Vaillant Basic set for 2 boilers back to back with condensate separator, Ø 200 mm

Product detailed description

Basic set for a cascade of 2 boilers back-to-back, Ø 200 mm – solution for boiler rooms with two opposite walls

Not every boiler room has one sufficiently long wall available for placing multiple boilers side by side (the "in-line" configuration). Where the layout offers two shorter, opposite walls instead, the cascade boilers are placed in a "back-to-back" configuration – i.e. one (or more) on each of the two opposite walls, with their common collecting pipe passing through the space between them (usually through the centre of the room or a shaft) into a single common riser.

This basic set solves exactly this connection of the first two boilers – one on each of the opposite walls – into a common collecting pipe with a diameter of 200 mm, including a condensate separator that captures the acidic condensate generated in the joined pipe of both boilers before it enters the further route.

Flue systems for Vaillant cascade boiler rooms

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

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

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

How the "back-to-back" configuration differs from the "in-line" connection

The geometry of this set is designed specifically for a situation where the outlet nozzles of two boilers are oriented facing each other (not side by side, as in the "in-line" connection) – the collecting and connecting fittings therefore have a different shape and connection angles than their counterpart for the in-line configuration (part no. 0020106428). For this reason, the two basic sets are not mutually interchangeable, and the choice between them must be made already at the boiler room design stage, according to the actual layout of the boilers in the space.

As with the "in-line" variant, the basic set here is a closed functional unit for exactly two boilers – when expanding the cascade with additional back-to-back boilers, it is supplemented with an expansion set (part no. 0020106431), designed specifically for adding another two boilers in this configuration.

Material and construction – why polypropylene (PP)

All parts in this range are made of polypropylene (PP) – a plastic used in condensing boiler flue systems precisely because it perfectly resists the chemically aggressive condensate that naturally forms during the operation of condensing technology. Compared to a classic (non-condensing) boiler, a condensing boiler also utilises the latent heat contained in the water vapour of the flue gases – this is cooled 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) flues can also withstand this load, but plastic PP systems are easier to handle, faster to install thanks to joints with sealing rings without the need for welding or special tools, and, at comparable quality, are usually also more cost-effective.

The operating temperature of flue gases in condensing boilers is relatively low (roughly up to approx. 80–120 °C depending on the operating mode and boiler output) – this is precisely why the use of plastic PP piping instead of a classic metal flue (common, for example, in 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 directly for cooperation with Vaillant condensing boilers of the corresponding output range and outlet type designation.

The joints of the individual parts are made by socket insertion with a rubber sealing ring (the so-called socket joint) – this design allows simple, tight and yet demountable installation without gluing or welding, which greatly simplifies any future route modifications, replacement of a damaged part, or expansion of the cascade with an additional boiler.

Practical example

In a technical room with two shorter opposite walls (instead of one long one), two Vaillant ecoTEC plus VC 806-1206/5-5 condensing boilers are placed on each of these walls, facing each other. Their common collecting pipe with the back-to-back basic set passes through the centre of the room (or a technical shaft) and connects both boilers together with the condensate separator into a single flue leading towards the chimney. This solution allows efficient use of even a less standard boiler room floor plan, where an "in-line" connection would not be spatially possible.

Comparison with the in-line configuration and further steps when expanding

Alongside this set for the "back-to-back" configuration, Vaillant also offers an analogous basic set for the "in-line" connection (part no. 0020106428) – intended for boiler rooms where boilers can be placed side by side on one sufficiently long wall. The configuration decision must be made already at the boiler room design stage, since the two basic sets have different geometries of the collecting fittings and are not interchangeable without replacing the entire set.

Ordering: When ordering, we recommend having available a floor plan of the boiler room with the marked boiler locations, so that we can confirm that the "back-to-back" configuration matches your layout, and plan the necessary number of subsequent expansion sets (part no. 0020106431) for any future expansion.

Installation and assembly

The installation of a flue gas discharge system for gas appliances (including cascade boiler rooms) in Slovakia is subject to the requirements of the standard 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 competent person – an authorised service technician or an installation company with the appropriate authorisation to install gas appliances and their flue systems. Commissioning of the boiler room also includes an inspection of the chimney/flue carried out by a chimney sweep company and the issuing of the relevant inspection report.

When designing the route of a cascade flue, the following must be taken into account in particular: the total rated heat output of all boilers in the cascade (this determines the required diameter of the collecting pipe – 160 mm or 200 mm), the maximum permissible route length and number of elbows (the manufacturer states equivalent lengths for individual fittings), the slope of horizontal sections back towards the boiler or the condensate separator (generally at least 3° so that condensate can drain by gravity and does not remain standing in the pipe), sufficient securing of the pipe with spacer holders at regular intervals (typically every 1–1.5 m) so that no sagging or excessive stress occurs on the socket joints, and maintaining access to inspection openings and inspection elbows for regular cleaning and inspection of patency.

When cascading several boilers into one collecting pipe, it is also essential to respect the order and direction of feeding the individual branches according to the manufacturer's installation instructions (including the recommended use of non-return flaps in cascades with three or more boilers, so that when one boiler is shut down, flue gases from the running boilers do not flow back into the shut-down unit) and to observe the prescribed minimum elevation and direction towards the common chimney or facade/roof outlet.

Care of the condensate separator in the set

As with the in-line connection variant, this set also includes a condensate separator that requires regular checking of the patency and functionality of the discharge into the sewer system. In the back-to-back configuration, it is advisable to choose an easily accessible location for the separator during installation (for example, in the middle of the connecting route between the two walls), so that its future inspection and maintenance is as easy as possible.

Service, cleaning and service life

Regular inspection and cleaning of the flue 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 the pipe can be checked and, if necessary, cleaned (e.g. of any deposits) without having to completely dismantle the entire route. The condensate separator, if part of the assembly, must be regularly checked and, if necessary, emptied/flushed to prevent it from clogging and condensate backing up into the pipe.

The service life of a quality PP flue system from the manufacturer, directly compatible with the given boiler range, is with correct installation and regular servicing comparable to the service life of the boiler itself – i.e. roughly 15 or more years 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, so that full joint compatibility and the validity of the warranty on the entire flue system are maintained.

Frequently asked questions

Why buy this Vaillant accessory at ATRIA.SK

If your boiler room layout offers two opposite walls rather than one long wall, this back-to-back basic set is the right choice for setting up a cascade of high-output Vaillant boilers – consult us already at the design stage so you choose the right configuration the first time.

When purchasing any part of the flue system, we are happy to advise you on choosing the right 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 of the delivery date if necessary.