ATTACK KT vertical/horizontal splitter diameter 60/100 - diameter 80/80, AL/PP

Product detailed description

ATTACK KT vertical/horizontal splitter diameter 60/100 - diameter 80/80, AL/PP is part of the original flue gas extraction and combustion air intake system ATTACK KT / KT PLUS, designed for ATTACK Condensing wall-mounted condensing gas boilers. This part belongs to the category: splitter – universal (vertical and horizontal), diameter 60/100 mm → 80/80 mm, made of aluminium (AL) on the exhaust branch, polypropylene (PP) on the intake branch.

Closed combustion chamber and flue gas extraction in ATTACK condensing boilers

ATTACK condensing gas boilers operate with a closed (turbo) combustion chamber – unlike older atmospheric boilers, they do not require air from the room in which they are installed, nor a functional masonry chimney. They draw combustion air directly from outside the building and discharge flue gases outside also by forced draught provided by a fan built into the boiler. This closed circuit is solved in practice in two ways: by coaxial (concentric) piping, where a smaller pipe for air intake runs inside a larger pipe and the annular space serves for flue gas discharge, or by a separate system with two independent pipes. The coaxial design with a diameter of 60/100 mm is the most common solution for boilers up to approximately 35 kW, as it allows both the extraction and the intake to be routed through a single opening in the wall or roof, is quick to install and aesthetically unobtrusive.

Every element of the extraction assembly – elbow, extension, condensate trap, chimney terminal and splitter – must be tight, resistant to flue gas temperatures as well as to the condensate that forms in large quantities during operation of a condensing boiler, precisely because the boiler is able to utilise the latent heat of the water vapour contained in the flue gases. It is precisely this condensate that is the reason why the ATTACK KT system cannot be replaced without risk by a common chimney component intended for atmospheric boilers – such components are not designed for permanent contact with acidic condensate or for the correct slope that returns condensate back to the boiler or to the condensate trap.

Since this part connects both systems, it is subject at the same time to the rules of coaxial routing (on the side of the connection to the boiler) and of the separate Ø80/Ø80 system (on the side of the continuing branches) – see also the explanation below in the section on the separate system.

At higher outputs or with more complex extraction routes (longer runs, more changes of direction, a shared flue for several boilers), the 60/100 mm coaxial pipe can no longer be used efficiently – the flow resistance would be too high and the boiler output would be limited. For these cases, a separate (twin-pipe) system with a diameter of 80 mm is used instead, where air intake and flue gas discharge are routed through two independent pipes, which can even follow different routes (for example, flue gas discharge above the roof and air intake through a side wall). This system is referred to in technical terminology as Ø80/Ø80 or C83/C93 depending on the method of termination and is common in boiler cascades, in higher-output boilers, or where a greater distance to the façade or roof needs to be covered.

The 80 mm diameter parts of the ATTACK KT separate system are made of polypropylene (PP) – a material that is long-term resistant to the acidic condensate arising from flue gas condensation, has a low weight and a low coefficient of friction, which reduces pressure losses over longer runs. As these are separate pipes, both (exhaust and intake) must be routed with the same slope and the same logic as the coaxial pipe – flue gases must not accumulate in horizontal sections and condensate must always drain by gravity back towards the boiler or into the condensate trap.

Splitter – transition from coaxial to separate system

The splitter is a component that divides a single 60/100 mm coaxial pipe coming from the boiler into two independent 80 mm diameter pipes – one for flue gas discharge and the other for combustion air intake. It is used wherever a longer route needs to be covered than the coaxial pipe alone allows, or where the intake and exhaust need to be routed along different paths (for example, exhaust above the roof and intake through the side wall of the plant room).

The "vertical/horizontal" (universal) design can be installed in either position according to the needs of the specific installation, while the "vertical" design is intended exclusively for vertical installation directly behind the boiler, from which two independent vertical (or subsequently deflected) branches continue. The aluminium/aluminium material combination is used where the intake branch is also routed through metal piping (for example due to a requirement for greater mechanical resistance of the route), while the aluminium/PP combination is more common – the exhaust (flue gas) branch remains aluminium and the intake branch switches to lighter polypropylene.

Example of a typical connection in a real installation:
boiler → flange → splitter 60/100 → 80/80 → separate flue gas branch (Ø80) above the roof + separate intake branch (Ø80) through the side wall.

Step-by-step installation procedure

1. Fit the splitter directly behind the boiler outlet (or behind the flange), and check the correct orientation according to the design (vertical/horizontal, or vertical only for the PLUS vertical type).
2. Plan the routes of both branches (exhaust and intake) so that each individually complies with the maximum length specified in the boiler manual.
3. Connect further components (pipes, elbows, chimney terminal) to the exhaust branch, maintaining a minimum slope of 3° towards the boiler.
4. Connect the intake branch, and check that its termination is not in close proximity to the exhaust termination (risk of flue gas re-intake).
5. After connecting both branches, check the tightness of all joints on the splitter and the connected components.

Material and construction

The splitter combines two materials according to the demands placed on the individual branches: the exhaust (flue gas) branch remains aluminium, as it is in direct contact with hot flue gases and must withstand higher temperatures at boiler start-up, while the intake branch switches to lighter polypropylene, which is sufficient for conveying cold combustion air and reduces both the overall weight and the price of the component.

System classification: transition from coaxial to separate system (splitter). Design: vertical and horizontal.

Compatibility with ATTACK boilers

Part PR51 is intended for the connection system common to the entire range of ATTACK wall-mounted condensing boilers ACKT20, ACKT28 and ACKT48 (Condensing KT range), ATTACK KST24 (Condensing KST) and ATTACK KZT25 (Condensing KZT). Before ordering, we recommend checking in the installation manual for the specific boiler model the exact type of connection socket and the maximum permitted length of the extraction route, as this may vary slightly depending on the boiler output (20, 28 or 48 kW for the KT range).

Installation and warnings

The splitter is installed directly behind the boiler outlet (or behind the flange), and the route design should already take into account that from this point onward, two independent branches continue, each with its own length limits according to the boiler manual. For horizontal installation of the universal design, the permitted orientation should be checked in the manufacturer's manual so as not to impair condensate drainage from the exhaust branch.

In general, horizontal sections of the extraction route must have a slope of at least 3° towards the boiler or towards the nearest condensate trap, so that condensate does not accumulate in the piping. Installation should be carried out by a person professionally qualified to install gas appliances and their extraction systems, in accordance with the installation manual for the specific boiler and with standard STN EN 15287.

Standards and safety requirements

Installation of flue gas extraction for condensing boilers in Slovakia is governed primarily by standard STN EN 15287 (Chimneys – Design, installation and commissioning of chimneys – Part 1: Chimneys for fan assisted appliances), which sets minimum distances of the terminal from windows, ventilation openings, neighbouring plots and ground level, as well as the minimum height of the terminal above the roof plane. The boiler itself and its extraction system must also meet the requirements of STN EN 483 (type C gas boilers) and be installed in accordance with the technical operating regulations applicable to gas appliances.

Installation may only be carried out by a person professionally qualified to install and service gas appliances, who, upon completion, issues an inspection report or commissioning protocol. In the event of any change to the route compared to the original approved design (e.g. additional extension of the route, change in the number of elbows), it is necessary to check whether the boiler is still within the parameters permitted by the manufacturer – otherwise there is a risk not only of boiler malfunction, but also of loss of warranty and, in extreme cases, a safety risk of flue gas leakage.

Maintenance and service inspection

During a service inspection of the splitter, the tightness of both outlet joints is checked, as well as whether unwanted condensation forms at the point of division outside the intended drainage path – especially at the transition from the metal to the plastic branch, where the materials may have different thermal expansion.

The recommended inspection interval for the entire extraction route is once a year, usually as part of the regular boiler service inspection carried out by an authorised service technician. On this occasion, this specific part is also checked, along with the patency of the condensate path and the overall condition of the joints along the entire route from the boiler to the outdoor termination.

Typical usage scenarios

Scenario 1 – long route exceeding the coaxial pipe limit: the distance from the boiler to the façade or roof exceeds the maximum permitted length for 60/100 mm piping, so the splitter converts the route to a separate Ø80/Ø80 system with lower pressure losses directly behind the boiler.

Scenario 2 – intake and exhaust need to be routed in different directions: the building layout requires the flue gases to be discharged above the roof, while combustion air is drawn in through a side wall of the plant room – the splitter allows both branches to be routed completely independently.

Related parts in the ATTACK KT range

The universal splitter with a mixed material (AL/PP) is complemented in the range by the vertical PLUS design PR51A (same material mix, vertical installation only) and the all-aluminium universal design PR51B. The PR51 choice is suitable where it is not certain in advance whether the splitter will be installed vertically or horizontally.

A complete overview of all components of the ATTACK KT / KT PLUS flue gas extraction system (elbows, extensions, chimney terminals, condensate traps and splitters for diameters 60/100 mm and 80 mm) can be found in the category Condensing boilers > flue gas extraction, flue pipes > accessories for brands > Attack on this e-shop.

Summary

The ATTACK KT vertical/horizontal splitter diameter 60/100 - diameter 80/80, AL/PP (code PR51) is a splitter-type part – universal (vertical and horizontal) with a diameter of 60/100 mm → 80/80 mm, made of aluminium (AL) on the exhaust branch, polypropylene (PP) on the intake branch, belonging to the transition from coaxial to separate system (splitter). Recommended installation orientation: vertical and horizontal. The part is designed for ATTACK ACKT20, ACKT28 and ACKT48 boilers (Condensing KT range), ATTACK KST24 (Condensing KST) and ATTACK KZT25 (Condensing KZT), and is part of the wider range of ATTACK KT extraction parts available on this e-shop, allowing you to assemble a complete flue gas extraction route exactly according to the layout of your specific installation.

Frequently Asked Questions

When should I choose the universal splitter PR51 instead of the vertical design PR51A?
The universal PR51 design can be installed in either a vertical or horizontal position according to the needs of the specific layout, which is especially useful for non-standard boiler placement (for example, a side outlet in a low-height space), while PR51A is intended exclusively for vertical installation directly behind a boiler with a vertical outlet.

Can the PR51 splitter be ordered additionally if the original installation was designed only for coaxial piping?
Yes, provided that the boiler's connection socket corresponds to the standard dimension of the ATTACK Condensing range, the PR51 splitter can also be added later when modifying an existing route, for example if it turns out that the originally designed length of coaxial pipe is insufficient.

Do I need a functional chimney with an ATTACK condensing boiler?
No. ATTACK Condensing KT, KST and KZT condensing boilers have a closed combustion chamber with forced draught – they draw combustion air from outside and discharge flue gases through their own extraction system (coaxial 60/100 mm or separate Ø80/Ø80). A masonry chimney is therefore not required; an opening through a wall or roof for the plastic-aluminium piping is sufficient.

What is the maximum length of flue gas extraction with 60/100 mm coaxial piping?
The exact value depends on the specific boiler model (ACKT20, ACKT28, ACKT48, KST24 or KZT25) and is stated in the installation manual – typically an equivalent length of 10–15 m, with a 90° elbow counted as approximately 1–1.5 m and a 45° elbow as approximately 0.5 m of straight pipe. Exceeding the limit increases resistance and can cause a boiler fault message.

Why does water actually drip from the flue gas extraction?
A condensing boiler cools the flue gases enough that the water vapour contained in them condenses – it is precisely from this additional heat that the boiler achieves its high efficiency. The resulting condensate is mildly acidic and must be drained via the condensate trap into the boiler's siphon; that is why all horizontal sections of piping have a prescribed slope towards the boiler or the condensate trap.

Can 60/100 mm coaxial piping be combined with the separate Ø80/Ø80 system?
Yes, that is exactly what the splitter (e.g. PR51, PR51A or PR51B) is for, dividing a single coaxial pipe from the boiler into two independent Ø80 mm pipes. It is used for longer routes or when the intake and exhaust need to be routed in different directions.

Can I combine parts of different diameters or from a different manufacturer with the ATTACK extraction system?
It is recommended to use a certified system from the same manufacturer as specified in the manual for the specific boiler (for ATTACK Condensing boilers this is the ATTACK KT/KT PLUS system). Combining parts of different diameters, materials or from other manufacturers can result in leaks, incorrect condensate drainage and loss of the boiler warranty.

How often should the extraction piping and condensate trap be checked?
A visual inspection of joint tightness and condensate trap patency is recommended at least once a year, ideally during the regular boiler service inspection. For façade or roof terminations, it is also necessary to check that the terminal grille is not blocked by leaves, insects or snow.

Does the flue gas extraction need to be insulated?
When the extraction is routed through a heated space, insulation is usually not necessary, as the surface temperature of the coaxial pipe is low. For longer sections routed through unheated space (attic, façade) or where there is a risk of moisture condensing on the pipe surface, additional insulation is recommended, especially at the condensate trap, to prevent freezing.

What happens if the flue gas extraction is undersized or too long?
If the maximum equivalent extraction length is exceeded or in the event of leaks, the boiler will typically report a fault related to flue gas/air flow (fan fault, pressure switch fault or flue gas path fault) and will shut down for safety reasons. The solution is to recalculate the route according to the manual and, if necessary, modify it (shorter route, fewer elbows, or switching to the separate Ø80/Ø80 system).

Can this part also be used in a cascade connection of several boilers?
In cascades with multiple boilers, a separate Ø80/Ø80 system with a shared collecting flue is typically used, or separate terminals for each boiler according to the cascade's project documentation. The specific components (extensions, elbows, splitters) are also compatible in this configuration, but the minimum distances between terminals according to STN EN 15287 must be observed.

How do I find out exactly which parts I need for my installation?
The most reliable approach is to base your choice on the installation manual for the specific boiler model (ACKT20/28/48, KST24, KZT25), which contains typical connection diagrams and maximum permitted lengths. For more complex or non-standard layouts (long routes, passing through several floors, cascades), we recommend consulting an installation company or directly with the seller before ordering the exact number of pieces.

Does condensate from the flue gas extraction need to be neutralised before being discharged into the sewer?
For typical family houses with a small boiler output, neutralisation is generally not required given the small amount of condensate and its dilution with other wastewater; however, applicable legislation and the requirements of the local sewer administrator must be observed. For higher outputs or boiler cascades, it is recommended to install a condensate neutralisation device before discharge into the public sewer.

Is operation of a condensing boiler with this type of extraction noisier than with a classic chimney?
Forced draught (from the boiler's fan) may be associated with a slight operational noise, which, however, is minimal with a correctly installed and mechanically secured route (without freely vibrating sections of piping) and is generally comparable to or lower than the noise of a classic atmospheric boiler with chimney extraction.

Can installation of this part be done by yourself, or is a professional required?
The mechanical connection of the parts itself (plug-in system) is simple, but connecting the extraction to the condensing boiler, calculating the maximum route length and commissioning the boiler must be carried out by a person professionally qualified to install gas appliances – this is both a manufacturer's condition and a legal requirement for maintaining the warranty and ensuring safe operation.

Does the number and type of these parts affect gas consumption or boiler efficiency?
They do not directly affect consumption, but they do so indirectly – the greater the resistance of the extraction route (many elbows, a long route close to the limit), the more energy the boiler's fan must expend to overcome this resistance, and the sooner the boiler may limit its output or report a fault. Designing the route with as few parts as necessary is therefore also advisable from the point of view of operating economy.

Warranty

This part of the ATTACK extraction system is covered by a 24-month warranty from the date of dispatch from the warehouse, the same as other accessories for ATTACK condensing boilers. In the event of a claim, we recommend keeping the proof of purchase and, if necessary, photographic documentation of the installation method, as with extraction systems the functionality is closely linked to the correctness of the installation (compliance with slope, maximum route length and clearances according to the manual).