© 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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