ATTACK Z 160 OKC/NTR/HV Stationary Tank

Product detailed description

ATTACK Stationary Storage Tank Z 160 OKC/NTR/HV is an indirectly heated stationary domestic hot water (DHW) storage tank with a volume of 160 litres, designed for freestanding placement next to a stationary ATTACK gas boiler (e.g. the EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI or EZ COMBI series). The tank in the standard OKC/NTR/HV design does not generate heat by itself - the water inside it is heated by heating water from the boiler, which flows through an internal steel heat exchanger (coil) located in 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 160 model is designed to complement an existing or newly installed boiler room with a standalone DHW source with a sufficient supply of hot water for a household, flat or smaller business. The stationary design allows easy placement on the floor of the 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 service life of the storage tank and is easily replaceable during a service inspection
• Hardened PUR foam thermal insulation wrapped in an outer jacket, which minimises heat losses during hot water storage
• Internal steel heating heat exchanger (coil) with a heat transfer area of 1.2 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 additional 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 drinking water tanks
• Made 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 storage tank's compatibility with the entire range of stationary ATTACK gas boilers as well as with other heat sources with an input for indirect heating (e.g. heat pumps with a suitable heat exchanger output). This is a proven standard design with an enamelled steel tank and a single heating heat exchanger.

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 into the wall), stability and the option to choose from a wider range of accessories (e.g. an additional electric heating element in the tank's pocket for additional heating outside the heating season).

Technical specification

Note: dimensions and weight are indicative estimates based on the volume and design type of the storage 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 160 OKC/NTR/HV storage tank is not a heat source - it has no burner or electric heating element of its own (this is only an optional accessory). The heating principle is as follows: heating water heated in the ATTACK gas boiler is pumped by a circulation pump into an internal steel heat exchanger (coil) immersed in the tank. Through the wall of the heat exchanger, it transfers heat to the domestic water that fills the internal volume of the 160-litre tank. The domestic and heating water never physically meet - they are separated by the heat exchanger wall, so there is no mixing or contamination of drinking water by the heating medium (which may contain corrosion inhibitors and other additives).

Heating control is provided by the boiler's regulation in cooperation with a temperature sensor (surface-mounted or immersed in the storage tank's pocket) and usually a three-way switching valve, which redirects the flow of heating water from the radiator circuit to the storage tank's heat exchanger when DHW is required. This gives priority to hot water preparation 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 storage tank retains a reserve 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 a Z series storage tank (100, 125 or 160 litres), it is recommended to base the choice primarily on the number of people in the household and hot water consumption habits:

• 100 litres - suitable for 1-3 people, a flat or smaller family house with standard consumption (showering, kitchen, bathroom without a bathtub or with occasional filling)
• 125 litres - suitable for 3-4 people, a typical family house, combination of shower and bathtub
• 160 litres - suitable for 4-5 or more people, households with higher demands for simultaneous consumption (for example, multiple bathrooms)

This particular ATTACK Stationary Storage Tank Z 160 OKC/NTR/HV model has a volume of 160 litres with a heat transfer area of 1.2 m². The larger the heat transfer area, the faster the storage tank can "recharge" the consumed hot water at the same boiler output - when choosing between a standard and "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 storage 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 provision for connecting an external DHW storage tank via a three-way valve. These boilers only prepare DHW instantaneously or not at all, and an external Z series storage tank adds the function of hot water storage to them. When combined with a heat pump or solar system, we recommend choosing specialised HP or SOL series models (other products in our range), which have a heat exchanger sized for lower heat transfer medium temperatures.

Installation and connection

The stationary storage tank is placed on a flat, solid and horizontal 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 height of the storage tank of approx. 1300 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 carried out by an authorised installer/heating engineer according to the manufacturer's installation instructions. Part of a correct installation is a safety valve on the cold water supply (sized according to the tank volume and network pressure), shut-off fittings on all connections and, if necessary, softening of the inlet water, which extends the service life of the tank and reduces limescale formation on the heat exchanger.

Maintenance and service

To ensure that the ATTACK Stationary Storage Tank Z 160 OKC/NTR/HV storage tank 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 from the inside accelerates
• Desludging/draining the tank via the drain valve once every 1-2 years, especially in areas with harder water, where limescale and sludge settle on the bottom of the tank
• Checking the safety valve on the cold water supply - regularly turning it to verify its functionality and the patency of the drip pipe
• Checking the tightness of connections and the heat exchanger at every annual boiler service inspection
• With hard water, consider installing a softening or dosing device, which significantly extends the service life of the heat exchanger and the tank

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

Safety, standards and legislation

The ATTACK Stationary Storage Tank Z 160 OKC/NTR/HV storage tank is a pressure vessel that must be installed and operated in accordance with applicable technical standards and regulations, primarily STN EN 12897 (indirectly heated water heaters) and related regulations for pressure equipment. Part of a correct installation is always a properly sized safety valve on the cold water supply, which protects the tank from excessive overpressure during heating - its discharge/drip pipe must be led freely into a space with a slope and must not be closed 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 that 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, resulting in unnecessary water loss.

Installation, connection to the boiler's heating circuit and initial commissioning should always be entrusted to a qualified person authorised to install gas and heating equipment. Only professionally performed installation and a regular annual service inspection (together with a boiler inspection) are also a prerequisite for warranty recognition in the event of a claim. The 160-litre storage tank is intended exclusively for heating drinking (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 160 OKC/NTR/HV storage tank 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 design SOL with two heat exchangers, or an HP design intended for heat pumps). Thanks to the wide range of variants, it is possible to find a storage tank tailored exactly to the boiler room layout and household needs.

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 provision for connecting an external DHW storage tank, since the boiler itself does not include a DHW storage tank.

Frequently asked questions

Do I still need a boiler for the 160 l storage tank, or does it work on its own?

The ATTACK Stationary Storage Tank Z 160 OKC/NTR/HV storage tank is an indirectly heated type - it does not generate heat on its own. It must always be connected to a heat source, most often a stationary ATTACK gas boiler with provision for an external DHW storage tank (via a three-way valve), or another suitable source with a sufficiently sized output.

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

Yes, in principle it can, however we recommend rather the specialised HP series models (for heat pumps, large-area heat exchanger for a low-temperature source) or SOL (with an additional solar heat exchanger), 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 storage tank without heating?

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

Is it possible to purchase electric additional heating?

Yes, the storage tank has provision (a pocket/outlet) for an electric heating element with a thermostat, which is purchased separately (for example, an 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 storage 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 dispatch, provided that installation conditions and regular maintenance (especially checking and replacing the anode) are observed.

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 (for example, when filling a bathtub while showering at the same time), 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 storage tank better than a wall-mounted one?

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

Warranty and service

For ATTACK brand products, we provide a warranty of 5 years on the insulated tank of the storage tank (provided that installation conditions and regular maintenance, including checking and replacing the magnesium anode, are observed) and 24 months on other parts and accessories from the date of dispatch 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 help you choose a suitable boiler or control system for this storage tank.