NATURAL DRAFT (OPEN COMBUSTION CHAMBER) BOILERS
Recommended lining tube: FuranFlex®
For many thousands of years mankind used heating devices that have open combustion chambers. To this very day the majority of
chimneys are connected to heating devices with such open combustion chambers. The operation of these chimneys is based on the
principle that the warm flue gas flowing inside it is lighter than the ambient air. As a result of this the flue gas flows upwards at a speed
of 4-6 m/s (14-21 km/h).
It creates a draft and a slight vacuum inside the chimney, as a result of which air is sucked into the combustion chamber, generally from
the living space.
If the boiler sucks in more air from the apartment than necessary, on the one hand this results in a loss of energy, and, on the other
hand, lack of air deriving from it may be dangerous. It also happens that the boiler receives less air than necessary. In such cases the
gas burns yellow, carbon monoxide is created (dangerous gas) and gas consumption increases. It is important that the living space
should have appropriate openings to allow air to flow in. A natural draft heating system can only operate well if all of its units are
properly designed. In this way frequently occurring cases of carbon monoxide poisoning can be avoided.
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A complete system operates efficiently only if all the units in the chimney circuit shown in the diagram are properly constructed (air intake, boiler, flue pipes, chimney). The system itself involves the possibility of carbon monoxide poisoning and in Hungary more than 40 people die every year and more than 100 cases of poisoning happen because of a fault in the chimney circuit.
In Hungary 90% of residential-purpose chimneys are natural draft chimneys.
FuranFlex® is beneficial in the case of natural draft chimneys, because it is made of a heat insulating material. Its thermal conductivity is 0.4 W/Km, while the same value in the case of stainless steel is 16 W/Km. Consequently the heat insulating capacity of FuranFlex® is 40 times better than that of stainless steel. It improves the draft and the efficiency of heating. |
In the case of natural draft chimneys the following junction pieces are needed for FuranFlex® installation:
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| 1. Rain-shield piece, smoke-stack cover and collar: to prevent rainwater or solid objects from getting in between FuranFlex® and the chimney wall or in the FuranFlex® lining tube. |
2.Open draft junction piece: for connecting boilers to chimneys.
| T-joint |
With wide strap |
With narrow strap |
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 3.Calibrating ring for open draft installation: piece for connecting the condensate and cleaning piece to the lining tube. |
 4.Open draft condensate and cleaning piece: for draining wastewater created during the operation of the chimney and for cleaning the chimney. |
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