© Vaillant, Gernot Walter

Flexible combustion for any gas mixture

The quality of gas for heating varies more and more frequently, meaning that the classic pneumatic mixture control in condensing units reaches its limits. The Vaillant Group therefore relies on an electronic solution in the form of its combustion system IoniDetect.


Until not so long ago, the issue of gas was still simple: For decades, a particular region was supplied from the same gas field. Boiler manufacturers were therefore reliably able to assume a constant gas quality when designing their combustion systems. But the market is changing. Large gas fields, such as in the Netherlands, are drying up and new sources are being tapped. And these are becoming ever more diverse: In addition to natural gas, in the future hydrogen, liquid gas, or biomethane will flow through the pipes.

We now need appliances that automatically adapt to different gas qualities.

Sven Schicke, Senior Project Manager, Vaillant Group

Sven Schicke, Senior Project Manager at the Vaillant Group, was therefore tasked with making gas condensing boilers fit for this future. He started at the company in Remscheid in Purchasing 23 years ago; today he is responsible for heat cells in Product Development. During his career, he has experienced how condensing boiler technology has replaced conventional heating systems, and is now witnessing another transformation. “We now need appliances that automatically adapt to the different gas qualities,” says Schicke.

From a pneumatic to electronic composite system

So-called pneumatic composite systems consisting of blowers, venturis, and gas valves have been state-of-the-art in condensing boilers so far. The principle: The blower draws in the air, a vacuum is generated by the tapering of the venturi, which controls the gas supply via the valve. When correctly adjusted, this results in the optimum mixture of oxygen and fuel. But if the gas quality changes, the mixture ratio is no longer correct and combustion no longer perfect.

“We therefore needed a system that could be used to automatically control the gas-air mixture,” says Schicke. The solution: An electronic composite system. Here, the mixing ratio is not controlled by the vacuum but by electronic control of the gas valve. To ensure that the valve knows how much gas it is to provide, it requires a characteristic value. One that provides information about the quality of combustion in order to be able to make re-adjustments in a targeted way. And where could this data be obtained better than in the flame itself?

It’s always good to carry out such developments with a supplier who’s already got experience and with whom you have collaborated for many years.

Sven Schicke, Senior Project Manager, Vaillant Group

Schicke and his team therefore chose a tried-and-tested solution: ionization technology. This utilizes the fact that the flame is electrically conductive. If a voltage is applied, the so-called ionization current can be measured directly in the flame using an electrode. This can be used to draw conclusions about the combustion quality: If the current is too weak, the valve receives the signal to supply more gas; if it is too high, it restricts it.

Here, with ebm-papst, Schicke conveniently had a partner at his side who already knew these kinds of systems. “It’s always good to carry out such developments with a supplier who’s already got experience and with whom you have collaborated for many years,” says Schicke. In close cooperation, the development partners worked out a solution tailored to Vaillant where a gas blower from the RadiMix series and the F01 gas valve designed for the electronic composite system are used. Vaillant called this new combustion system ­IoniDetect.

Greater modulation possible

However, it is not just the more precise combustion control that is a major advantage. With the electronic composite system, a higher modulation level can also be achieved. Instead of 1 : 5, as is normally realized in the pneumatic system, a control range of 1 : 10 is now possible. “If you just want to wash your hands, you don’t need full power,” says Schicke.

In the long term, the electronic composite systems will replace the pneumatic systems.

Sven Schicke, Senior Project Manager, Vaillant Group

The Vaillant Group gradually wants to expand the IoniDetect technology for all appliances. They have already started with their wall-mounted appliances. Schicke is convinced: “In the long term, the electronic composite systems will replace the pneumatic systems. But it will take some time still before this changeover process is complete. Just like it was with the change from conventional boilers to condensing boilers.” 

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