ATTACK KT elbow 90°, diameter 60/100, painted

Product detailed description

ATTACK KT elbow 90°, diameter 60/100, painted is part of the original flue gas exhaust and combustion air intake system ATTACK KT / KT PLUS, designed for ATTACK Condensing wall-mounted condensing gas boilers. This part belongs to the category: 90° elbow, diameter 60/100 mm, made of galvanized steel with painted surface finish.

Closed combustion chamber and flue exhaust in ATTACK condensing boilers

ATTACK condensing gas boilers operate with a closed (turbo) combustion chamber – unlike older atmospheric boilers, they do not need 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 outward also by forced draught provided by a fan built into the boiler. In practice, this closed circuit is solved in two ways: coaxial (concentric) piping, where a smaller pipe for air intake runs inside a larger pipe with the annular space used for flue gas exhaust, or 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 exhaust and intake to be routed through a single opening in the wall or roof, is quick to install and aesthetically unobtrusive.

Every element of the exhaust assembly – elbow, extension, condensate collector, chimney terminal and splitter – must be tight, resistant to flue gas temperatures as well as to condensate, which is produced in large quantities during operation of a condensing boiler precisely because the boiler is able to utilize the latent heat of water vapor contained in the flue gases. It is precisely this condensate that is the reason why the ATTACK KT system cannot be safely replaced by a common chimney part intended for atmospheric boilers – such parts are not designed for permanent contact with acidic condensate nor for the correct slope that directs condensate back to the boiler or to the collector.

Elbow – change of direction in the exhaust route

Elbows are used wherever the direction of the piping needs to be changed – most often from the horizontal boiler outlet to a vertical riser toward the roof, or conversely when exiting through a side facade. The 90° design is used for a right-angle change of direction (typically immediately behind the boiler or just before passing through the roof/wall), while a 45° elbow is chosen where a milder change of direction is sufficient and it is desirable to reduce the pressure loss compared to a sharp 90° elbow, or to bypass an obstacle (a beam, piping of another installation).

Each elbow increases the resistance to flue gas flow and intake air flow, so the equivalent length of the elbow is taken into account when designing the route (added to the total permitted exhaust length), and it is recommended to use the smallest number of elbows needed for the given room layout.

Angle of direction change: 90°.

Example of a typical connection in a real installation:
boiler → 90° elbow → vertical extension → chimney through the roof (or: boiler → 45° elbow → angled section along the roof truss → 45° elbow → continuing vertically).

Step-by-step installation procedure

1. Check the boiler manual for the maximum permitted equivalent route length and include the equivalent length of this elbow in the total.
2. Install the elbow in the direction of flow according to the marking on the part, check its orientation relative to adjoining parts.
3. Seal the connection and secure it mechanically so that the elbow cannot rotate on its own during operation.
4. If combining several elbows in sequence, continuously check that the sum of equivalent lengths does not exceed the boiler's limit.
5. After connecting the entire route, perform a tightness check of the joints.

Material and construction

This part is made of galvanized steel with an additional painted surface finish, which increases resistance to weather conditions on the exterior part of the route (for example the chimney terminal on the roof) while also giving the part an aesthetic, uniform appearance matching the design of ATTACK Condensing boilers. The surface finish withstands normal flue gas temperatures from a condensing boiler and brief contact with condensate when the pipe has the correct slope, which ensures that condensate does not stand in the part for long periods.

System classification: coaxial (concentric). Design: 90° change of direction.

Compatibility with ATTACK boilers

Part PR40 is designed for the connection system common to the entire range of ATTACK wall-mounted condensing boilers ACKT20, ACKT28 and ACKT48 (Condensing KT series), ATTACK KST24 (Condensing KST) and ATTACK KZT25 (Condensing KZT). Before ordering, we recommend checking the exact type of connection port and the maximum permitted exhaust route length in the installation manual for the specific boiler model, as it may vary slightly depending on boiler output (20, 28 or 48 kW for the KT series).

Installation and warnings

Elbows are installed in the direction of flow according to the marking on the part (an arrow or diagram in the manual), and the joint is secured so that it cannot rotate during operation. When using several elbows in sequence (for example 2× 45° instead of 1× 90°), their equivalent length is added together and must be taken into account when calculating the maximum permitted route length.

As a general rule, horizontal sections of the exhaust route must have a slope of at least 3° toward the boiler or the nearest condensate collector so that condensate does not accumulate in the piping. Installation should be carried out by a person with professional qualification for installing gas appliances and their exhaust systems, in accordance with the installation manual for the specific boiler and with standard STN EN 15287.

Standards and safety requirements

In Slovakia, the installation of flue gas exhaust for condensing boilers 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 clearances of the terminal from windows, ventilation openings, neighboring properties and ground level, as well as the minimum height of the terminal above the roof plane. The boiler itself and its exhaust system must also meet the requirements of STN EN 483 (type C gas boilers) and be installed in accordance with the technical and operational regulations (TPP) applicable to gas equipment.

Installation may only be carried out by a person with professional qualification for the installation and servicing of gas appliances, who will issue an inspection report or commissioning certificate upon completion. In case of any change to the route compared to the originally 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

When correctly installed, elbows do not require special maintenance; during a service inspection it is only recommended to visually check the tightness of the joint and that the part has not rotated from its original position during operation.

The recommended inspection interval for the entire exhaust route is once a year, usually as part of the boiler's regular service inspection carried out by an authorized 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 terminal.

Typical usage scenarios

Scenario 1 – change from horizontal boiler outlet to vertical riser: the boiler outlet exits to the side, a 90° elbow immediately behind the boiler directs the route upward toward the roof.

Scenario 2 – bypassing an obstacle in the route (ceiling beam, other piping): instead of one sharp elbow, two elbows with a milder angle are used, deflecting the route around the obstacle and then returning it to the original direction.

Related parts in the ATTACK KT range

The 90° elbow complements the milder 45° elbow PR41 in the range – both parts can be combined with each other as needed (e.g. 90° immediately behind the boiler and 45° when bypassing an obstacle further along the route). The choice between them depends on the required change of direction and the effort to minimize the overall pressure loss of the route.

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

Summary

ATTACK KT elbow 90°, diameter 60/100, painted (code PR40) is a 90° elbow type part with a diameter of 60/100 mm made of galvanized steel with a painted surface finish, belonging to the coaxial (concentric) system. Recommended installation orientation: 90° change of direction. The part is designed for ATTACK ACKT20, ACKT28 and ACKT48 (Condensing KT series), ATTACK KST24 (Condensing KST) and ATTACK KZT25 (Condensing KZT) boilers and is part of the wider range of ATTACK KT exhaust parts available on this e-shop, allowing a complete flue exhaust route to be assembled exactly according to the layout of a specific installation.

Frequently asked questions

What is the difference between the 90° elbow (PR40) and the 45° elbow (PR41) in terms of pressure loss?
The 90° elbow represents a greater obstacle to flow than the 45° elbow, and is therefore counted with a higher equivalent length in the calculation of the maximum route length (approx. 1–1.5 m compared to approx. 0.5 m for the 45° elbow). Where a milder change of direction is sufficient, it is therefore preferable to choose the 45° elbow.

What is the maximum recommended number of 90° elbows to use in one route?
The exact limit is set by the manual for the specific boiler model through the maximum total equivalent route length – in general, it is recommended to use the smallest number of elbows needed for the given layout, so that there remains sufficient space for the required length of straight sections.

Do I need a functional chimney for 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 exhaust system (coaxial 60/100 mm or separate Ø80/Ø80). A masonry chimney is therefore not necessary, an opening through the wall or roof for the plastic-aluminum piping is sufficient.

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

Why does water actually drip from the flue exhaust?
A condensing boiler cools the flue gases enough that the water vapor 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 collector into the boiler's siphon; that is why all horizontal sections of piping have a prescribed slope toward the boiler or the collector.

Can the 60/100 mm coaxial piping be combined with a separate Ø80/Ø80 system?
Yes, that is exactly what a splitter is for (e.g. PR51, PR51A or PR51B), which splits one coaxial pipe from the boiler into two separate 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 another manufacturer with the ATTACK exhaust system?
It is recommended to use a certified system from the same manufacturer 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 may result in leaks, incorrect condensate drainage and loss of the boiler warranty.

How often should the exhaust piping and condensate collector be checked?
A visual inspection of joint tightness and patency of the condensate collector is recommended at least once a year, ideally during the boiler's regular service inspection. In the case of a facade or roof terminal, it is also necessary to check that the terminal grille is not blocked by leaves, insects or snow.

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

What happens if the flue exhaust is undersized or too long?
If the maximum equivalent exhaust length is exceeded or in case of leaks, the boiler usually reports a fault related to flue gas/air flow (fan fault, pressure switch fault or flue path fault) and shuts down for safety reasons. The solution is to recalculate the route according to the manual and make adjustments if necessary (shorter route, fewer elbows, or switching to a separate Ø80/Ø80 system).

Can this part be used for cascade connection of multiple boilers?
For cascades with multiple boilers, a separate Ø80/Ø80 system with a common collecting chimney is usually 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 arrangement, but the minimum terminal clearances according to STN EN 15287 must be observed.

How do I find out exactly which parts I need for my installation?
The most reliable way is to refer to the installation manual for the specific boiler model (ACKT20/28/48, KST24, KZT25), which contains diagrams of typical connections and maximum permitted lengths. For a more complex or non-standard layout (long route, passage through multiple floors, cascade), we recommend consulting with an installation company or directly with the seller before ordering the exact number of pieces.

Does condensate from the flue exhaust need to be neutralized before being discharged into the sewer?
For typical family homes with a small boiler output, neutralization is usually not required due to the small amount of condensate and its dilution by other wastewater, but the applicable legislation and requirements of the local sewer administrator must be followed. For larger outputs or boiler cascades, it is recommended to install a condensate neutralization device before discharge into the public sewer.

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

Can installation of this part be done by yourself, or is a professional necessary?
The mechanical joining of the parts itself (plug-in system) is simple, but connecting the exhaust to a condensing boiler, calculating the maximum route length and commissioning the boiler must be carried out by a person with professional qualification for installing gas appliances – this is both a manufacturer's condition and a legal requirement for maintaining the warranty and 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 exhaust 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 reduce output or report a fault. Designing the route with the smallest necessary number of parts is therefore also advisable from the point of view of operating economy.

Warranty

This ATTACK exhaust system part 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 case of a claim, we recommend keeping the proof of purchase and, if necessary, photo documentation of the installation method, as with exhaust systems the functionality is closely linked to the correctness of the installation (compliance with slope, maximum route length and clearances according to the manual).