uniSTOR plus VIH RW 300

Product detailed description

Hot water storage tank Vaillant uniSTOR plus VIH RW 300

Vaillant uniSTOR plus VIH RW 300 is a stationary, indirectly heated hot water storage tank with a volume of 281 liters, specifically designed for use with heat pumps. It is a medium-sized model within the uniSTOR plus range, suitable for the needs of a typical 3–4 person household with average to slightly higher hot water consumption. The tank combines a compact footprint with sufficient capacity to fit into most standard family homes and apartments with their own boiler room or technical room.

Like other models in the uniSTOR plus range, the VIH RW 300 is intended for operation with one heat source, typically a Vaillant aroTHERM or flexoTHERM heat pump. The internal tank is made of steel with a high-quality glazed surface (enamel) on the potable water side, which provides long-term resistance to corrosion, and is equipped with a magnesium protective anode ensuring active cathodic protection throughout the product's lifetime.

Technical specifications of VIH RW 300

• Tank volume: 281 liters
• Tank height (with casing): 1804 mm
• Width (with casing): 650 mm
• Depth (with casing): 755 mm
• Empty tank weight (without water): approximately 141 kg
• Weight of the filled tank in operation: approximately 422 kg
• Maximum operating pressure (domestic water): 10 bar
• Maximum operating pressure (heating circuit): 10 bar
• Maximum hot water temperature: 85 °C
• Integrated magnesium protective anode against corrosion
• Glazed internal tank surface (enamel)
• One heating heat exchanger with a smooth tube for connection to a heat pump

Construction and thermal insulation

The tank of the VIH RW 300 is insulated with rigid PU foam applied directly to the steel casing without an air gap, minimizing thermal bridges and standby heat losses. The outer cover is made of durable, easily cleanable plastic in white color, which fits well into modern technical rooms. The volume of 281 liters represents a balanced compromise between tank size and available hot water comfort – it can cover the peak demand from multiple simultaneous draw-off points (shower, kitchen, bathroom) without a significant drop in temperature.

The heating heat exchanger is designed for efficient cooperation with the lower output temperatures of the heat pump, which means a shorter heating time and fewer compressor switching cycles compared to an undersized tank. The higher weight of the filled tank (422 kg) should be considered in the static assessment of the floor, especially in multi-story installations or when mounted on a wooden ceiling.

Installation and connection

The tank is installed as a free-standing unit on height-adjustable feet, which allow precise leveling of the position. Connections for cold and hot water, circulation and heating circuit are located at the top of the tank and are solved with standard threaded connections compatible with common plumbing fittings. Due to the height of 1804 mm, it is necessary to consider sufficient clear height in the room during installation, ideally at least 2000 mm, to maintain a margin for installation and possible service.

We recommend leaving at least 400–500 mm of free space on one side of the tank for access to the inspection hatch and the magnesium anode. The tank is fully compatible with Vaillant heat pump controls (senzoCOMFORT, multiMATIC), which allow setting the priority of hot water heating, time programs and so-called legionella protection program with regular heating above 60 °C.

Compatible accessories

For the VIH RW 300 tank, it is possible to add a connection kit with a safety valve for the domestic water side, an expansion vessel for hot water, insulation sleeves for the connecting pipes and a temperature sensor for the tank compatible with the control unit of the Vaillant heat pump. In the case of a greater distance between the heat pump and the tank, we recommend considering additional insulation of the connecting pipes, which will reduce heat losses along the route.

For whom is the RW 300 model suitable

The RW 300 model is a suitable choice for a 3–4 person household with normal hot water consumption, where there is also a sufficiently large technical room available. Thanks to the volume of 281 liters, it provides a reserve even when drawing off from multiple points in the household, for example during morning peaks, when several household members shower one after another.

Frequently asked questions (FAQ)

How much space do I need for the installation of the RW 300 tank?
Considering the dimensions of 1804 × 650 × 755 mm, we recommend calculating at least a floor space of 90 × 100 cm and a clear room height of at least 2000 mm.

Will a standard floor support the weight of the filled tank of 422 kg?
This is usually not a problem in ground floor masonry buildings, but when installing on an upper floor or on a wooden structure, we recommend consulting with a structural engineer.

Can the RW 300 tank be operated with a gas boiler?
Yes, although it is optimized for lower temperatures typical of heat pumps, its one heat exchanger can withstand a higher temperature rise up to 85 °C from another heat source.

How long will the hot water in the tank last without reheating?
Thanks to the high-quality PU insulation, the heat losses in standby mode are low, so the water will maintain a usable temperature for several hours even without active reheating.

Is regular maintenance required?
Yes, it is recommended to check the magnesium anode and the function of the safety valve once a year, ideally during the service inspection of the heat pump.

Operation with a heat pump

Heat pumps operate most efficiently at heating water temperatures around 35–55 °C, which is significantly less than with a conventional gas boiler. The VIH RW 300 tank is directly shaped by this fact – the size and shape of the heating coil and the quality of the insulation are adapted so that even with a lower temperature difference, it can effectively prepare a sufficient amount of hot water to cover the household's peak demand. An optimally dimensioned tank reduces the number of heat pump compressor starts, which reduces wear and extends its lifespan.

Maintenance and service

Basic maintenance consists of regular inspection of the magnesium anode (recommended frequency once a year, more frequently in areas with harder water), checking the tightness of the connections and the function of the safety valve on the domestic water side. In areas with higher water hardness, occasional descaling of the tank is advisable, which prolongs its life and maintains the declared performance of the heat exchanger. Access to the inspection hatch is from the front side of the casing, which allows service without the need to disconnect the tank from the distribution system.

Comparison within the uniSTOR plus range

Within the uniSTOR plus range, the RW 300 follows the smallest model RW 250 and continues with larger models RW 400 and RW 500. If your household regularly experiences simultaneous hot water draw-off in multiple bathrooms or you are planning to expand your household, we recommend considering a larger model from the same range, which offers a higher hot water reserve while maintaining the same quality of processing and technology.

Economic and ecological benefits

In combination with a heat pump, which draws most of its energy from the surrounding environment (air, ground or water), the VIH RW 300 tank represents a significantly more cost-effective solution for hot water heating compared to a conventional electric water heater. The high-quality thermal insulation of the tank minimizes losses between individual draw-offs, so the investment in a heat pump directly translates into real energy bill savings. When designing an appropriate heat pump capacity for the 281 liter volume, we recommend consulting with a designer or installation company to take into account the actual daily hot water consumption in the household and the consumption profile (for example, an evening peak in a multi-person family).

Operational safety

The VIH RW 300 tank is designed for a maximum operating pressure of 10 bar on both the domestic and heating water side, which covers the standard requirements of household water supply systems in both single-family homes and apartment units. Nevertheless, it is essential to install a certified safety valve on the hot water side at each installation with an opening pressure corresponding to local regulations, which protects the tank from overpressure caused by thermal expansion of water during heating. It is also recommended to add an expansion vessel on the hot water side, which reduces the frequency of the safety valve opening and extends its lifespan.