ATTACK AK 800 Storage Tank (insulation included in price)

Product detailed description

Why a storage tank determines heating efficiency

ATTACK Storage Tank AK 800 (insulation included in price) is a steel storage (balancing, buffer) tank with a volume of 800 litres, designed for storing 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 via a storage water heater or a flow module.

The greatest benefit of a storage 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 whole load of wood "in one go" without throttling the air supply. Without a storage 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 Storage Tank AK 800 (insulation included in price), the boiler burns the fuel at full output at once, and the excess heat is stored in the water reserve in the tank - from there 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 applies with an electric boiler or heat pump: the 800 l tank allows the heat source to work in longer, less frequent cycles instead of constant on/off switching in short intervals, which extends the lifespan of the compressor/heating elements and reduces energy consumption. This volume is suitable for larger family houses, two-generation houses or smaller facilities where several heat sources are combined (e.g. a wood gasification boiler together with a heat pump or solar collectors) and it is necessary to balance larger fluctuations between heat production and consumption.

Key features of the AK800K tank

• 800 litre volume - designed to provide a sufficient heat reserve between heating cycles at a recommended heat source output of 32 - 40 kW.
• Soft, removable polyester insulation 100 mm thick - significantly reduces heat loss to the surroundings during long-term storage of hot water, while it can be easily unfastened for inspection or servicing of the tank and connections.
• Outer insulation cover made of leatherette (PVC fabric) in silver-grey - resistant to abrasion and easy to maintain, visually blends into the boiler room interior rather than looking like a "technical" element.
• 6 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 (booster heating), venting, drainage and temperature sensors.
• Steel shell with an internal corrosion-resistant surface treatment, rated for a maximum operating pressure of 3 bar and a maximum temperature of 95 °C - a safe margin above typical operating temperatures of heating water (60-80 °C).
• Suitable for vertical position thanks to legs/stand, which at this volume facilitates precise temperature layering (stratification) - warmer water naturally stays at the top, cooler at the bottom, increasing the usability of the accumulated heat.
• Option of additional installation of 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 a failure of the main heat source.
• Without a built-in heat exchanger - the tank is designed purely for heating water accumulation; if you also need DHW preparation via a built-in heat exchanger, see 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 approximate estimates corresponding to the given volume; we recommend verifying the exact dimensions with the seller before ordering, prior to installation (e.g. in cases of limited boiler room space or narrow doors/staircases).

How to correctly choose the storage tank volume

The most common recommended rule when choosing a storage tank for a solid fuel gasification boiler is: allow approximately 20 to 25 litres of storage 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 the heating system gradually consumes it. For an 800 litre tank, this means it is suitable for a heat source with an output of approximately 32 to 40 kW.

If, for example, you have a wood gasification boiler with an output in this range (from the ATTACK range these include some models of the DPX or SLX series - both Standard and Profi versions), the ATTACK Storage Tank AK 800 (insulation included in price) is appropriately sized for your system. For a higher boiler output, or if you plan to combine several 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 storage volume corresponds to the sum of the outputs of the connected sources.

At a volume of 800 l, it also holds 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 able to heat for 12 to 24 hours on a single boiler load and one storage 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 part of the stored heat to be used than high-temperature radiator systems).

It should also not be forgotten that a storage 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 lifespan of the compressor, circulation pumps and electronics.

Connection, installation and heating options

The ATTACK Storage Tank AK 800 (insulation included in price) is typically connected as a hydraulically separated balancing 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 ports, the heating system draws heat via the other pair, thereby hydraulically separating both circuits, and the system operates more stably even with fluctuating flow on the source side. The remaining ports (there are 6 in total on this tank) serve, for example, for installing a temperature sensor, air vent, safety valve, or for connecting an additional electric heating element.

The option to install 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 a failure of the main heat 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 G6/4" thread - compatible with the ports of this storage tank. We recommend choosing the element's output to suit the tank volume and the desired heating-up speed.

When installing the ATTACK Storage Tank AK 800 (insulation included in price), allow sufficient handling space in the boiler room - given a diameter with insulation of approximately 1100 mm and a height of approximately 1650 mm (both values approximate, see above), it is necessary to verify in advance that doors, staircases and the room itself allow passage. We also recommend leaving a free space of at least 300-500 mm around the tank on the side with the connection ports, to ensure comfortable access for servicing, seal replacement or checking/adding 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 inner walls and shortens the lifespan of the entire system, including the boiler and circulation pumps.

Connection with other heating system components

The ATTACK Storage Tank AK 800 (insulation included in price) is just 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 approximately 15-35 kW), with the boiler's output matching the recommended 32-40 kW range mentioned above. When combined with a heat pump or electric boiler, the tank serves as a hydraulic separator and heat store, reducing the number of source switching cycles. 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 range - 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 Storage Tank AK 800 (insulation included in price) requires minimal but regular maintenance. We recommend checking once a year (e.g. before the start of the heating season) the tightness of all 6 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 leatherette 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 buildup is thus significantly lower than with DHW storage tanks, but we still recommend visually inspecting the inside of the tank via an inspection opening every few years (e.g. during a system shutdown), if the model is equipped with one, 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 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 inner 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 buy a heat exchanger for this tank as well?

No, this AK800K model cannot be additionally fitted with a built-in heat exchanger - it serves purely for accumulating heating water. If you need both DHW preparation via a heat exchanger in one 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 800 litres, we recommend a heat source with an output of approximately 32 to 40 kW, based on the rule of 20-25 litres of storage per 1 kW of output. For a more powerful source, it is preferable 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 AK800K storage tank works equally well with a heat pump, electric boiler, gas boiler or solar collectors - in every case it reduces the number of source switching cycles 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 cover made of leatherette in silver-grey.

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

Yes, the tank has 6 connection ports, one of which can be used for installing 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 the typical operating temperatures of heating water of 60-80 °C.

What are the exact dimensions and weight of the tank?

Approximately, the diameter with insulation is about 1100 mm, the height about 1650 mm, and the weight of the empty tank about 130 kg. These are estimated values corresponding to an 800 l volume - we recommend verifying the exact dimensions with the seller before installation in confined spaces.

What is the warranty period for the storage tank?

We provide a 24-month warranty from commissioning for ATTACK storage tanks, but no more than 30 months from the date of dispatch from the factory.

Warranty and final recommendation

For the ATTACK Storage Tank AK 800 (insulation included in price), the manufacturer ATTACK s.r.o. provides a standard warranty of 24 months from commissioning, but no more than 30 months from the dispatch 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 ports. We are happy to advise on choosing the right tank volume by phone or e-mail - just let us know the type and output of your heat source and we will recommend the most suitable model from the ATTACK range.