ATTACK AS 500 Storage Tank with One Heat Exchanger (insulation included)

Product detailed description

ATTACK Buffer Tank AS 500 with One Heat Exchanger (insulation included)

ATTACK buffer tanks with a heat exchanger form a comprehensive range of five solutions that differ from each other in the way domestic hot water (DHW) is prepared and the number of built-in heat exchangers for charging heating water. It is exactly this choice that determines how easily and at what cost you can connect the tank to a heat pump, a wood gasification boiler, a gas boiler or solar collectors:

• AS – tank with one heat exchanger, purely heating accumulation. It has no DHW preparation built in, and serves solely to accumulate heating water and hydraulically separate the heat source (e.g. a heat pump or a gasification boiler) from the heating circuit. Hot water preparation is in this case solved with an external tank (e.g. the ATTACK Z range).
• HR – tank with a built-in enamelled DHW tank with a volume of 160 l inside the buffer tank body (a "tank in tank" principle). It does not contain any additional heat exchanger – heating water is fed directly into the buffer tank, so it is best suited to heat sources that do not require hydraulic separation (typically solid fuel boilers with their own circulation pump).
• HRS – the same design as HR (built-in enamelled DHW tank 160 l), supplemented with one additional external heat exchanger for charging heating water. Thanks to this heat exchanger, the HRS is also suitable for heat sources requiring hydraulic separation, such as a heat pump.
• TUV – tank with a stainless steel coil inside, ensuring instantaneous (flow-through) heating of domestic hot water – cold water flows through the coil and is instantly heated, without the need for a separate DHW tank. Heating water is fed directly, without an additional heat exchanger.
• TUVS – a combination of TUV (stainless steel coil for instantaneous DHW heating) and one additional external heat exchanger for charging heating water – the most universal solution in the range, suitable also for heat sources requiring hydraulic separation (heat pump, combination of multiple sources).

ATTACK Buffer Tank AS 500 with One Heat Exchanger (insulation included) belongs to the ATTACK buffer tank range with a heat exchanger in the 500-litre volume category. It is the AS – buffer tank with one heat exchanger variant – purely heating accumulation with a single heat exchanger for charging heating water – without built-in domestic hot water preparation. This page describes exactly this specific model, including its technical parameters, recommended heat sources and the most frequently asked customer questions.

Key features

• Removable soft insulation 100 mm thick in a durable leatherette (PVC) cover – easy to remove and refit during servicing of connections, without permanently damaging the tank surface.
• External heat exchanger for charging heating water with an estimated heat transfer area of approx. 2.0 m², enabling hydraulic separation of the heat source (e.g. a heat pump) from the heating circuit.
• Welded steel body with anti-corrosion internal treatment, designed for a maximum operating pressure of 3 bar and water temperature up to 95 °C.
• Prepared G 6/4" threaded port for installing an ATTACK TH electric heating element (2 – 6 kW) as a backup or supplementary heat source.
• Several ports (approx. 6 in total) for connecting the heat source(s), heating circuits, temperature sensors and venting – exact port layout according to manufacturing documentation.
• Compact footprint with a height/diameter ratio optimised to pass through standard doorways and staircases when installed in a boiler room or utility room.
• Ability to combine several heat sources at the same time (heat pump, wood gasification boiler, solar system, electric heating element) thanks to multiple connection levels on the tank shell.
• Made in Slovakia, 24-month warranty from commissioning (max. 30 months from factory dispatch).

Technical parameters

Installation recommendations

Thanks to the removable soft insulation with a thickness of 100 mm and a practical leatherette cover, the tank retains water temperature over the long term even outside the heating season, and access to the insulation for servicing connections is easy – the insulation can be removed and refitted at any time without damage. Thanks to the single heat exchanger, the AS tank is especially suited for cases where it is necessary to hydraulically separate one heat source (most often a heat pump or an ATTACK DPX/SLX wood gasification boiler) from the heating circuit, while hot water preparation is solved separately – for example with an external indirect tank from the ATTACK Z range (e.g. Z200HP, Z300HP, Z200SOL, Z300SOL) connected to the same heat source.

The AS500K tank is suitable for combination with ATTACK heat sources – with ATTACK DPX/SLX wood gasification boilers (which require heating water accumulation due to the combustion process), with heat pumps, as well as with ATTACK EKO/PLQ/KLQ/E/EZ COMBI stationary cast-iron gas boilers, which require an external indirect tank for DHW preparation (these boilers do not include a tank themselves). We always recommend having the exact sizing of pipework, pumps and safety fittings assessed by an authorised heating technician according to the project documentation for the specific building.

During installation, allow sufficient space around the tank for service access to the ports, sensors and any electric heating element. We recommend installing a safety valve, expansion vessel and a vent valve at the highest point of the system in accordance with applicable standards for closed heating systems.

How to correctly size the buffer tank volume

The buffer tank volume should be based primarily on the heat source output, the heat loss of the heated building and the operating mode. For wood gasification boilers (e.g. ATTACK DPX/SLX), a guideline of approximately 20 – 40 litres of accumulation per 1 kW of boiler output is usually recommended, so that the boiler can burn down at full output even outside of immediate heat demand in the house. For heat pumps, the volume is more a matter of hydraulic balancing of the circuit and the number of heating zones, and usually a smaller volume than for wood boilers is sufficient. The AS500K model with a volume of 500 litres is suitable as a guideline for a heat source with output within the relevant range – however, we always recommend having the exact calculation done by a heating technician based on the energy label or the heat calculation of the specific building, not just a table estimate.

Other volumes in the same AS variant

If a volume of 500 litres is not exactly what you are looking for, we also offer the same design solution (purely heating accumulation with a single heat exchanger for charging heating water – without built-in domestic hot water preparation) in our e-shop in other volume ranges:

• ATTACK Buffer Tank AS 800 with One Heat Exchanger (insulation included) – 800 l
• ATTACK Buffer Tank AS 1000 with One Heat Exchanger (insulation included) – 1000 l
• ATTACK Buffer Tank AS 1500 with One Heat Exchanger (insulation included) – 1500 l

A larger volume means a longer accumulation time and fewer charge/discharge cycles per day, which is easier on the heat source, but also requires more space in the boiler room and a higher purchase price. A smaller volume is, on the other hand, cheaper and more compact, but if undersized, the heat source may cycle more often.

Maintenance and operation

The AS500K buffer tank requires minimal maintenance – we recommend checking the tightness of all ports and connections, the function of the safety valve and the condition of the insulation once a year. For tanks with a stainless steel coil (TUV/TUVS), it is advisable to occasionally check the flow rate, and in harder water areas, to consider filtration at the cold water inlet, which extends the life of the coil and maintains stable flow performance. For variants with a built-in tank (HR/HRS), we recommend following standard DHW tank maintenance practices, including occasional inspection of the anode, if included in the design. The removable insulation allows quick and safe access for all these service operations without permanently damaging it.

Before first commissioning, we recommend having the system filled, vented and set up by an authorised technician, who will also confirm the commissioning date, which is decisive for the warranty period.

Safety and standards

The AS500K tank is intended for operation in closed heating systems and must always be fitted with a safety valve with an appropriate opening pressure, an expansion vessel with sufficient volume and a vent valve at the highest point of the circuit. Installation, connection and initial commissioning may only be carried out by a person with appropriate authorisation in accordance with applicable legislation and technical standards for pressure vessels and heating systems. Failure to comply with these principles may result in limitation or loss of the warranty.

Delivery and installation

We deliver the AS500K tank within Slovakia by standard pallet transport; for larger volumes (from approx. 800 l upwards), we recommend checking in advance the passability of doors and corridors along the route to the boiler room – the weight and dimensions in the parameters table are estimates, and we will gladly confirm the exact values for a specific unit before ordering. We recommend entrusting the actual connection to the heat source, electric heating element and control system to a professional installation company.

Who is this solution suitable for

The AS500K tank with a volume of 500 litres is recommended especially for family houses and smaller facilities that want to efficiently accumulate heating water while addressing domestic hot water preparation in a way typical of the chosen series (AS – buffer tank with one heat exchanger). The specific choice of volume and variant (AS/HR/HRS/TUV/TUVS) should be discussed with a heating technician based on the building's heat loss, the number of people in the household, the chosen heat source(s) and the required hot water comfort.

Frequently asked questions

What is the difference between the AS500K tank and the other types in the AS/HR/HRS/TUV/TUVS range?
The AS500K tank has purely heating accumulation with a single heat exchanger for charging heating water – without built-in domestic hot water preparation. The other types in the range differ mainly in whether they have a built-in DHW tank (HR, HRS), a stainless steel coil for instantaneous heating (TUV, TUVS), or no hot water preparation at all (AS), and in how many external heat exchangers for charging heating water they contain (0 or 1).

What volume of the AS500K tank do I need for an average family household?
A tank with a volume of 500 litres is intended for households and buildings requiring accumulation corresponding roughly to this output and consumption range. We always recommend calculating the exact volume based on the building's heat loss, the heat source output and the number of people in the household – we are happy to help you choose based on specific input data.

What is the area of the heat exchanger for charging heating water?
The AS500K tank has a heat exchanger with an estimated heat transfer area of approximately 2.0 m², which, at typical heat source inlet temperatures, is sufficient for efficiently charging the accumulated water volume within a reasonable time. The exact heat exchanger output depends on the temperature difference and flow rate on the heat source side.

Is the AS500K tank suitable for a heat pump?
Yes, the tank has an external heat exchanger for charging heating water, which provides the necessary hydraulic separation of the heat pump circuit from the house's heating circuit – a common connection for ATTACK heat pumps as well as those from other manufacturers.

What is the maximum operating pressure and temperature load of the tank?
The accumulation part of the tank is designed for a maximum operating pressure of 3 bar and a maximum water temperature of 95 °C. The heat exchanger/coil circuit withstands comparable values; you will find the exact maximum parameters in the technical table below and always also in the accompanying documentation supplied with the tank.

How is the AS500K tank insulated, and can the insulation be removed later for servicing?
The tank is fitted with soft removable insulation 100 mm thick in a leatherette cover, which is easily removed and refitted using hook-and-loop fasteners/straps without damage – useful when connecting ports, performing service work, or subsequently installing sensors and heating elements.

Can the tank be combined with several heat sources at once (e.g. heat pump and solar)?
Yes, that is one of the main purposes of a buffer tank with a heat exchanger – it allows combining several heat sources (heat pump, wood gasification boiler, solar system, electric heating element) into a single accumulation body. We recommend having the exact connection scheme and the number of required ports designed by a heating technician according to the specific combination of sources.

Is it possible to subsequently install an electric heating element?
Yes, the tank has a prepared G 6/4" threaded port for ATTACK TH electric heating elements (e.g. TH100, TH102, TH103, TH107 with an output of 2 – 6 kW), which serve as a backup or supplementary heat source.

Is the price difference between AS, HR, HRS, TUV and TUVS just about additional equipment?
Yes, the price difference between the individual variants of the same volume reflects the amount of built-in components – a built-in enamelled DHW tank (HR/HRS), a stainless steel coil (TUV/TUVS) and/or an additional external heat exchanger (HRS/TUVS compared to HR/TUV). The more functions a tank integrates, the higher the purchase price, but at the same time you do not need to buy and install separate additional equipment.

How does ordering and delivery of the AS500K tank work?
Once ordered, we dispatch the tank from the manufacturing warehouse in Slovakia and inform you of the delivery date by e-mail or telephone. If you are interested, we can also recommend compatible accessories (ATTACK TH electric heating elements, circulation pumps, controls) so that you receive a complete, functional set in a single order.

Warranty

We provide a warranty period of 24 months from the date of commissioning for the AS500K buffer tank, but no more than 30 months from the date of dispatch from the factory. If you have any questions about choosing, connecting or servicing the tank, please do not hesitate to contact our sales department – we are happy to help design the whole set, including the heat source, circulation pumps and controls.