Selecting the Right Chimney System
By Docherty Trade
It’s important to understand which chimney flue system is correct for your customer. One of the key features of the European Standard for metal chimneys is a user-readable classification system that designates the features of the product.
A label showing the classification must go with each flue component. Understanding the classification can make the job of selecting the right flue much easier and will allow you to compare different flues. It’s easy to use so long as you know the keys. The diagram below unlocks the coded information.
EN 1443 – T400 N2 D 3 Gxx
EN 1443 – T400 N2 D 3 Gxx is the minimum designation for a system chimney suitable for solid fuel.
Temperature class
Is the maximum flue operating temperature it has been approved for.
Pressure class
Is the pressure it has been tested to N negative, P positive, H high pressure. The accompanying number is the amount of leakage at pressure tested at.
Resistance to condensate class
Is whether suitable for Dry or Wet application. D or W
Corrosion resistance class
Is what type of fuel it may be used for. 1,2,3, (see table)
- Resistant to attack from products of combustion from gas and kerosene.
- Resistant to attack from products of combustion from gas, oil, and wood in an open appliance.
- Resistant to the products of combustion from gas, oil, wood in an open and closed appliance, coal, and peat
Sootfire resistance class
G means it has been tested to 1000 deg C for 30 minutes within a test and the gas tightness was still met after the test.
The xx is the distance to combustibles declared by the manufacturer when tested.
The letter O means it has not been sootfire tested and thus is not suitable for use with solid fuel. It will show either G or O.
EN 1856-1:2009
Each type of chimney system has a test method, for a metal chimney it is BS EN1856-1:2009 so within this test we have to meet the general requirements of EN 1443 using specified materials and test methods.
One of the key features of the European Standard for metal chimneys (EN 1856) is a user-readable classification system that designates the features of the product. A label showing the classification must go with each flue component. Understanding the classification can make the job of selecting the right flue much easier and will allow you to compare different flues. It’s easy to use so long as you know the keys. The diagram above unlocks the coded information.
Picking out a few of the main points:
Temperature Rating Maximum temperature (°C) for continuous use of the flue. T400 is suitable for multi-fuel.
Pressure class – is the pressure it has been tested to N negative, P positive, H high pressure. Minimum is N1 which has been tested at 40Pa with a maximum leakage of 2ltrs/sec/m2
Resistance to condensate class – is whether suitable for Dry or Wet application. D or W
Corrosion Resistance This is fuel dependent as follows
V1, V2, V3 are tested corrosion resistance levels.
VM – Not tested but rating declared by the manufacturer.
L40045 – Twin Wall Inner Material and Thickness, the minimum for solid fuel is 316 (L40 Stainless Steel). However, 316L (L50 Stainless Steel) is more commonly used for solid fuel as it has better corrosive qualities. The minimum thickness of the inner is 0.40mm. (The example above shows 0.45mm). Light oil is less corrosive and normally 304 (L20) has proved adequate in dry conditions, but in the increasingly common wet conditions created by high efficiency condensing boilers, the higher grade is required (316L).
Soot Fire Resistance and Distance to Combustibles Expressed as either G, for soot fire resistance or O for not, followed by xx the declared minimum distance to combustibles and maybe used for the ventilation clearances required within an enclosure expressed in mm. To obtain the G classification means that the product has been tested at 1000°C for 30 minutes and remains intact.
