Vaillant S2 - basic flue connection set Ø130 mm for shaft installation

Product detailed description

Vaillant S2 - basic flue connection set Ø130 mm for installation into a chimney shaft

The S2 set is an original connection kit from Vaillant, used for safe and code-compliant connection of an ecoCRAFT condensing boiler (or other Vaillant gas condensing boilers with an output for which this set is intended by the manufacturer) to an existing masonry or prefabricated chimney shaft. This solution is intended primarily for installations where the flue gas discharge and combustion air supply (in the case of concentric ducting), or just the flue gas discharge alone (in the case of separate ducting), are carried out through an existing vertical chimney flue in the building - typically in boiler rooms of larger buildings, apartment blocks, industrial and commercial premises, where several boilers or one larger boiler are connected to a shared or individual shaft.

What the S2 set contains and what it is used for

The designation "S2" is part of the manufacturer's system of defined connection sets (S1, S2, S3...), which Vaillant offers for various boiler-to-flue connection configurations - both individually and in a cascade. The S2 set represents the basic (entry) connection unit for connecting the first boiler to the system, where the flue is then routed into an existing shaft. Physically, the set contains a set of parts made of pressure-resistant polypropylene (PP) with a nominal diameter of Ø130 mm, which ensure:

• a tight and mechanically strong connection to the boiler's flue gas outlet (if needed, in combination with a reducer from a larger boiler outlet diameter),
• a short section of ducting needed to reach the axis of the shaft,
• fastening and sealing components for entry into the shaft (a sleeve/fastening element for entry into the masonry structure),
• the necessary seals (rubber O-rings) ensuring gas-tightness of the joint even during positive pressure operation.

The exact contents of the packaged set may vary depending on the manufacturer's current version, but functionally it is always a complete set needed to create the first connecting section between the boiler and the vertical shaft, without the need to purchase small connecting parts separately.

Technical characteristics

• Nominal diameter: Ø130 mm (part of the Ø130 mm flue component range used for higher-output Vaillant condensing boilers and cascade connections)
• Material: polypropylene (PP), resistant to condensate and the aggressive environment of flue gases from condensing operation
• Operation type: positive pressure system (type C according to STN EN 1443/1856-2), suitable for condensing boilers with forced flue gas discharge
• Maximum operating temperature: up to approx. 120 °C (temperature resistance class for PP flue systems)
• Joint sealing: rubber sealing O-rings, push-fit (socket) joints without the need for gluing
• Purpose: connecting the boiler to an existing masonry/prefabricated shaft, standalone installation or the first component of a cascade system
• Country of origin / manufacturer: Vaillant Group
• Warranty: 2 years

When to choose the S2 set (difference from S1 and S3)

Vaillant divides connection sets according to the boiler's position in the installation and the way it is connected to the shared flue. While basic sets (e.g. S1) are used for direct connection of a single boiler to a chimney without additional extension elements, the S2 set is typically chosen where installation into an existing shaft needs to be addressed - i.e. during boiler room renovations, replacement of old boilers with condensing units, or during the first phase of building a cascade system, to which additional boilers can later be added using extension sets (e.g. S3, intended for the 3rd and 4th boiler in a cascade with a Ø80/130 mm reducer). The choice between S1 and S2 depends on the specific on-site construction situation - if in doubt about the correct choice, it is advisable to consult an authorized Vaillant service technician or a heating system designer, as an incorrectly chosen connection set can lead to leaks or inadequate flue gas discharge.

Installation procedure - recommendations

Installation of the S2 connection set should always be carried out by a professionally qualified person (heating engineer, Vaillant service technician, or a company authorized to install gas appliances and chimney structures). The general procedure includes:

1. Checking the condition and clearance of the existing shaft, its dimensions and the tightness of its walls against possible flue gas leakage into surrounding structures.
2. Installing the set's entry element into the shaft wall at the location specified by the project, ensuring the correct slope (usually a minimum of 3° towards the boiler or the nearest inspection/condensate point) for condensate drainage.
3. Connecting the boiler outlet to the set's inlet spigot - in case of diameter mismatch (e.g. a Ø150 mm boiler outlet), the appropriate reducer must be used (see the separate product "flue reducer Ø150/130 mm").
4. Securing all joints against mechanical stress and checking tightness after assembly (visual inspection of sealing rings, or a pressure test according to the manufacturer's instructions).
5. Recording the installation in the chimney/flue gas path inspection log, as required by applicable legislation (in Slovakia, in particular the regulation on chimney sweeping work and STN 73 4201).

Before putting the boiler into operation, an inspection by an authorized chimney sweep is required to confirm the satisfactory condition of the flue gas path, including the newly installed connection set.

Compatibility

The S2 set is part of the complete Ø130 mm flue component range from Vaillant, which also includes straight extensions (1.0 m and 2.0 m), elbows at angles of 87°, 45°, 30° and 15°, an inspection T-piece with a control/cleaning opening, spacer brackets for fastening the pipe in the shaft, and extension sets for cascade connections (e.g. S3). All these components are mutually compatible thanks to the uniform Ø130 mm diameter and the same push-fit joint system, allowing a complete flue gas path to be assembled exactly according to the layout of a specific boiler room. The set is intended for Vaillant ecoCRAFT condensing boilers, which are commonly installed in larger buildings and in cascade systems with output exceeding the capabilities of standard wall-mounted boilers.

Maintenance and inspection

A polypropylene flue system is generally maintenance-free as far as the pipe material itself is concerned - it does not corrode and is resistant to condensate. Nevertheless, regular inspection is required for:

• the tightness of joints, especially after the first heating season and subsequently during regular chimney sweep inspections,
• the flow and drainage of condensate (especially in places with insufficient slope),
• the mechanical fastening of the pipe in the shaft (spacer brackets, anchoring elements),
• the condition of the sealing rings in the socket joints - in case of signs of wear, we recommend replacement with original Vaillant spare parts.

The recommended inspection frequency corresponds to applicable legislation on regular inspection of flue gas paths (usually at least once a year for gas appliances; the specific interval is determined by the chimney sweep based on the type of fuel and the output of the appliance).

Why choose an original Vaillant component

Using an original Vaillant connection set instead of a universal alternative flue offers several important advantages. Above all, it is a system that has been directly tested and certified by the boiler manufacturer in combination with the specific type of appliance - this means guaranteed compliance in terms of tightness, pressure resistance and the temperature class needed for trouble-free and safe operation of the condensing boiler. Using non-original or incompatible parts poses a risk of leaks, improper condensate drainage, as well as problems with the manufacturer honoring the warranty on the boiler itself. An original component also guarantees precise dimensional compatibility with the other components of the Ø130 mm range, so installation can be carried out without the need for additional on-site adjustments.

Frequently Asked Questions

Operation under positive pressure - what this means for the user

Vaillant ecoCRAFT condensing boilers operate with forced (fan-assisted) flue gas discharge, which means that a slight positive pressure is created inside the flue compared to the surrounding environment - unlike older atmospheric boilers, where flue gases leave through the chimney's natural draught. This difference has a fundamental impact on the requirements placed on the material and construction of the flue gas path: the flue must be perfectly gas-tight along its entire length, because any leak during positive pressure operation could lead to flue gases penetrating into the shaft space or adjacent structures, not just to draught losses, as would be the case with negative pressure systems. This is why all components of the Ø130 mm range - including the S2 connection set - are made of polypropylene with precisely defined sealing elements at every joint, tested by the manufacturer for tightness under the operating pressure corresponding to the boiler's real operating conditions.

This type of operation also allows the flue gas path to be routed horizontally or at an angle over longer distances, or through several changes of direction (using 87°, 45°, 30° or 15° elbows from this accessory range), without loss of flue gas discharge function - which would not be possible with a classic naturally draught chimney without significantly oversizing the cross-section. This flexibility is one of the reasons why Ø130 mm flue systems are commonly used even in more complex boiler room layouts, including cascade connections of multiple boilers to shared or individual shafts.

Cascade installations and the role of the S2 set in the overall concept

In larger boiler rooms, industrial facilities, apartment buildings or commercial premises, several smaller Vaillant condensing boilers connected in a cascade are often installed instead of one large boiler. Such a solution offers advantages in terms of better output regulation according to current needs, backup in case of failure of one boiler, and more efficient operation under partial load. Each boiler in the cascade needs its own connection to the shared collector flue or an individual shaft - and this is where the S1/S2/S3 set system comes into play: basic sets (S1, S2) are used to connect the first boiler (differing according to the type of ducting - freely routed system vs. installation into a shaft), while extension sets such as S3 are used to connect additional boilers (3rd and 4th) in the cascade with a reducer from their smaller outlet diameter (Ø80 mm) to the common Ø130 mm diameter. For larger cascades (3 or more boilers), the manufacturer recommends also adding non-return flaps, which prevent the backflow of flue gases between individual boilers when some of them are not in operation.

The S2 set can thus represent the entry point of the entire cascade system, to which additional boilers are subsequently connected using extension sets, while the shared route to the shaft or chimney is supplemented with the required number of straight extensions and elbows according to the actual layout of the boiler room.

Standards and legislative requirements in Slovakia

The installation of flue gas paths for condensing boilers in Slovakia is subject to several technical standards and legislative regulations, in particular STN 73 4201 (Chimneys and flues - Design, construction and connection of fuel-burning appliances) and related European standards of the STN EN 1856 series (Chimneys - Requirements for metal/plastic chimneys) and STN EN 14471 (Chimney systems with plastic flue liners). In addition, a regulation governing the activity of chimney sweeps and the obligation for regular inspection and cleaning of flue gas paths applies. When installing Vaillant flue accessories, it is therefore necessary to observe not only the manufacturer's technical recommendations but also compliance with the above standards, which in practice is ensured through cooperation with a professionally qualified installation company and subsequent inspection by an authorized chimney sweep before commissioning the boiler.

Storage and handling before installation

Polypropylene components should be stored in a dry environment before installation, protected from direct sunlight and mechanical damage that could compromise the sealing surfaces of the push-fit joints. During transport and handling, we recommend avoiding impacts to edges and sealing elements to prevent deformation that could affect the resulting tightness of the assembled system. In case of longer storage before installation, it is advisable to keep the components in their original packaging.

Summary

The Vaillant S2 Ø130 mm connection set represents a reliable, standard-compliant solution for connecting an ecoCRAFT condensing boiler to an existing chimney shaft. Thanks to its compatibility with the entire Ø130 mm flue accessory range, it allows easy expansion or modification of the flue gas path in the future, for example when transitioning to a cascade connection of multiple boilers. We recommend combining it with original additional components from the same range and entrusting installation and subsequent regular inspection to a professionally qualified person.