Vaillant adapter from coaxial flue to separate, Ø 80/80 mm

Product detailed description

Vaillant converter from a coaxial flue to a separate Ø 80/80 mm system

The converter with code 0020147470 is a special transition component of the Vaillant flue system that allows a single concentric (coaxial) section of the flue gas route to be split into two separate, individual pipes with a diameter of 80 mm – one for flue gas discharge and the other for combustion air supply. It is an important element for the transition between two different flue gas routing concepts, which in practice are commonly combined depending on the layout options of a particular building.

Principle of concentric and separate flue routing

Condensing boilers with a sealed combustion chamber (type C) require two functional circuits at the same time: discharge of flue gases outside the building and supply of fresh combustion air from the outside environment to the burner. These two circuits can be solved either concentrically – i.e. with a single outer pipe in which both flows are routed separately in the inner and outer ring of the same pipe (a typical solution with a diameter of, for example, 60/100 mm or 80/125 mm), or separately – with two completely independent pipes routed possibly along entirely different paths (for example, flue gas discharge through the roof and air supply through the façade, or both routed in parallel but in separate pipes).

This converter serves exactly for the transition between these two concepts – at the point where the concentric section of the route ends (for example, right at the boiler outlet) and the section with separate pipes begins, it splits a single concentric inlet into two separate outlets with a diameter of 80 mm each.

When this converter is used

• Limited space for concentric routing in part of the route – for example, if passing through a ceiling or wall structure does not allow routing a concentric pipe with a larger outer diameter, but separate pipes with a smaller 80 mm diameter fit through,
• Need to route flue gas discharge and air supply along different paths – for example, when it is more advantageous to draw combustion air from one side of the building (e.g. a shaded, cooler area) and discharge flue gases via a different route (e.g. through the roof),
• Transition from the boiler room to a shared shaft with separate ducts – some older or specific shaft systems have separate ducts for air supply and flue gas discharge instead of a unified concentric route,
• Optimisation of pressure losses on longer routes – on very long routes, it may be more advantageous aerodynamically to route part of the route separately rather than concentrically.

Technical design

The converter is designed to receive a concentric pipe with a standard connection matching the boiler outlet on one side, and to provide two separate 80 mm diameter outlets on the other side – one for flue gases and the other for combustion air. The internal routing of the converter is designed so that the separation of both flows occurs without mixing them, and with the lowest possible additional pressure loss, since any undesired mixing of flue gases with combustion air or excessive resistance at this point of the route would negatively affect the combustion process and the safe operation of the boiler.

The converter's material is identical to other components of the Vaillant flue system – resistant to the acidic condensate formed on the flue gas duct side and to normal weather and temperature conditions on the air supply duct side.

Installation and installation principles

Installing this converter requires careful planning of the route of both outlet pipes from the split point to their separate exit outside the building or into separate shafts. It is essential to observe the prescribed length and direction limitations for both separate sections according to the manufacturer's technical documentation, since the maximum permissible route length for separate routing is calculated independently for the flue gas duct and for the air supply duct, with the equivalent length of each elbow used included in the total length.

It is equally important to ensure that the combustion air supply outlet is not located near a source of contaminated air (for example, the exhaust of another appliance, a chimney, or even the boiler's own flue gas outlet), to prevent re-intake of flue gases into the combustion process, which would reduce combustion efficiency and could pose a safety risk.

Compatibility

The converter is intended for Vaillant condensing gas boilers with a sealed combustion chamber (type C), using a concentric connection on the boiler side and the possibility of transitioning to the System 80 separate routing system with an 80 mm diameter on both separate ducts. Before ordering, we recommend checking the technical documentation of the specific boiler model to verify whether the given type is compatible with the transition to separate routing and what the maximum permissible lengths of both separate route sections are for the given power range.

Advantages of separate routing over concentric routing

Separate routing of flue gases and combustion air offers certain advantages compared to a concentric solution – in particular, greater flexibility in route design in more complex building layouts, the possibility of achieving greater total route lengths (since the pressure losses of separate pipes with a smaller diameter can be lower at the same flow rate than with a single concentric pipe), and the possibility of routing air supply and flue gas discharge along different, structurally more convenient routes. The disadvantage is somewhat more complex installation with two separate routes instead of one, which requires more careful planning and more space for routing both pipes.

Maintenance

As a component without moving parts, the converter does not require specific maintenance; however, it is recommended to visually check the tightness of the joints on all three sides of the converter (concentric inlet and two separate outlets) during the boiler's regular annual service inspection, and to make sure there is no leakage of flue gases or intake of false air at the point where the route splits, which could negatively affect the boiler's combustion process.

Why a genuine Vaillant part

The transition between concentric and separate routing is a sensitive point of the flue gas route in terms of correctly separating the flue gas and combustion air streams without them affecting each other. Using a genuine Vaillant converter guarantees that this separation is carried out exactly according to the parameters for which the boiler is certified, including the maximum permissible pressure losses and lengths of both separate sections. A non-genuine or incorrectly sized solution for this transition can lead to disruption of the combustion process, reduced efficiency, or in extreme cases, safety risks associated with an incorrect ratio of combustion air to fuel.

Frequently Asked Questions (FAQ)

Can I use this converter with any Vaillant condensing boiler?
The use of the converter is tied to models with the possibility of transitioning from concentric to separate flue gas and air routing – not all boiler types and power ranges support this option, so we recommend checking compatibility in the technical documentation of the specific model.

What is the maximum length of the separate route after the converter?
The maximum length depends on the specific boiler model and power and is stated in its technical documentation – generally, the equivalent length of each elbow used and other route components is also included in the total permitted length.

Do both separate pipes (flue gas and air) have to be the same length?
Not necessarily; both ducts can have different lengths and routes, as long as each individually meets the maximum permissible parameters set by the manufacturer for the given boiler type.

Is it necessary to reconfigure the boiler or change its settings when transitioning to separate routing?
When transitioning to separate routing with a correctly sized route, no intervention in the boiler's combustion settings is usually required; however, we recommend having a service technician check the combustion process after installation is completed to verify the correct combustion parameters for the given flue gas route configuration.

Where can and cannot the air supply outlet be located?
The combustion air supply outlet must not be placed near any source of contaminated air, including the boiler's own flue gas outlet, exhausts of other appliances, or ventilation openings for contaminated air – the exact clearance distances are determined by the manufacturer's technical documentation and applicable technical standards.

Is this converter also suitable for cascade connections with multiple boilers?
The converter is primarily used to solve the route for a single boiler, but in principle there is nothing preventing its use within a cascade as well, if the layout conditions of a specific boiler in the assembly require a transition from concentric to separate routing – verifying compatibility with the given boiler type and power is always decisive.

Summary

The Vaillant converter from a coaxial flue to a separate Ø 80/80 mm system is a specialised yet practical solution for installations where the building's layout conditions require a combination of concentric and separate flue gas routing within a single route. It allows flexible adaptation of the flue route to specific construction conditions while maintaining safe and effective separation of the flue gas stream from the combustion air supply.

Practical usage scenarios in renovations

In renovations of older buildings, this converter is often used in situations where the existing building structure does not allow routing a concentric pipe along the entire length of the planned route – for example, due to narrow installation shafts originally designed for a different type of heating source. In such a case, the part of the route near the boiler is solved concentrically (where there is sufficient space), and the rest of the route, after passing through this converter, is solved with two separate pipes with a smaller 80 mm diameter, which fit more easily into cramped existing installation openings or shafts.

Aerodynamic aspects of the transition from concentric to separate routing

When transitioning from a single concentric pipe to two separate pipes, the velocity profile of the flow of both media – flue gases and combustion air – changes. While in the concentric section combustion air flows in the outer ring around the inner pipe carrying flue gases (which also has the side effect of preheating the intake air with heat from the flue gases, slightly increasing combustion efficiency), after splitting into two separate pipes this effect of mutual thermal influence between the flows disappears, and both flows behave independently of each other. The route designer should take this fact into account when calculating the overall heat balance and pressure losses of the route, especially for longer separate sections routed through cold, uninsulated areas of the building.

Effect of the converter's position in the route on ease of installation

From a practical point of view, it is recommended to place this converter as close as possible to the boiler outlet, i.e. right at the beginning of the flue gas route, since this position generally provides the most space for the subsequent routing of the two separate pipes in different directions according to the layout options of the room in which the boiler is located. Placing the converter in the middle or at the end of a longer concentric route is technically possible, but it can complicate the subsequent routing of both separate sections, especially in spatially cramped installations.

Safety aspects of incorrect flow separation

A critical safety aspect of this component is ensuring that the flue gas stream and the combustion air stream do not mix again at any point after separation, whether due to leakage of the converter itself or due to incorrectly designed routing of both outlet pipes (for example, if the air supply outlet were placed too close to the flue gas outlet, causing recirculation of flue gases back into the combustion air). Recirculation of flue gases into the combustion air reduces the oxygen content of the intake air, which can lead to incomplete combustion, increased carbon monoxide formation, and reduced boiler efficiency. This is why it is important to observe all clearance distances and directional recommendations set by the manufacturer for the placement of both outlets.

Service technicians' experience with this type of connection

Service technicians who regularly encounter installations using this type of converter recommend paying special attention to the boiler commissioning phase after installation with separate routing – specifically, measuring flue gas parameters (CO2, O2, and possibly CO content) under various boiler operating states, in order to detect any deficiencies in the route design or execution in time, before handing over the work to the customer. This check is part of the standard commissioning procedure, which should be performed exclusively by an authorised Vaillant service technician.

Connection to flue gas route inspection

Since this converter changes the concept of flue gas route routing directly within its path, it is important that its exact type, position, and connection method be recorded in the flue gas route inspection log kept by an authorised person (chimney sweep) during regular mandatory inspections. This record makes future inspection and any potential service intervention easier, especially if the route configuration is not immediately obvious from a visual inspection (for example, if the separate route sections are routed through hidden installation spaces).

Recommendations for project preparation

Investors and designers considering a solution with a transition from concentric to separate routing should include this concept in the heating project documentation already at the design stage, together with the exact determination of the routes of both separate pipes, their lengths, the number of elbows, and the outlet locations. Solving such a transition additionally after the building shell is completed is generally considerably more complicated, as it may require additional penetrations through already finished structures that were not originally prepared for this purpose.

Cost-effectiveness assessment of the solution

Even though the converter itself represents only a small item in the overall budget of a condensing boiler installation, its use can in some cases bring significant savings in construction costs compared to an alternative solution that would require larger structural penetrations for a concentric pipe along the entire route length. This consideration is particularly relevant in renovations with limited possibilities for intervention in the existing building structure, where it would otherwise be necessary to create new, larger penetrations across multiple floors or structures of the building.

From a long-term operation perspective, it is also important to emphasise that a correctly designed and executed transition to separate routing does not involve any compromise in the reliability or safety of the system compared to a purely concentric solution – it is simply an alternative, equally full-fledged concept of flue gas route routing, which Vaillant includes in its system accessory range precisely for such cases.