Chimneys For A Gas Boiler: What Is It, How To Choose, How To Make And Install Correctly

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

How to choose and install a gas boiler chimney

In the Russian climate, heating is the most important element that ensures comfortable and safe living in a house. Particular attention is paid to chimneys, since they remove hazardous fuel combustion products from the room.

Content

• 1 Why is the chimney so important for a gas boiler
• 2 What is the device

• 3 Choosing a chimney for a gas boiler

  • 3.1 Brick chimneys

    3.1.1 Video: chimney sleeve

  • 3.2 Metal chimneys
  • 3.3 Ceramic chimney pipes
  • 3.4 Asbestos-cement flues

• 4 DIY installation

  • 4.1 Brick chimneys

  • 4.2 Chimneys from metal pipes

    • 4.2.1 External chimney made of metal
    • 4.2.2 Video: installing a wall-mounted chimney
    • 4.2.3 Internal metal flue
  • 4.3 Coaxial flues
  • 4.4 Video: heating a private house - coaxial chimney
  • 4.5 Asbestos and ceramic flues

  • 4.6 Insulation of chimneys for a gas boiler

    4.6.1 Photo gallery: methods of insulating chimneys

• 5 Features of operation

  • 5.1 Checking the draft in the chimney of a gas boiler

    5.1.1 Video: checking the draft in the chimney of a gas boiler

• 6 Traction adjustment
• 7 What to do if the boiler furnace blows out
• 8 Precautions and tips for using gas boilers
• 9 Consumer reviews about chimneys

Why is the chimney so important for a gas boiler

The most important element of a gas-fired heating system is a device for removing fuel combustion products. This is confirmed by the attitude of the gas service workers, which makes special requirements for such structures. Flue gases in such boilers do not have a specific odor, but they immediately poison the human body. Therefore, special attention should be paid to the flue ducts both at the stage of choosing the design and materials, and during the regular operation of the heating system.

The products of fuel combustion in a gas boiler are very dangerous for the human body, therefore the chimney must work accurately and without interruptions.

The arrangement of chimneys must comply with the requirements of SNiP 2.04.05–91 and DBN V 2.5.20–2001. When planning the installation of the boiler and chimney, you must first of all study the requirements of these documents and strictly observe them from the design stage to commissioning. The design of the device must be agreed with the gas service.

The initial data when choosing a chimney for a gas boiler are as follows:

1. The temperature of the flue gases is in the order of 150 ^° C, so pipes of any material can be used. Structurally, it is better to build a chimney from double-walled sandwich pipes with basalt insulation, which will reduce the condensation of furnace gases.
2. When using a gas boiler, it is necessary to install exhaust ventilation equipment with a diameter of at least 100 mm.
3. The development and approval of a project for a heating and ventilation device is mandatory.

A natural solution is to choose a double-walled pipe made of austenitic grade stainless steel that is resistant to chemicals, especially for the inner pipe. You can check this with a magnet - a good stainless steel does not attract it. The outer pipe can be made of galvanized sheet.

The sandwich pipe is a double-walled structure of metal pipes filled with insulation

The ventilation duct from the boiler room is installed simultaneously with the chimney. You can use plastic pipes for it.

Upon completion of the installation of the chimney and ventilation system, it is necessary to obtain an act of commissioning from the VDPO (All-Union Voluntary Fire Society).

When choosing a boiler for heating, you need to take into account the real conditions of its installation.

1. As a first approximation, the boiler power should be at least 1 kW per 10 square meters of area.
2. If, in addition to heating, the boiler is planned to be used for domestic hot water supply, it is necessary to install two-circuit units with an indirect or direct heating boiler. The DHW circuit for one or two sampling points can be arranged by a branch from the heating main in a single-circuit boiler.
3. It should be borne in mind that all wall-mounted boilers are volatile, since their control system operates on electricity, in case of interruptions in its supply, the consumer is left without heat.
4. The most reliable in this regard will be a floor-standing gas boiler with manual adjustments to the combustion mode.
5. For wall-mounted volatile boilers, it is possible to use an uninterruptible power supply that supports the operation of the boiler for several hours after a power outage.

6. The safest are boilers with closed-type furnaces and a coaxial chimney.

   

   Chimneys for boilers with a closed combustion chamber are a "pipe in a pipe" system: through the gap between the pipes, fresh air enters the combustion chamber, and flue gases are discharged through the inner pipe

What is the device

The classic chimney device of a gas boiler consists of the following components:

1. The flue is a connecting link between the boiler and the chimney.
2. Additional elements - tees, adapters, bends, clamps. These are the details for the formation of the exhaust duct.
3. Brackets - for fixing the outer part of the chimney.
4. Revision - a hatch for cleaning the chimney from soot.
5. Condensate collector in the form of a tee with a device for draining it.

The chimney also includes special elements:

1. The device for adjusting the draft in the smoke channel can be flat (damper) or rotary (damper).

2. A deflector is a device at the upper end of the chimney that protects it from clogging. In addition, it protects the chimney from being blown out by the wind, increasing the draft.

   

   The chimney for a gas boiler can pass through the interior of the house or immediately go outside

When designing a chimney, it should be borne in mind that it cannot contain more than three channel bends. Otherwise, the thrust is sharply reduced, which can lead to serious consequences.

Choosing a chimney for a gas boiler

There are many methods of chimney construction using various materials.

Brick chimneys

Bricklaying a chimney is a time consuming and complex process that requires certain skills. The result is a square or rectangular channel. Its disadvantage is that it does not correspond to the conditions of gas movement. They move, twisting in a spiral, as a result of which stagnant zones are formed in the corners. In these places, intense condensation occurs and soot deposits are formed. In addition, the outer part of the chimney is subject to destruction due to atmospheric conditions.

A traditional brick chimney is poorly suited for gas boilers, because it does not provide an optimal mode of gas movement

The situation is corrected by installing a round pipe liner inside the brick chimney. It can be made of specialty plastics, ceramics, steel or asbestos. In this case, an audit is required. The insertion of the liner is called casing.

The brick chimney must be insulated in the outer area above the roof.

The chimney will last longer if you make it sleeve

Video: chimney sleeve

youtube.com/watch?v=K16JoX_5rn0

Metal chimneys

The use of metal for the combustion product removal system is very common. The advantage of this material is ease of installation and durability, especially if it is stainless steel. The inner surface of the metal pipe has a smooth surface, which facilitates condensation drainage and reduced soot formation. This is especially effective on gas heating units, since the temperature of the outgoing gases does not exceed 150 ^o C. For the same reason, there is no rapid burning of the pipe walls.

With the help of a metal pipe, you can make a chimney with any permissible configuration

Ceramic chimney pipes

Clay is the oldest building material. Currently, the scope of its application has expanded significantly. One of the uses is ceramic chimneys. They are made in the form of separate sections 50–100 centimeters long, at the ends of which grooves and protrusions are arranged for precise connection of the elements. Installation is carried out using expanded clay concrete blocks of a special shape, which are the frame of a fragile chimney.

Ceramic chimneys must be lined with special expanded clay concrete blocks to protect it from mechanical stress

During installation, the pipe is simultaneously insulated with basalt wool and the structure is reinforced through special openings in the blocks.

A feature of ceramic chimneys is their mandatory installation in a strictly vertical position. Therefore, they are installed on a separate foundation and in a place that allows the chimney to be routed without crossing the supporting structures of the house. Bends and bends of the ceramic chimney are not allowed.

Asbestos-cement chimneys

It should be noted that heat-resistant pipes are not manufactured from this material. The thermal resistance limit of asbestos pipes is 300 ^o C, so they are quite suitable for gas heating units. The disadvantages of pipes made of such material are that it is impossible to arrange a viewing window in them, and they must be installed strictly vertically. The connection is made by couplings with thread sealing with an asbestos cord. It is believed that fine asbestos fibers are released from the pipe during operation, harming the human body.

The inner surface of the asbestos pipe is rough, which contributes to the increased formation of soot on the walls. The installation of the asbestos pipe on the chimney is carried out with support on a separate foundation.

The use of asbestos pipes for the construction of chimneys in gas boilers is quite acceptable, since the temperature of the gases at the exit from the boiler is much less than 300 degrees

When choosing a chimney for a gas pipe, there are practically no material restrictions. The main criterion is the cost of the purchase itself and the complexity of the work.

DIY installation

The order of work for all chimneys is almost the same. Differences appear during the installation process and depend on the type of chimney material selected.

Brick chimneys

They are installed in the following order:

1. The heavy construction of a brick chimney is built on a separate foundation. An inspection window is installed in the lower part for inspection and cleaning of the chimney.

2. Masonry from the foundation is carried out with ordinary solid bricks using refractory masonry mortar. A clay-sand mixture is also used, which is quite strong and stable for furnace work.

   

   For laying chimneys, ordinary red refractory brick is used

3. At the height of the boiler flue, a hole is left in the wall of the masonry for it.

   

   At the required height in the chimney, a window is left for entering the pipe from the boiler

4. Upon reaching the overlap, the masonry is fluffed up - the pipe is laid out with broadening at least twice. The opening in the ceiling slab must be sealed with basalt wool or sewn up with an asbestos sheet. Further, laying is done with the original order.

   

   At the place of passage through the ceiling in the masonry, a special element is made - fluff, while the diameter of the inner channel remains unchanged

5. The crucial moment is the passage of the roofing pie. In this place, another expansion element of the chimney is made, which is called an otter. The gaps between the opening made in the roof and the chimney are filled with basalt wool, and the intersection plane is closed with a sheet of the corresponding profile. A bituminous sealant can be used to obtain a tight connection.

   

   The intersection of the otter and the roof overlaps is laid with insulation, and from the side of the roofing material it is sealed with a special apron made of metal plates

6. At the very top of the chimney, a widening is also made to prevent water from entering the outer walls of the chimney. A cap is attached to it, which protects the smoke channel from debris.

The design of the chimney along its entire length must comply with the requirements of the technical documentation specified above

For masonry of a brick chimney, a solid ceramic brick of the M50 or M75 brand is used. The minimum cross-sectional size of the chimney must be at least 140x140 mm, and in case of sleeve lining, at least 150 mm along the inner diameter of the sleeve. If the chimney has a height of less than five meters (from the grate to the head), its size must be increased to 140x200 mm or to a diameter of 180 mm.

A prerequisite is the passage of smoke channels inside the heated premises, otherwise their cooling and a drop in draft are inevitable. If there are several heating units in the house, it is advisable to group the chimneys in such a way that they have one multi-channel outlet above the roof. In addition to improving the conditions for fuel combustion, this will reduce construction costs.

Chimneys from metal pipes

As noted, this is the most popular chimney material. Its distribution is associated with ease of installation and a wide range of various components that allow you to arrange a chimney of any configuration.

Three main types of metal chimneys are common:

• outdoor, arranged along the wall of the building;
• internal, carried out inside the premises through the ceilings and roof;
• coaxial, specially designed for closed gas boilers.

External chimney made of metal

To install an external chimney, a hole is cut in the wall of the boiler room through which the chimney pipe is led out at an angle of 45 or 90 degrees. The length of the horizontal section should not exceed one meter. The inner part of the pipeline is made of a single-wall pipe so that the heat from it remains inside the house. The horizontal section is equipped with a tee, at the bottom of which a valve is installed to drain condensate from the vertical part of the pipe.

The vertical section of the chimney is insulated with refractory material, most often basalt wool is used for this, on top of which a protective jacket made of foil film or galvanized steel is arranged.

If the chimney is planned to be mounted on the street, it is taken out through a hole in the wall and directed upwards using a tee with a condensate trap

The vertical parts of outdoor chimneys are usually made of sandwich pipes. In them, the inner pipe is surrounded by insulation, and the outer one is a protective casing. The pipe ends are prepared for pipe-to-pipe connection during production.

Vertical sections of chimneys of gas boilers are collected "by condensate", that is, insert the upper pipe into the lower

The connection is made "by smoke" or "by condensate". In the first case, ideal conditions are created for the release of combustion products, in the second, for condensate drainage. But in any case, the connection is sealed with special sealants.

The chimney is attached to the walls of the building with brackets; at high heights, the upper part must be fastened with stainless wire braces.

Metal pipes are attached with special brackets to the wall, and if the height of the overhead part is high, they are fastened to the roof surface

A protective device in the form of a hood or a deflector must be installed at the upper end of the chimney.

Video: installing a wall chimney

Internal metal chimney

The chimney can be carried out inside the premises of the house with the intersection of at least one floor and roof, therefore its installation has its own characteristics.

The internal chimney crosses at least one floor and the roof structure

The flue gases are removed from the boiler through a horizontal or vertical flue from a single-wall pipe. The vertical section of the sandwich pipe begins before crossing the floor . The joint device inside the transition is categorically unacceptable. To arrange the intersection, you must:

1. Cut out a part of the ceiling at a distance of 12-15 centimeters from the pipe.

2. At the bottom, on the ceiling of the boiler room, install a steel sheet 1.5 mm thick, which is attached to the base with self-tapping screws.

   

   A metal sheet is fixed to the ceiling, which can be connected to a box for laying bulk insulation

3. Build an opening in the ceiling with basalt wool.

   

   From above, the free space is laid with basalt wool or covered with expanded clay (if a box was mounted for it), then a metal sheet is laid

4. On top of the basalt wool, place a steel sheet similar to the bottom one.

The intersection with the roof is done in the same way. When metal pipes are used, standard pipe covers are used to isolate the passage. They are produced with different angles of inclination or universal with plastic bases that can accept any inclination.

Coaxial chimneys

Coaxial chimneys are a relatively recent invention that is only used with closed gas boilers. Air from the boiler room does not enter such a heating unit, but is sucked in from the external space. The chimney pipe is a double-walled product, in which longitudinal partitions are installed instead of a heater.

In the coaxial design, the smoke removal is the inner channel of the smaller pipe, and air enters the combustion chamber through the annular space

When the fuel burns, the furnace gases begin to displace the cold air through the inner pipe, and since the heating unit is isolated from the boiler room space, air is sucked in through the outer part of the coaxial chimney.

The coaxial chimney is led out through the wall. This is done because there is no need to create natural draft in it - in closed systems, draft is generated forcibly due to the rotation of a fan built into the smoke channel.

Coaxial chimneys are not subject to the rules established for natural draft systems, here draft is created forcibly

Video: heating a private house - coaxial chimney

Asbestos and ceramic chimneys

Asbestos and ceramic chimneys are installed in compliance with the same requirements as metal ones. A feature of their installation is the need for a strictly vertical arrangement of the smoke channel and the installation of a separate foundation.

Insulation of chimneys for a gas boiler

Chimney insulation must be done for the following reasons:

1. Heat loss in the chimney occurs when exposed to cold outside air. At the same time, the temperature of the furnace gases also decreases, and, consequently, the speed of their movement decreases, that is, the thrust decreases. And if you add to this a decrease in thrust due to soot in the chimney or the unfavorable effects of wind, it is quite possible that reverse thrust occurs with the flow of carbon monoxide into the room. This is fraught with serious consequences.
2. A well-heated pipe provides sufficient thrust for active combustion of the fuel and its high heat transfer. As a result, the efficiency of the heating unit increases. This is especially important for gas boilers with low flue gas temperatures.

Chimneys are insulated in various ways:

1. Brick chimneys in the under-roof space can be effectively insulated with a layer of plaster, and if the attic is not insulated, rolled non-combustible materials in the form of stone, slag or basalt wool can be used. To ensure the safety of the insulation, it can be covered on top with foil or thin sheets of metal.
2. In the same way, you can insulate the outer part of the brick chimney, it depends on the climatic conditions in the area.
3. Metal chimneys are also insulated with insulation, the protection of the insulated surface can be done with galvanized or aluminum sheet.
4. Ceramic chimneys are insulated during installation with expanded clay blocks and mineral wool, as mentioned above.
5. Care should be taken when insulating asbestos pipes. When overheated, this material can explode with predictable consequences.

Photo gallery: methods of insulating chimneys

Minvata is fireproof and stores heat well

The insulation must be protected from destruction by a metal casing

Stone wool and expanded clay block reliably insulate the ceramic pipe

Brick chimneys are insulated with basalt or mineral wool, laid in a frame fixed to the pipe

Features of operation

The installation of a gas boiler chimney and its connection is such a responsible event that it is better to entrust it to a specialist in the gas industry. But if you decide to do it yourself, you need to firmly fulfill the following requirements:

1. Connecting more than one gas boiler to the chimney by combining pipes is unacceptable. With this design, combustion products will enter the house.
2. It is forbidden to combine galvanized elements with brick, asbestos and aluminum.
3. The work can be started only after careful calculations of the chimney cross-section in accordance with the parameters of the purchased gas boiler.

4. The length of the chimney must be at least 5 meters from the lower level of the furnace to the upper end.

   

   When installing any type of chimney other than coaxial, it is important to position it at the correct height

5. When installing a chimney on a building with a flat roof, the height of the chimney above the roof must be more than 1.5 meters.
6. The head of the pipe, the axis of which is located at a distance of 1 to 3 meters from the ridge, must not be below its level.
7. If the distance from the pipe to the ridge is less than 0.5 meters, the elevation of the pipe above the junction line of the slopes must be at least 0.5 meters.
8. If the length of the part of the pipe above the roof is more than two meters, it must be reinforced with additional braces in an amount of at least three pieces.

9. A deflector must be installed on the pipe head.

   

   Installing a deflector increases thrust by 20-25%

Checking the draft in the chimney of a gas boiler

The reason for checking is the obvious indicators of improper combustion of the boiler, which can be recognized by the following signs:

1. The smell of gas and the feeling of smoke in the room.
2. Burner flame color changes towards red. This is a clear sign of incomplete fuel combustion.

If these circumstances exist, you must immediately shut off the gas supply and ventilate the premises. After that, check the draft in the pipe and determine the cause of its failure:

1. Check the position of the draft control devices: gate or butterfly valve. They must be in an open or intermediate position.
2. Use an anemometer to measure the air velocity in the area of the firebox window. Although hardly anyone will buy an expensive device, since you can use folk methods.

3. Bring a strip of newsprint or toilet paper to the opening. With normal draft, it will actively bend towards the boiler. The test can also be carried out with the flame of a candle, lighter or match.

   

   The presence of draft is easiest to check by holding a match to the firebox - the flame should deflect towards the chimney

The reasons for the drop in thrust can be:

1. Insufficient pipe height. Under certain weather conditions, traction may deteriorate or disappear altogether.
2. Chimney contamination with soot, resulting in a critical change in the effective section of the duct.
3. Absence of a deflector at the upper end of the pipe. At a certain direction and strength of the wind, air currents can occur, preventing the exit of combustion products from the chimney until the formation of reverse draft.

It is necessary to reliably establish the cause of the draft drop and eliminate it. There must be an alternative heat source in the house. Then, measures to eliminate the causes of the drop in thrust can be carried out in a calm atmosphere and in comfortable conditions.

Video: checking the draft in the chimney of a gas boiler

youtube.com/watch?v=44GtClQZ8s8

Traction adjustment

Each boiler and fume extraction device is individual and their characteristics may change over time. Therefore, you will have to spend some time to understand the features of the traction settings for different weather conditions. This is especially important during the transition period at temperatures around zero degrees. The principle and methods of regulation are as follows:

1. The draft is adjusted with a gate mounted on the chimney. Its position is indicated by a pen.
2. Traction adjustment and automatic settings should be done in the fall, when the temperature reaches 5-10 degrees below zero, as well as in spring, during thaws with temperatures up to 5 degrees below zero.
3. Autumn regulation is built taking into account a further decrease in temperature, at which the pressure of cold air on the exhaust gases increases.
4. In clear frosty weather, the position of the gate should be set to the maximum gas flow rate. Gradually closing the chimney, we achieve that the burner flame becomes yellowish, which indicates incomplete combustion of the gas. In this case, the combustion should be even, without popping. The flame deflects towards the burner, which indicates the presence of traction and the health of the boiler. After that, the position of the gate must be set to the middle position at an angle of 45 degrees.

The spring adjustment is made upside-down for the expected temperature rise. Complete shut-off of the gate is unacceptable.

What to do if the boiler furnace blows out

There may be several reasons for this:

1. Insufficient pipe height.
2. Chimney freezing.
3. Excessive pipe breaks.
4. Placing the pipe.
5. The blowing of the pipe by the wind.

To get rid of the blowing out of the boiler, it is necessary to establish and eliminate the cause of this phenomenon.

The burner can blow out for various reasons, some of which are temporary.

A cardinal way to improve draft is to install a deflector at the upper end of the chimney. This device increases the extraction efficiency by 20-25%. And the use of a rotary deflector turns the wind from an enemy of the boiler into its ally. The deflector rotor rotated by the wind creates forced draft in the chimney.

With all the variety of models of deflectors, they perform one task - to increase the chimney draft

Precautions and Tips for Using Gas Boilers

The most dangerous situation occurs when all burners go out, including the igniter. This can lead to gas build-up in the room and explosion. The reasons for this situation may be:

1. Drop in pressure in the gas line or short-term interruption of the fuel supply.
2. Lack of draft in the chimney.
3. Interruption of supply voltage.
4. Igniter damping.

The first action in the event of one of the above situations is to immediately stop the gas supply manually. Modern gas boilers have a built-in security system, consisting of a mandatory set of sensors:

• flame sensor;
• traction control device;
• gas supply blocking device in case of short-term pressure drop in the network;
• a device that turns off the boiler in the event of a voltage failure in the boiler control network;
• a device for shutting down the boiler when the fuel consumption is below the established norms.

This set of control equipment is mandatory for every boiler. If any of the above circumstances arise, the first step is to stop the gas supply and ventilate the room. Only then can you use electrical appliances capable of creating a spark. In a certain place, you need to keep an LED flashlight ready for safe movement around the house.

Consumer reviews about chimneys

As can be seen from the feedback from consumers of chimney pipes, the most important parameter is safety, which can only be ensured with the help of quality products from well-known manufacturers. Therefore, it is better to overpay for the brand than to expose your own life to serious danger. I wish you success!