Today, brick pipes have been replaced by sandwich-module structures (steel + insulation). With observance of production and assembly technologies, they provide fire safety and excellent traction. However, sometimes the chimney refuses to work properly. On the forum of the site IVD.ru and specialized Internet resources on heating, we chose descriptions of the symptoms of the most common “diseases” of chimneys. Engineers of manufacturing companies and building practitioners helped us in making “diagnoses” and searching for “medicines”.
The fireplace does not melt well, the firewood does not burn, but smolders, the glass of the furnace door is quickly covered with soot, wisps of smoke break through the air holes.
Signs of poor traction are listed. The most common reason is severe contamination of the chimney. If a newly built fireplace smokes, then a chimney of insufficient length (less than 5 m), too many bends, narrowings and extended horizontal sections can be a source of problems. With insufficient traction, it often helps to increase the height of the pipe by 1–2 m, and it is necessary to use only well-insulated modules and attach the extension to the building structures with cable braces or studs so that it is not blown away by the wind. If after this the draft does not return to normal, the chimney needs a complete reconstruction — an increase in diameter and a straightening of the “main”. Another way is to install an electric smoke exhauster, but it has drawbacks (we will talk about devices to improve traction separately).
The reason for the poor performance of the chimney is most often the mistakes of designers and installers, and only sometimes — manufacturers
As a rule, the fireplace heats up normally, but occasionally large clouds of smoke break through the air holes.
This phenomenon is called pull-back. It is possible that the chimney is not properly aligned relative to the ridge, and downward swirls of air flow periodically occur in the area of the head. The probability of draft overturning by the wind increases with insufficient insulation of the upper part of the pipe: the smoke has time to cool, its speed decreases sharply, and gusts of wind easily disrupt the operation of the fireplace. The cause of the trouble may be an unsuccessful umbrella design that creates aerodynamic resistance.
Chimney insulation helps to solve the problem. If it is not possible to replace the upper modules, you should order a shell (outer casing), the diameter of which will allow you to install an additional layer of thermal insulation with a thickness of 30–50 mm. It is better to use special basalt wool insulation, such as Rockwool Fire Batts (non-foiled). Wind vane deflector can become an additional protection against overturning thrust by the wind.
The fireplace consumes a lot of fuel and gives little heat.
A straight-through chimney of circular cross section with a height of more than 6 m often draws too much, and it is not possible to slow down combustion, even by completely closing the dampers of the air inlets (after all, a residual gap is always provided). In this case, the efficiency of the device is very low.
To regulate the draft, it is necessary to install a gate at the outlet of the furnace (alas, you have to disassemble the entire pipe). In addition, heat-removing or heat-storing modules in the lower part of the chimney will be useful. The former are equipped with metal ribs and operate on the principle of a radiator, the latter are double-walled, but the insulation in them is replaced by stone chips or perlite sand.
Some sections of the chimney are very hot, sometimes their temperature exceeds 100 ° C.
Most likely, this problem is caused by local thermal degradation or shrinkage of low-quality insulation. The probability of leakage of the inner tube is small, but still it cannot be ruled out. Overheating of the shell is dangerous, especially if combustible structures are located nearby (closer than 0.5 m), because overdried wood can ignite spontaneously at a relatively low temperature. In addition, the deterioration of thermal insulation leads to an increase in the amount of smoke condensate: the container for it will quickly overflow, and if equipment is installed that allows the condensate to be drained into the sewer (neutralizer), the consumption of an expensive reagent will increase.
A chimney with a similar defect must be replaced. As a temporary measure, you can limit yourself to installing an additional thermally insulating casing (for example, from GVL, filled with stone wool), but first you need to check the condition of the walls of the smoke channel — this service is provided by service companies.
An incorrectly selected deflector nozzle can cause sudden draft disturbances and carbon monoxide penetration into living rooms.
Once the pipe was very hot all over, crackling was heard in it, the smell of hot metal appeared in the rooms. Then everything returned to normal, only the galvanized umbrella darkened and began to rust.
The classic symptoms of a soot fire in a pipe are described. A chimney made of quality materials (working channel — stainless steel grade 321, 430 or 439 according to AISI classification, insulation — basalt or ceramic wool) must withstand such a test. After the incident, it is necessary to monitor the temperature of the shell for some time, and in addition, it is advisable to take photographs of the smoke channel. In general, it is better to prevent a fire in the chimney, for which it is enough to clean the chimney once a year (when using long-burning stoves — 2 times).
After several years of operation, condensate began to seep through the joints, especially in the upper part of the chimney, in the attic.
Obviously, the chimney is poorly insulated, which causes intense formation of condensate, and at the same time it is incorrectly manufactured and assembled: its elements are oriented downwards with sockets. (It is necessary that the sockets of the smoke channel parts face upwards.) Trying to seal the joints with oven sealant is useless in this case. The chimney can be operated for some more time, but after waiting for the warm season, it should be reconstructed.
In the spring, brown streaks began to be seen on the roof, near the chimney.
Most likely, an umbrella of considerable size is to blame, on the cold surfaces of which condensation fell out. Even more caustic liquid can form on the walls of a metal box with a roof, arranged for several pipes (flue and exhaust). Such a box must be filled with expanded clay almost to the pipe cuts, and the area of u200bu200bthe umbrella should be reduced. A little rain and snow is harmless to the chimney and heating equipment, but it is almost impossible to remove traces of condensate from the roof and walls.
Quite often, to correct errors made in the design of the chimney, special nozzles are used on the pipe.
Vane deflector closes the mouth of the chimney from horizontal and vortex air flows. It consists of an inclined shield movably fixed on a vertical axis, equipped with a “feathering”, due to which the shield is located on the windward side of the pipe head. In moderate winds, the deflector stabilizes and enhances traction, greatly reducing the likelihood of it tipping over.
Rotating deflector is a spherical turbine. Under the influence of wind (regardless of direction), its blades rotate and create a vacuum in the pipe. Such devices have proven their effectiveness as elements of roof ventilation systems. However, they are almost unsuitable for chimneys, since they worsen draft in calm weather, and in winter they can freeze, completely blocking the path to flue gases, which is extremely dangerous.
Electric smoke exhauster The simplest design is a nozzle on a pipe with a fan, the blades of which rotate directly in the smoke channel. It is desirable that the performance of the device can be adjusted — in this way, it will be possible to provide quick kindling, and then moderate the cravings.
The smoke exhauster is reliable, since its moving parts are protected from moisture and ice (as well as from the effects of caustic substances and high temperatures), economical (power consumption 40–100 W / h) and almost silent. Its main disadvantages are the need for periodic cleaning of tar and soot and dependence on power supply. However, the second disadvantage is easily overcome by installing a backup power source. A smoke exhauster is sometimes used as a “cure” for poor draft, but it is mainly intended for the convenience of using open-hearth fireplaces and island hearths.