Vaillant flue reducer Ø150/130 mm - connection of ecoCRAFT boiler to S1/S2 set (up to 160 kW)

Product detailed description

Vaillant flue reduction Ø150/130 mm - connecting the ecoCRAFT boiler to the S1/S2 kit (up to 160 kW)

This plastic reducer insert is an original Vaillant connecting component used to narrow the flue gas outlet of an ecoCRAFT series condensing boiler from a diameter of Ø150 mm to Ø130 mm, the diameter used throughout the range of flue accessories (extensions, elbows, inspection T-piece, connection kits S1/S2/S3). It is intended exclusively for boilers whose nominal heat output does not exceed 160 kW - at higher outputs the manufacturer specifies a different flue gas path diameter, since the pipe cross-section must correspond to the volume of exhaust gases and their flow velocity so that both functionality and safety of the exhaust are maintained.

Why the reduction piece is needed

Larger Vaillant ecoCRAFT condensing boilers come from the factory with a flue outlet neck of Ø150 mm, corresponding to their higher heat output and larger volume of exhaust gases at full load. However, most standard flue accessories in this range (extensions, elbows, T-pieces, connection kits S1/S2/S3) are designed for a diameter of Ø130 mm, which is the common standard for most apartment buildings, commercial premises and smaller industrial boiler rooms. Without this reduction piece, it would not be possible to connect a boiler with a Ø150 mm outlet to a flue gas path built from Ø130 mm components - the reduction piece therefore represents a key connecting element between the boiler and the rest of the flue system.

It is important to emphasize that this particular reduction piece is intended only for boilers up to 160 kW output - with this condition, the manufacturer ensures that even after narrowing the diameter, the flue gas flow velocity and pressure conditions in the system remain within the safe limits defined for the given combination of boiler output and flue diameter. For boilers with higher output, the flue gas discharge must be solved differently (e.g. by keeping a larger diameter throughout the entire route or by using a different reduction/connection kit intended for a higher output range), which is why the actual output of the installed boiler should always be verified before ordering.

Technical characteristics

• Inlet diameter (boiler side): Ø150 mm
• Outlet diameter (flue side): Ø130 mm
• Material: plastic (polypropylene), resistant to condensate and to the temperatures of flue gases from condensing operation
• Maximum output of connected boiler: up to 160 kW
• Type of operation: pressurized (type C), suitable for forced flue gas extraction by the boiler's fan
• Purpose: connecting the ecoCRAFT boiler to the S1 or S2 kit (and subsequent Ø130 mm flue accessories)
• Type of joint: plug-in (socket type), with rubber seal
• Manufacturer: Vaillant Group
• Warranty: 2 years

Where exactly the reduction piece is used in the system

The reduction piece is fitted directly onto the boiler's outlet neck as the first component of the flue gas path, before the S1 or S2 connection kit. Only after the reduction piece does the rest of the route continue with standard Ø130 mm components - straight extensions (1.0 m or 2.0 m), elbows (87°, 45°, 30°, 15°) as needed to change direction, or an inspection T-piece where access for cleaning and condensate drainage is required. Without this reduction piece, the S1/S2 connection kit (dimensioned for Ø130 mm) could not be connected directly to the boiler outlet with a Ø150 mm neck.

Installation

Installation of the reduction piece, like the entire flue system, should be carried out by a professionally qualified person - a Vaillant service technician or a heating company with the appropriate authorization. During installation, attention must be paid to:

1. Correct fitting of the reduction piece onto the boiler's outlet neck, including checking the sealing ring (O-ring) to prevent flue gas leakage.
2. Ensuring the mechanical stability of the joint, since the reduction piece is followed by another component (connection kit or elbow), whose weight and any vibrations must be transferred through this joint without risk of loosening.
3. Checking the direction of the plug-in joint - parts of flue systems generally have a defined insertion direction (in the direction of condensate flow), which must also be respected for the reduction piece.
4. Visual and, if possible, pressure inspection of tightness after completing the installation of the entire flue gas path.

Compatibility

The reduction piece is designed specifically for Vaillant ecoCRAFT series condensing boilers with a Ø150 mm outlet neck and an output of up to 160 kW, in combination with the S1 or S2 kits and the subsequent Ø130 mm range of accessories (extensions, elbows, inspection T-piece, spacer holders, expansion kits for cascades such as S3). It is not intended for boilers with higher output or for boilers from other manufacturers without an individual assessment of the outlet neck dimension compatibility.

Why choose the original Vaillant component

Reduction pieces from the boiler manufacturer are designed and tested directly in combination with the specific range of appliances, eliminating the risk of leaks or incorrect flue gas flow that could occur when using a universal reduction piece not specifically intended for the given boiler type. The original component also ensures material compatibility (resistance to temperature and condensate) with the other elements of the flue gas path, which is particularly important for long-term durability and operational safety.

Safety, standards and inspections

Installation of the reduction piece and the entire flue gas path must comply with applicable standards (in particular STN 73 4201, STN EN 1856 and related standards for plastic chimney systems) and must be carried out by a professionally qualified person. Before commissioning the boiler, an inspection by an authorized chimney sweep is required, confirming the correctness and tightness of the entire flue gas path including the newly installed reduction piece. Regular inspections then take place at intervals set by legislation and manufacturer recommendations, usually at least once a year for gas appliances.

Why verify the boiler output before ordering

Since this reduction piece is limited by the manufacturer to boilers up to 160 kW output, we strongly recommend verifying the actual nominal heat output of the installed or planned ecoCRAFT boiler before ordering (the information is stated in the boiler's technical documentation, on the rating plate, or can be confirmed by a designer or service technician). Using the reduction piece with a boiler of higher output could lead to an insufficient cross-section of the flue gas path, increased flow resistance, and in the worst case incorrect functioning of the flue gas discharge, which is a safety risk that can easily be avoided by properly verifying the output.

Frequently asked questions

Pressurized operation and its impact on the choice of reduction piece

Like other components of this range of flue accessories, this reduction piece must reliably function under the pressurized operation typical of condensing boilers with forced flue gas extraction. This means that the joint between the boiler, the reduction piece and the subsequent connection kit must be perfectly gas-tight across the entire range of operating pressures and temperatures generated by the ecoCRAFT boiler at the given output. This is precisely why the manufacturer sets an exact output limit (160 kW), up to which this specific combination of diameters (Ø150/130 mm) is verified as safe and functional - above this limit, the flow velocity of flue gases in the narrowed Ø130 mm cross-section could exceed the values for which the system is designed, which could negatively affect both the functioning of condensate drainage and the overall lifespan of the components.

Storage and handling

Before installation, we recommend storing the plastic reduction piece in a dry environment away from direct sunlight, which could over the long term affect the properties of the plastic. During handling, take care to protect the sealing surfaces from mechanical damage, which could reduce the resulting tightness of the joint after assembly.

Vaillant ecoCRAFT boilers - what this range of appliances is

The ecoCRAFT range represents larger stationary (floor-standing) Vaillant condensing boilers intended primarily for commercial, industrial and larger residential buildings, where a higher heating output is required than that offered by common wall-mounted condensing boilers for family houses. These boilers are commonly installed either individually or in a cascade arrangement of several units, achieving high total output while maintaining good controllability and a backup in case one of the boilers fails. It is precisely for this type of application that the flue gas path must be adapted to the specific layout of the boiler room - from a simple connection to an existing shaft, through freely routed paths with multiple direction changes, to more complex cascade manifolds with a shared chimney structure. The Ø150/130 mm reduction piece is one of the basic building blocks that enable this flexibility - thanks to it, the installer can use the same range of Ø130 mm accessories regardless of whether the connected boiler is equipped with a larger or smaller outlet neck.

Difference between negative-pressure and pressurized operation from the perspective of choosing a reduction piece

Historically, flue gas paths were built primarily as negative-pressure systems (traditional masonry chimneys with natural draft), where a slight leak in a joint did not pose such a significant risk of flue gas escaping into the surroundings, since the pressure inside the chimney was lower than the surrounding atmospheric pressure. Modern condensing boilers, including the ecoCRAFT range, however operate in a pressurized mode - flue gases are pushed through the entire length of the flue gas path by the boiler's fan, meaning that the pressure inside the pipe is higher than the surrounding pressure. This change places much higher demands on the tightness of every single joint in the system, including reduction pieces - which is why this Ø150/130 mm reduction piece is designed with a precisely defined sealing ring and tested by the manufacturer directly in combination with the given boiler platform, to guarantee tightness at the actual operating pressures generated by the ecoCRAFT boiler's fan.

How the reduction piece affects flue gas flow velocity

Narrowing the pipe diameter from Ø150 mm to Ø130 mm inevitably increases the flow velocity of flue gases at and beyond the point of reduction, since the same volume of flue gas must pass through a smaller cross-section. This increased velocity has a direct impact on the pressure loss throughout the subsequent route and on the behavior of the condensate (faster flow can better carry condensate towards the drainage point, but at the same time places higher demands on the tightness and mechanical resistance of the joints). This is precisely why the manufacturer sets an exact output limit of 160 kW, up to which this combination of diameters is verified as safe - it is an engineering-verified compromise between the practicality of unifying the accessory range to a Ø130 mm diameter and the physical limits of flue gas flow at the given boiler output.

Further maintenance after installation

Although the plastic component itself is practically maintenance-free (it does not abrade, does not corrode, and is resistant to condensate), we recommend checking the condition of the sealing ring at the reduction piece during regular inspections of the flue gas path (carried out by an authorized chimney sweep), since this is one of the most stressed joints in the system (different diameters, slightly different thermal expansion of materials). At any signs of seal wear, we recommend immediate replacement with an original Vaillant spare part to prevent the risk of flue gas leakage.

Additional questions

Summary

The Ø150/130 mm reduction piece is an irreplaceable connecting link between the Vaillant ecoCRAFT condensing boiler (Ø150 mm outlet) and the rest of the Ø130 mm flue system (S1/S2 connection kits, extensions, elbows, T-piece and other accessories). Its use is clearly limited to boilers up to 160 kW output - therefore, always verify the actual output of your boiler before ordering. Entrust the installation to a professionally qualified person, and after completion have the flue gas path inspected by an authorized chimney sweep.