The necessity to use a double-walled chimney in the fan package

As you know, many heating equipments such as heaters, water heaters, and central heating boilers in the country are gas-burning. On the other hand, according to the statistics published by the Forensic Medicine Organization, unfortunately, in 1400, more than 840 people died due to poisoning caused by inhaling poisonous carbon monoxide gas!

According to this organization, if any gas-burning device consumes ambient oxygen for combustion, it will cause the production and release of deadly carbon monoxide gas and suffocation of the people present in the place.
We also know that one of the most widely used types of equipment in the field of building heating installations is gas-burning heating boilers, which are produced in two types, with and without fans. The difference between these two types of packages is in the way air enters and exits combustion gases from the device. Considering that in fan packages (closed combustion chamber), an air suction fan performs the action of sucking the air required for combustion from the free space into the device and discharging the combustion gases to the outside through the inner part of the double-walled chimney. One of the ways to prevent poisoning caused by carbon monoxide gas is to use double-walled chimneys for fan packages, which will be discussed in the following.

A few important points:

• According to the national building regulations, the use of a package with a standard mark is allowed for units with a size of less than 65 square meters only by observing certain conditions such as installation by the company's authorized services and technical approval by the supervising engineer.
• According to valid standards and even the standard of national building regulations in Iran, if any type of gas-consuming equipment is used inside residential units, at least 2 fresh air supply valves must be installed for that unit.
• Also, compliance with important matters such as having a standard mark, a technical certificate from the building and housing research center, installation by authorized services, and finally general approval by the supervising engineer, for all units after installing the central heating boilers and all other facilities, such as doors and windows and It is mandatory to make the unit habitable.
• The use of carbon monoxide gas sensors is highly recommended in units that use heating equipment that consumes natural gas.

What is a double-walled chimney?

Double-walled chimneys consist of two walls at the same center and inside each other, which simultaneously perform the two actions of entering the outside air into the device and discharging the combustion gases out of the package.

In other words, double-walled chimneys usually have a path with a diameter of 10 cm for the air to enter and supply the oxygen required for the package from the outside, and a path inside it with a diameter of 6 cm (in the center) for the exit of combustion gases, including the deadly gas of monoxide. Carbon and carbon dioxide gas are taken out of the building.

The sheet material of double-walled chimneys should be aluminum or steel sheet 304 and galvanized sheet should not be used, because due to the high reactivity of galvanized sheet with combustion vapors and the creation of dew point in the device's chimney, after a few years caused corrosion and numerous holes in the chimney, and as a result, the deadly carbon monoxide gas enters inside, which itself leads to the risk of death for the residents due to gas suffocation!

The advantages of using a double-walled chimney

In short, double-walled chimneys have the following advantages:
• Preventing the consumption of ambient oxygen
• Preventing the entry of deadly carbon monoxide gas inside
• Preventing the reaction of oxygen with carbon monoxide
• Increasing the efficiency of the gas heating package

Comparison between a double-walled chimney and a single-walled chimney

A single-walled chimney is actually a simple chimney that is connected to any type of package or gas-burning heater and creates only one outlet for the smoke from combustion. When a single-walled chimney is used, the device uses ambient oxygen for combustion, and as it was said, according to international standards, installing this type of chimney is not legal in many environments.
In many cases, unfortunately, by not observing the safety precautions, single-walled chimneys are installed only on the inner diameter of the outlet flange of the fan package chimney! While double-walled chimneys, by using two separate paths for the entry of fresh air and the exit of toxic gases and smoke from combustion (from the closed combustion chamber of fan packages), prevent gassing and also reduce the temperature of the smoke resulting from combustion during It comes out of the device, which, in addition to reducing the damage to the environment, will have a positive effect on the efficiency of the device by 2 to 3 percent.

Safety tips for installing a double-walled chimney

• The maximum length of the horizontal or vertical pipe of aluminum or steel 304 double-walled fan packages with a diameter of 60/100 (mm) is about 4 meters and a chimney with a diameter of 125/80 (mm) is about 11 meters.
• The double-walled chimney must extend at least 30 cm outside to exit the building
• The minimum distance of the double-walled chimney of the fan package is 25 cm from the wall, and it must be removed from the building by installing a steel grid on it.
• If each 90° bend is 1 meter and 45° bend is 0.5 meters, and if two bends are installed in a row, 2 meters should be reduced from the length of the double-walled chimney pipe.

Important note: when installing a double-walled chimney (aluminum or steel), you must pay attention to the fact that the chimney has a slight downward slope so that the perspiration caused by the difference in the temperature of the incoming air and the outgoing gases (which creates an acidic liquid) enters the package. It does not return and does not cause damage and decay to the combustion chamber and burner inside the device and is completely transferred outside the device and building.

Also, it is better that the double-walled chimney brand and the standard fan package are both from the same reputable company.

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final word

In this article, we discussed the necessity of using a double-walled chimney in fan central heating boiler, taking into account its safety points. Damatajhiz store site has provided you with technical information and specifications of hundreds of models of heating packages and gives this opportunity to dear customers to buy the products they need by guaranteeing the originality of the product, providing after-sales service, valid warranty, and price. If you need to get more information or get advice from the experts of Damatajhiz group during office hours, please call 021-88822550.

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