uniSTOR plus VIH RW 250

Product detailed description

Vaillant uniSTOR plus VIH RW 250 hot water storage tank

Vaillant uniSTOR plus VIH RW 250 is a stationary indirectly heated hot water storage tank with a volume of 246 liters, developed specifically for use with heat pumps. It belongs to the smallest version of the uniSTOR plus series and is primarily intended for smaller households, apartments, chalets, or as an additional tank in systems where there is no large space available for installation. Thanks to its slim diameter of 596 mm and a height of 1572 mm, it fits even into confined technical rooms, bathrooms, or storage rooms, while offering the same quality of processing and technology as the larger models in this series.

The tank is designed for operation with one heat source – most often with the Vaillant aroTHERM or flexoTHERM heat pump, or alternatively with another heating source of suitable performance. The inner tank is made of high-quality steel with a high-quality glazed (enamel) surface on the potable water side, which long-term resists corrosion and limescale deposits. The standard delivery includes a magnesium protective anode, which actively protects the inner tank surface against corrosion throughout the tank's lifetime.

Technical specifications of VIH RW 250

• Nominal/actual tank volume: 246 liters
• Height of the tank (with casing): 1572 mm
• Width / diameter (with casing): 596 mm
• Folded dimension (for handling during installation): 1682 mm
• Weight of the empty tank (without water): approximately 90 kg
• Weight of the filled tank in operation: approximately 349.5 kg
• Heat transfer area of the heating coil: 1.8 m²
• Volume of the heat exchanger charge: 13.5 liters
• Maximum operating pressure (domestic water): 10 bar
• Maximum operating pressure (heating circuit): 10 bar
• Maximum temperature of hot water: 85 °C
• Standby heat loss: 1.53 kWh/24h
• Energy efficiency class for water heating: A+
• Integrated magnesium protective anode against corrosion
• Glazed inner surface of the tank (enamel)

Construction and thermal insulation

The casing of the VIH RW 250 tank is insulated with rigid PU foam of high density, applied directly to the steel tank without a gap, thus eliminating thermal bridges and significantly reducing heat losses during standby mode. The outer casing is made of durable plastic in white color, which is easy to clean and resistant to mechanical damage during normal operation. The low value of standby heat loss of 1.53 kWh per 24 hours places this model among very energy-efficient solutions in its volume category, which directly translates into lower operating costs for the household, especially when combined with a heat pump, where the efficiency of water heating is crucial.

One heating heat exchanger with a smooth tube of 1.8 m² is designed to efficiently heat domestic water to the desired temperature even at lower heat pump output temperatures (typically 35 – 55 °C) with minimal heat transfer losses. The large heat transfer area in relation to the tank volume shortens the heating time and reduces the number and duration of heat pump switching cycles, thus prolonging its lifespan.

Installation and connection

The tank is installed as a stationary, floor-standing unit with adjustable feet, allowing precise leveling even on uneven floors. Due to its compact dimensions, it is also suitable for smaller technical rooms, pantries, or bathroom niches. The connection of cold and hot water, circulation, and heating circuit is solved by standard threaded connections located at the top of the tank, which facilitates access during installation and in case of servicing.

During installation, we recommend maintaining minimum distances from the walls for access to the inspection opening and anode, as well as sufficient space for the replacement of the magnesium anode during regular service (annual inspection is recommended). The tank can be combined with the Vaillant senzoCOMFORT or multiMATIC heat pump control, which is able to control the heating temperature, time programs, and the priority of hot water heating over heating.

Compatible accessories

For the VIH RW 250 tank, it is possible to add a set of connecting valves, a safety valve for the domestic water side, an expansion vessel for hot water, and insulating sleeves for the connecting pipes to eliminate heat losses in the distribution system. For systems with a Vaillant heat pump, we recommend using original connecting sets and tank temperature sensors compatible with the heat pump control unit, which ensure accurate measurement and optimal heating control.

Who is the RW 250 model suitable for

The RW 250 model is an optimal choice for a 1 – 3 person household, apartment, smaller family house, or recreational property, where high daily consumption of hot water is not required, but at the same time the installation space is limited. Thanks to its compact dimensions, it is one of the few tanks on the market that can fit even into standard built-in cabinets or low technical rooms.

Frequently asked questions (FAQ)

How much space do I need for installation?
Due to the diameter of 596 mm and height of 1572 mm, a floor area of approximately 70 × 70 cm is sufficient, but you should also consider the folded dimension of 1682 mm during handling during installation, especially if the ceiling is low.

Can the RW 250 tank be connected to a gas boiler instead of a heat pump?
Construction-wise, the tank is optimized for lower temperatures typical for heat pumps, but due to one heat exchanger, it can also be operated with another heat source of suitable performance and supply temperature up to 85 °C.

How often should the magnesium anode be checked?
It is recommended to perform a visual inspection once a year, more frequently in areas with hard water, since the rate of anode wear depends on the quality and hardness of the incoming water.

What is the difference between the 90 kg and 349.5 kg weight mentioned in the parameters?
90 kg is the weight of the empty tank ready for transport, 349.5 kg is the weight of the tank filled with water in normal operation – this data is important for the static assessment of the floor at the installation site.

Is it possible to purchase the RW 250 tank for an existing Vaillant heat pump?
Yes, the tank is fully compatible with Vaillant heat pump control units and can be additionally connected as a separate source of hot water.

Water heating principle with a heat pump

Unlike a gas boiler, which can supply heating water at temperatures of 70 – 80 °C, a heat pump operates most efficiently at lower output temperatures around 35 – 55 °C. Therefore, the construction of the VIH RW 250 tank – the size of the heat transfer area, the shape of the heating coil, and the thickness of the insulation – is specifically adapted to this lower temperature difference. A larger heat exchanger area in relation to the tank volume ensures that even at a lower temperature of the heating water from the heat pump, enough heat is transferred to the tank in a shorter time, thus reducing the number of compressor switching cycles and prolonging its lifespan. The high quality of insulation with rigid PU foam without thermal bridges also ensures that the heated water maintains its temperature for a longer time even without further heating, which is especially important at the lower performance of the heat pump.

Maintenance and service

Regular maintenance of the VIH RW 250 tank mainly consists of checking and, if necessary, replacing the magnesium protective anode, checking the functionality of the safety valve on the domestic water side, and preventive descaling of the tank, which prolongs its lifespan, especially in areas with hard water. It is recommended to perform the service at least once a year, ideally as part of the regular annual inspection of the heat pump. Access to the inspection opening and anode is located on the front side of the casing, which allows service without the need to disconnect the tank from the piping system or move it.

Thanks to the glazed inner surface in combination with the active cathodic protection by the magnesium anode, the inside of the tank is protected against corrosion throughout the product's lifetime, provided the recommended service intervals are followed. The high-quality welding and glazing processing corresponds to the long-term experience of the Vaillant brand in the production of hot water tanks in Europe.

Comparison within the uniSTOR plus series

The model VIH RW 250 is the smallest representative of the uniSTOR plus series with one heat exchanger for heat pumps, followed by models RW 300, RW 400 and RW 500 with increasing volume for larger households. If the planned hot water consumption in the household exceeds the usual comfort level for 2 – 3 people, or if expansion of the household is planned in the future, we recommend considering a larger volume model from the same series, which offers a higher hot water reserve and longer comfortable withdrawal at peak demand while maintaining the same processing quality.

Eco-friendly and economic benefits

The low standby heat loss of 1.53 kWh per 24 hours combined with efficient heat transfer means that the tank VIH RW 250 minimizes energy losses even during longer periods between hot water withdrawals, which is typical especially for smaller households or recreational buildings with irregular occupancy. In combination with a heat pump that uses renewable energy from the surrounding environment, this tank contributes to a significant reduction in operating costs for heating hot water compared to a conventional electric water heater or instantaneous heating.