Gas condensing boilers

Topics at a glance

Wall-mounted gas condensing boilers
Floor-standing gas condensing boilers
Environmental aspect
Function
Protection from the future
Advantages
Services
Product range

When it comes to convenient heat production using natural gas, Viessmann offers a variety of technologies to suit every need and situation. The product range includes gas heating systems for new and existing buildings, as well as apartments and detached houses. Large-scale projects in the residential, commercial, and municipal sectors are also possible.

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Compact boilers – a space-saving miracle

Wall-mounted gas condensing boilers are particularly suitable for use in new buildings and small apartments. These extremely compact units can fit virtually any room. They are used either exclusively for domestic hot water (DHW) or also for space heating. In the latter case, they are called combination boilers. Both options operate on the principle of instantaneous hot water heating. Therefore, they typically do not have a storage water heater and heat water only when needed. This means they respond very quickly to changing needs. The disadvantage of instantaneous hot water heating is that hot water is not immediately available. To avoid the need to run water from the tap for a long time before it heats up, some wall-mounted gas condensing boilers have a small built-in storage water heater.

Floor-standing gas condensing boilers for greater efficiency when high demand for hot water is required

Floor-standing gas condensing boilers take up slightly more space. This is primarily due to their larger storage water heater, which maintains hot water at a constant temperature for a longer period of time. This is especially effective if large volumes of water are regularly required.

If you plan to connect a solar system for domestic hot water heating, we recommend choosing a floor-standing gas condensing boiler with a built-in solar indirect heat exchanger. It is installed on the buffer tank or near the draw-off point and heats the domestic hot water. In such combined systems, the heating water and domestic hot water do not mix. Floor-standing units are already designed for dual-mode operation, meaning they can easily be combined with another heat generator to meet heating needs. Viessmann gas condensing boilers are state-of-the-art in terms of technology and cover a power range from two to 100 kilowatts (kW). This allows them to efficiently and reliably heat detached houses, semi-detached houses, and small apartment buildings at any time.

Floor-standing gas condensing boilers are also available in larger sizes. They are primarily used in buildings with high heat demand, typically apartment complexes, public buildings, and commercial spaces. The cascade function allows for the quick connection of multiple units into a single unit, ensuring reliable heat even in these areas.

Technology Brochure - Gas Condensate Technology

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Combining climate protection and financial aid

Vitodens 343-F gas condensing boiler

In Germany alone, approximately two million heating systems over 25 years old are still in use. By replacing these boilers with highly efficient gas condensing boilers, consumers can save significant amounts of energy – up to 35% if a modern gas heating system is combined with solar technology. This will reduce Germany’s overall energy needs by ten percent, while reducing annual CO₂ emissions by 54 million tons.

Savings are possible because condensing technology uses energy extremely efficiently. This is because it converts virtually all of the fuel’s energy into heat. Therefore, anyone who chooses, for example, a gas condensing boiler can maintain low heating costs in the long run while simultaneously reducing their environmental impact. After all, less fuel burned means fewer CO₂ emissions.

All Viessmann gas condensing boilers meet pan-European requirements for efficient condensing technology. 98 percent or more of the energy consumed is converted into heat. Thanks to this unrivaled level of efficiency, anyone who chooses one of these gas heating systems makes a positive contribution to climate and environmental protection.

How does gas heating with condensing technology work?

As mentioned, condensing technology utilizes energy very efficiently. It utilizes not only the heat generated during combustion, in the form of the measurable temperature of the hot gases (net calorific value), but also the water vapor content (gross calorific value). This contains “latent” heat, which in older heating systems is released into the open air through the chimney. This latent heat can be recovered by passing the flue gases generated during combustion through a heat exchanger until the water vapor contained in the gases condenses. The condensation process releases thermal energy, which is then used to preheat the heating water.

Carsten Kuhlmann explains how condensation technology works.

A detailed description of heating technology can also be found in the “Gas Condensing Technology” section. Furthermore, comprehensive information can be found in the heizung.de gas heating guide .

Viessmann Vitodens 200-W wall-mounted gas condensing boiler

Promising, reliable heating technologies are already here

Calls for resource-efficient heating technologies are growing louder. New gas condensing boilers must operate not only cleanly but also environmentally friendly. In response, Viessmann is already developing future-proof gas condensing heating systems. Thanks to a combustion controller, these boilers automatically adjust to various gas types, including biogas mixtures. Furthermore, our products are currently suitable for natural gas-hydrogen mixtures containing up to 20 percent hydrogen. However, we would like to increase this percentage even further.

100% hydrogen operation is planned from 2025

Find out more about Viessmann “H2 ready” heating appliances.

Advantages of wall-mounted and floor-standing gas condensing boilers

Condensing technology is now the benchmark for new gas heating systems. System owners who choose this technology enjoy numerous benefits:

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The energy contained in the fuel is converted into heat with virtually no loss.

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Proven technology ensures high operational reliability and reduces the risk of unexpected failures

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Government subsidies for combination with renewable energy sources reduce purchase costs

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Efficient fuel combustion reduces heating costs and CO₂ emissions

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Possibility of combination with renewable heating systems

Choosing a gas condensing heating system also means eliminating the need for fuel storage in the home. If a gas connection is available, a tank is not required. Compact gas condensing boilers also take up little space.

House with a Viessmann gas condensing boiler in the basement and a solar thermal system on the roof

Easily compatible with renewable heating systems

As mentioned at the beginning, one of the advantages of gas condensing technology is its high level of compatibility. In practice, this means that most gas condensing boilers are shipped from the factory already configured for operation. The combination of a gas condensing boiler and a solar thermal system has proven to be both environmentally friendly and cost-effective. In this configuration, the solar thermal system is responsible for heating the hot water using free solar energy. This means the gas boiler doesn’t have to do as much work, which also reduces heating costs.

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Combining with a heat pump is another option. With this dual-mode operation, the heat pump not only provides hot water for domestic use year-round but also heating. During peak loads, when the weather is very cold, the gas boiler is activated.

A gas condensing boiler can also be used in a biomass heating system. Whether it’s a log, pellet, or wood chip boiler, the gas boiler should only be turned on when heat demand unexpectedly increases.

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Viessmann Services

Whether you’re looking for app-based control, extended warranty coverage, or heating supply contracts, discover the wide range of services offered by Viessmann.

Control new gas condensing boilers online with an app

The ViCare app offers a convenient way to manage your Viessmann gas heating system and save energy—anytime, anywhere. It allows you to always monitor the system’s status.

ViCare App Information and Requirements

5-year extended warranty*

If you choose to connect your new Viessmann gas heating system to the internet via the Vitoconnect interface, you receive an extended five-year warranty. The ViCare app allows you to easily and conveniently manage your gas heating system online.

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Renting new gas condensing boilers as an alternative to purchasing

Do you want to enjoy maximum service and convenience? Are planning reliability and long warranties important to you? Then learn more about our Viessmann Wärme offer. With Viessmann Wärme, you can rent a new gas heating system instead of buying one.

Renting a new gas heating system as an alternative to purchasing one

Product range

Whether it’s gas condensing boilers, floor-standing units with integrated solar indirect heat exchanger or cascade heating units for high heat requirements, Viessmann can offer the right gas condensing heating system for a wide range of needs.