ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX

Product detailed description

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX is a buffer (balancing) tank made of stainless steel with a volume of 100 litres, designed for accumulating heating or cooling water in systems with an ATTACK heat pump. The tank functions 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 corrosion-resistant regardless of the quality of the heating water, does not require cathodic protection with a magnesium anode, and has a long service life even with year-round operation in both cooling and heating modes.

Key features

• Volume of 100 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 loss to the surroundings
• Set of G 6/4" threaded ports for connecting heating circuits, pumps, sensors and air venting
• Option to fit an electric heating element (e.g. from the ATTACK TH range) into a 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 heat pump system

Heat pumps, especially inverter types such as the ATTACK Inverter R32, operate most efficiently in 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 (so-called short cycling). In such a case, the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX is connected as a hydraulic separator (common header) between the primary circuit of the heat pump and the secondary heating or cooling circuits - it ensures sufficient and constant flow on the heat pump side regardless of how many secondary circuits are currently open.

The same principle applies to summer operation in cooling mode - the tank accumulates cooled water and ensures a stable build-up of 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 of the buffer/balancing tank for a heat pump, the main factors considered are the output of the heat source, the type of heat emission system (underfloor heating has a significantly higher intrinsic 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 rough guide, we provide the following overview of the entire 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 specific model - ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX - belongs to the above range with a volume of 100 l.

Installation and use

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 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. 25.0 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 added to or topped up in the system. 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 corrosion of the tank itself 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, piping). We recommend using treated (softened, or possibly demineralised) water when filling the system, 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

ATTACK Inverter R32 inverter heat pumps achieve their highest seasonal efficiency (SCOP) with long, smooth compressor runs with a minimum number of starts and stops. Without a sufficient water volume in the circuit, closing individual heating zones can lead to frequent compressor cycling, which increases electricity consumption, mechanical wear and equipment noise. By installing the ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 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 use cases

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 100 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 equipment wear.

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 100 INOX also serves as a buffer for cooled water, which stabilises the build-up of cooling capacity and reduces temperature fluctuations of the water supplied to individual appliances.

Compatibility with ATTACK heat pumps and boilers

The ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX is a suitable complement especially to heat pumps from the ATTACK Inverter R32 Air/Water range (both split and compact versions), where it serves as a hydraulic separator or buffer tank for heating/cooling water. In larger installations, the tank can also be combined with several ATTACK FCU fan coil units (cassette and wall-mounted versions), which distribute heat or cooling from the tank directly to individual rooms. In bivalent systems, the tank can also be used together with ATTACK stationary boilers as a common heat accumulation point from multiple sources.

Safety elements and related standards

A complete buffer tank installation should always include a safety valve with an appropriate opening overpressure, an expansion tank sized for the total system volume (including the volume of this tank), and an air vent 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

Regular 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 port. Since the tank is made of stainless steel, there is no need to maintain cathodic protection, which is common with classic enamelled steel tanks.

Environmental and sustainability aspects

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 is replaced and less waste is generated over the entire life of the product compared to classic enamelled tanks.

Delivery and handling

The product is delivered by pallet freight, 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. 25.0 kg), we recommend arranging suitable handling equipment (pallet truck, or a second person) when receiving the shipment, and checking the packaging for damage 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 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 according to the 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 grounded or protected with 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 an annual check of the tightness of flanges and insulation 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 connecting piping, including covering with a vapour barrier, to prevent surface condensation.

What tank volume should I choose for my heat pump?

As a rough guide, approximately 10-20 litres per 1 kW of heat pump output is used; the more precise amount depends on the type of heat 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 simply as a buffer tank. 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 fitted 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 softened insulation depending on the specific range), which minimises heat loss 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) allowing the connection of circulation pumps, an electric heating element (booster heater), thermometers and an air vent 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 booster heating?

Yes, most tanks have a prepared G 6/4" threaded port for fitting an electric booster heater (e.g. from the ATTACK TH range), which is used as a bivalent source or in the event of a heat pump failure.

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

The tank is not tied to a specific building type; its use is limited more by the size and hydraulic scheme 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 designer.

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 upon registration of commissioning by an authorised service technician, an extended warranty can also be arranged - please check the specific terms 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 full warranty coverage.

Summary

ATTACK Stainless Steel Buffer Tank for Heating/Cooling Water AK 100 INOX - a stainless steel buffer tank with a volume of 100 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.