ATTACK Z 100 PLUS OKH NTR/HV Stationary Storage Tank

Product detailed description

ATTACK Stationary Cylinder Z 100 PLUS OKH NTR/HV is an indirectly heated stationary domestic hot water (DHW) cylinder with a capacity of 100 litres, designed to be placed freely next to a stationary ATTACK gas boiler (e.g. EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI or EZ COMBI series). The cylinder, with improved thicker insulation for lower heat losses (PLUS version), does not generate heat 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 100 PLUS model is designed to complement an existing or newly installed boiler room with a separate DHW source, providing a sufficient supply of hot water for a household, apartment, or smaller business. 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 cylinder's lifespan and is easily replaceable during a service inspection
• Hardened PUR foam thermal insulation wrapped in an outer jacket, which minimizes heat losses during hot water storage
• Internal steel heating coil heat exchanger with a heat transfer surface of 1.0 m² for indirect water heating from the boiler
• Suitable for connection to ATTACK stationary gas boilers (EKO COMBI, PLQ COMBI, KLQ COMBI, E COMBI, EZ COMBI series) as well as to other heat sources with a correctly sized heat exchanger
• Opening/socket for a thermometer or thermostatic probe 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 drinking water tanks
• Manufactured under the ATTACK brand - a proven Slovak manufacturer of heating technology

Type and Design

The designation PLUS in the name indicates an improved version with a thicker layer of thermal insulation made of hardened PUR foam, which reduces the standby heat losses of the cylinder - water stays hot longer, reducing operating costs to maintain it. This is especially worthwhile where the boiler does not run continuously and the cylinder needs to maintain temperature longer between heating cycles.

The stationary design (as opposed to 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 a filled cylinder to the wall), stability, and the option to choose from a wider range of accessories (e.g. an additional electric heating element in the cylinder's socket for heating outside the heating season).

Technical Specification

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

How Indirect Hot Water Heating Works

The ATTACK Stationary Cylinder Z 100 PLUS OKH NTR/HV is not a heat source - it has no burner or electric heating element of its own (that 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) submerged in the cylinder tank. Through the wall of the heat exchanger, heat is transferred to the domestic water filling the tank's internal volume of 100 litres. The domestic water and heating water never physically meet - they are separated by the heat exchanger wall, so there is no mixing or contamination of drinking water with 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 cylinder's socket) and usually a three-way switching valve, which redirects the flow of heating water from the radiator circuit to the cylinder's heat exchanger when DHW is required. This means hot water preparation takes 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 cylinder) is that the cylinder stores a supply of already heated water - this allows a larger amount of hot water to be drawn at once (e.g. filling a bathtub) without the output limitation that instantaneous heating in a boiler has.

How to Choose the Right Cylinder for Your Boiler

When choosing the capacity of a Z series cylinder (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 bathtub 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 water use (e.g. multiple bathrooms)

This specific model, the ATTACK Stationary Cylinder Z 100 PLUS OKH NTR/HV, has a capacity of 100 litres with a heat transfer surface of 1.0 m². The larger the heat transfer surface, the faster the cylinder can "recharge" hot water consumed at the same boiler output - when choosing between a standard and "enlarged" heat exchanger (where both are manufactured, e.g. OKC 125/160 series), also consider your boiler's output: 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.

The cylinder 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 cylinder via a three-way valve. These boilers only prepare DHW on an instantaneous basis or not at all, and an external Z series cylinder adds the function of hot water storage. When combined with a heat pump or solar system, we recommend choosing specialized 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 cylinder 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 cylinder's height of approx. 1000 mm plus the 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 authorized plumber/heating technician according to the manufacturer's installation instructions. Proper installation includes a safety valve on the cold water supply (sized according to the tank's capacity and mains pressure), shut-off valves on all connections, and, if needed, softening of the inlet water, which extends the tank's lifespan and reduces limescale build-up on the heat exchanger.

Maintenance and Service

To ensure the ATTACK Stationary Cylinder Z 100 PLUS OKH NTR/HV lasts as long as possible, we recommend following a regular service schedule:

• Check the magnesium anode at least once a year (more frequently in areas with harder water) - a worn anode must be replaced in time, otherwise it loses its protective function and accelerates corrosion of the tank from the inside
• Descale/drain the tank via the drain valve once every 1-2 years, especially in areas with harder water, where limescale and sludge accumulate on the bottom of the tank
• Check the safety valve on the cold water supply - regularly turn it to verify its functionality and the drain pipe's patency
• Check 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 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 Cylinder Z 100 PLUS OKH NTR/HV is a pressure vessel that must be installed and operated in accordance with applicable technical standards and regulations, primarily EN 12897 (indirectly heated unvented water heaters) and related regulations for pressure equipment. Proper installation always includes a safety valve sized for the cold water supply, which protects the tank from excessive pressure during heating - its discharge/drain pipe must lead 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 supply that prevents water from flowing back into the water mains as it heats up and expands). Without an expansion vessel, the safety valve may open repeatedly, causing unnecessary water loss.

Always entrust 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 the boiler inspection) are also a prerequisite for warranty acceptance in the event of a claim. The 100-litre cylinder is intended exclusively for heating drinking (domestic) water in the internal plumbing of buildings, not for other technological purposes.

Position in the ATTACK Range

The ATTACK Stationary Cylinder Z 100 PLUS OKH NTR/HV belongs to the Z series - indirectly heated DHW cylinders from ATTACK, which, besides this model, also includes other capacities (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 cylinder 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 cylinder that fits the boiler room layout and household needs exactly.

This model is primarily recommended for combination 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 cylinder, since the boiler itself does not include a DHW cylinder.

Frequently Asked Questions

Do I need a boiler in addition to the 100 l cylinder, or does it work on its own?

The ATTACK Stationary Cylinder Z 100 PLUS OKH 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 cylinder (via a three-way valve), or another suitable source with a sufficiently sized output.

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

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

How long does hot water stay hot in the cylinder 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 relative to the water temperature. Generally, under normal conditions, the cylinder maintains a usable water temperature for several hours up to overnight; for longer standby periods without the boiler, it is advisable to add the optional electric heating element.

Is it possible to purchase electric heating as an additional feature?

Yes, the cylinder has provision (a socket/outlet) for an electric heating element with a thermostat, which is purchased separately (e.g. 2-6 kW output 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 cylinder?

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 followed.

How often does the magnesium anode need to be replaced?

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

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

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 cylinder 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 limited.

Warranty and Service

For ATTACK brand products, we provide a 5-year warranty on the insulated tank of the cylinder (provided installation conditions and regular maintenance are followed, 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 warranty claims, do not hesitate to contact us - we are happy to help with choosing a suitable boiler or control system for this cylinder as well.