Vaillant 3-way switching valve for heat pump and allSTOR storage tank with DHW preparation

Product detailed description

Vaillant 3-way switching valve for connecting a heat pump and an allSTOR storage tank with domestic hot water preparation

The motorized Vaillant 3-way switching valve is hydraulic accessory designed for installations combining a heat pump with a multi-purpose allSTOR buffer storage tank, where domestic hot water preparation is also part of the setup. Its role is to automatically switch the flow of the heat carrier medium between two operating modes — heating (delivering heat to the heating circuit) and hot water charging (delivering heat to the storage tank section or to a station designated for domestic hot water preparation) — without requiring a complex, individually designed hydraulic solution from the installation company. The valve is compatible with allSTOR exclusive, allSTOR plus and auroFLOW plus systems.

Why switching between heating and hot water preparation matters

A heat pump operates most efficiently when the difference between the source temperature (e.g. outdoor air) and the required output temperature is as small as possible. The heating circuit (especially underfloor heating) generally requires a lower output temperature, while domestic hot water preparation requires reaching a higher temperature (typically above 55°C, and periodically even higher for hygienic reasons related to preventing Legionella growth). If the heat pump had to constantly maintain both circuits at the highest required temperature simultaneously, it would operate in a less efficient mode over the long term, even during heating when such a high temperature is not needed. Automatic switching between modes via the 3-way valve allows the heat pump to alternately operate in the mode corresponding to the current need — lower temperature during heating, higher temperature only during shorter periodic hot water charging cycles — thereby increasing the overall seasonal coefficient of performance (SCOP) of the system and reducing electricity consumption.

This switching logic also has a direct impact on the hygienic safety of hot water preparation — regularly reaching a sufficiently high temperature in the storage tank or the relevant station during the charging cycle is one of the standard measures against Legionella growth in domestic hot water systems. Automated switching ensures that these charging cycles take place reliably and regularly, without depending on manual intervention by the operator.

Technical characteristics

The valve is designed as a motor-driven 3-way switching element with a Kvs value of 7.7 m³/h — this value expresses the water flow rate in m³ per hour at which a pressure drop of 1 bar occurs across the valve, and it allows the designer to verify whether the valve is suitably sized for the given hydraulic circuit in terms of pressure losses at the designed flow rate. The valve is equipped with three connection stubs with an outer diameter of 28 mm with support sleeves and three G 1 1/4" union nuts with flat gaskets, corresponding to the common standard of hydraulic connections in allSTOR systems. The valve body is made of a material typical for this type of fitting in the hydraulic circuits of heating systems (typically brass or a similar alloy resistant to long-term contact with the heat carrier medium) — we recommend verifying the exact material composition in the manufacturer's technical sheet if this information is critical for your project. The valve is supplied without additional accessories or decoration, i.e. as a standalone functional part intended for installation into the hydraulic scheme.

Installation and electrical connection

Installing this valve involves both hydraulic connection into the relevant branch of the circuit between the heat pump and the allSTOR storage tank (according to the recommended hydraulic scheme for the given setup), and electrical connection of the valve's actuator to the heat pump's control system, which manages switching between heating and hot water preparation modes according to current demand (e.g. based on the temperature in the storage tank, the hot water heating time schedule, or the current need of the heating circuit). This installation, including correct connection of the control signals, must be carried out by a qualified technician familiar with the heat pump's control system and the allSTOR storage solution, as incorrect control wiring could lead to incorrect or incomplete switching between modes.

When designing the valve's location in the hydraulic scheme, the direction of medium flow and the orientation of the valve according to the markings on its body must also be taken into account, as incorrect orientation could result in non-functional or incorrect switching between the circuit branches.

Compatibility

The valve is intended for use in allSTOR exclusive, allSTOR plus and auroFLOW plus systems — i.e. in Vaillant multi-purpose buffer storage solutions combined with a heat pump or a solar circuit, where automatic switching between the heating circuit and hot water preparation is required. This is the only compatibility confirmed by the manufacturer for this part — full hydraulic or control compatibility with the Vaillant control system cannot be guaranteed for other systems or generic 3-way valves from other sources.

Maintenance

The valve's motorized actuator, as well as the valve mechanism itself, should be part of the regular annual service inspection of the entire heat pump and storage tank system. We recommend checking the smoothness of the switching mechanism's movement (without sticking or incomplete switching between positions), checking the tightness of the connections and union nuts, and in areas with harder water, also monitoring for possible limescale buildup on the internal parts of the valve, which could affect the smoothness of switching over the long term. If any unusual signs are detected (e.g. incomplete reaching of the hot water temperature, or conversely insufficient heating circuit performance while the valve is operating in a given position), we recommend contacting a service technician to verify the functionality of the valve and its actuator.

Why choose a genuine Vaillant part instead of a generic 3-way valve

Using a genuine, manufacturer-verified 3-way valve instead of a generic solution from another source has several advantages: guaranteed hydraulic compatibility (a correctly sized Kvs value matching the designed flow rates in the allSTOR system), guaranteed compatibility with the control signals of the Vaillant heat pump's control system (without the need for additional adaptation or the risk of incorrect communication between the valve actuator and the controller), and preservation of the warranty conditions for the entire system — using a non-genuine part in a critical hydraulic junction of the system could jeopardize warranty claims for related components in the event of a failure related to incorrect functioning of this junction.

Impact on the heat pump's operational reliability

In addition to energy efficiency, correctly functioning automatic switching between heating and hot water preparation also has a direct impact on the mechanical stress placed on the heat pump as a whole. Frequent, uncoordinated switching between modes (e.g. due to faulty or incorrectly set controls) can lead to an increased number of starts and stops of the heat pump's compressor, which is one of the main factors affecting its long-term service life. This valve, combined with correctly configured controls, on the other hand, enables smooth switching dependent on actual demand with an appropriate number of cycles, thereby contributing to gentler operation of the entire heat pump and extending its service life compared to a less sophisticated or incorrectly sized switching solution.

Valve location in the hydraulic scheme and relation to other components

In a typical hydraulic scheme for connecting a heat pump with an allSTOR storage tank, this 3-way valve is located on the outlet branch after the heat pump, from where it directs the flow of heated medium either towards the heating circuit or towards the storage tank section or the station designated for hot water preparation. A complete hydraulic scheme generally also includes other elements such as circulation pumps for the individual circuits, temperature sensors for control purposes, and possibly additional switching or mixing valves for individual heating zones. The exact location and connection of this valve within the overall scheme should be based on the project documentation prepared for the specific installation, taking into account all connected heat sources, appliances and the desired method of controlling them.

Note on choosing between the genuine and an alternative switching solution

Some installation companies may consider, instead of this catalog part, their own custom-designed switching solution using separately procured components. Although such an approach is in principle possible, it carries the risk of incorrect sizing (e.g. an unsuitable Kvs value for the given flow rate), the need to design communication between the valve actuator and the heat pump's control system on one's own (which, with the genuine Vaillant part, works without additional programming), and above all the loss of certainty that the entire solution complies with the manufacturer's recommendations for the given system. For these reasons, we recommend that projects using the allSTOR system in combination with a heat pump favor this genuine catalog part over an individually designed alternative solution.

When ordering this valve for your specific project, we recommend consulting our sales team, who, based on information about the heat pump's output, the type of allSTOR storage tank, and the planned hydraulic scheme, will confirm whether this particular part with a Kvs value of 7.7 m³/h is suitable for your installation, or whether your project requires a different variant of switching fitting from Vaillant's accessory range.

Frequently Asked Questions

Broader context — hydraulic design of heat pump + buffer storage tank + hot water preparation systems

Combining a heat pump with a multi-purpose allSTOR buffer storage tank represents an increasingly common solution in both renovations and new buildings, as it allows both heating and domestic hot water preparation needs to be efficiently covered from a single heat source without requiring a separate electric water heater. A key element of such a system is precisely the correct hydraulic solution for switching between the two consumption points — a too-simple solution (e.g. manual switching taps) would not allow automatic, demand-dependent operation, while an overly complex individual solution custom-designed by the installation company could carry a risk of design or implementation errors without a manufacturer's guarantee for the functioning of the entire junction.

That is precisely why Vaillant offers this motorized 3-way valve as a proven, catalog part with clearly defined parameters (Kvs value, connection dimensions) and confirmed compatibility with the heat pump's control system and with the hydraulic concept of allSTOR storage tanks. The designer can thus easily include this part in the hydraulic scheme with the certainty that its parameters correspond to the flow rates common in these systems, and the installation company has a clear manufacturer's installation guide available instead of having to design its own, unverified switching solution.

In projects where, besides the heat pump, a solar circuit (auroFLOW plus system) is also planned to be connected, this valve also plays a role in coordinating between multiple heat sources charging the same storage tank — it ensures that, regardless of which source is currently supplying heat to the storage tank, the flow of medium between the heating circuit and the hot water preparation circuit is controlled in a unified, reliable manner.