Fuel Burning

A chimney operates on the principle of having a natural up draught. One factor in creating the up draught is maintaining a warm flue gas temperature.

The recommended temperature range in Document J is between 150˚C and 450˚C. The upper temperature in the new BS EN 15287-1 has been reduced to 400˚C. 

Burning wood or multi fuel slowly with insufficient air supply, particularly on stoves or closed appliances must be avoided. Low flue gas temperatures will cause condensation and greatly increases the risk of producing excessive tar and corrosive soot deposits. This is a common problem, particularly when burning wet wood or coal and should be avoided. If soot and condensate deposits are allowed to accumulate in a flue, the deposits can ignite causing a chimney fire. These deposits can also be very corrosive and if they are not regularly removed can cause corrosion of the metal parts of both the chimney and the appliance.

When burning wood it is important to ensure that it is dry and well-seasoned. The HETAS Wood Fuel Guide provides useful information on the use of wood as a fuel. Always use suitable solid fuels. Some processed fuels can produce abnormally high temperatures together with very corrosive deposits. The HETAS Guide also contains a list of suitable fuels. An Approved Solid Fuel Merchant should also be able to give advice. Never burn household waste, plastics or chemicals, which can produce harmful fumes and corrosive vapours. These vapours can be dangerous to health and cause premature corrosion of metals. Where the appliance is slumbered overnight or for long periods it is advisable to run the appliance at high fire in a controlled manner for a period of at least 30 minutes. Slumbering is a contributing factor to premature liner failure through corrosion. It is important to ensure a sufficiently high flue gas temperature to minimise the products of combustion condensing out of the flue gases.