ATTACK Stationary Tank Z 100 OKC/NTR/HV

Product detailed description

ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV is an indirectly heated stationary domestic hot water (DHW) storage tank with a volume of 100 litres, designed for free standing placement next to a stationary ATTACK gas boiler (e.g. EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI or EZ COMBI series). In its standard OKC/NTR/HV version, the tank does not generate heat on its own - the water inside it is heated by heating water from the boiler, which flows through an internal steel heat exchanger (coil) located inside the tank. Thanks to this indirect heating principle, hot water is available quickly, hygienically and without the risk of mixing with the heating circuit.

The Z 100 model is designed to complement an existing or newly installed boiler room with a standalone DHW source with sufficient hot water supply for a household, apartment or smaller facility. The stationary design allows for easy placement on the floor of a boiler room, utility room or pantry, without the need for wall mounting.

Key features

• Inner tank made of steel sheet with a high-quality enamelled (glazed) surface resistant to corrosion and limescale build-up
• Magnesium protective anode against electrochemical corrosion of the tank - extends the tank's lifespan and is easily replaceable during a service inspection
• Hardened PUR foam thermal insulation covered by an outer jacket, which minimizes heat losses during hot water storage
• Internal steel heating coil (heat exchanger) with a heat exchange area of 0.8 m² for indirect heating of water from the boiler
• Suitable for connection to stationary ATTACK gas boilers (EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI, EZ COMBI series) as well as other heat sources with a correctly sized heat exchanger
• Opening/pocket for a thermometer or thermostatic sensor for heating control
• Outlet for an optional electric heating element (purchased separately) for water heating outside the heating season, when the boiler is not running
• Drain valve for easy draining and maintenance of the tank
• Robust construction with enamelling tested according to European standards for potable water tanks
• Manufactured under the ATTACK brand - a proven Slovak manufacturer of heating technology

Type and design

The designation OKC/NTR/HV in the name refers to the tank's compatibility with the entire range of stationary ATTACK gas boilers as well as other heat sources with an input for indirect heating (e.g. heat pumps with a suitable heat exchanger output). It is a proven standard design with an enamelled steel tank and a single heating coil.

The stationary design (unlike the wall-mounted OKC or horizontal OKCV models) is placed directly on the floor next to the boiler. The advantage is easier installation (no need to anchor the full weight of the filled tank to the wall), stability and a wider selection of accessories (e.g. an additional electric heating element in the tank's pocket for heating outside the heating season).

Technical specification

Note: dimensions and weight are approximate estimates based on the volume and design type of the tank; exact values can be found in the manufacturer's technical data sheet or requested when ordering.

How indirect hot water heating works

The ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV is not a heat source itself - it has no burner or electric heating insert of its own (the latter is only an optional accessory). The heating principle is as follows: heating water heated in the ATTACK gas boiler flows via a circulation pump into an internal steel heat exchanger (coil) submerged in the tank. Through the wall of the exchanger, it transfers heat to the domestic water filling the tank's internal volume of 100 litres. Domestic water and heating water never physically meet - they are separated by the wall of the heat exchanger, so there is no mixing or contamination of the potable water by the heating medium (which may contain corrosion inhibitors and other additives).

Heating is controlled by the boiler's control system in cooperation with a temperature sensor (surface-mounted or immersed in the tank's pocket) and usually a three-way switching valve, which redirects the flow of heating water from the radiator circuit to the tank's heat exchanger when DHW is requested. This gives hot water preparation priority over space heating, and the household has hot water available practically immediately after the circulation pump starts.

The advantage of this solution over instantaneous heating (a combi boiler without a storage tank) is that the tank stores a supply of already heated water - it is therefore possible to draw a larger amount of hot water at once (for example, filling a bathtub) without the output limitation that instantaneous heating in a boiler has.

How to choose the right storage tank for your boiler

When choosing the volume of the Z series tank (100, 125 or 160 litres), it is recommended to base the decision primarily on the number of people in the household and hot water consumption habits:

• 100 litres - suitable for 1-3 people, an apartment or smaller family house with standard consumption (showering, kitchen, bathroom without a tub or with occasional filling)
• 125 litres - suitable for 3-4 people, a typical family house, a combination of shower and bathtub
• 160 litres - suitable for 4-5 or more people, households with higher demand for simultaneous draw (e.g. multiple bathrooms)

This particular model, the ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV, has a volume of 100 litres with a heat exchange area of 0.8 m². The larger the heat exchange area, the faster the tank can "recharge" the consumed hot water at the same boiler output - when choosing between a standard and an "enlarged" heat exchanger (where both are manufactured, e.g. the OKC 125/160 series), also consider the output of your boiler: for boilers with higher output (25-30 kW), it is worth choosing the variant with a larger heat exchanger so that its output can actually be used for fast DHW heating as well.

The tank itself does not generate heat - it must be connected to a suitable source, usually a stationary ATTACK cast iron gas boiler (EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI or EZ COMBI series), which has a provision for connecting an external DHW tank via a three-way valve. These boilers prepare DHW themselves only instantaneously or not at all, and it is precisely the external Z series tank that adds the hot water storage function. When combining with a heat pump or solar system, we recommend choosing specialized models of the HP or SOL series (other products in our range), which have a heat exchanger sized for lower heat carrier temperatures.

Installation and connection

The stationary tank is placed on a flat, solid and level floor next to the boiler, with sufficient space for access to connections, inspection openings and possible anode replacement. The recommended minimum ceiling height of the room takes into account the tank height of approx. 950 mm plus handling space above it.

Connection of cold and hot water, circulation (if used) and the heat exchanger circuit to the heating boiler is performed by an authorized plumber/heating technician according to the manufacturer's installation instructions. Correct installation includes a safety valve on the cold water inlet (sized according to the tank volume and network pressure), shut-off valves on all connections, and if necessary, softening of the inlet water, which extends the tank's lifespan and reduces limescale formation on the heat exchanger.

Maintenance and service

To ensure the ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV serves as long as possible, we recommend following a regular service cycle:

• Checking the magnesium anode at least once a year (more often with harder water) - a worn anode must be replaced in time, otherwise it loses its protective function and corrosion of the tank accelerates from the inside
• Descaling/draining the tank via the drain valve once every 1-2 years, especially in areas with harder water, where limescale and sludge settle at the bottom of the tank
• Checking the safety valve on the cold water inlet - regularly turning it to verify its function and the patency of the drip pipe
• Checking the tightness of connections and the heat exchanger during each annual boiler service inspection
• With hard water, consider installing a softening or dosing device, which significantly extends the lifespan of both the heat exchanger and the tank

Regular maintenance is also a condition for warranty acceptance in the event of a fault caused by corrosion or limescale deposits.

Safety, standards and legislation

The ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV is a pressure vessel that must be installed and operated in accordance with applicable technical standards and regulations, in particular STN EN 12897 (indirectly heated water heaters) and related regulations for pressure equipment. Correct installation always includes a safety valve sized for the cold water inlet, which protects the tank from excessive pressure during heating - its discharge/drip pipe must be routed freely into a space with a slope and must not be closed off or blocked in any way.

We also recommend installing an expansion vessel on the cold water side (especially if there is a check valve or pressure reducing valve on the inlet, which prevents water from flowing back into the water supply network during heating and thermal expansion). Without an expansion vessel, the safety valve may open repeatedly, causing unnecessary water loss.

Always entrust the installation, connection to the boiler's heating circuit and initial commissioning to a qualified person authorized to install gas and heating equipment. Only professionally performed installation and a regular annual service inspection (together with a boiler inspection) is also a prerequisite for warranty acceptance in the event of a claim. The 100-litre tank is intended exclusively for heating potable (domestic) water in the internal distribution systems of buildings, not for other technological purposes.

Position in the ATTACK product range

The ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV belongs to the Z series - indirectly heated DHW storage tanks by ATTACK, which, in addition to this model, also includes other volumes (100, 125, 160, 200 litres), designs (stationary OKH NTR/HV, wall-mounted OKC, horizontal wall-mounted OKCV) and special variants (e.g. with an additional 2.2 kW electric element built into the tank body, a solar version SOL with two heat exchangers, or an HP version designed for heat pumps). Thanks to the wide range of variants, it is possible to find a tank tailored exactly to the boiler room layout and the needs of the household.

We recommend combining this model primarily with stationary ATTACK cast iron gas boilers of the EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI and EZ COMBI series, which have a provision for connecting an external DHW tank, since the boiler itself does not contain a DHW tank.

Frequently Asked Questions

Do I still need a boiler for the 100 l tank, or does it work standalone?

The ATTACK Stationary Storage Tank Z 100 OKC/NTR/HV is an indirectly heated type - it does not generate heat on its own. It must always be connected to a heat source, most commonly a stationary ATTACK gas boiler with provision for an external DHW tank (via a three-way valve), or another suitable source with sufficiently sized output.

Can the tank also be connected to a heat pump or solar collectors?

Yes, in principle it can, however we recommend rather the specialized HP series (for heat pumps, large-area heat exchanger for a low-temperature source) or SOL (with an additional solar heat exchanger) models, which are directly sized for these sources. This Z series model is primarily intended for a classic gas boiler.

How long does hot water stay in the tank without heating?

Thanks to the quality PUR insulation, standby losses are low, but the exact time depends on the room temperature and the difference from the water temperature. Generally, under normal conditions, the tank maintains a usable water temperature for several hours up to overnight; for a longer idle period without the boiler, it is advisable to add the optional electric heating element.

Is it possible to add electric heating?

Yes, the tank has a provision (pocket/outlet) for an electric heating element with a thermostat, which is purchased separately (e.g. output of 2-6 kW depending on the model). This allows DHW heating even outside the heating season, when the boiler is shut down.

What is the warranty on the tank?

We provide a 5-year warranty on the insulated tank, and 24 months on other parts (e.g. anode, seals, accessories) from the date of shipment, provided installation conditions and regular maintenance (especially anode inspection and replacement) are met.

How often does the magnesium anode need to be replaced?

We recommend checking the anode at least once a year during the boiler service inspection. With more aggressive or harder water, more frequent checks and earlier replacement may be necessary - a worn anode loses its anti-corrosion function.

What is the difference between the 100, 125 and 160 litre volumes?

The difference is mainly in capacity - a larger volume means more accumulated hot water available at once (e.g. when filling a bathtub while showering simultaneously), but also larger physical dimensions and weight. The choice depends on the number of people in the household and water consumption habits.

Is a stationary tank better than a wall-mounted one?

Neither type is universally "better" - the choice depends on the boiler room layout. The stationary (free-standing) design is easier to install and does not load the wall, while the wall-mounted design saves floor space where it is scarce.

Warranty and service

For ATTACK brand products, we provide a 5-year warranty on the insulated tank of the storage tank (provided installation conditions and regular maintenance are met, including inspection and replacement of the magnesium anode) and 24 months on other parts and accessories from the date of shipment from production. Service and spare parts (e.g. anodes, seals, accessories) are available in Slovakia. If you have any questions about selection, installation or claims, do not hesitate to contact us - we will also be happy to advise you on choosing a suitable boiler or control system for this tank.