STOVE GUIDE - The Stove Yard

THE FLUE SYSTEM…
…THE ENGINE OF THE STOVE
FLUE DRAUGHT AND COMBUSTION
There are three important considerations necessary to maximise the
performance of your stove:
1. Perfect post-combustion with pre-heated air – automatic tertiary air.
2. The correct fuel – good burning, well-seasoned wood with less
than 18 % moisture content.
3. a flue system with good up-draught – the ‘engine’ of the stove.
a stove does not produce its own up-draught. This is created through
differences in air pressure between the inside of the house and the
pressure of the outside air caused by the difference between the two
temperatures causing the normally warmer internal air to rise through
the flue system. a chimney with the wrong dimensions (ie a much
greater cross-section than the stove flue outlet) will hinder the development
of good up-draught. Weather and atmospheric conditions will
also affect the draught performance.
all Dan SKan stoves are manufactured using the latest laser technology
to create a uniform quality criteria to ensure that they all deliver
the same special high performance combustion, but like a car this performance
will very much depend upon a good engine and good fuel.
SIMPLE PERFORMANCE TESTS
if you want to test the performance of the stove yourself, try the
following simple tests:
1. Safety Match Test for Up-draught
When the stove is cold, open the stove door – just a small gap, and
then hold a burning match just in front of the gap (about 50 mm / 2").
if the flame is drawn into the fire chamber, the flue system has updraught.
However, if the flame is not drawn in, or is pushed outwards
into the room then the flue could have no up-draught at all or possibly
a down-draught problem. if the match is drawn in so strongly that it
goes out, then you probably have very good up-draught.
2. Ash Pan Fire Test for Air Wash Function
With the ClaSSiC linE, again, when the stove is cold, fully open the
pull control, then open up the ash pan and place crumbled-up
newspaper inside it. after setting the paper alight, quickly close up
the ash pan, making sure it is fully closed. You should see smoke,
firstly coming out of the lower air wash channels (towards the base
of the window) and eventually coming out of the upper air wash
channels. This demonstrates that the air wash channels are open
and functioning properly.
3. Soot Test for Fuel Quality
Should you see persistent carbon deposits on the fire chamber fittings
or darkening of the glass then we recommend that you undertake
the following simple visual checks. remove the Skamol panel or
‘lid’ at the inside top of the fire chamber or alternatively remove the
inspection hatch on the flue pipe. Check for the build-up of flakey
soot / carbon which may also have an unpleasant acrid smell would
be a clear sign that poor quality or damp fuel has been burned.
These deposits could eventually ‘fur’ up the flue system, reduce the
up-draught, or potentially cause a chimney fire. a fine covering of
dry ash powder which can be easily rubbed away with your finger is
perfectly normal.
CORRECT DIMENSIONS OF THE CHIMNEY / FLUE
SYSTEM
The prerequisite for a proper functioning stove is the suitability of the
chimney or flue system (minimum cross-section, effective stack height
and positioning etc.) which should conform to all local and national
Building regulations – Document J for England & Wales (Scotland and
northern ireland have their own versions) and approved Document J:
Heat Producing appliances for the republic of ireland.
Chimneys with a cross-sectional internal diameter of more than 200
mm (8") and / or less than 5 m (15") stack height measured from the
top of the fire box could cause draught problems.
in our experience the simplest and most cost-effective way to reduce
the cross-sectional diameter of an existing chimney is to fit an
approved solid fuel flexible chimney liner of approximately 150 mm
(6") diameter.
Your installer or Dan SKan partner will be able to advise you on
this as well as various methods to compensate for insufficient stack
height and poor up-draught. a chimney or flue system which matches
the flue outlet diameter of the stove combined with a flue height of
more than 6 m (20") is advantageous and strongly recommended.
The chimney or flue system internal pressure should ideally reach at
least 11 or 12 Pa.
HEATING IN THE TRANSITION BETWEEN SUMMER AND
WINTER
in the autumn air temperatures can vary extremely quickly and this
could adversely affect your flue draught and the performance of your
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stove, making it difficult to light the fire and making it very slow to burn
as normal. For example, a sudden rise in temperature will disturb the
pressure balance that normally makes the flue work so that the flue
gases find it difficult to rise. Strong winds can have a similar effect and
is most noticeable when opening the stove door to add fuel.
if in doubt always try the safety match test discussed above. Using
this method you can easily see whether you have sufficient up-draught
or if there is likely to be a down-draught problem.
in such instances we always recommend lighting with the ‘top fire’
method described on the inside back cover of this brochure and with
a larger than normal ‘pre-fire’ to help get the draught moving in the
right direction.
it is important that before you light the larger pre-fire you open a
window or door (in the opposite direction of the wind) so that a lower
pressure can be quickly achieved in the room where the stove is
located than that in the flue system. Once your fire begins to burn
normally then the door or window should be closed.
MAINTAINING A CLEAN BURN
To maintain a high performing clean burning stove you must ensure
that the flue gases always move through the chimney or flue system
as quickly as possible limiting anything which might slow them down
and therefore cool the gas and smoke to the point where they can
create creosote and soot deposits which will further enhance the
slowing and cooling process. We recommend that the flueways are
cleaned by an experienced chimney sweep at least once a year
and preferably before the beginning of the heating season. The
performance of the air wash system and its ability to maintain a clean
glass, both up and down, will also depend on the speedy removal of
the flue gases through a flue system which has a good up-draught.
Smoke escaping from the stove into the room during reloading could
indicate that you have a temporary problem with the weather
conditions. Persistent smoke escape could indicate a problem with
the flue system, possibly sooting up, and this should be investigated
as a matter of urgency by the installer or chimney sweep. if you plan
to use an existing chimney which has a much greater cross-sectional
area than recommended by Dan SKan (see page 85) then it is probably
advisable to choose a stove with double doors, where only one door
needs to be opened for refuelling, thus limiting the disturbance to the
fire chamber pressure and up-draught.
ENCOURAGING FLAMES
a good chimney draught depends on good flames. Without heat
producing flame the up-draught is limited and so too is the air wash
performance.
remember that poor burning woods (eg laburnum, leylandii etc)
and damp or unseasoned wood with a moisture content of more
than 18% will produce a lot of smoke and soot as well as a very poor
flame. Slow burning hardwoods, such as Beech and Oak, work better
when started with some highly flammable wood such as Spruce or
Pine to encourage the flames.
Beech wood contains a lot of tar and is better mixed to help reduce
the sticky black spots it may leave on the glass, which even our
superior air wash system will find difficult to clear.
if the fire has burned down so that only a few embers are left, when
any new fuel is added, always open the glass door slightly to encourage
a strong up-draught which will perform like a blacksmith‘s
bellows and quickly help the new logs to light. This should only take
a minute or two and then the door should be closed to avoid dangerously
over-firing the stove.
PROMOTING A GOOD UP-DRAUGHT
always start your fire with a good starting or pre-fire – this will save time
in the long run (see the inside back cover for our ‘Top fire’ instructions).
Only when the whole system, the stove and the chimney, have good
basic heat throughout, can the correct conditions for an efficient
up-draught and clean burning be achieved. Only a warm system can
supply sufficient up-draught.
When it is very cold outside then the bigger your pre-fire should be so
that the rising hot gases from the pre-fire quickly warm the flue system
to encourage a good up-draught – just like starting an engine!
if your chimney or flue system performs poorly then you may be able
to improve this by reducing the size of the baffle plate by trimming a
little bit at a time from the front edge until you arrive at the best ‘setting’.
The Skamol baffle plate can be easily cut using a manual saw or
electric jig-saw. You can even try operating the stove without the
baffle plate.
This will be safe because your Dan SKan stove is manufactured to
the highest standards so that the bodywork will easily withstand the
heat and still remain perfectly stable.