ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX

Product detailed description

ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX is a buffer (balancing) tank made of stainless steel with a volume of 50 litres, designed for accumulating heating or cooling water in systems with an ATTACK heat pump. The tank acts as a hydraulic separator of dynamic pressures between the primary circuit of the heat pump and the secondary heating/cooling circuits of the building, thereby limiting frequent compressor cycling, extending its service life and increasing the overall operating efficiency (seasonal COP/SCOP) of the heat pump.

Thanks to its stainless steel (INOX) construction, the tank is fully resistant to corrosion regardless of the quality of the heating water, does not require cathodic protection by a magnesium anode, and has a long service life even during year-round operation in both cooling and heating modes.

Key features

• Volume of 50 litres, suitable as a hydraulic separator or buffer tank for the ATTACK Inverter R32 heat pump
• Stainless steel (INOX) body - permanent corrosion resistance, no magnesium anode, minimal maintenance
• Suitable for operation with both heating and cooled water (summer cooling mode of the heat pump)
• Thermal insulation jacket approx. 50 mm thick, reducing heat losses to the surroundings
• Set of G 6/4" threaded connections for connecting heating circuits, pumps, sensors and venting
• Possibility of fitting an electric heating element (e.g. ATTACK TH series) into the prepared connection
• Compact dimensions allowing installation even in smaller boiler rooms and technical rooms
• Long service life and low maintenance requirements thanks to the absence of corrosion processes inside the tank

How a buffer tank works in a system with a heat pump

Heat pumps, especially inverter types such as the ATTACK Inverter R32, work most efficiently with longer, smooth operating cycles with a minimum number of compressor starts and stops. If the volume of water in the heating system itself (radiators, underfloor heating, piping) is too small, or if the system is divided into several independently controlled circuits with thermostatic heads or zone valves, there is a risk that the flow through the heat pump will drop below the minimum permitted value and the compressor will start cycling frequently. In such a case, the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX is connected as a hydraulic separator (common manifold) between the primary circuit of the heat pump and the secondary heating or cooling circuits - it ensures sufficient and stable flow on the heat pump side, regardless of how many secondary circuits are currently open.

The same principle applies during summer operation in cooling mode - the tank accumulates cooled water and ensures a stable start-up of the cooling capacity for fan-coil units or cooled floor/ceiling systems connected to the system.

Choosing the right tank size

When designing a suitable volume for a buffer/balancing tank for a heat pump, the main factors to consider are the output of the heat source, the type of emission system (underfloor heating has a significantly higher own water volume than panel radiators), and how many independently controlled heating circuits (with zone valves or thermostatic heads) are connected in the system. As a general guide, we provide the following overview of the entire ATTACK AK ANTIKOR series - however, we recommend always verifying the specific recommendation for your project with a designer or directly with our technical department.

This particular model - ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX - belongs to the above series with a volume of 50 l.

Installation and use

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX must be installed exclusively in a vertical (upright) position on a flat, sufficiently load-bearing base, taking into account its total weight when filled with water (empty weight approx. 18.5 kg, significantly more once filled). We recommend leaving sufficient working space around the tank for any future servicing of flanges, sensors and connections. Connection to the heating/cooling circuit is made via G 6/4" threaded connections; the system must be vented every time water is added or refilled. When operating in cooling mode, we also recommend insulating the connecting piping to prevent surface condensation in the boiler room.

Quality and preparation of heating/cooling water

Although the tank is made of stainless steel and there is no risk of corrosion to the tank itself, the quality of the heat transfer medium still affects the service life of other system components (pumps, valves, heat pump heat exchangers, piping). When filling the system, we recommend using treated (softened, or possibly demineralised) water in accordance with the heat pump manufacturer's recommendations, thoroughly venting the system, and, if necessary, adding a suitable corrosion inhibitor compatible with aluminium heat pump heat exchangers. In cooling mode and for piping routed through unheated areas, it is also advisable to consider adding antifreeze (glycol) at the recommended concentration, which, however, slightly reduces the thermal capacity of the medium and must be taken into account in the hydraulic calculation.

Benefit of a balancing tank for heat pump efficiency

Inverter heat pumps such as the ATTACK Inverter R32 achieve their highest seasonal efficiency (SCOP) with long, smooth compressor runs and a minimum number of starts and stops. Without a sufficient volume of water in the circuit, closing individual heating zones can lead to frequent compressor cycling, which increases electricity consumption, mechanical wear and noise levels. By adding the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX as a hydraulic separator or buffer tank, this effect is eliminated, which in practice results in lower operating costs and a longer service life of the heat pump compressor.

Practical usage examples

Family house with underfloor heating: In a family house with an ATTACK Inverter R32 heat pump and several independently controlled heating zones (room thermostats, zone valves), the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX is connected as a hydraulic separator right after the heat pump. This ensures sufficient flow through the heat pump's heat exchanger even when only part of the heating circuits are open, preventing compressor cycling and unnecessary wear on the equipment.

Combination of heating and summer cooling: In buildings where the heat pump switches to cooling mode in summer (e.g. in combination with ATTACK FCU fan-coil units or a cooled ceiling/floor), the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX also serves as a buffer for cooled water, stabilising the start-up of cooling capacity and reducing temperature fluctuations of the water supplied to individual consumers.

Compatibility with ATTACK heat pumps and boilers

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX is a suitable complement especially to ATTACK Inverter R32 Air/Water heat pumps (both split and compact versions), where it serves as a hydraulic separator or buffer for heating/cooling water. In larger installations, the tank can also be combined with several ATTACK FCU fan-coil units (both cassette and wall-mounted versions), which distribute heat or cooling from the tank directly to individual rooms. In bivalent setups, the tank can also be used together with ATTACK stationary boilers as a common heat accumulation point from multiple sources.

Safety features and related standards

A complete installation of the buffer tank should always include a safety valve with an appropriate opening overpressure, an expansion tank sized for the total volume of the system (including the volume of this tank), and a venting valve at the highest point of the system. The design and installation of a heating system with a buffer tank should comply with the requirements of the relevant technical standards (e.g. EN 12828 for hot water heating systems) and should be carried out by a professionally qualified heating technician.

Tank maintenance

Routine maintenance of the buffer tank consists of an annual visual inspection of the tightness of flanges, connections and insulation, checking the function of the safety valve and, if necessary, desludging the system through the prepared connection. Since the tank is made of stainless steel, there is no need to worry about cathodic protection, which is common with conventional enamelled steel tanks.

Environmental and sustainability aspect

As a balancing/buffer tank, it helps to reduce the number of heat pump compressor starts, thereby contributing to lower electricity consumption from the grid and a longer service life of the equipment. The stainless steel design also eliminates the need to replace a magnesium anode, meaning less material and waste are used over the product's entire lifetime compared to conventional enamelled tanks.

Delivery and handling

The product is delivered by pallet transport, usually within a few working days of ordering (we will confirm the exact delivery date after receiving your order, as some models are manufactured or assembled to order). Given the weight of the product (approx. 18.5 kg), we recommend using suitable handling equipment (pallet truck, or a second person) when receiving the shipment, and checking that the packaging is undamaged upon delivery in order to preserve any claim for damage caused during transport.

About the manufacturer ATTACK

ATTACK, s.r.o. is a Slovak manufacturer of heating technology with a long tradition in the development and production of solid fuel boilers, gas boilers, heat pumps and related accessories, including buffer and storage tanks. In-house development and production in Slovakia allow the manufacturer to respond flexibly to market demands and maintain the availability of spare parts and service support for both end customers and installation companies.

Technical parameters

Note: dimensions, weight and insulation thickness are approximate estimates for the given model range based on tank volume; please verify the exact values in the manufacturer's current technical data sheet or request them when ordering.

Frequently asked questions

Does the stainless steel tank need to be earthed or protected by a magnesium anode?

No. The tank is made of stainless steel (INOX), so it is not subject to electrochemical corrosion like enamelled steel tanks, and does not require a magnesium anode or its regular inspection/replacement. The only regular maintenance required is checking the tightness of flanges and insulation once a year during a service inspection.

Can the tank also work with cooled water in summer (cooling via the heat pump)?

Yes, the tank is designed as a buffer/balancing tank for both heating and cooling water. When operating with cooled water (heat pump cooling mode), we recommend insulating the tank and the connecting piping as well, including a vapour barrier overlap, to prevent condensation forming on the surface.

What tank volume should I choose for my heat pump?

As a general guideline, approx. 10-20 litres per 1 kW of heat pump output is used; the more precise amount depends on the type of emission system (underfloor heating has a higher water volume than radiators), the number of heating circuits, and whether the tank is connected as a hydraulic separator of dynamic pressures or only as a buffer. We recommend discussing the design with a designer or directly with our technical department.

Can the tank be installed horizontally, or only vertically?

The tank is designed and equipped with flanges for vertical (upright) installation. Horizontal installation is not standardly supported and could affect proper venting and temperature stratification within the tank.

Is thermal insulation included in the delivery?

Yes, the tank is supplied with a thermal insulation jacket (foam polyester/foam or soft insulation depending on the specific series), which minimises heat losses to the surroundings during energy storage.

What connections (threads) does the tank have and what can it be fitted with?

The tank is equipped with a set of threaded connections (usually G 6/4" for heating water, plus smaller connections for sensors and venting/desludging), allowing the connection of circulation pumps, an electric heating element (for supplementary heating), thermometers and a venting valve. The exact layout of the connections can be found in the technical data sheet for the given model.

Can an electric heating element be added to the tank for supplementary heating?

Yes, most tanks have a prepared G 6/4" threaded connection for fitting an electric heating element (e.g. ATTACK TH series), which is used as a bivalent source or in case of a heat pump malfunction.

Can the tank be used in an apartment building, or only in a family house?

The tank is not tied to a specific type of building; its use is limited more by the size and hydraulic design of the heating system. In apartment buildings or commercial buildings, larger volumes or several tanks connected in parallel are usually used - in such cases, we recommend consulting the design with a heating engineer.

Warranty and service

This ATTACK brand product is covered by a standard warranty period of 24 months from commissioning, but no more than 30 months from the date of dispatch from the factory. For selected products, and when commissioning is registered by an authorised service technician, an extended warranty may also be arranged - please check the specific conditions when ordering or with our sales department. Service and spare parts are provided by the network of authorised ATTACK service partners in Slovakia; spare parts are usually kept in stock.

Before commissioning, we recommend having the connection and filling of the system checked by a professionally qualified person (heating engineer/service technician) in order to meet the conditions for the full warranty period.

Summary

ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 50 INOX - a stainless steel buffer tank with a volume of 50 l for both heating and cooling water, requiring no anode protection, suitable as a hydraulic separator or buffer tank for ATTACK Inverter R32 heat pumps and as a complement to ATTACK FCU fan-coil units for cooling.