Vaillant Extension Set for 2 Boilers Back to Back, Ø 200 mm

Product detailed description

Extension kit for 2 back-to-back boilers, Ø 200 mm – expanding the cascade to four boilers

Where the basic back-to-back kit (order no. 0020106430) established a cascade of the first two boilers on two opposite walls, this extension kit allows two additional boilers to be added to the setup – again one on each of the original opposite walls – thereby expanding the cascade to a total of four high-output condensing boilers (typically from the Vaillant ecoTEC plus VC 806-1206/5-5 range) sharing a single common flue exhaust.

The exact composition of the kit is known from the manufacturer's technical documentation: it includes two 0.5-metre extensions with a diameter of 110 mm, two 87° elbows with an inspection opening (110 mm diameter), one 45° elbow (110 mm diameter), and a collector piece with a diameter of 200 mm, which has two angled inlets for connecting the Ø 110 mm connections from the individual boilers into the common Ø 200 mm collector pipe.

Flue exhaust systems for Vaillant cascade boiler rooms

When a single condensing boiler cannot cover the heating demand of a building – an apartment building, hotel, industrial hall, office building, or larger technological boiler room – the solution is usually not one large boiler, but a cascade of several smaller or medium-output Vaillant condensing boilers connected in parallel. The advantage of a cascade solution is higher operational reliability (the failure of one boiler does not mean the failure of heating for the entire building), better output regulation according to current demand (the number of running boilers and the output of each can be modulated), and easier future expandability of the boiler room with an additional boiler if heat demand increases.

Each boiler in the cascade has its own flue exhaust and combustion air intake socket, but for practical, economic, and structural reasons, the flue gases from all boilers are usually led out through a single common flue collector (manifold) into one chimney or through one roof/facade duct. This is exactly the purpose of the range of components described below – these are parts of a separate (not concentric) flue exhaust system with a diameter of 160 mm or 200 mm, which connects to the sockets of the individual boilers and joins them into one common pipe.

The system is modular – it consists of basic connection kits (for the first two boilers of the cascade, including the fitting needed to drain condensate), extension kits (for each additional boiler added to the cascade), individual elbows of various angles for bypassing obstacles and changing the direction of the route, extensions of various lengths for bridging the distance between boilers and the riser, and finally a kit for connecting the whole assembly to a masonry chimney shaft.

How the kit connects to the existing cascade

The kit connects to the existing collector piece created by the previous (basic or extension) kit in sequence – meaning the third and fourth boilers of the back-to-back cascade are connected by this kit to the collector piece of the basic kit for the first two boilers. Thanks to the built-in inspection openings on the 87° elbows, the ability to inspect and clean the route near the new connection points remains available even after expansion, without the need to dismantle older, already run-in sections of pipe.

Similarly to the in-line variant, this extension kit also does not include its own condensate separator – that remains part of the original basic kit and handles condensate drainage for the entire common pipe as a whole.

Material and construction – why polypropylene (PP)

All parts in this range are made of polypropylene (PP) – a plastic used in condensing boiler exhaust systems precisely because it perfectly withstands the chemically aggressive condensate that naturally forms during the operation of condensing technology. A condensing boiler, unlike a classic (non-condensing) boiler, also uses the latent heat contained in the water vapour of the flue gases – this cools below the dew point in the flue gas heat exchanger and condenses, and the resulting condensate is mildly acidic (pH approximately 3–5, depending on the fuel type and operating conditions). Metal (e.g. stainless steel) flue pipes can also withstand this load, but plastic PP systems are lighter to handle, faster to install thanks to joints with sealing rings without the need for welding or special tools, and, for comparable quality, are usually also more cost-effective.

The operating temperature of flue gases in condensing boilers is relatively low (typically up to approximately 80–120 °C depending on the operating mode and boiler output) – which is precisely why using plastic PP piping instead of a classic metal flue (common, for example, with older atmospheric or low-temperature boilers) is not only possible but also more suitable in terms of resistance to condensate. The system is certified and dimensioned by the manufacturer specifically for cooperation with Vaillant condensing boilers of the corresponding output range and socket type designation.

The joints between individual parts are made using a socket connection with a rubber sealing ring – this design allows for simple, tight, yet detachable installation without gluing or welding, which greatly simplifies any future modifications to the route, replacement of a damaged part, or expansion of the cascade with an additional boiler.

Practical example

An industrial building with a boiler room originally designed for two back-to-back boilers (on two opposite walls of the technical room) undergoes an expansion of the production hall, increasing heat demand as well. Instead of building a second, separate boiler room, two additional boilers are added to the original two boilers on the same two walls and connected using this extension kit to the existing collector piece – the result is a compact cascade of four high-output boilers sharing a single common flue exhaust through the original chimney.

Planning the expansion of a back-to-back cascade

Since this extension kit handles the connection of two additional boilers at once (one on each of the opposite walls), it is advisable to already consider, when designing the original two-boiler cascade, whether an expansion to four boilers is planned for the future – and to dimension the technical room space, service access routes, and the capacity of the common chimney or roof outlet accordingly.

Ordering: When ordering, we recommend indicating which basic kit (order no. 0020106430) is already installed in the boiler room, so that we can confirm full compatibility of the subsequent connection of the two additional boilers.

Installation

The installation of a flue exhaust system for gas appliances (including cascade boiler rooms) in Slovakia is subject to the requirements of the standards STN EN 1443 (Chimneys), STN 73 4201 (Chimneys and flues), and related gas industry technical rules (TPP), and must be carried out by an authorised and professionally qualified person – an authorised service technician or installation company with the appropriate authorisation to install gas appliances and their exhaust systems. Commissioning the boiler room also includes an inspection of the chimney/flue carried out by a chimney sweep company and the issuance of the relevant inspection report.

When designing the route of a cascade flue, it is particularly necessary to take into account: the total rated heat output of all boilers in the cascade (this determines the required diameter of the common pipe – 160 mm or 200 mm), the maximum permissible length of the route and the number of elbows (the manufacturer states equivalent lengths for individual fittings), the slope of horizontal sections back towards the boiler or condensate separator (generally at least 3°, so that condensate can flow away by gravity and not remain standing in the pipe), sufficient securing of the pipe with spacer holders at regular intervals (typically every 1–1.5 m) to prevent sagging or excessive stress on the socket joints, and maintaining access to inspection openings and inspection elbows for regular cleaning and inspection of clearance.

When cascading several boilers into one common pipe, it is also necessary to respect the order and direction of connection of the individual branches according to the manufacturer's installation instructions (including the recommended use of check valves in cascades with three or more boilers, to prevent backflow of flue gases from running boilers into a shut-down unit when one boiler is taken out of operation), and to maintain the prescribed minimum rise and direction towards the common chimney or facade/roof outlet.

Care of the connection after expansion

After expanding the cascade with an additional pair of boilers using this kit, it is advisable to check, at the next service inspection, the tightness of both new connections (on each of the opposite walls) as well as the functionality of the inspection openings on the supplied 87° elbows, which facilitate future inspection of precisely this, newly added section of the route.

Service, cleaning, and service life

Regular inspection and cleaning of the exhaust system is part of the standard annual service inspection of a condensing boiler room. Thanks to the inspection openings and inspection elbows in the assembly, individual sections of pipe can be checked and, if necessary, cleaned (e.g. of any deposits) without the need to fully dismantle the entire route. The condensate separator, if part of the assembly, needs to be regularly checked and, if necessary, emptied/flushed to prevent it from clogging and causing condensate to back up into the pipe.

The service life of a quality PP exhaust system from the manufacturer directly compatible with the given boiler range is, with proper installation and regular servicing, comparable to the service life of the boiler itself – i.e. roughly 15 years or more of operation. When replacing or adding individual parts in the future (for example, when expanding the cascade with an additional boiler), it is advisable to use original components of the same manufacturer and diameter, in order to maintain full compatibility of the joints as well as the validity of the warranty for the entire exhaust system.

Frequently asked questions

Why buy this Vaillant accessory at ATRIA.SK

If you are planning to expand an existing back-to-back boiler cascade with an additional pair of units, this extension kit contains a precisely defined, manufacturer-verified combination of parts needed for a trouble-free connection to your existing common flue collector.

When purchasing any part of the exhaust system, we will be happy to help you choose the correct combination of components for your specific boiler room – just contact us with details about the type and number of boilers, or with the project documentation. We usually dispatch goods within 24–48 hours of ordering; for larger assemblies, we will inform you in advance about the delivery date if necessary.