Frequently asked questions about Attack Electric boilers

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Frequently asked questions about Attack Electric electric boilers – the complete guide

Over the years of working with Attack Electric boilers, I keep encountering the same questions – from the very basics through technical details to tricky installation and operation issues. I put together this article as a living document: not as an advertisement, but as a response to what people actually deal with before purchasing, during installation, and in regular operation. If you're looking for specific answers, you'll find them here.

What is an Attack Electric electric boiler and how does it work?

An electric boiler is essentially a simple device: electrical energy is converted into heat using heating elements (resistive coils), which heat the water in the primary circuit. This water then circulates through radiators or floor heating. Unlike gas or solid fuel boilers, there is no combustion, no chimney is needed, and no special ventilation room is required – the boiler can be placed in the kitchen, in the entrance hall, in a utility room, or even in the bathroom (if the IP rating is appropriate).

The Attack Electric series are produced in two basic lines: Excellent and Easy. Both operate on the same physical principle, but differ in equipment, power and regulation options. The detailed differences between models can be found in the article Attack Electric Excellent vs. Easy: what are the differences and which one to choose?

What power boiler should I aim for?

This is the most common question and also the one where the most mistakes are made. The simplified rule – "1 kW per 10 m²" – works only for old, poorly insulated houses from the 80s. In a new build with good insulation (wall λ ≤ 0.18 W/m²K), you may need only 0.3–0.5 kW per m².

Approximate calculation procedure:

Old, non-insulated house (before 1990): 80–100 W/m² of floor area × living area
Partially insulated house: 50–70 W/m²
New build with low-energy standard: 30–45 W/m²
Passive house: less than 20 W/m²

Practical example: An older row house from 1978, 120 m² of living area, 2.8 m ceilings, partially replaced windows, non-insulated walls. The heat loss is approximately 9–11 kW. A suitable boiler: Attack Electric Excellent 8, 7.5 kW would be at the lower limit – a more realistic choice is a model with 12–15 kW, ideally with the option to switch power levels. If the house has an addition or you plan to use the same boiler for DHW, go for Attack Electric Excellent 15 kW.

More about calculating heat loss and choosing power can be found in the separate article What power electric boiler do I need for my house?

Is it possible to connect an Attack Electric boiler to DHW preparation?

Yes, but not directly – Attack Electric electric boilers are in the basic configuration intended only for heating (closed circuit). For DHW preparation, an external tank (boiler) and so-called DHW module are needed.

DHW module set (DHW preparation in an external tank) is an accessory that allows the boiler to regulate the heating of water in an external indirect tank. The boiler alternately supplies heat to the heating circuit and to the DHW tank according to the priorities set in the regulation. In practice, this works so that DHW has priority – when the temperature in the tank drops below the set value, the boiler temporarily stops heating and heats the water in the tank.

Important: the tank must be indirect (with a coil / heat exchanger), not an electric boiler. The tank volume is selected according to the number of people and consumption – approximately 50–80 liters per person, commonly 150–200 liters for a 3–4 person family. How the whole system works is described in the article DHW module for electric boiler: how DHW preparation works in an external tank?

What are the differences between the Excellent and Easy models?

The Easy series is intended for simpler applications and smaller buildings. The Attack Electric Easy 8 is a compact boiler with an 8 kW output, basic regulation and simple control. It has fewer inputs for an external thermostat and lacks some advanced features – for example, the ability to fully control the TÚV module or a programmable weekly schedule directly in the boiler.

The Excellent series is more comprehensive. Models such as Attack Electric Excellent 8, 7,5 kW, Attack Electric Excellent 15 kW or Attack Electric Excellent 24, 22 kW are equipped with:

Smooth or stepped power regulation (for example, the 15 kW model can operate at 5 – 10 – 15 kW)
An input for an external room thermostat or OpenTherm controller
Compatibility with the TÚV module
A larger display and clearer parameter settings
Protection features: anti-frost function, safety thermostat, pump blockage protection

In general: for a house up to 80 m² with basic requirements, Easy may be sufficient. For larger houses, TÚV, extended regulation or photovoltaics – always choose Excellent.

What about the electrical connection? Do I need three-phase power?

It depends on the boiler's power. This is a technical topic where many people make mistakes and unnecessarily pay for electrical installation – or, on the contrary, do not plan it and have to do it additionally later.

General rule valid for Attack Electric boilers:

Up to 3,5 kW: single-phase power supply 230 V, standard circuit breaker 16 A
3,5 – 7,5 kW: single-phase 230 V is technically possible (the boiler allows it), but requires a 32 A circuit breaker and dimensioned cable, so the electrician usually recommends three-phase power
8 kW and more: exclusively three-phase power supply 400 V, circuit breaker according to power (3×16 A for 8–12 kW, 3×25 A for 15 kW, 3×32–40 A for 22–24 kW)

Important note: electrical installation must be carried out by a qualified person (an electrician with the appropriate qualification). As part of the inspection report, the boiler must be registered as a consumer. Without an inspection report, there may be problems in the case of an insured event or when requesting a lower distribution fee (tariff D07/D05 for electric heating).

Do I need any permit for installation?

The electrical part of the installation must be carried out by a qualified electrician and an inspection report must be prepared – this is mandatory. The heating (plumbing) part – that is, connecting the boiler to the heating circuit, expansion tank, safety valve, air venting – is a technical job that is usually done by a heating plumber. It is not a building permit in the true sense of the word, but in some apartment buildings or when connecting to common lines, the consent of the manager or SVB may be required.

To change the tariff to the distribution tariff for electric heating (D07 or D05 for low power) it is necessary to submit an application to the distributor (e.g. ZSE, SSE, VSE) and attach a technical report or installation certificate of the boiler. More about the entire installation process can be found in the article Installation of the Attack Electric boiler: procedure, requirements and connection.

What water temperature can I achieve? Is the boiler suitable for floor heating?

Attack Electric electric boilers can heat water in the circuit to a temperature of 20 – 85 °C. The exact setting depends on the model, but the standard range is 30 – 75 °C for radiator heating and 30 – 50 °C for floor heating.

The Attack Electric boiler is very suitable for floor heating – a low primary temperature (35 – 45 °C) is easily achievable for an electric boiler and is also optimal in terms of efficiency and the lifespan of the floor construction. A mixing valve is not needed (unlike gas boilers with a higher operating point), which simplifies the hydraulics.

For a combined system – part floor heating, part radiators – a three-way valve with a thermostatic actuator on the floor heating branch is recommended to limit the temperature even when the boiler is set higher. This is a common configuration in new buildings.

How much does the operation of an electric boiler cost annually?

This is a question that every customer asks – and rightly so. Electric heating has high efficiency (100 % conversion of electrical energy to heat directly in the boiler), but the price of electricity is higher than the price of gas or wood. Therefore, it depends on:

The actual heat loss of the building (not a rough estimate)
The tariff – distribution tariffs D05 and D07 are significantly more advantageous for electric heating than the basic tariff
The quality of regulation and settings – good thermostat and time schedule settings can reduce consumption by 20–30 %
Combination with photovoltaics – in practice, we see that an FV system with a power of 5–8 kWp can cover TÚV almost for free in the summer and significantly reduce heating costs in the transitional period

Example calculation: A house of 120 m², heat loss of 10 kW, annual heat consumption of approximately 15 000–20 000 kWh (depends on the location and habits). At tariff D07 (approx. 0.12–0.14 €/kWh), the annual cost of electric heating comes to 1 800 – 2 800 €. For comparison – gas at a price of 0.08–0.10 €/kWh and 90 % boiler efficiency comes to 1 300 – 2 200 €. The difference is not dramatic if you take into account the zero service costs of a gas boiler, chimney lining and gas inspections. A detailed comparison can be found in the article Electric boiler vs. gas boiler: when is electric heating worth it?

What to do if the boiler displays an error code or is not working?

Electric boilers from Attack Electric have a display that shows error messages (E01, E02, etc.). Each code has a different meaning – the most common issues include:

Temperature sensor error: the boiler reports a fault with the temperature sensor in the output or return pipe. Solution: check the sensor wiring, or replace it if necessary.
Overheat protection thermostat triggered: the boiler overheats the water above the safe temperature (usually above 90 °C) and shuts down. Possible causes include a faulty circulation pump, a closed valve in the circuit, air in the system, or low water pressure.
Low pressure in the system: the pressure gauge shows less than 0.8 bar (in cold state, pressure should be 1.0 – 1.5 bar, in warm state 1.5 – 2.0 bar). Solution: add water via the filling valve.
Boiler does not restart after a power outage: most models require a manual reset or will restart automatically after power is restored – this depends on the settings.

For more information on troubleshooting, see the article Common faults in Attack Electric electric boilers and how to resolve them. For regular maintenance and prevention of faults, refer to the article Maintenance and service of Attack Electric electric boiler: what and when to check?

How to save on electricity when operating an electric boiler?

This topic is crucial – yet often underestimated. Many customers buy a good boiler but let it run at full power throughout the winter without regulation. It's like letting a car run at full throttle on red lights.

Practical recommendations:

Night setback: reducing the temperature by 3–5 °C at night can save 10–15 % of energy. The Excellent model has a built-in timer program.
Outdoor regulation (equithermal): the boiler adjusts the output water temperature according to the outdoor temperature. When it is -10 °C outside, it heats at 70 °C; when it is +5 °C outside, it heats only at 45 °C. In practice, this saves 15–25 % of energy compared to a fixed boiler temperature.
Room thermostat: even a basic mechanical thermostat in the room is better than nothing. A programmable or smart thermostat (e.g., Honeywell, Danfoss) can save an additional 10–20 %.
Tariff D07: a two-tier tariff for electric heating – the low tariff at night (22:00 – 06:00 and other hours) is significantly cheaper. If the boiler is properly set up to use the low tariff, savings can be 20–35 % compared to a single tariff.

A detailed guide on setting up the boiler and regulation can be found in the article Regulation and setup of Attack Electric electric boiler: how to save on electricity?

Is it possible to connect Attack Electric to a photovoltaic system?

Yes – and this is currently one of the most interesting combinations. An electric boiler is an ideal "consumer" for excess solar energy from a PV system. The principle is simple: when PV produces more energy than the house consumes, the excess goes to the boiler – either for heating or (with the TÚV module) for heating water in the storage tank.

This combination works best with a smart controller (e.g., Victron ESS, SolarEdge Home Energy Control or specific solutions from PV manufacturers) + Attack Electric Excellent boiler with PWM or 0–10 V power control capability. A typical setup for a standard family house: PV 6 kWp + battery 5 kWh + Attack Electric Excellent 15 kW + TÚV storage tank 200 l with module.

What accessories are available and which ones do you really need?

Common accessories for the basic Attack Electric boiler include:

TÚV module + storage tank: if you want hot water from the boiler – the TÚV module set is essential.
Room thermostat: basic accessory, without which the boiler will operate "blindly" according to the set temperature without feedback from the room.
Outdoor temperature sensor: for equithermal regulation.
Expansion tank: the boiler may have an internal one (depending on the model), but an external one is needed for larger systems.
Pressure relief valve 3 bar: mandatory safety component.
Automatic air vent: automatic or manual at the highest point in the system.

What you usually don't need: hydraulic balancer (for simple systems with one pump group), tank room thermostat (unnecessary complication for a simple house).

Common customer questions (FAQ)

Can I install the Attack Electric boiler myself, without an electrician?

The plumbing part of the installation can be done by yourself if you have the skills and know what you are doing. The electrical connection – connecting the boiler to the distribution board, fusing, earthing – must be done by a licensed electrician and a revision report must be issued. Without that revision report, the boiler will technically work, but you may have problems in case of an insurance incident or when requesting a discounted distribution tariff. I recommend not to skip this step.

Why is the boiler heating, but some rooms are cold?

It is usually due to hydraulic imbalance – the boiler heats the water, but it only flows through some radiators (usually those closest to the pump). Solution: hydraulic balancing of the system (adjusting the flow to each heating unit using a regulating valve or a thermostatic head). Another possible cause is air in the distant radiators – simply bleed them. A third cause may be insufficient boiler power – if it is undersized, distant rooms will be colder in freezing weather.

What size expansion tank is needed?

For a standard home heating system, the rule of thumb is: the expansion tank volume should be about 10–15% of the total water volume in the system. The system volume can be determined by adding up the volumes of the boiler, piping, and radiators (approximately 10–12 liters per each 1 kW of radiator power). For a home with a 10 kW heating system, you can expect about 100–120 liters of water in the system → an expansion tank of 12–18 liters (usually 18 l is installed). The internal tank in the Attack Electric boiler (if it has one) usually does not cover a larger system – an external tank is therefore almost always added during renovations.

Can I connect the boiler to an existing system after a gas boiler?

Yes, and this transition is quite common. Existing pipes and radiators usually remain unchanged. However, you should check: (1) the condition of the pipes and radiators (corrosion damage in older systems can be a problem), (2) the capacity of the radiators – older systems were designed for higher temperatures (80/60 °C), an electric boiler can also operate at lower temperatures, but in that case the radiators may be undersized, (3) the electrical installation – the power supply must match the performance of the new boiler. It is also recommended to flush and possibly chemically clean the system before filling it with new water.

How long will the Attack Electric electric boiler last?

With proper installation, regular maintenance, and topping up water in the system, the boiler should operate for 15–20 years without major problems. The most commonly replaced parts are the heating elements (after 8–12 years with hard water without treatment) and the circulation pump (after 10–15 years). With soft or chemically treated water (pH 7–8.5, no aggressive hardness), the lifespan is significantly longer. Compare this to a gas boiler, which requires annual service costing 80–150 €, chimney inspection, and possible replacement of the burner or heat exchanger.

Can the Attack Electric be controlled remotely via mobile?

The Attack Electric boilers themselves do not have a built-in WiFi module or a native app. Remote control is possible via an external smart thermostat or an OpenTherm controller with WiFi connectivity (e.g., Honeywell Evohome, Heatmiser, Danfoss) – these connect to the thermostat input on the boiler and allow control via an app. An alternative is a smart thermostat with a relay output, which simply turns the boiler on and off – this works for basic control, but you lose the ability for equithermal regulation, since the thermostat does not tell the boiler what water temperature to reach, it only turns it on or off.

Conclusion: what to take away

Electric Attack Electric boilers are reliable, technically well-designed, and relatively simple to install and operate. Most of the problems users encounter are not due to boiler faults, but to undersized power, a poorly designed hydraulic system, lack of regulation, or an unsuitable electricity tariff. If you get these things right from the start, electric heating will work smoothly for many years.

Before purchasing, we recommend reading the article How to choose an Attack Electric electric boiler: power, model, and accessories, where you will find a systematic selection process. If you are dealing with a specific type of house or renovation, feel free to contact us – in your project description, include the area, construction type, existing piping, and preferred control method, and we will help you choose the right setup.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.