ATTACK AK 300 Storage Tank (insulation included in price)

Product detailed description

Why a buffer tank determines heating efficiency

The ATTACK Buffer Tank AK 300 (insulation included in the price) is a steel buffer (accumulation) tank with a volume of 300 litres, designed to store hot heating water from any heat source - a wood gasification boiler, heat pump, electric boiler, gas boiler or solar collectors. This is a tank without a built-in heat exchanger (sometimes also referred to as a "hydraulic separator" or "buffer tank"), which serves purely for storing heating water - heating of domestic hot water (DHW) with this type of tank is solved externally, for example through a storage water heater or a flow module.

The greatest benefit of a buffer tank can be 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 avoid overheating the system), which leads to poorer combustion, higher tar formation and shorter boiler and chimney lifespan. With the ATTACK Buffer Tank AK 300 (insulation included in the price), the boiler burns the fuel at full output at once and the excess heat is stored in the tank's water reserve - from there the heating system gradually draws it as needed by the household, even several hours after the boiler has burned out.

The same principle applies to an electric boiler or a heat pump: a 300 l tank allows the heat source to operate in longer, less frequent cycles instead of constantly switching on and off for short intervals, which extends the lifespan of the compressor/heating elements and reduces energy consumption. This is a typical volume for a standard 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 to the heating system over the following days, significantly reducing the number of boiler starts and stops.

Key features of the AK300K tank

• Volume of 300 litres - designed to provide a sufficient heat reserve between heating cycles at a recommended heat source output of 12 - 15 kW.
• Soft, removable polyester insulation 100 mm thick - significantly limits heat loss to the surroundings during long-term storage of hot water, while being easy to remove for inspection or servicing of the tank and fittings.
• Outer insulation cover made of leatherette (PVC fabric) in silver-grey - resistant to abrasion and easy to maintain, visually blending into the boiler room interior rather than looking like a "technical" element.
• 5 connection fittings 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 an internal corrosion-resistant surface treatment, rated for a max. operating pressure of 3 bar and max. temperature of 95 °C - a safe margin over typical heating water operating temperatures (60-80 °C).
• Suitable for vertical position thanks to feet/a base, which at this volume facilitates precise temperature layering (stratification) - warmer water naturally stays on top, cooler water at the bottom, increasing the usability of the accumulated heat.
• Option of additionally installing an electric heating element (e.g. ATTACK TH100, TH102, TH103 or TH107) directly into one of the tank's fittings - suitable as a backup or supplementary heat source outside the heating season or in case of failure of the main source.
• No built-in heat exchanger - the tank is designed purely for accumulating heating water; if you also need to prepare domestic hot water via a built-in heat exchanger, see our range of AS/HR/HRS/TUV/TUVS tanks with heat exchanger.

Technical parameters

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

How to correctly choose the volume of a buffer tank

The most common recommended rule when choosing a buffer tank for a solid fuel gasification boiler is: count on approximately 20 to 25 litres of buffer volume for every 1 kW of the boiler's rated output. This rule is based on the fact that a 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 the heating system gradually consumes it. For a 300-litre tank, this means it is suitable for a heat source with an output of approximately 12 to 15 kW.

If, for example, you have a wood gasification boiler with an output in this range (from the ATTACK range, these are, for example, some models of the DPX or SLX series - both Standard and Profi versions), the ATTACK Buffer Tank AK 300 (insulation included in the price) is appropriately sized for your system. For a higher boiler output, or if you plan to combine multiple heat sources (e.g. wood boiler + heat pump, or boiler + solar collectors), we recommend choosing a larger volume, or connecting several tanks in a cascade - so that the buffer volume corresponds to the sum of the outputs of the connected sources.

For a volume of 300 l, the general rule also applies: 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 heat for 12 to 24 hours from a single boiler load and one 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 more of the stored heat to be used than high-temperature radiator systems).

It should also be noted that a buffer tank is worthwhile even in combination with automatic heat sources such as an electric boiler or a 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 lifespan of the compressor, circulation pumps and electronics.

Connection, installation and backup heating options

The ATTACK Buffer Tank AK 300 (insulation included in the 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 via one pair of fittings, and the heating system draws heat via the other pair, hydraulically separating both circuits so that the system operates more stably even with fluctuating flow on the source side. The remaining fittings (there are 5 in total on this tank) are used, for example, for fitting a temperature sensor, a venting valve, a safety valve, or for connecting an additional electric heating element.

The option of fitting an electric heating element is a practical solution for periods when you don't want to heat with solid fuel (e.g. outside the main heating season) or as a backup in case of failure of the main source. 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 fittings of this buffer tank. We recommend choosing the element's output according to the tank volume and the desired heating-up speed.

When installing the ATTACK Buffer Tank AK 300 (insulation included in the price), allow for sufficient handling space in the boiler room - given a diameter with insulation of approximately 850 mm and a height of approximately 1150 mm (both approximate values, see above), it is necessary to check in advance the passability of doors, staircases and the room itself. We also recommend leaving a free space of at least 300-500 mm around the tank on the side with the connection fittings, to ensure convenient access for servicing, gasket replacement or checking/topping up sensors.

We recommend filling the tank only with treated heating water in accordance with the applicable standard (e.g. 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 lifespan of the entire system, including the boiler and circulation pumps.

Connection with other heating system components

The ATTACK Buffer Tank AK 300 (insulation included in the price) forms just one link in the heating chain. Customers most often combine it with the ATTACK DPX or ATTACK SLX wood gasification boiler (Standard and Profi versions, output range approximately 15-35 kW), with the boiler output ideally matching the recommended range of 12-15 kW mentioned above. When combined with a heat pump or electric boiler, the tank serves as a hydraulic separator and heat storage, 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 supplementing the system with a separate DHW storage water heater (e.g. from the ATTACK Z range - Z100, Z125, Z160, Z200 and others, available in our range), or choosing one of the AS/HR/HRS/TUV/TUVS series models instead of this tank, which have the heat exchanger built directly into the tank.

Maintenance and inspection of the tank during operation

The ATTACK Buffer Tank AK 300 (insulation included in the 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 fittings, the condition of the venting valve and the safety valve of the heating circuit, as well as the overall condition of the outer insulation cover - the leatherette cover in silver-grey is resistant to normal wear, but in case of mechanical damage (e.g. during relocation or handling in the boiler room) we recommend repairing the damaged spot promptly to avoid unnecessary heat losses.

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

During a 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 internal surface from corrosion caused by air exposure. If you plan to take the tank completely out of operation for a longer period, consult a qualified installer about the appropriate preservation procedure.

Frequently asked questions

Do I need to purchase a heat exchanger for this tank as well?

No, this AK300K model cannot be additionally fitted with a built-in heat exchanger - it serves purely for accumulating heating water. If you need to prepare domestic hot water via a heat exchanger in a single tank, choose from our AS, HR, HRS, TUV or TUVS series.

How big a boiler can I connect to this tank?

For a volume of 300 litres, we recommend a heat source with an output of approximately 12 to 15 kW, according to the rule of 20-25 litres of accumulation per 1 kW of output. For a higher-output source, it is more suitable 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 AK300K buffer tank works equally well with a heat pump, electric boiler, gas boiler or solar collectors - in each case it reduces the number of switching cycles of the source and evens out 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 leatherette cover in silver-grey.

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

Yes, the tank has 5 connection fittings, 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 over typical heating water operating temperatures of 60-80 °C.

What are the exact dimensions and weight of the tank?

Approximately, this is a diameter with insulation of about 850 mm, a height of about 1150 mm and an empty tank weight of about 60 kg. These are estimated values corresponding to a volume of 300 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 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 on the ATTACK Buffer Tank AK 300 (insulation included in the price), but no more than 30 months from the shipment date from the manufacturing plant. To maintain the warranty, we recommend connecting and commissioning the tank in accordance with the installation manual and applicable standards for heating technology, using treated heating water and regularly checking the condition of the insulation and the tightness of the connection fittings. We are happy to advise on choosing the right tank volume by phone or e-mail - just state the type and output of your heat source and we will recommend the most suitable model from the ATTACK range.