ATTACK Stainless Steel Accumulation Tank for Heating/Cooling Water AK 200 INOX

Product detailed description

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 200 INOX is a buffer (balancing) tank made of stainless steel with a volume of 200 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 reducing 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 corrosion resistant regardless of the quality of the heating water, does not require cathodic protection by a magnesium anode, and has a long service life even with year-round operation in both cooling and heating modes.

Key features

• Volume of 200 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, limiting heat losses to the surroundings
• Set of G 6/4" threaded ports for connecting heating circuits, pumps, sensors and venting
• Option to fit an electric heater (e.g. ATTACK TH series) into the prepared port
• Compact dimensions allowing installation even in smaller boiler rooms and utility 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 of compressor starts and stops. If the volume of water in the heating system itself (radiators, underfloor heating, pipework) is too small, or 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 200 INOX is connected as a hydraulic separator (common manifold) between the primary circuit of the heat pump and the secondary heating or cooling circuits - ensuring sufficient and constant 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 ramp-up of cooling capacity for fan coil units or cooled floor/ceiling systems connected to the system.

Choosing the right tank size

When designing the appropriate volume of a buffer/balancing tank for a heat pump, the main factors are the output of the heat source, the type of emission system (underfloor heating has a significantly higher inherent 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 guideline, we provide the following overview of the whole ATTACK AK ANTIKOR range - 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 200 INOX - belongs to the above range with a volume of 200 l.

Installation and use

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 200 INOX must be installed exclusively in a vertical (upright) position on a flat, sufficiently load-bearing surface, taking into account its total weight when filled with water (empty weight approx. 40.0 kg, significantly more once filled). We recommend leaving sufficient clearance around the tank for possible servicing of flanges, sensors and connections. Connection to the heating/cooling circuit is made via G 6/4" threaded ports; the system must be vented every time water is filled or topped up in the system. During operation in cooling mode, we also recommend insulating the connecting pipework to prevent surface condensation in the boiler room.

Quality and preparation of heating/cooling water

Although the tank itself is made of stainless steel and corrosion of the tank is not a risk, the quality of the heat transfer medium still affects the service life of other system components (pumps, valves, heat pump heat exchangers, pipework). When filling the system, we recommend using treated (softened, or possibly demineralised) water according to the heat pump manufacturer's recommendations, thoroughly venting the system, and, if necessary, adding a suitable corrosion inhibitor compatible with the aluminium heat exchangers of heat pumps. In cooling mode and for pipework routed through unheated spaces, it is also advisable to consider adding antifreeze (glycol) at the recommended concentration, although this slightly reduces the thermal capacity of the medium and must be taken into account in the hydraulic calculation.

Benefits of a balancing tank for heat pump efficiency

Inverter heat pumps of the ATTACK Inverter R32 series achieve their highest seasonal efficiency (SCOP) with long, smooth compressor runs with a minimum of starts and stops. Without a sufficient volume of water in the circuit, closing individual heating zones risks frequent compressor cycling, which increases electricity consumption, mechanical wear and equipment noise. By adding the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 200 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 for the heat pump compressor.

Practical examples of use

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 200 INOX is connected as a hydraulic separator directly 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 200 INOX also serves as a buffer for cooled water, stabilising the ramp-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 200 INOX is a suitable complement especially for 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 series fan coil units (cassette and wall-mounted versions), which distribute heat or cold directly from the tank into 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 a buffer tank should always include a safety valve with the appropriate opening pressure, 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 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 via the prepared port. Since the tank is made of stainless steel, there is no need to care for cathodic protection, which is common with conventional enamelled steel tanks.

Ecological and sustainability aspect

As a balancing/buffer tank, it helps 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 the magnesium anode, meaning less material and waste over the product's entire service life 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. 40.0 kg), we recommend arranging suitable handling equipment (pallet truck, or a second person) when receiving the shipment, and checking that the packaging is intact upon receipt in order to preserve any potential claim for transport-related damage.

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 manufacturing in Slovakia allow the manufacturer to respond flexibly to market demands and maintain the availability of spare parts and service support for end customers and installation companies alike.

Technical parameters

Note: dimensions, weight and insulation thickness are indicative estimates for the given type range based on tank volume; please verify 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 is checking the tightness of the flanges and insulation once a year during a service inspection.

Can the tank also work with cooled water in summer (cooling via a 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 also insulating the tank and connecting pipework with a vapour barrier overlap to prevent surface condensation.

What size tank should I choose for my heat pump?

As a rough guide, approximately 10-20 litres per 1 kW of heat pump output is used for calculation; 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 just 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 upright?

The tank is designed and equipped with flanges for vertical (upright) installation. Horizontal installation is not supported as standard 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 (foamed polyester/foam or softened insulation depending on the specific range), 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 ports (usually G 6/4" for heating water, plus smaller ports for sensors and venting/desludging) enabling the connection of circulation pumps, an electric heating element (auxiliary heating), thermometers and a venting valve. The exact layout of the ports can be found in the technical data sheet for the specific model.

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

Yes, most tanks have a prepared G 6/4" threaded port for fitting an electric heater (e.g. ATTACK TH series), which is used as a bivalent source or in the event 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 layout of the heating system. Apartment buildings or commercial buildings usually use larger volumes or several tanks connected in parallel - in such cases, we recommend consulting the design with a heating designer.

Warranty and service

This ATTACK 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, and spare parts are usually kept in stock.

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

Summary

ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 200 INOX - a stainless steel buffer tank with a volume of 200 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.