Vaillant flue pipe reducer Ø 80/110 mm

Product detailed description

Vaillant flue gas pipe reducer Ø 80/110 mm – connecting different diameters of the flue duct

The reducer with a diameter of 80/110 mm (code 0020234898) is a simple yet important transition part of the Vaillant flue gas system, enabling a smooth connection between two sections of the flue duct with different diameters – in this case from the smaller 80 mm diameter to the larger 110 mm diameter. Unlike the combined part with a backflow flap, this is a purely passive fitting without any moving parts, whose only function is to safely and tightly bridge the diameter change along the flue duct route.

When is a reducer needed

The need for a diameter reducer arises in several common situations during the design and installation of flue ducts for condensing boilers:

• Connecting a boiler with a smaller connection diameter to a larger common branch – typically in cascade installations, where the common flue duct must have a larger diameter corresponding to the sum of the outputs of all connected sources,
• Transition between different system series of the flue duct – for example when combining components of the 80/125 mm system with elements of the 110/160 mm series or vice versa,
• Connection to an existing chimney or shaft with a different diameter – during renovations, where a new condensing boiler with a standard connection diameter needs to be connected to an older or differently sized vertical route,
• Adapting the route to limited space conditions – in some cases the designer deliberately chooses a combination of different diameters on different sections of the route with regard to the available space in the building structure.

Construction and material

The reducer is made of materials identical to other components of the Vaillant flue gas system, i.e. resistant to the acidic condensate generated during operation of condensing appliances (pH approximately 3.5 to 5.5) and to the operating temperatures of the flue gases. The internal profile of the fitting is designed so that the diameter change occurs smoothly, without sharp edges that would cause unnecessary flow turbulence, increased pressure loss, or undesirable increase in flow noise at that point of the route.

The connecting ends of the reducer use the standard Vaillant flue duct connection system (plug-in joints with a sealing ring), which ensures an airtight and watertight (against condensate) connection with adjoining components of the route without the need for additional sealing with adhesive or silicone.

Installation

Installing the reducer is simple – the part is inserted into the plug-in joint between two adjoining flue duct components with the appropriate diameters, while paying attention to the correct installation direction according to the manufacturer's instructions (usually with regard to the direction of condensate drainage, which must flow smoothly back towards the boiler throughout the entire route). As with other flue duct components, installation should be part of the overall flue duct installation carried out by a professionally qualified person, not an additional DIY intervention into an already functioning system.

Effect on flue duct sizing

Although it is a relatively simple component, a change in diameter along the flue duct route affects the aerodynamic behaviour of the entire flue path and must be taken into account when sizing it. The chimney or flue duct designer should include this reducer, together with all other route components (bends, extensions, any flaps), in the overall pressure loss calculation, so that the resulting route remains within the parameters guaranteed by the boiler manufacturer for the given type of connection, and so that no output limitation or fault conditions occur due to excessive flue duct resistance.

Compatibility

This reducer is designed for flue gas systems of Vaillant condensing gas boilers using diameters of 80 mm and 110 mm, i.e. primarily the ecoTEC, ecoTEC plus, ecoTEC exclusiv series and related models, as well as cascade and collecting systems built on these diameter series. Before ordering, we recommend verifying that both diameters match your specific project, as Vaillant offers reducers in several diameter combinations for different flue duct system series.

Maintenance

As a passive component without moving parts, the reducer requires no specific maintenance beyond the regular inspection of the flue duct carried out as part of the boiler's regular service and the mandatory chimney inspection by a chimney sweep. It is recommended to occasionally visually check the tightness of the joints on both sides of the reducer and check for any excessive accumulation of condensate deposits at the point of diameter change, where the flow velocity of the flue gases, and therefore the self-cleaning effect of the flow, may be somewhat lower than in adjacent straight sections of pipe.

Why choose the original part

Using an original Vaillant reducer instead of a universal fitting from another manufacturer guarantees exact dimensional compatibility with the Vaillant flue duct plug-in connection system, which is a prerequisite for the airtightness and watertightness of the entire route. A non-original part with slightly different joint dimensions may cause a leak through which flue gases or condensate could escape into the surrounding space, which is unacceptable in a condensing boiler's flue duct both from a safety perspective and in terms of maintaining the manufacturer's warranty.

Typical combinations with other components

In practice, this reducer is commonly combined with other components of the Vaillant flue gas system – for example extensions of various lengths, 45° or 87° bends to change the direction of the route, inspection pieces enabling future inspection and cleaning of the route, backflow flaps for cascade installations, or roof or facade terminations at the point where the route exits the building. A complete flue duct route is thus usually composed of several such parts chosen precisely according to the height and directional layout of the specific installation.

Frequently Asked Questions (FAQ)

Can I use this reducer with flue duct systems other than Vaillant?
The reducer is designed with the exact dimensions of the Vaillant plug-in joint system, and we do not recommend using it with flue ducts from other manufacturers without verifying joint dimension compatibility, as different manufacturers may use slightly different joint dimension standards even for the same nominal diameter.

Does the diameter reducer affect the boiler's efficiency?
With correct sizing of the entire flue duct by a designer who takes into account the pressure loss of the reducer together with other route components, the diameter reducer has no negative effect on the boiler's efficiency or output.

Is it possible to add the reducer to an existing flue duct route at a later date?
Yes, as long as the plug-in joint design of the existing route matches the Vaillant system, the reducer can also be added later, for example when expanding a boiler room with an additional source with a different connection diameter.

What is the difference between this reducer and a reducing backflow flap?
This reducer is a purely passive transition part without moving parts, whereas a reducing backflow flap also contains a movable flap preventing backflow of flue gases – this is used exclusively in cascade installations with multiple sources on a common flue duct.

Do I need additional sealing when installing the reducer?
No, the plug-in joint with an integrated sealing ring ensures sufficient tightness when installed correctly, without the need for additional sealant or adhesive.

Can this reducer be used outside of cascade installations, for example with a single standalone boiler?
Yes, the reducer is used wherever a change in diameter is needed along the flue duct route, not only in cascades – for example also when connecting a single boiler to an existing shaft or chimney with a different diameter than the boiler's standard connection.

Difference between coaxial and separate flue systems and its effect on choosing the reducer

In Vaillant condensing boilers, flue gases are discharged either via a concentric (coaxial) system, in which a single outer pipe simultaneously carries the flue gas discharge and combustion air supply through separate annular spaces, or via a system with separate pipes, where the flue gas discharge and air supply each have their own separate pipe. A diameter of 80 mm commonly occurs in practice as the diameter of a single separate pipe in a separate flue system (the so-called System 80), while a diameter of 110 mm may occur both as separate piping for larger output series and as the internal diameter of some concentric assemblies. When ordering this reducer, it is therefore important to be clear about whether it is a connection within a separate flue system or another configuration, as this determines the correct choice of subsequent route components.

Practical example of use in a cascade boiler room

Let us consider a typical cascade boiler room with two condensing boilers with an output for which the manufacturer specifies a flue connection diameter of 80 mm for each individual boiler. According to the chimney sizing calculation, the common collecting branch into which both boilers discharge must be designed for a diameter of 110 mm in order to handle the sum of the flue gas flows of both sources during simultaneous operation. It is precisely at this point of connecting an individual boiler to the common branch that this reducer is used (or its variant with an integrated backflow flap, if required by the cascade's safety concept) – it ensures a smooth transition from the boiler's smaller connection diameter to the larger diameter of the common branch without unnecessary pressure losses and turbulence.

Effect of temperature and humidity on the reducer material

Condensing boilers operate with flue gas temperatures that are significantly lower compared to classic (non-condensing) boilers, which is precisely the basis of their higher efficiency – part of the heat contained in the water vapour of the flue gases is used for condensation and transferred back into the heating circuit. This lower flue gas temperature results in condensate forming along a large part of the flue duct route, which is mildly acidic. The material of this reducer, like the other components of the system, is therefore designed with an emphasis on long-term resistance to this acidic environment, in order to prevent corrosion damage that could occur over the years of operation if unsuitable materials (such as ordinary galvanised steel without special surface treatment) were used.

Procedure for ordering the correct type of reducer

When ordering, we recommend proceeding as follows: first check the exact diameter of the boiler's flue connection from the project documentation or the technical data sheet of the specific boiler, then determine from the chimney sizing calculation the required diameter of the adjoining section of the route (for example the common branch in a cascade or an existing shaft during renovation), and only then, based on these two figures, choose the correct combination of reducer diameters. If in doubt, we recommend consulting the supplier's technical support or an authorised Vaillant service technician, who can recommend the correct component based on the specific installation parameters.

Summary

The Vaillant flue gas pipe reducer Ø 80/110 mm is a simple yet functionally important component enabling a smooth and tight connection between sections of the flue duct with different diameters. As an original Vaillant part, it guarantees exact compatibility with the plug-in connection system of the entire flue duct system, which is a prerequisite for long-term trouble-free and safe operation of the condensing boiler.

Additional recommendations for designers

When designing a flue duct route with a combination of different diameters, we recommend minimising the number of diameter changes to the necessary minimum, as each reducer represents an additional pressure loss and a potential point of increased condensate accumulation. Where technically possible, it is preferable to choose a uniform diameter along the entire length of the route corresponding to the requirements of the most demanding section (for example the common collecting branch in a cascade), and to use the reducer only at the necessary point of connecting an individual source with a different connection diameter.

Relation to future system expandability

When designing new installations, it is also advisable to consider possible future expansion of the system – for example a planned addition of another boiler to the cascade within a few years. In such a case, it may be advantageous to choose a slightly larger diameter for the main collecting branch than is currently strictly necessary, and to use the reducer already now to connect the first boiler, which will facilitate any future expansion without the need to replace already installed sections of the route. This consideration is part of a broader concept of designing flue ducts with a reserve for the future development of the boiler room, which is worth considering already at the initial project stage.

Storage and transport

The reducer is supplied as a separate part, and until installation we recommend storing it in a dry environment protected from mechanical damage, especially in the area of the plug-in joints, where damage to the sealing ring or deformation of the edge could negatively affect the tightness of the future joint. When transporting to the construction site, we recommend protecting the part from impacts and compression together with the other flue duct components.

The reducer's place in the overall range of Vaillant flue duct accessories

This reducer is one of many components from which a complete flue duct route for a Vaillant condensing boiler can be assembled from the atria.sk range, precisely according to the needs of a specific building. In addition to reducers with various diameter combinations, the range also includes extensions of various lengths, 45° and 87° bends, inspection pieces allowing inspection and cleaning of the route, backflow flaps for cascade installations, roof transitions and extensions for vertical discharge, as well as terminations for horizontal discharge through a facade. This comprehensive range allows both customers and installation companies to order all the necessary parts from a single supplier and be assured of their mutual compatibility.

Summary of key parameters for a quick overview

For customers who need a quick overview of the key properties of this part: it is an original Vaillant transition component with a diameter of 80 mm on one side and 110 mm on the other, without moving parts, made of a material resistant to condensate and the operating temperatures of flue gases from condensing appliances, with a standard plug-in joint compatible with other components of the Vaillant flue gas system, designed primarily for connecting a boiler with a connection diameter of 80 mm to a flue duct or collecting branch with a diameter of 110 mm, with an emphasis on a smooth diameter transition minimising pressure losses and flow noise at that point of the route.

If you have any doubts about the suitability of this part for a specific installation, we recommend contacting customer service or directly an authorised Vaillant service technician, who can confirm the correct choice of this component based on the project documentation and the boiler's technical parameters before it is installed in the flue duct, thus avoiding unnecessary complications and additional costs from later replacing an incorrectly chosen part.