Product detailed description

ATTACK Z100.1 OKC ENTR HV 2.2 - DHW cylinder with built-in 2.2 kW electric heating

The Z100.1 OKC ENTR HV 2.2 model (order code Z100OKCENTRHV22) extends the standard OKC indirectly heated cylinder with a built-in electric heating element with an output of 2.2 kW and its own thermostat. This is therefore a hybrid solution: primary heating is provided by the heating coil connected to a gas, solid-fuel or electric boiler, while secondary (backup or supplementary) heating is provided by the built-in electric element powered directly from the 230 V mains.

How combined heating works

The Z100.1 OKC ENTR HV 2.2 cylinder has one heating coil inside the tank for connection to an external heat source, and at the same time a flange fitted with a 2.2 kW electric heating element with its own operating thermostat. During normal operation in the heating season, DHW is heated conventionally from the boiler via the coil - quickly and with low operating costs. When the boiler is out of operation (summer shutdown, planned maintenance, malfunction, a cottage without permanent heating), the electric element automatically or manually takes over heating, and at 2.2 kW output heats 100 litres of water in approximately 3-5 hours depending on the inlet temperature.

The electric element has an integrated adjustable thermostat that maintains the set DHW temperature (typically 55-60 °C) and protects against overheating; the element is also equipped with a thermal fuse against dry running and overheating of the heating coil.

Key features

• Volume of 100 litres, vertical design for hanging/standing
• One heating coil for connection to the boiler
• Built-in electric heating element 2.2 kW / 230 V with thermostat
• Independent DHW heating even without a running boiler (summer operation, cottage, boiler failure)
• Enamelled steel tank with magnesium anode
• Rigid PU insulation with low heat loss
• Thermal fuse against dry running and overheating
• Compact dimensions suitable even for smaller utility rooms

Technical parameters

Assembly and installation

The cylinder is installed in the same way as the classic Z 100 OKC model - by hanging under the boiler or on a separate bracket, with the coil connected to the boiler's heating circuit and the DHW distribution with a safety valve (max. 0.6 MPa). Additionally, the electric element must be connected to a separately protected 230 V circuit (we recommend an RCD and a separate circuit breaker of at least 16 A) in accordance with the applicable electrical installation standard - this part of the installation must be carried out by a qualified electrician.

Switching between boiler heating and electric heating can be done manually (via the electric element's switch) or automatically using an external timer switch or a smart socket, which activates the electric element only when the boiler is not in operation.

Maintenance and lifespan

In addition to the standard annual check of the magnesium anode, we also recommend checking the functionality of the thermostat and thermal fuse of the electric element for this model, ideally during a service inspection before the start of the heating season. In case of failure, the electric heating element can be replaced separately without having to drain the entire cylinder, if it is equipped with a ball valve under the flange.

Step-by-step commissioning procedure

1. Hanging the cylinder under the boiler or on a separate bracket
2. Connecting the coil to the boiler's heating circuit
3. Connecting the electric heating element to a separately protected 230 V circuit by an electrician
4. Connecting the cold and hot water distribution with a DHW safety valve (max. 0.6 MPa)
5. Filling and venting the cylinder and the heating circuit
6. Setting the thermostat of the electric element and the boiler temperature (recommended 55-60 °C)
7. Functional test of both heat sources separately and in combination
8. Pressure test and leak-tightness check of all joints
9. Handover of documentation and instructing the user on switching between heat sources

Safety warnings

The electric heating element must be powered from a separately protected circuit with an RCD; the electrical part must be installed exclusively by a qualified electrician. The DHW safety valve (0.6 MPa) must always remain functional and must not be shut off. When operating the boiler and electric element simultaneously, make sure the maximum water temperature does not exceed 95 °C and the pressure does not exceed 0.6 MPa - we recommend setting both sources to a reasonable operating temperature of 55-60 °C.

Operating economics

Combined heating allows flexible selection of the cheaper available energy source - during the heating season, heating from the boiler is generally more advantageous (especially with solid fuel), while outside the season or with a surplus of your own photovoltaic production, electric heating via the built-in 2.2 kW element may be more advantageous. This flexibility makes the Z100.1 OKC ENTR HV 2.2 model particularly interesting for households with a photovoltaic power plant that want to maximise the use of their own generated electricity instead of selling it to the grid at a low purchase price.

Who the Z100.1 OKC ENTR HV 2.2 is suitable for

You will especially appreciate this model if: you operate a cottage or cabin without year-round heating, you want to have hot water guaranteed even during a boiler shutdown or failure, or you want to switch off the boiler completely in summer and heat DHW more cheaply from your own photovoltaics via the electric element. 100 litres is a suitable volume for a smaller flat or cottage (2-3 people).

How to navigate the ATTACK Z / PZO range of cylinders

The ATTACK brand offers several types of hot water cylinders, which differ in the method of heating and intended use. Below is a brief overview to help you orient yourself when choosing a related or replacement product:

• Z .. OKC / OKCV - Basic indirectly heated cylinder with one coil, connected to the boiler. The simplest and most affordable solution for DHW preparation, if you already have or plan to have a boiler.
• Z .. OKC ENTR HV 2.2 ▸ this is the product you are currently viewing - Same principle as OKC, plus a built-in 2.2 kW electric element - a choice for cottages, summer operation without a boiler, or as a safeguard in case of boiler failure.
• Z .. SOL - Two coils - boiler and large-area solar. A choice for households with solar collectors who want to also use free solar heat.
• Z .. HP - One large-area coil optimised for the low outlet temperatures of a heat pump. A choice for households with a heat pump as the main heat source.
• PZO .. PLUS - Directly heated, own gas burner, does not need a boiler at all. A choice for cottages, workshops and premises without central heating.

For all indirectly heated variants (OKC, ENTR, SOL, HP), the heating output can be supplemented or backed up with an ATTACK TH electric heating element (outputs 2/2.5/4.5/6 kW) via a 6/4" flange, which is included in our range as a separate product.

Common mistakes in selection and installation

A common misunderstanding is expecting the 2.2 kW electric element to fully replace the boiler's output during simultaneous high consumption - in reality it is a backup/supplementary source, not a full replacement for fast heating from the boiler. Another common mistake is forgetting to install separate protection for the electric element's circuit or undersizing it, as well as neglecting the annual check of the magnesium anode, just as with the standard OKC model. When choosing between the Z100.1 model and a regular OKC without an electric element, consider whether you will actually use the independence from the boiler, or whether the cheaper basic model will suffice.

Frequently asked questions

How do I switch between boiler heating and electric heating?

The basic design allows simple manual switching on/off of the electric element via a switch; for automatic control, we recommend adding an external timer switch or a smart socket.

Can both heat sources (boiler and electricity) be switched on at the same time?

Yes, technically this is not a problem, but in practice it does not make sense - in practice, one source is used according to current needs and energy costs.

How long does it take the 2.2 kW element to heat the entire volume?

Approximately 3-5 hours from 15 °C to 55-60 °C, depending on the volume of 100 l and the inlet water temperature.

Is the electric element protected against dry running?

Yes, the element has a built-in thermal fuse that disconnects it from the power supply in case of overheating (e.g. when running without water).

Can the electric element be replaced separately in case of failure?

Yes, the element is fitted in a separate flange, and in case of failure only it can be replaced, without the need to replace the entire cylinder.

Do I need a separate electrical circuit?

Yes, we recommend a separately protected 230 V circuit with an RCD; the installation must be carried out by a qualified electrician.

Does the cylinder work even without a boiler connection, on electricity alone?

Yes, the cylinder can operate exclusively on electric heating if you do not yet have a boiler connected or it is out of operation - this is a standard method of use, for example in new buildings before the boiler room is completed.

What is the difference compared to the standard Z OKC model without an electric element?

Functionally, the cylinder is identical; it only adds a built-in 2.2 kW electric element with a thermostat, which the standard OKC model does not have and would require additional installation of a separate ATTACK TH element.

Can I use the electric element for heating from photovoltaics?

Yes, this is a common and increasingly popular solution - a surplus regulator from a photovoltaic power plant directs surplus generated energy to water heating instead of selling it to the distribution grid.

What is the electricity consumption for heating the entire volume?

Approximately, at an output of 2.2 kW and a heating time of 3-5 hours, the consumption is approximately 6.6-11 kWh per heating of the entire 100-litre volume; the exact value depends on the inlet and target temperature.

Can the 2.2 kW element be subsequently replaced with a more powerful one?

Yes, when replacing it, an ATTACK TH element with a higher output (e.g. 4.5 or 6 kW) can be fitted, provided this is allowed by the building's electrical connection and protection.

Is the electric element included in the price of the cylinder, or is it an extra charge?

The 2.2 kW element is already included in this model from the factory and is included in the price; there is no need to purchase it separately.

Does the element protect the cylinder against freezing in an unheated cottage?

Not directly; the element serves to heat DHW according to the thermostat's set temperature, not as frost protection. If there is a risk of the entire system freezing in frost, we recommend draining the cylinder and pipes for winter or ensuring permanent heating of the building.

How long does the electric heating coil last with regular use?

With proper installation, compliance with the rated voltage and regular inspection (annual inspection of the magnesium anode and thermostat), the lifespan of the coil is comparable to that of standalone ATTACK TH elements, i.e. usually many years of trouble-free operation.

Is the model with an electric element also suitable for a flat with central heating?

Yes, even in a flat with central heat supply it can be useful as a supplementary source, for example during a summer shutdown of the central heat supply for maintenance, when hot water is otherwise not available from the central source either.

When is the surcharge for a built-in electric element worth it

When deciding between the Z100.1 OKC ENTR HV 2.2 model and a regular OKC cylinder without an electric element, consider how often you would actually use independence from the boiler. If you have a cottage with summer operation without heating, are planning photovoltaics, or simply want a safeguard in case of boiler failure, the surcharge for the built-in 2.2 kW element will quickly pay for itself in the form of comfort and guaranteed hot water at any time of the year. If, on the other hand, your boiler runs year-round and you do not need independence, the cheaper basic OKC model without an electric element will suffice.

Comparison of the two volumes in the ENTR range

We offer the ENTR range in two volumes - 100 and 125 litres. The 100-litre model is more compact and suitable especially for smaller flats, cottages or households of up to 2-3 people, where compactness is a priority over space. The 125-litre model provides slightly higher comfort with simultaneous draw-off from multiple points and is more suitable for a 3-4 person household. The price difference between the volumes is relatively small compared to the difference in comfort, so if in doubt, we recommend considering the larger volume, provided the space in the utility room allows it.

Summary

The Z100.1 OKC ENTR HV 2.2 model is an ideal choice wherever you want to have guaranteed hot water independent of the boiler's status - thanks to the built-in 2.2 kW electric element, it is a practical combination of the reliability of boiler heating and the flexibility of electric backup heating in one compact cylinder. This is a solution particularly popular among owners of cottages and recreational properties, where the heating boiler is not used year-round, but the need for hot water persists regardless of the season.

Warranty and service

The manufacturer ATTACK provides a 5-year warranty on the cylinder tank from the date of sale, subject to the conditions stated in the warranty certificate (regular anode inspection, compliance with maximum operating pressure and temperature, installation of safety equipment in accordance with applicable legislation). A standard warranty period of 24 months applies to the other components of the cylinder (insulation, casing, electrical components, sensors, accessories). Service and spare parts for the entire ATTACK range are provided by a network of authorised service partners in Slovakia and the Czech Republic; our team will be happy to help you choose the right part or contact the nearest service centre if needed.