed over to the customer with a fully functional HVAC installation. However the AB-QM with a Danfoss actuator will automatically control the flow, even when other parts of the installation are still unfinished. It’s not needed
to adjust the AB-QM after finalisation of the project.
• Commissioning costs, the costs are close to zero because of a convenient setting procedure without the need for flow charts, calculations or measuring equipment. The AB-QM valves can be set to a precise design value even when the system is up and running.
• Halved mounting costs as the AB-QM valve covers two functions, Balancing & Control.
The AB-QM has a linear control characteristic. The AB-QM is pressure independent which means that the control characteristic is independent from the available pressure and is not influenced by a low authority. The flow limitation on the AB-QM is achieved by limiting the stroke and the Danfoss actuators calibrate to the stroke of the valves. This means that the AB-QM keeps its linear characteristic independent of the setting or differential pressure.
Because of the predictable characteristic the actuators on the AB-QM can be used to change the response from linear to logarithmic (equal percentage). That makes the AB-QM suitable for all applications, including AHUs, where the equal percentage characteristic is needed to get a stable control loop. The actuators can be switched from linear to logarithmic by changing a DIP switch setting on the actuator.
1. Variable flow systems.
An AB-QM with a Danfoss actuator is used as a control valve for terminal units, like an AHU (Air Handling Unit), FCU (Fan Coil Unit) or radiation panel. The AB-QM ensures and control the required flow on every terminal unit and maintains hydronic balance in the system. Because of the integrated differential pressure controller the control valve always has 100 % authority and therefore offers always stable control. At partial load there is no overflow, contrary to conventional solutions, because the AB-QM will always limit the flow to exactly what is needed. By installing the AB-QM the whole system is divided in completely independent control loops.
There is a full range of Danfoss actuators available for the AB-QM, suitable for every control strategy. Actuators are available for On/Off, 0-10 Volt, 4-20 mA or floating point.
2. Constant flow systems.
In constant flow system with FCUs or in a one pipe heating system the AB-QM can be installed as an automatic balancing valve in every riser. The AB-QM limits the flow to the set value, thus automatically achieving hydronic balance in the system.
• No Kv or authority calculations needed. Flow is the only parameter to be considered when designing.
• The AB-QM always fits the application because the maximum setting of the AB-QM corresponds with international standards for flow velocity in pipes.
• The AB-QM can be used for all HVAC applications since it can have a linear or logarithmic characteristic when combined with thermal electric or gear actuators.
• Compact design, essential when only limited space is available. For example in fan-coil units.
• Easy commissioning. No specialized staff or
measuring equipment needed.
• Easy trouble shooting.
• Fast start-up because AB-QM valves don’t need to be flushed or de-aired before use.
• Trouble-free segmentation of the building project. The AB-QM will automatically control the flow, even when parts of the installation are still unfinished. It’s not needed to adjust the AB-QM after finalisation of the building project.
Technical data AB‑QM (threaded version)
1) Factory setting of the valve is done at nominal setting range.
2) Regardless of the setting, the valve can modulate below 1 % of set flow.
3) When set above 100 %, minimum starting pressure needed is higher, see figures in the ().
4) Actuator with compatible stroke must be selected.
5) At min differential pressure valve reaches at least 90% of nominal flow. Declaration of performance is available upon request.
*) If the medium temperature is below 2°C for AB-QM DN10-32 refrig. insulation must be used to cover both the valve and actuator: Code 003Z4787-003Z4790. For AB-QM DN40-100 stem heaters must be used: Code 065B2171, 065Z0315 or 065Z7022.
According suitability and usage especially in not oxygen tight systems please mind the instructions given by the coolant producer.
Pc – pressure controller part
Cv – Control valve part