A flue damper is a cast iron or steel plate on a spindle fitted inside a flue system (usually in the first length of vitreous enamel flue pipe) which can be rotated by a small handle outside the flue pipe to reduce the adverse affects of a strong flue up-draught or 'pull'. It does this like a 'butterfly valve' by simply moving the plate against the flue gas flow to help slow it down.
Whilst a good up-draught is a fundamental requirement for the successful operation of your stove, a flue draught which is too strong however can limit the control you have over the stove. It generally means that you can't successfully turn down the stove when it is getting too hot or when you want to put the stove in 'slumber' mode. This obviously means that your stove will consume more fuel than it needs to, and in some cases, send most of the excess heat generated straight out through the flue system.
Under normal operating circumstances a damper is never required and for safety reasons, in the UK and Ireland, flue dampers should only ever be retro-fitted by a Hetas Registered Installer or other specialist. If you think about it, anything that restricts the flow of dangerous flue gas out of the stove, could potentially be a bad thing and therefore all factory-made dampers still leave enough space in the flue pipe to maintain a reasonable up-draught. In Europe, particularly Scandinavia and Germany, a flue damper is fitted within the flue system as standard – but it is important to point out, that there are strict laws in these countries governing the regular cleaning and maintenance of flues for insurance purpose. Without regular cleaning a damper could very quickly become clogged and easily restrict the flow of flue gases further to an extremely dangerous level.
At The Stove Yard we would NOT recommend fitting a flue damper without consulting a Hetas Registered Installer first and for that reason we do not sell them to the public on our website.