Vaillant intelligent electric heating coil 0.5-3.5 kW for 300-500 l tanks

Product detailed description

Vaillant intelligent electric heating element 0.5 – 3.5 kW for 300 – 500 l cylinders, suitable for photovoltaic systems

This intelligent electric heating element is a more advanced alternative to the classic switchable 2/4/6 kW element – instead of fixed output stages, it offers continuously regulated output in the range of 0.5 to 3.5 kW, which can constantly adapt to the currently available amount of electrical energy. It is intended primarily for households with their own photovoltaic system that, instead of selling surplus generated electricity to the distribution grid at a low feed-in price, would rather convert this energy directly into heat in the hot water cylinder – i.e. use it within their own household (the so-called increase in the self-consumption rate of the PV system), which, at current electricity price levels and feed-in tariffs for surpluses, usually pays off more than selling to the grid.

Just like the classic version, this element is installed in the large-volume Vaillant cylinders of the uniSTOR VIH R 300/400/500 and auroSTOR VIH S 300/400/500 series via a G1½" flange connection (the mounting flange is sold separately), but its internal electronics and power control are considerably more sophisticated, as it must continuously react to the changing amount of available surplus energy from the photovoltaic panels throughout the day. This ability to smoothly modulate output (as opposed to a simple on/off switching between fixed stages) is key precisely because PV generation changes continuously throughout the day – from zero in the early morning hours, through a gradual increase towards noon, to a decline again in the evening, and the heating element must adapt to this pattern in real time in order to avoid unnecessary electricity draw from the grid as well as unused surplus.

Technical characteristics

Principle of intelligent power control

While a classic electric heating element only knows on/off states at one of three fixed power stages, the intelligent version can smoothly modulate output across the entire 0.5 to 3.5 kW range according to the currently available amount of "free" electrical energy. In practice, this works so that the household's control system (an energy manager or a PV inverter with the relevant output) continuously evaluates the difference between the current output of the photovoltaic panels and the current consumption of other household appliances – if a surplus arises (for example around noon on a clear day with low consumption from other appliances), part or all of this surplus is directed to the electric heating element instead of being sold to the distribution grid, usually at a lower feed-in price than the purchase price of electricity from the grid.

This form of surplus utilisation is referred to in technical terminology as "power to heat" and is one of the simplest and most affordable ways, in terms of investment, to increase the self-consumption rate of a photovoltaic system without having to invest in more expensive battery storage – hot water in the cylinder in effect acts as a simple "thermal battery" of energy.

Installation and wiring

Installing the heating element body itself into the cylinder is essentially the same as with the classic version – it requires a pre-installed G1½" mounting flange (sold separately) and must be carried out by a qualified electrician. In addition to the classic version, a connection to the photovoltaic control system or home energy manager is required, which provides the heating element with information about the currently available power surplus – this connection is implemented according to the specific inverter type and its communication interface (for example a digital or analogue control signal, or a communication protocol depending on the inverter design). Before ordering, we recommend verifying compatibility with the specific type of inverter or control unit of your photovoltaic system, or consulting the service technician who installed the PV system.

Who this accessory is suitable for

• households with their own photovoltaic system who want to maximise the self-consumption rate of the electricity generated,
• households considering a simpler "thermal" use of surplus instead of (or alongside) more expensive battery storage,
• owners of large-volume Vaillant cylinders of 300 – 500 l who want to maximise the use of their existing investment in photovoltaics,
• households with variable electricity pricing (e.g. spot tariffs), where intelligent control can also respond to price signals, not just to PV surplus, if the given energy manager allows it.

Difference compared to the classic switchable heating element

The main difference compared to the classic version with fixed 2/4/6 kW stages lies precisely in the smooth output regulation and the ability to communicate with the photovoltaic control system. The classic heating element is suitable where a simple manual or thermostatically controlled top-up heating without any link to electricity generation is sufficient (for example summer top-up heating with a solid fuel boiler), while the intelligent version makes sense specifically and only in combination with a photovoltaic system – without it, it loses its main advantage and its higher purchase price has no way to pay off.

Expected benefit and payback

The exact financial benefit depends on the size of the photovoltaic system, the household's consumption profile, the size of the hot water cylinder, the season, and how much surplus energy would otherwise be sold to the grid at a low feed-in price. In general, households with significant daily generation surpluses (for example a larger PV system without significant household consumption during the day, when residents are at work) gain the most benefit from this investment, as otherwise unused energy is converted into real savings on water heating costs instead of an almost worthless sale of surplus to the grid.

Safety and maintenance

Just like the classic version, this heating element is also equipped with a built-in safety temperature limiter (STB), which protects the cylinder from overheating in the event of a fault in the main control thermostat. A regular annual check of the functionality of the thermostat, the temperature limiter, and the connection to the photovoltaic control system should be part of the cylinder's routine servicing. In areas with harder water, one should also expect the possibility of limescale build-up on the surface of the heating element body, which reduces heat transfer efficiency – we therefore recommend a regular visual inspection during service checks.

Comparison with battery storage

Households with a photovoltaic system generally consider two main ways to make better use of surplus generated electricity – investment in battery storage, or simpler "thermal" use of the surplus through devices such as this intelligent electric heating element. Battery storage can later return the stored electricity back to the household electrical grid in the form of electricity (for example for evening lighting or other appliances), while the electric heating element converts the surplus directly and irreversibly into heat in the hot water cylinder. The investment in the heating element is, however, significantly lower than the investment in battery storage of comparable capacity, which is why in practice it is often recommended as a first, affordable step towards better utilisation of PV surplus, with the possibility of later adding battery storage if the PV system owner wishes.

Why choose this accessory

If you already own or are planning a photovoltaic system and also have or are planning a large-volume Vaillant hot water cylinder, this intelligent heating element represents one of the simplest ways to increase the self-consumption rate of the generated electricity without having to invest in expensive battery storage. It is an original accessory directly from the cylinder manufacturer with guaranteed compatibility of mounting dimensions.

Compatible cylinder models

Just like the classic switchable version, the intelligent heating element is intended for large-volume Vaillant cylinders with a G1½" flange connection – primarily uniSTOR VIH R 300, VIH R 400 and VIH R 500 (indirect cylinders), geoSTOR VIH RW 300 (a cylinder for heat pumps), and auroSTOR VIH S 300, VIH S 400 and VIH S 500 (bivalent solar cylinders). Combination with the auroSTOR models is particularly logical from a conceptual point of view – the cylinder can thus simultaneously use up to three energy sources for water heating: solar collectors (solar circuit), the main heat source (boiler or heat pump), and photovoltaic surplus via the intelligent electric heating element, representing one of the most comprehensive available solutions for almost free hot water preparation from renewable sources for most of the year.

Package contents

The package includes the body of the intelligent electric heating element with built-in electronics for output control, a thermostat, a safety temperature limiter, and a gasket for fitting into the mounting flange. The G1½" mounting flange itself, the connecting cabling to the photovoltaic control system, electrical fuse protection, and any communication module (depending on inverter type) are supplied and ordered separately depending on the specific configuration of the photovoltaic system.

Safety aspects of integration with photovoltaics

When connecting the electric heating element to the control system of the photovoltaic system, it is important that the wiring complies with the applicable standards for home electrical installations and that it is properly protected independently of other household circuits. Since the heating element can operate at a variable output level depending on the current generation of the PV system, we recommend that the wiring and setting of the control parameters be carried out by a technician experienced with photovoltaic systems, who will also confirm correct communication between the inverter and the heating element during actual operation (for example by checking during a sunny day with a real generation surplus).

Frequently Asked Questions

Final note: when designing a combination of photovoltaics and an intelligent electric heating element, we always recommend basing your decision on actual measured data on generation and consumption for your specific household (for example from the PV inverter's app over the last 12 months), not just on rough estimates – only in this way can you correctly assess what portion of the annual surplus this heating element can actually utilise, and thus what the truly expected payback period of the investment in this accessory is for your specific home.