Installation of a coaxial chimney with your own hands

A working, effective heating system is essential for keeping our homes warm and comfortable during the winter. The chimney is a crucial part of this system since it allows hazardous gases to escape while maintaining adequate airflow. Coaxial chimneys have become more and more popular recently due to their creative design and simplicity of installation. We’ll go into how to install a coaxial chimney yourself in this post, giving you the ability to take charge of the heating system in your house.

Two concentric pipes, one inside the other, make up a coaxial chimney, which enables the passage of both intake air and exhaust gases through a single structure. This design improves efficiency and safety while also making installation simpler. Homeowners can minimize heat loss and lower their risk of carbon monoxide buildup in their homes by installing a coaxial chimney.

Getting all the tools and supplies needed is crucial before starting the installation process. These usually consist of the inner and outer pipes from the coaxial chimney kit, as well as any extra parts like sealant, flashing, and brackets. Basic tools like a drill, screwdriver, level, tape measure, and safety equipment like gloves and goggles are also necessary.

The installation procedure needs to be carefully planned after you’ve assembled your supplies. First, decide where the chimney should go and make sure it complies with any applicable building codes. Selecting a location that allows easy access for maintenance and inspection and enough distance from combustible materials is essential.

The device of a chimney for a turbo boiler

A coaxial gas duct is a "pipe in a pipe" with two walls that serves as both the intake of combustion air from the street and the output of smoke to the outside at the same time. Warm gases travel through the inner channel, while air flows through the outer channel (between two walls) in the direction of the hot gases.

Important point. The gas boiler fan forces the combustion products and air to move; a natural draft is ineffective in this situation. In addition, turbo units powered by diesel, pellet, or wood cannot be connected to coaxial chimneys.

The following benefits are provided by the 2-in-1 air/combustion products chimney system:

1. The glowing gases give up part of their heat to the air stream, the combustion process is improved and the efficiency of the heat generator is increased.
2. The coaxial pipe is led out horizontally, by the shortest possible route through an opening in the outer wall. Vertical installation is possible in some cases.
3. Thanks to the double-wall construction of the gas duct, a turbo boiler or a heater can be installed in almost any room without a traditional flue duct – kitchen of a country cottage, garage, basement and even in a bathhouse. The room must comply with the requirements for gas boilers.
4. The owner does not need to take care of additional air supply needed for combustion. Although the general exchange ventilation will still have to be done.

To be clear. It is forbidden to lead the horizontal flue channel through a wall in an apartment building to the street.

The freezing of the end cap during heavy frosts is a drawback of the chimney system. When the intake air makes contact with the inner pipe’s heated wall, condensate is released and an icicle is formed. Installing a customized stainless steel extension fixes the issue.

The coaxial chimney’s primary components are:

• straight section with a headband at the end;
• the same double-walled outlet at 90° or 45°;
• adapter – adapter to the coaxial outlet of the boiler;
• connecting clamps, flanges;
• elastic sleeves, aprons;
• inspection section with condensate drain (for vertical installation);
• fixing.

Note: Various adapters can be utilized to connect to various heaters. For instance, a flange and spigot are already included with Viessmann Vitopend wall-mounted boilers, but these components are sold separately on Vaillant Turbo heat generators.

We’ll explain how to install coaxial elements correctly later on. However, we first suggest studying.

Installation requirements

The installation of a coaxial chimney separately is not required by normative documents. Two guidelines must be followed: the manufacturer’s recommendations for the gas boiler and the general specifications for the extraction of combustion products from gas-using installations.

• maximum length of the horizontal pipe section is 3 m;
• the passage section of the smoke flue must correspond to the size of the outlet pipe of the heat generator;
• If 2 gas water heating appliances are installed in the furnace room (e.g., heater + boiler), it is necessary to make two separate coaxial pipes, it is forbidden to combine them into one;
• at the intersection of walls and floors of non-combustible materials (aerated concrete, brick, reinforced concrete) is sufficient to install a metal or asbestos sleeve;
• In a wooden house it is necessary to make a fire separation in the wall, i.e. to ensure a minimum distance from the wall of the chimney to the combustible structure of 380 mm.

An additional detail is the placement of an umbrella over the top of the gas duct, which is led through the roof vertically. The regulations forbid using hoods to cover the chimney flues of gas heat generators. On the other hand, the coaxial system needs to shield the unit from precipitation.

Advice: It is easy to resolve conflicts that result from an imperfect regulatory framework. Find out the precise requirements for the installation of air/combustion product systems by getting in touch with the local gas service. You still need to get their approval, order a project, and commission the facility before you can install the boiler.

Manufacturers of heating units stipulate in their installation instructions that the following guidelines must be followed:

• minimum distance from the ceiling to the horizontally laid chimney – 200 mm;
• distance from the wall to the end of the chimney – at least 30 cm;
• the height of the cap above ground level – not less than 2 m, preferably 2.5 м;
• between the cut of the chimney and the nearest building or fence must remain a gap of 600 mm, optimally – 1.5 м;
• When selecting the location of the exhaust duct, it is important to ensure a distance of 60 cm from the window or air inlet;
• The slope of the chimney of the turbo boiler is made towards the street (value – 10 mm per meter of pipe length);
• condensing units use the energy of water vapor, so the coaxial chimney is installed with a slope towards the heat generator.

Homeowners frequently post questions on forums about whether a coaxial chimney requires the boiler room to be ventilated. The fan draws in the necessary amount of air for combustion through the system’s external duct. Three-fold air exchange ventilation in the furnace room is still required to remove carbon monoxide, methane, or propane in the event of a leak.

Installation scheme and selection of components

Installing coaxial systems only requires two basic layouts, with the remaining layouts being variations on those two:

• horizontally from the boiler to the outside by the shortest possible route;
• vertically through the ceiling and roof.

The second scheme is rarely used in the case of double-walled chimneys due to its difficulty in implementation. When it is not possible to lead the channel into the wall, such as near a high fence, multiple windows, or other obstructions to correct installation, the floor is laid through.

The most popular scheme, number 1, installs coaxial chimneys horizontally. You measure the length, draw out the pipe routing, and purchase the pre-made set of parts mentioned in the publication’s first section.

What subtleties should be considered?

1. The diameter of the duct is selected strictly according to the coaxial outlet of the hot water appliance. Most heat generators use 2 sizes – 60/100 and 80/125 mm. The first figure shows the diameter of the gas duct, the second – the external duct.
2. To connect the air-smoke duct with the heating unit, an adapter – adaptor suitable for the specific boiler model is used.
3. The gap between the pipe and the wall case is sealed with non-combustible material – basalt wool, asbestos cord. Do not blow the cracks with polyurethane foam installation.
4. The chimney can be extended (increased by additional straight sections), not exceeding the value specified in the boiler passport. The value depends on the fan capacity.
5. If the gas duct is too short, it is necessary to put a limiting diaphragm of a certain diameter. Otherwise, the smoke pump will pump more air into the furnace than necessary.
6. In regions with a cold climate, it is necessary to use a nozzle that prevents icing of the header.
7. Smoke duct, passing in transit through an unheated room, it is better to insulate the outside with a layer of basalt fiber.

Aid. The diameters of the diaphragms to be installed are specified in the Viessmann Vitopend air boiler passport based on the length of the chimney. For instance, a 44 mm diaphragm is fitted into a 60/100 mm pipe that can be up to 3 meters long.

It is required to install a revision section with a condensate drain fitting when the coaxial gas duct needs to exit vertically from the ground floor or basement. If the route’s overall length surpasses the allowable limit, two separate pipes—a chimney and a duct measuring 80 mm by 80 mm—are laid in place of a single, double-walled pipe. At the boiler outlet is a special adapter-splitter, as seen in the picture.

In the realm of home heating and insulation, ensuring safe and efficient chimney installation is paramount. Installing a coaxial chimney, often done with professional assistance, can also be tackled as a DIY project with the right knowledge and precautions. A coaxial chimney comprises an inner pipe for exhaust gases and an outer pipe for air intake, maximizing efficiency while minimizing risks like heat loss and condensation. Key steps involve choosing suitable materials, understanding local building codes, and meticulously following manufacturer instructions. Prioritize safety by double-checking measurements, securing proper clearances, and using appropriate tools. Regular maintenance, including annual inspections and cleaning, guarantees continued performance and safety. By mastering the art of coaxial chimney installation, homeowners can enhance both comfort and safety in their abodes while potentially saving on installation costs.

How to install a coaxial chimney correctly

The air/flue gas system is relatively easy to install. Since the inner channel already has an O-ring, the elbow and pipe section are joined "in the socket" without the need for sealants or gaskets. How a horizontal chimney is installed:

1. Install the wall or floor standing boiler in the project position. Make an external hole, mark the routing path with a pencil on the wall.
2. Connect a 90° branch or a straight section to the boiler connection, depending on the installation scheme. Different adapters are used here – in some models it is necessary to put a metal bushing first, in others – to screw a flange to the unit body.
3. Connect the next section, before joining, put an elastic collar on the pipe.
4. Pull the collar over the joint, place the clamp on top, then screw it together with the screws provided.
5. Put an inner decorative apron over the pipe passing through the wall. Install a section of coaxial chimney with an external header (splitter), seal the gaps.
6. If the gas duct was extended during the installation process, fix the pipe to the wall with special clamps.

Vital. It is a flagrant violation of fire codes for the joint of the two sections to be in the wall’s thickness. The pipe that goes through the wall or floor needs to be one unit.

A few words regarding how to shorten the coaxial pipe in the event that the chimney protrudes 40–50 centimeters outside. Avoid touching the header when trimming the straight duct’s end on the heater’s side. Since the ends of the two pipes do not line up when assembled, remove the inner gas duct and cut the pipes apart. The master in the video will be informed of further installation details:

For homeowners who want to upgrade their insulation and heating systems, installing a coaxial chimney can be a wise choice. It guarantees the secure extraction of combustion gases and contributes to the preservation of indoor air quality. It is quite possible to handle this project yourself if you take the right precautions and follow the right procedures.

It’s important to familiarize yourself with local building codes and regulations before beginning installation. The right location and materials needed for your coaxial chimney are specified by these guidelines. Ignoring this step could result in expensive errors or even present a risk to your safety. The first step to a successful installation is ensuring compliance with regulations.

Purchasing premium components is crucial when it comes to materials. Choosing strong, heat-resistant materials will extend the life and maximize the effectiveness of your chimney system. While it could be alluring to skimp on quality in favor of less expensive solutions, doing so could ultimately jeopardize the functionality and security of your installation.

A coaxial chimney must be installed precisely and with great attention to detail. The result of taking the time to precisely measure, align, and secure each component is a system that works as intended. Additionally, to avoid costly mistakes and guarantee optimal performance, refer to the manufacturer’s guidelines and, if necessary, seek professional advice.

In conclusion, homeowners looking to upgrade their insulation and heating systems may find it possible to install a coaxial chimney themselves. You can reap the benefits of a safe and effective chimney system for many years to come by following local codes, making quality material investments, and handling the installation process carefully and precisely.

Video on the topic

What is the diaphragm used for in a turbo gas boiler | Installing a coaxial chimney?

Installation of coaxial chimney with your own hands.

Coaxial chimney of a wall-mounted boiler