Viessmann Vitodens 100-W, 3,2 - 32 kW + 120 l tank + controller

Frequently Asked Questions

• How exactly do I choose the output of a Viessmann condensing boiler? The basis is the calculated heat loss of the heated building (most reliably taken from the project documentation or an energy certificate). If you do not have a project, you can estimate roughly 60-100 W per m² of floor area for a commonly insulated house built after 2000, or 100-150 W/m² for an older, non-insulated house - however, the exact figure varies depending on the number of floors, ceiling height, the number and quality of windows, and the building's orientation. A boiler oversized for the required output switches on and off more often (so-called cycling), which shortens its service life and reduces efficiency; conversely, an undersized boiler will not be able to heat the house sufficiently on frosty days.

This particular Viessmann model is supplied in the output range of 3,2 - 32 kW. For boilers with output modulation, always choose based on your highest demand (the coldest days of the year), since the boiler can regulate its output downwards on its own.

• Why is a condensing boiler more economical than a conventional one? A condensing boiler additionally makes use of the heat hidden in the water vapour produced when gas is burned - in a conventional boiler this vapour escapes unused through the flue, whereas in a condensing boiler it is cooled below the so-called dew point, the vapour condenses, and the released heat is returned to the heating circuit. Thanks to this, condensing boilers achieve an efficiency of approximately 105-110% relative to the calorific value of the gas, compared to a typical 85-92% for conventional boilers.
• What type of flue gas discharge does this boiler need? Most modern condensing boilers are so-called turbo boilers (with a sealed combustion chamber) and require a coaxial (concentric) or separate flue gas discharge and combustion air supply routed through an external wall or the roof - so a functioning chimney is not needed. The exact type and maximum length of the discharge (depending on the 60/100 or 80/125 mm diameter) can be found in the technical documentation for the specific model, or you can consult our customer service.
• What does the ErP energy class indicated for the boiler mean? This is a mandatory efficiency label for heating appliances under the EU ErP (Ecodesign) directive, similar to the energy labels used for refrigerators. Condensing boilers commonly achieve class A, or higher in combination with room controls (e.g. A+ when using weather-compensated control and a room thermostat).
• Can I install and connect this boiler myself? No. By law, connection to the natural gas supply, the electrical network, and the flue gas discharge may only be carried out by a person with the appropriate authorisation (most often an authorised service technician of the given brand or a gas appliance inspection technician). After installation, the boiler must be commissioned by the manufacturer's authorised service, which is usually also a condition for the warranty to be valid.
• What about servicing and warranty? Most manufacturers require a regular annual service inspection by an authorised service provider in order to keep the warranty valid even after its standard period expires (an extended warranty for regular servicing is common especially with the Vaillant, Protherm and Viessmann brands). You can find the exact warranty conditions in the warranty certificate supplied with the boiler.
• What is included in the delivery of this specific product? The exact package contents (the boiler itself, or a hot water tank, room controls and other accessories in the case of a set) are stated in the product name and in its technical parameters above on this page.