Chimneys From A Sandwich Pipe: How To Choose, Features Of DIY Installation And Operation

2024 Author: Bailey Albertson | [email protected]. Last modified: 2024-01-17 22:26

Chimneys from a sandwich pipe: selection, installation and operating rules

When we use the word "chimney", many of us imagine a bulky brick chimney - a whole structure resting on a solid foundation. But such constructions are gradually receding into the past, and soon they can be found no more often than a living dinosaur. Nowadays, sandwich chimneys are much more popular and in demand, which we will now talk about.

Content

• 1 What is a sandwich chimney

• 2 How to choose a sandwich pipe

  • 2.1 Inner pipe diameter

    2.1.1 Table: dependence of the inner diameter of the sandwich pipe on the boiler power

  • 2.2 Steel grade and thickness
  • 2.3 Brand and thickness of insulation

• 3 Self-assembly of a sandwich chimney

  • 3.1 Connecting the chimney to the heating unit
  • 3.2 Methods of connecting sandwich pipes

  • 3.3 Installation of the vertical section of the flue

    3.3.1 Video: DIY sandwich chimney installation - nuances, tips

  • 3.4 Features of the passage of the chimney through the roof and ceilings

    3.4.1 Video: device for a fire-safe passage of the chimney through the ceiling

• 4 Operation of a sandwich chimney

  4.1 Video: cleaning a sandwich chimney

• 5 Reviews about sandwich pipe chimneys

What is a sandwich chimney

This design is also called a modular chimney. Modules are parts from which you can assemble a chimney of any configuration: pipe sections, tees, bends with an angle of 45 and 90 degrees, revisions, condensate traps, etc. Each element is made of stainless steel, wrapped in stone wool (one of the most effective heat insulators) and enclosed in a protective and decorative casing made of cheap stainless steel or galvanized steel. Richer customers purchase sandwich chimneys in a protective casing made of copper or aluminum.

A sandwich pipe consists of three layers: metal, insulation, metal

Each module is equipped with structural elements that provide reliable tight connection with other parts of the structure

In addition to the modules, all additional parts are manufactured that may be needed when installing a chimney: brackets, fastening clamps, cuts (used in places where the chimney crosses building structures), aprons for sealing the passage through the roof, spark arresters, deflectors and much more.

The list of advantages of a sandwich chimney looks very convincing:

1. The pipe has a very low weight, so there is no need to build a foundation for it: you can fasten it to the wall (a special bracket with a support platform is screwed on) or lean directly on the heat generator.
2. Installation takes only a few hours, and no special skills are required, as is the case with a brick pipe.
3. All modules have a circular cross-section, which is best suited for the chimney. In a rectangular pipe, vortices form at the corners (this is due to the spiral movement of smoke), which impair traction.
4. The owner does not have to waste time looking for components: the manufacturer offers everything that may be needed to assemble a pipe of the most complex configuration, and all the parts are made in the same style and are ideally suited to one another structurally.
5. After assembly, the chimney does not need to be insulated, since each module is already equipped with a built-in heat insulator.

6. Due to the "corporate" design and perfect matching of details, the sandwich chimney looks very presentable.

   

   Prefabricated modules are made in the same style and provide reliable connections and a presentable look of the chimney

The stainless steel from which the inner pipe is made has three advantages at once:

1. Has a smooth wall to which soot does not adhere well.
2. It does not absorb condensate, which means that it cannot be destroyed when it freezes (in contrast to steel, brick and mortar are porous materials).
3. It warms up quickly, as a result of which condensation forms during firing up in minimal volumes.

A sandwich chimney is inferior to a brick one only in strength and durability (it lasts about 15 years). As for the cost, a brick pipe, taking into account the payment for the work of a professional bricklayer, will cost much more.

The basic set of a sandwich chimney consists of the following parts:

1. An adapter (adapter) to be put on the heater flue gas outlet.
2. 90 degree elbow to change direction from vertical to horizontal.
3. Rectangular tee for changing direction from horizontal to vertical (one branch pipe turns downwards and a condensate trap is installed on it).
4. Section with an inspection and cleaning hatch (revision).
5. Support platform designed to support the vertical section of the chimney with a condensate drain valve pointing down.
6. The same platform with the crane pointing to the side.
7. Oblique tee for connecting another device to the chimney, for example, a gas water heater.
8. A 45 degree bend to move the chimney axis when bypassing the floor beam or rafters.
9. Plug for transition to a single wall pipe.
10. Connecting clamp.
11. Bracket for fixing the chimney to the wall without vertical load.
12. Pipe section 0.5 m long.
13. Support bracket (the support platform is fixed on it).
14. An intermediate support platform (unloading) with a through-pipe, part of the pipe weight is redistributed to it, if it is too long.
15. Pipe section 0.5 m long for installation in the place of the roof passage.
16. A conical roof covering the gap between the roof and the chimney on small slopes.
17. Cone roof canopy for steep slopes.
18. A frame or apron is a protective cover for a roof.
19. Pipe 1 m long.
20. Head-mounted cone.
21. Fungus on a cone.
22. Weathervane.
23. Thermofungus.
24. Deflector (prevents chimney blowing out and increases draft).

25. Spark arrester.

    

    With so many different adapters, connectors, pass-through service elements and other parts, you can assemble a chimney of any configuration

The spark arrester is installed when two conditions are met: the roof is covered with a combustible material (bituminous tiles, ondulin, roll materials), and the heat generator connected to the chimney runs on solid fuel

How to choose a sandwich pipe

Modules for a sandwich chimney differ in the following parameters:

• inner diameter;
• the brand and thickness of stainless steel, from which the inner (working) part is made;
• brand and thickness of insulation.

Let's consider each of the characteristics in more detail.

Inner pipe diameter

The selection of the diameter is a key point in the design of a chimney. Errors can lead to serious consequences, both downward and upward: in the first case, the thrust will be weak due to the high aerodynamic resistance of the pipe, in the second - due to excessive cooling of the flue gases. In general, engineers perform a rather complex calculation that takes into account many factors - from the type and moisture content of the fuel to the wind speed.

And even in the case of using software systems, you have to tinker a lot until you can find a successful combination of parameters. But in the simplest version, when it comes to a straight vertical pipe of constant cross-section with a height of 5 m or a little more, you can use the ready-made data given in the table.

Table: dependence of the inner diameter of the sandwich pipe on the boiler power

Boiler power, kW	Inner diameter, mm
up to 3.5	158
3.5-5.2	189
5.2-7.2	220
7.2-10.5	226
10.5-14	263
more than 14	300

These values should be considered as minimum, that is, when choosing a chimney from the standard range of diameters, you must choose the nearest larger, not smaller.

Owners of prefabricated boilers and furnaces should take into account that the chimney must not have a smaller cross-section than the chimney of the installation.

Steel grade and thickness

Flue gases from various heat generators differ both in temperature and in content (the acidity of the condensate depends on it). It is important to select a steel that would have a reasonable cost and at the same time fully meet specific conditions. The exhaust temperatures of gas and diesel fueled installations are the lowest.

The hottest combustion products are produced by solid fuel heat generators, especially coal ones. As for acidity, the most caustic exhaust is from liquid fuel heaters (they are also diesel) and solid fuel stoves such as "Professor Butakov" or "Buleryan", operated in the smoldering mode. The latter combine the low temperature of the flue gases (moisture condenses abundantly) and incomplete combustion of the fuel, as a result of which a large amount of heavy hydrocarbon radicals goes into the pipe (when reacting with water, they form a caustic acid cocktail).

Sandwich chimneys connected to furnaces that operate in smoldering mode have the most severe operating conditions.

Usually, the buyer is offered the following grades of stainless steels:

1. AISI 430: the cheapest stainless steel option with the smallest amount of alloying components. Only casings are made of such stainless steel. If the working part is also made of it, then it is better not to buy such a sandwich-chimney, since its service life will most likely be short.
2. AISI 439: similar in composition to the previous version, but with the addition of titanium. The latter increases the strength and corrosion resistance of steel and thus makes it suitable for the manufacture of chimneys for low-power gas installations.
3. AISI 316: steel resistant to acids and high temperatures (up to 800 ^o C) due to the presence of nickel, molybdenum and titanium in the composition.
4. AISI 304: compositionally identical to AISI 316 steel, but all additives are used in smaller quantities to reduce the cost As a result, the material is less resistant to temperatures and acids, and therefore does not last so long. The purpose is the same as for AISI 316 - gas installations (0.5 mm thick enough).
5. AISI 321: this steel exhibits increased resistance to aggressive factors, which makes it possible to use it in chimneys of fireplaces and heating and cooking stoves (with a thickness of 0.5 to 1 mm), sauna stoves (a thickness of 0.8 to 1 mm is required), solid fuel boilers (from 1 mm), gas turbine and gas piston engines (1–1.5 mm).
6. AISI 309 and 310: ultra-durable expensive steels with a large amount of nickel (about 20%) and chromium (about 25%). With a thickness of 1 mm, they work well with solid fuel equipment. There is a version with increased thermal stability: AISI 310S steel works at temperatures up to 1000 ^o C. It is the most expensive, but it can successfully work even with pyrolysis heat generators of the highest power.

The best option for installations operating on gas fuel, regardless of capacity, is AISI 316. Available in:

• AISI 316L: designed for use in chimneys of liquid fuel installations (0.5 mm thick enough);
• AISI 316Ti: with a thickness of 1–1.5 mm, it can be used in the chimneys of diesel generators, gas turbine and gas piston installations.

The steel grade is the most important characteristic of a sandwich chimney, therefore it must certainly be indicated in the documentation or in the form of a stamp on the product itself. You can distinguish real stainless steel from ordinary steel used in fakes using a magnet: it is not attracted to stainless steel.

The grade of steel can be approximately determined by a spark: for example, food grade stainless steel gives an abundant bunch of light yellow sparks under the emery wheel, almost without branches at the ends

Insulation grade and thickness

As you know, natural draft is due to the high temperature of the flue gases, therefore, insulation plays an important role in the functioning of the chimney. It should be noted that the heat insulator is exposed not only to high temperature, but also to temperature changes, that is, the operating conditions are rather difficult. All of the above prompts, when choosing a sandwich chimney, to pay special attention to the quality of the applied thermal insulation.

The heat-insulating layer of a sandwich chimney works in harsh temperature conditions, therefore, when choosing a pipe, it needs to be paid close attention

It is best to choose products that have been insulated with a well-known brand of mineral wool, such as Paroc Rob or Rockwool Wired

The thickness of the insulating layer can be from 25 to 100 mm. If the chimney is supposed to be placed outside, it is advisable to purchase modules with as thick insulation as possible. For internal installation, the thickness should be selected taking into account the flue gas temperature:

• for the "coldest" installations operating on gas or liquid fuel (exhaust temperature below 250 ^o C), you can buy a sandwich chimney with a minimum insulation layer of 25 mm;
• for wood-burning - 50-75 mm;
• for coal and pyrolysis - 100 mm.

Self-assembly of a sandwich chimney

Before proceeding with the installation of the chimney, you need to decide whether it will be located outside or inside. Each option has both advantages and disadvantages.

Internal placement advantages:

• the heat of flue gases, which penetrates through the thermal insulation, remains in the house;
• the exterior of the house remains flawless;
• there is no impact of negative weather factors, which helps to extend the life of the structure;

• the initial section of the chimney can be equipped with a water heater or a stove.

  

  One of the main advantages of the internal placement of the chimney is the possibility of rational use of heat from its heating, for example, for a water heater

Flue gases cool less, therefore:

• traction is maintained at a good level;
• the moisture contained in the smoke condenses to a minimum;
• you can save on thermal insulation.

Disadvantages:

• there is a risk of fire or carbon monoxide entering the room;

  

  If the thermal insulation of the floors is improperly performed, wooden structures next to the chimney may catch fire

• you will have to go through at least two structures - the ceiling and the roof, while taking into account the relative complexity of the process of sealing the roof passage. When placed outdoors, the opening will need to be punched only once - in the wall, while instead of sealing, decorative plugs are simply installed;
• because of the chimney, the volume of free space in the house decreases.

Note that in the case of using a furnace designed for the smoldering mode ("Buleryan" and the like), only the external location of the chimney is possible. This is due to the fact that extremely toxic condensate is abundantly formed from the flue gases of such installations.

Having decided on the placement method, you need to draw a chimney diagram. The following restrictions are taken into account:

• the number of channel bends should not exceed three;
• the maximum permissible length of the horizontal section is 1 m;
• when passing through a ceiling or roof, the pipe should be placed, if possible, at an equal distance from the beams or rafters, between which it was.

The scheme must provide sections with revisions through which it will be possible to clean the chimney and visually monitor its condition

In the chimney diagram, it is necessary to display all structural elements with their markings and dimensions

Chimney connection to the heating unit

1. The flue pipe of the heat generator is lubricated with a special heat-resistant sealant (retains working qualities at temperatures of 1000 - 1500 ^o C), after which a sandwich flue adapter is put on it. The part is fixed with a clamp.

2. Further, a section without a heat insulator is attached to the adapter. It will get particularly hot, so it needs a good heat sink. Otherwise, the steel will burn out. Typically this section has a gate valve for traction control.

   

   A single-wall pipe of the corresponding diameter is first put on the flue pipe, and only then a sandwich structure is connected to it

3. The sandwich part is installed next. In this case, the insulation on the side of the boiler must be closed with a special plug. The fact is that basalt wool absorbs moisture well, while losing its thermal insulation properties, so it must be insulated.

Sandwich pipe connection methods

A few words should be said about the ways of connecting the modules. There can be three of them:

• flanged;
• bayonet;
• socket (most common).

In the case of a bayonet or socket connection, the chimney can be assembled in two ways:

• insert the next part into the socket of the previous one. This connection in the best way facilitates the drainage of condensate, which is why it is called so - "by condensate". But in this case, smoke can seep through the gap between the sections;
• put on the next part on the previous one. Such a connection, on the contrary, contributes to the unimpeded movement of smoke, which is why it is called "smoke connection". Now the condensate runs the risk of seeping into the insulation.

Sandwich chimney modules can be connected in two different ways

It is recommended to collect horizontal sections “by smoke”, and vertical ones “by condensation”

The outer casing (street part) is always assembled in only one way: the casing of the next part is pushed onto the casing of the previous one ("through smoke").

When installing a new module, perform the following procedure:

1. The thermal insulation with the casing is moved as far as possible, exposing the edge of the inner element.
2. Further, the parts are mated, after which the edge of the casing of the previously installed module is lubricated with sealant.
3. The previously moved thermal insulation on the new module is returned to its place, while the edge of the casing is put on the casing of the previous module and tightened with a clamp.

If the chimney of the heat generator is facing upwards, the chimney can be supported directly on it. If the branch pipe looks to the side and the chimney is supposed to be run along the wall, even inside the house, even outside, it is necessary to fix a support bracket with a supporting platform and a tee on it. The horizontal section of the chimney coming from the boiler will abut against the branch of the tee.

The horizontal section must be laid with a slope of 3 degrees from the heat generator, which is necessary for the condensate to drain off. Considering this, some manufacturers even make the angle of the tee elbow equal not 90, but 87 degrees

A condensate collector with a drain cock is attached to the lower branch pipe of the tee, if it was not included in the support platform kit.

In the place of transition of the horizontal section into the vertical one, a special wall bracket is placed, which takes the main weight of the structure

Installation of the vertical section of the chimney

1. The chimney is built up to the desired height by screwing it to the wall brackets with clamps. The latter should be located in increments of no more than 2 m on vertical sections and no more than 1 m on horizontal or inclined ones.

   

   On vertical and inclined sections, the chimney is attached to the wall with clamps and brackets

2. If necessary, another support bracket with an unloading platform is installed on the wall near the roof.

3. If the pipe was led out through the roof and rises above it by more than 1.5 m, the head should be fixed with braces. To do this, a special clamp with equally spaced lugs (3 pieces) is put on it, to which you need to attach stretch marks.

   

   With a high height of the roof part of the chimney, it is additionally reinforced with stretch marks using a special clamp

4. A deflector, spark arrestor or other element is installed on the head, the use of which is required in each specific case.

Video: do-it-yourself sandwich chimney installation - nuances, tips

Features of the passage of the chimney through the roof and ceilings

Separately, it should be said about the intersection of the chimney wall, ceiling and roof. If the wall or ceiling is made of combustible material, an opening is made in them of such dimensions that its edges are at least 200 mm from the outer surface of the pipe. Inside, this opening is upholstered with non-combustible material - basalt cardboard or minerite, after which a passage block is inserted into it. This block, consisting of two concentric parts (frame in frame), is not difficult to make yourself. The pipe is inserted into the inner frame, after which the passage block is filled with non-combustible insulation and sewn on both sides with decorative elements or simply with tin. Basalt or glass wool is used as a heater in the wall opening, and expanded clay is most often used in the ceiling.

At the place of passage through the ceilings, a metal box with insulated walls is mounted, then a pipe is inserted and the remaining space is filled with non-combustible insulation

So, you shouldn't give up mineral wool, and the choice in its favor will also save you money: the prices for basalt wool are significantly overstated due to its “untwisted”. It should be remembered that both materials produce fine, prickly dust, the ingress of which on the mucous membrane, respiratory tract or eyes is fraught with serious consequences, therefore, you need to work with them with gloves, glasses and a respirator. Throw away clothing after installation.

Ready-made passage blocks of different sizes, already filled with insulation, can be purchased complete with a sandwich chimney.

To facilitate the installation work, it is advisable to purchase a ready-made pass-through block with insulation

In a wall or ceiling made of non-combustible materials, the installation of a passage block is not required. It is enough to place the chimney in an asbestos pipe or basalt cardboard sleeve.

When making an opening in the roof, roll materials are cut crosswise, after which the resulting "petals" are folded back and sewn to the lathing. A pipe is installed in the opening, after which a plastic part is put on it - a rat, which will close the gap between the chimney and the roof. The lower edge of the canopy is, if possible, launched under the roof covering, after which it is fixed to the pipe with an entrenchment. All gaps must be filled with outdoor sealant.

Instead of the standard one, you can use the "Master Flash" rat made of elastic polymer. Due to its flexibility and elasticity, it adheres more closely to the pipe and roof.

The "Master Flash" canopy is made of heat-resistant rubber or silicone, so it can precisely take the shape of any surface, carefully sealing all joints

It is forbidden to place the joint of the sandwich chimney modules inside the building structure: for safety reasons, it must remain in sight and not less than 25 - 30 cm from the wall or ceiling

Video: device for a fireproof chimney passage through the ceiling

Operation of a sandwich chimney

At the beginning of the heating season, check the condition of the chimney and, if necessary, clean it. A straight vertical pipe can be inspected with a mirror: you need to bring it into the inspection hole and evaluate how wide the pipe lumen is. It is quite possible that you will have to climb to the roof: by the end of summer, bird nests are often found in the head.

The chimney should be cleaned before each heating season.

The chimney is cleaned with brushes and scrapers with stackable handles. To reduce the intensity of the formation of soot deposits, it is useful to periodically burn various prophylactic preparations in the firebox, for example, the popular today "Poleno Chimney Sweep".

It is forbidden to burn out the soot accumulated in the chimney, as this, firstly, shortens its service life, and secondly, it can provoke a fire

Video: cleaning a sandwich chimney

Reviews of sandwich pipe chimneys

After familiarizing yourself with the characteristics of a sandwich chimney, it is difficult to argue that its installation is the best solution to the problem of smoke removal. A convincing confirmation of this conclusion is the enviable popularity of such designs. Installation, as has been shown, can easily be performed by a non-professional, but all the requirements of the instructions must be carefully followed, otherwise the chimney can pose a threat to the health and even the life of household members.