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Advice on your Multi Fuel Stove installation. |
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For many years now Multi Fuel stoves have become increasingly more
popular. Recommended for problem open fires and also for homes not using
fires often, to prevent heat loss when the appliance is idle. As a space
heater or fitted with a boiler, they can be a complete heating system,
whatever you choose, you can be sure of a very versatile unit, and extremely
efficient. This being said, they have some underlying problems from a chimney
and flue function point of view, for which we have produced two leaflets.
This leaflet deals with the installation issues. We have found through 15 years of working with these products that, as
you might expect, when you give a homeowner the chance to economise, they will...no one blames you. The
problem is your poor old chimney needs heat to carry the combustion products
up the flue to escape. The basis physics of a chimney performance is not
rocket science. If you burn something slowly, you will not produce enough
heat to take the smoke fully through the flue, and we now have to deal with a
condensing problem. Simply put, flue gasses don’t escape quickly enough
through the flue, therefore they cool and condense. This, where stoves and
especially wood burning stoves are concerned, create a tar and creosote build
up. When allowed to build up this substance is a serious fire hazard. With
open fires, where you have no real control over the burning rate, although
still a problem, this crust doesn’t build up as quickly as a slow burning
appliance. We would offer this advice, before you install the stove. Firstly,
make sure the flue you are using is in perfect condition. We have had a lot of problems with stoves being fitted to
damp old chimneys, some not even flue lined, and if they are lined, the
liners have either been installed upside down, not sealed, insulated or
protected from damp. If you are in any doubt as to the integrity of the flue
you intend to use, we would strongly suggest the flue be sleeved with class
one stainless steel flexible flue (figure 1) This can then be insulated and
an adapter be fitted connecting it to the vitreous pipe coming off the stove.
This type of installation will ensure the flue performs correctly, even when
low burning because the steel flue will come up to working temperature
quickly and the insulation will maintain these flue gas temperatures. We would also suggest that the stove be vented from the top of the
stove as opposed to the rear. From a chimney sweeping point of view it is more convenient to sweep from the stove
up through the flue as opposed to down from the top, but more importantly,
heat rises, and if flue gasses are allowed to rise directly up into the flue
chase, they will travel more rapidly. Any kind of bend in a flue, if
absolutely necessary, should be no greater than 30degrees. The only justifiable reason for having a bend in a flue is to make sure the top
of the chimney is terminating at the highest point of a roof. (look at older
properties and you will know what we mean. A living room and perhaps a
kitchen and two bedroom flues would have had bends incorporated to allow them
to join the one chimney stack at the highest part of the roof) With a stove
these bends are just a cause for flue gasses to slow and deposit soot, tar
and creosote. The ideal flue should be vertical, indeed Scandinavian
and American chimneys are almost always straight up. 90 degree bends and horizontal runs should be
avoided at all costs. It has been recommended by manufacturers of stoves, retailers, chimney
technicians and the fire safety personnel that you avoid any kind of damp
wood. If you don’t have a plentiful supply of seasoned dry wood and a place
to store volumes of blocks to keep it dry, we would suggest you think about
avoiding wood altogether. Figure 2 shows the accumulation caused in a new
flue after only two months burning fresh wood with a high sticky sap content,
causing a treacle type deposit to “Grow” through the
flue restricting the performance. Think of “furred Arteries.” The Scandinavian and American wood burner
has a three year rotational wood supply under a lean to roof at the side of
the house for a very good reason...they know how to burn wood correctly….do
you remember “little house on the prairie” Finally, we would suggest that the chimney pot be fitted with a
critter guard. This cover is made of steel and galvanised. It will protect
against birds entering and potentially building a nest, but it also prevents
rain entering the flue which will cause a cooling effect on the up-flow of
hot gasses. The cover is ideal to prevent damp while the stove is not used
for long periods during the summer, but it is advisable to leave the door of
the stove slightly open during these periods to allow air movement. FEEL
FREE TO CONTACT US FOR A NO OBLIGATION APPOINTMENT TO ASSESS
YOUR INSTALLATION NEEDS BEFORE BUYING A STOVE. |
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Figure
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Figure
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