Heat pumps - combined storage

Heat pump combination storage tank WK – Legionella-safe domestic hot water heating

Brief description

The WK heat pump combination storage tank combines hygienic domestic hot water heating and buffer storage in a single compact container and is specifically designed for heat pump systems. Thanks to the integrated stainless steel corrugated pipe in the upper part of the tank, domestic hot water is heated without a large storage volume, thus reducing legionella growth and minimizing maintenance.

Construction and materials

The storage tank is made of high-quality steel S235JRG2 according to DIN 4753 and European standard EN 12897; the domestic hot water heat exchanger is a stainless steel corrugated pipe (1.4404) manufactured in Germany. The tank is unfinished inside, primed outside, and divided into two thermally separated sections: domestic hot water heating at the top and a heating buffer at the bottom.

Operating principle and protection against Legionella

In the upper section, the stainless steel corrugated pipe heats drinking water on demand, meaning only small amounts of water need to be stored and the risk of Legionella is significantly reduced. The separate buffer tank in the lower section stores heating energy for the heat pump operation and simultaneously allows for large temperature differences between the two sections.

Heat exchangers and performance characteristics

The stainless steel heat exchanger offers high hot water output and fast heating times due to its large surface area. Both storage areas are equipped with separate sockets for electric heating elements, making it easy to integrate additional heating.

Insulation options

The combination storage tank is available with various insulation options: 100 mm EPS (efficiency class C), 130 mm EPS AirPor® (efficiency class B), or 150 mm PU super rigid foam (efficiency class A, for 600–1000 l). Each version is removable and features a silver-grey plastic casing and a sealing strip.

EPS AirPor® insulation

The innovative EPS AirPor® insulation combines expanded polystyrene with graphite nanoparticles for improved heat reflection. This construction reduces heat loss compared to conventional solutions, is easy to install, fits precisely, and is recyclable.

PU super-rigid foam insulation

The 150 mm PU combination insulation (PU + PV fleece) offers very low thermal conductivity and prevents convection losses at the container walls, lid, and joints. It is robust, skin-friendly, 100% recyclable, and ensures maximum energy efficiency (Class A).

Assembly, connections and transport

All connections are located on the side; both storage units can be disassembled and transported separately. The insulation is removable, facilitating installation and servicing, even in confined spaces.

Advantages for operators

The combined storage tank reduces heat losses, minimizes maintenance by eliminating the need for a sacrificial anode, enables simultaneous heating and cooling of the underfloor heating system, and increases the efficiency of heat pump systems through optimized stratification and a large heat exchanger surface.

Areas of application and planning guidelines

Ideal for residential buildings, apartment buildings, and commercial projects with heat pumps and underfloor heating or cooling systems. When selecting the insulation option, storage capacity, desired energy efficiency, and installation conditions should be considered; we are happy to assist with the design.

Technical data & Operation

Maximum operating pressure of the tank: 5 bar; maximum operating pressure of the domestic hot water heat exchanger: 10 bar. Tank made of S235JRG2 steel; heat exchanger made of 1.4404 stainless steel. Efficiency classes depend on insulation: A (150 mm PU), B (130 mm EPS AirPor®), C (100 mm EPS). Both storage areas have sockets for electric heating elements.

Scope of delivery

• Heat pumps - Combination storage tank of your choice
• including selected insulation
• Assembly & Operating instructions