Vaillant charging set with pump for ecoVIT boilers

Product detailed description

Charging kit with pump for Vaillant ecoVIT boilers

The charging kit with pump is a genuine Vaillant hydraulic accessory used to connect ecoVIT series stationary boilers (for example ecoVIT pro VKK) to an external hot water storage tank, typically from the Vaillant uniSTOR range. ecoVIT boilers do not have an integrated storage tank or instantaneous domestic hot water heating – they are designed purely as a heat source for the heating circuit and a separate charging circuit to an external tank, which is exactly what this kit provides. Without this kit, the boiler would not be able to prepare domestic hot water at all, even if a suitable tank were physically connected to it, since a simple pipe connection without controlled circulation and a check valve cannot ensure a functional and safe transfer of heat between the two units.

The kit primarily consists of a charging circulation pump, which, upon a request for domestic hot water heating (signalled by a thermostat or temperature sensor in the tank), pumps heating water from the boiler through the tank's heating coil or heat exchanger and back, and a check valve, which prevents unwanted reverse water flow outside the active charging period. Together, the complete kit forms a functional link between the boiler circuit and the tank's charging circuit.

Technical characteristics

• Intended for: Vaillant ecoVIT stationary boilers (e.g. ecoVIT pro VKK) in combination with an external hot water storage tank
• Main function: controlled circulation of heating water between the boiler and the tank during domestic hot water charging (heating)
• Included in delivery: charging circulation pump, check valve, connecting fittings and seals, mounting material
• Pump control: switching on and off controlled by the boiler's electronics based on a signal from the thermostat or temperature sensor in the tank
• Fittings material: brass and steel components resistant to the usual parameters of treated heating water
• Max. operating temperature: up to 110 °C
• Max. operating pressure: up to 6 bar
• Installation: between the boiler outlet and the charging circuit of the storage tank, according to the hydraulic diagram supplied with the boiler

Why this kit is necessary

Stationary ecoVIT boilers belong to the so-called heating-only boilers (without integrated domestic hot water preparation), whose concept assumes that the investor or designer will choose an external hot water tank with a volume exactly matching the needs of the given household or facility – independently of the boiler's own output. This flexibility, however, requires a separate hydraulic component that functionally handles the connection between the boiler and the tank, meaning it ensures water circulation only when the tank actually needs to be reheated, and prevents unwanted water flow otherwise (for example, cooling of the tank back into the boiler circuit once the tank is already heated).

Without this kit, the ecoVIT boiler would not be able to perform the function of domestic hot water preparation at all, even if physically connected to a tank via piping – which is why this is a standard and, in practice, always necessary accessory for every ecoVIT boiler installation where domestic hot water is prepared this way.

Installation and hydraulic connection

The kit must be installed exclusively by an authorised technician qualified to install gas and heating equipment, in accordance with the hydraulic diagram of the specific installation. The kit is connected between the boiler outlet designated for the charging circuit and the corresponding inlet/outlet of the storage tank's heating coil or heat exchanger. After installation, the charging circuit is filled and vented, the desired domestic hot water temperature is set on the boiler controller, and a functional test of the correct start-up and shut-down of the charging pump according to actual heating demand is carried out.

For larger tanks or more complex hydraulic schemes (for example with multiple tanks or in combination with another heat source, such as a solar system), we recommend consulting the design and connection with a heating system designer to ensure correct priority heating of domestic hot water as well as a balance between the heating and charging circuits.

Compatibility

The kit is intended for Vaillant ecoVIT series stationary boilers (for example ecoVIT pro VKK 256/5 and related models in this series) in combination with external hot water storage tanks, typically from the Vaillant uniSTOR range in a suitable volume version. When combining with other types of tanks (for example from a different manufacturer), we recommend verifying hydraulic and dimensional compatibility of the connecting ports directly with the supplier or system designer in advance.

When ordering, we recommend always specifying the exact boiler type and, if necessary, the intended tank type, so that the supplier can confirm that the chosen combination of components is fully functional from both a hydraulic and control point of view.

Maintenance and care

As part of the boiler's regular annual service inspection, we recommend also checking the charging kit, specifically:

• the function of the charging pump – smooth start-up and operation without unusual noises,
• the function of the check valve – its role is to prevent unwanted water flow outside active charging; its wear can be indicated, for example, by slower cooling of the boiler through the unused charging circuit,
• the tightness of all connecting fittings of the kit,
• the speed and reliability of tank heating when charging is activated – a significant increase in heating time may indicate a problem with the kit, the tank's heat exchanger, or deposits in the system.

The quality of the heating water throughout the entire system (including the charging circuit) should meet the recommendations of the VDI 2035 guideline, since improperly treated water accelerates wear of the pump and other components of the kit.

We recommend including this check as a fixed part of every annual service inspection of the ecoVIT boiler, since a fault in the charging kit will only manifest externally as slower or insufficient domestic hot water heating, and a layperson could easily mistake it for a problem with the tank itself or with the controller settings.

Why choose a genuine Vaillant part

The genuine charging kit is designed to work precisely together with the ecoVIT boiler's control electronics – that is, with the signal from the thermostat or tank temperature sensor that determines when the charging pump should be active. Using a non-genuine or incorrectly sized replacement can lead to unreliable or slow domestic hot water heating, or to unwanted water flow outside the active charging period if the check valve is missing or faulty.

Typical hydraulic connection diagram

In a typical installation, the charging kit is fitted between the ecoVIT boiler outlet reserved for domestic hot water preparation and the inlet/outlet of the storage tank's heating coil (heat exchanger). Upon a request for domestic hot water heating, the boiler's control electronics starts the charging pump, which pumps heated heating water from the boiler through the tank's coil, where it transfers heat to the domestic water in the tank, and then returns back to the boiler for reheating. Once the set temperature in the tank is reached (measured by the relevant sensor), the pump switches off and the check valve prevents any further unwanted water flow between the boiler and the tank until the next charging request.

This principle of so-called indirect heating via an external tank is also referred to in practice as a "separate boiler and cylinder" connection, as opposed to compact solutions with an integrated tank (for example the ecoCOMPACT series), where this entire hydraulic system is pre-built by the manufacturer directly in a single unit. The advantage of the ecoVIT boiler solution with a separate charging kit is precisely the possibility of choosing the tank volume and type independently of the boiler, which is especially appreciated by designers when creating custom-tailored systems for a specific building.

Combination with other heat sources

In some installations, the hot water tank connected this way to the ecoVIT boiler is additionally heated from another source – for example solar collectors or an electric heating element – in which case it is a so-called bivalent tank with two independent heat exchangers or with one heat exchanger and supplementary electric heating. The charging kit deals exclusively with the connection between the boiler and the tank; other components (for example solar control and the solar circuit circulation pump) that form part of the complete bivalent solution are then ordered and installed separately according to the specific project.