ATTACK AK 500 Storage Tank (insulation included in price)

Product detailed description

Why a buffer tank determines heating efficiency

The ATTACK Buffer Tank AK 500 (insulation included in price) is a steel buffer (accumulation) tank with a volume of 500 litres, designed for storing hot heating water from any heat source - a wood gasification boiler, heat pump, electric boiler, gas boiler or solar collectors. It is a tank without a built-in heat exchanger (sometimes also referred to as a "hydraulic separator" or "buffer tank"), which serves purely to store heating water - heating of domestic hot water (DHW) with this type of tank is handled externally, for example via a storage water heater or a flow module.

The greatest benefit of a buffer tank is seen when combined with a solid fuel gasification boiler, such as the ATTACK DPX or ATTACK SLX. These boilers achieve the highest efficiency and cleanest combustion precisely when burning at full, rated output - i.e. when they burn a full load of wood "in one go" without throttling the air supply. Without a buffer tank, the boiler would often have to operate in a throttled mode (to prevent overheating of the system), which leads to worse combustion, higher tar formation and shorter service life for both the boiler and the chimney. With the ATTACK Buffer Tank AK 500 (insulation included in price), the boiler burns the fuel at full output at once, and the surplus heat is stored in the water reserve in the tank - from which the heating system gradually draws it according to the household's current needs, even several hours after the boiler has burned out.

The same principle also applies to an electric boiler or heat pump: the 500 l tank allows the heat source to work in longer, less frequent cycles instead of constantly switching on and off for short intervals, which extends the service life of the compressor/heating elements and reduces energy consumption. This is a typical volume for an ordinary family house heated with an ATTACK DPX or SLX wood gasification boiler - a tank of this size can hold the heat from one or more boiler loads and gradually release it into the heating system over the following days, significantly reducing the number of boiler starts and stops.

Key features of the AK500K tank

• 500-litre volume - designed to provide a sufficient heat reserve between heating cycles at a recommended heat source output of 20 - 25 kW.
• Soft, removable polyester insulation, 100 mm thick - significantly reduces heat loss to the surroundings during long-term storage of hot water, while allowing easy removal for inspection or servicing of the tank and fittings.
• Outer insulation cover made of synthetic leather (PVC fabric) in silver-grey - resistant to abrasion and easy to maintain, visually blending in as part of the boiler room interior rather than looking like a "technical" element.
• 5 connection ports distributed around the shell and on the top/bottom of the tank, allowing connection of the heat source, heating circuits, an additional electric heating element (backup heating), venting, draining and temperature sensors.
• Steel shell with a corrosion-resistant internal coating, rated for a maximum operating pressure of 3 bar and maximum temperature of 95 °C - a safe margin above typical heating water operating temperatures (60-80 °C).
• Suitable for vertical installation thanks to feet/a stand, which at this volume facilitates precise temperature layering (stratification) - warmer water naturally stays at the top, cooler water at the bottom, increasing the usability of the stored heat.
• Option of additionally installing an electric heating element (e.g. ATTACK TH100, TH102, TH103 or TH107) directly into one of the tank's ports - suitable as a backup or supplementary heat source outside the heating season or in case of failure of the main heat source.
• No built-in heat exchanger - the tank is designed purely for accumulating heating water; if you also need DHW preparation via a built-in heat exchanger, check out our range of AS/HR/HRS/TUV/TUVS tanks with a heat exchanger.

Technical parameters

Note: the dimensions and weight of the empty tank are indicative estimates corresponding to the given volume; we recommend verifying the exact dimensions with the seller before ordering, especially before installation (e.g. in case of a limited boiler room space or narrow doors/staircase).

How to correctly choose the buffer tank volume

The most common recommended rule when choosing a buffer tank for a solid fuel gasification boiler is: allow approximately 20 to 25 litres of buffer volume per 1 kW of the boiler's rated output. This rule is based on the fact that the boiler burns one load of fuel at full output in approximately 1.5 to 3 hours, and the heat from this load needs to be stored somewhere until it is gradually consumed by the heating system. For a 500-litre tank, this means it is suitable for a heat source with an output of approximately 20 to 25 kW.

If you have, for example, a wood gasification boiler with an output in this range (from the ATTACK range, these include, for example, some models of the DPX or SLX series - both Standard and Profi versions), the ATTACK Buffer Tank AK 500 (insulation included in price) is appropriately sized for your system. For a boiler with higher output, or if you plan to combine multiple heat sources (e.g. a wood boiler + heat pump, or a boiler + solar collectors), we recommend choosing a larger volume, or possibly connecting several tanks in a cascade - so that the buffer volume matches the combined output of the connected sources.

With a 500 l volume, it also holds true that the larger the tank, the longer it can supply heat even after the boiler has completely burned out - with a well-designed and sufficiently large system, it is common for a family house to be heated for 12 to 24 hours from a single boiler load and a single buffer tank, depending on the outdoor temperature, the house's heat losses and the temperature gradient of the heating system (lower temperatures, e.g. with underfloor heating, allow a larger share of the stored heat to be used than high-temperature radiator systems).

It should also be remembered that a buffer tank is worthwhile in combination with automatic heat sources such as an electric boiler or heat pump - although these sources can modulate output more smoothly than a solid fuel boiler, they still benefit from the tank by reducing the number of switching cycles, which saves the service life of the compressor, circulation pumps and electronics.

Connection, installation and backup heating options

The ATTACK Buffer Tank AK 500 (insulation included in price) is typically connected as a hydraulically separated buffer element between the heat source and the heating system (radiators, underfloor heating, fan-coil units, etc.) - the heat source charges the tank through one pair of ports, while the heating system draws heat through the other pair, hydraulically separating both circuits and allowing the system to run more stably even with fluctuating flow on the source side. The remaining ports (there are 5 in total on this tank) can be used, for example, for a temperature sensor, an air vent, a safety valve, or connecting a supplementary electric heating element.

The option to install an electric heating element is a practical solution for periods when you do not want to heat with solid fuel (e.g. outside the main heating season) or as a backup in case the main heat source fails. Our range includes the electric heating elements ATTACK TH100 (2.5 kW), TH102 (4.5 kW), TH103 (6 kW) and TH107 (2 kW), all with their own thermostat and a G6/4" thread - compatible with the ports of this buffer tank. We recommend matching the element's output to the tank volume and the desired backup heating speed.

When installing the ATTACK Buffer Tank AK 500 (insulation included in price), make sure there is sufficient handling space in the boiler room - given the diameter with insulation of approximately 950 mm and a height of approximately 1450 mm (both values are indicative, see above), it is necessary to check in advance whether the doorway, staircase and the room itself allow passage. We also recommend leaving at least 300-500 mm of free space around the tank on the side with the connection ports to ensure convenient access for servicing, seal replacement, or sensor inspection/maintenance.

We recommend filling the tank only with treated heating water in accordance with the applicable standard (e.g. STN EN 14868 or the boiler manufacturer's recommendation) - hard water with a high mineral content accelerates limescale formation on the internal walls and shortens the service life of the whole system, including the boiler and circulation pumps.

Connection with other heating system components

The ATTACK Buffer Tank AK 500 (insulation included in price) is only one link in the heating chain. Customers most often combine it with the ATTACK DPX or ATTACK SLX wood gasification boiler (both Standard and Profi versions, output range of approximately 15-35 kW), with the boiler's output matching the recommended range of 20-25 kW stated above. When combined with a heat pump or electric boiler, the tank serves as a hydraulic separator and heat store, reducing the number of switching cycles of the source. If you also need to prepare domestic hot water, since this particular tank is a version without a heat exchanger, we recommend adding a separate DHW storage water heater to the system (e.g. from the ATTACK Z series - Z100, Z125, Z160, Z200 and others, available in our range), or choosing one of the AS/HR/HRS/TUV/TUVS models instead of this tank, which have a heat exchanger built directly into the tank.

Maintenance and inspection of the tank during operation

The ATTACK Buffer Tank AK 500 (insulation included in price) requires minimal but regular maintenance. We recommend checking once a year (for example before the start of the heating season) the tightness of all 5 connection ports, the condition of the air vent and the safety valve of the heating circuit, as well as the overall condition of the outer insulation cover - the synthetic leather cover in silver-grey is resistant to normal wear, but in case of mechanical damage (e.g. during moving or handling in the boiler room) we recommend repairing the damaged spot promptly to avoid unnecessary heat loss.

Since this is a tank without a built-in heat exchanger, the inside of the tank only comes into contact with treated heating water, not drinking water - the risk of limescale build-up is thus significantly lower than with DHW storage tanks, but we still recommend visually inspecting the inside of the tank through the inspection opening (if the model is equipped with one) once every few years (for example during a system shutdown), or at least monitoring the quality and colour of the heating water when draining sludge from the system. Cloudy or rusty water may indicate a need for water treatment or a check for corrosion in the system.

During long-term shutdown (e.g. outside the heating season), it is not necessary to drain the tank - on the contrary, leaving water in the system protects the inner surface from corrosion caused by exposure to air. If you plan to take the tank completely out of operation for a longer period, consult a professional installer about the appropriate preservation procedure.

Frequently Asked Questions

Do I also need to buy a heat exchanger for this tank?

No, this AK500K model cannot be additionally fitted with a built-in heat exchanger - it serves purely to accumulate heating water. If you need DHW preparation via a heat exchanger in a single tank, choose from our AS, HR, HRS, TUV or TUVS range.

How large a boiler can I connect to this tank?

For a volume of 500 litres, we recommend a heat source with an output of approximately 20 to 25 kW, according to the rule of 20-25 litres of buffer volume per 1 kW of output. For a more powerful source, it is better to choose a larger volume or connect several tanks in a cascade.

Can the tank also be used with a heat pump or electric boiler?

Yes, the AK500K buffer tank works just as well with a heat pump, electric boiler, gas boiler or solar collectors - in every case it reduces the number of switching cycles of the source and balances differences between heat production and consumption.

Is insulation included in the delivery?

Yes, the tank is supplied including soft, removable polyester insulation, 100 mm thick, with an outer synthetic leather cover in silver-grey.

Can I install an electric heating element in the tank for backup heating?

Yes, the tank has 5 connection ports, one of which can be used to install an electric heating element, such as the ATTACK TH100, TH102, TH103 or TH107 with a G6/4" thread.

What is the maximum operating pressure and temperature of the tank?

The tank is rated for a maximum operating pressure of 3 bar and a maximum operating temperature of 95 °C, which provides a safe margin above typical heating water operating temperatures of 60-80 °C.

What are the exact dimensions and weight of the tank?

Approximately, the diameter with insulation is about 950 mm, the height is about 1450 mm, and the weight of the empty tank is about 90 kg. These are estimated values corresponding to a volume of 500 l - we recommend verifying the exact dimensions with the seller before installation in confined spaces.

What is the warranty period for the buffer tank?

We provide a 24-month warranty on ATTACK buffer tanks from the date of commissioning, but no more than 30 months from the date of shipment from the factory.

Warranty and final recommendation

The manufacturer ATTACK s.r.o. provides a standard warranty of 24 months from commissioning, but no more than 30 months from the shipment date from the factory, on the ATTACK Buffer Tank AK 500 (insulation included in price). To maintain the warranty, we recommend connecting and commissioning the tank in accordance with the installation manual and applicable heating technology standards, using treated heating water, and regularly checking the condition of the insulation and the tightness of the connection ports. We are happy to advise you by phone or e-mail when choosing the right tank volume - just let us know the type and output of your heat source, and we will recommend the most suitable model from the ATTACK range.