Traditionally, stoves were intended to burn wood and only wood, then multi-fuel stoves were created to give you the option of heating your home with either coal or wood. So , .. Multi Fuel or Wood Burning stove ?
First off, you should know that it is NOT advisable to burn both coal and wood in your stove at the same time as this can and will damage your flue lining and stove itself.
Why is it not wise to mix fuels
Why can’t you mix fuels ? because corrosive materials such as halogens and sulphur found in coal will combine with the moisture in wood creating nasty, Sulphurous acid & other solutions that stick to and then erodes your whole stove system.
Whilst multi-fuel stoves bring with them the versatility of being able to choose which fuel you’d rather use at a particular time , their one limitation is the use of ONLY One fuel at a time! Mixing fuels is not cool !
Only coal as fuel? ..Simple use Smokeless
You should always check your owner’s manual for the final word from the manufacturer on what fuels are recommended for use. Although most multi-fuel stoves are equipped to burn normal house coal, (aka bituminous coal) often most stove manufacturers will advise against this because of the high amount of soot in house coal.
**High soot content results in your stove system becoming rapidly clogged up**.
Using smokeless coal avoids this problem by agglomerating particles and reducing the amount of smoke and soot going up your flue , is also better for the environment and thus suitable for use in smoke control areas.
Knowing which stove is which , just by what you can see
Multi Fuel or Wood Burning stove , the most obvious examples you can see immediately by eye are the:
1. External primary PRC & SRC secondary air flow regulator controls and
2. Internal raised grate of multi fuel burners or the flat bottom non grate of wood burners.
Coal burns best on a ‘raised grate’ since it needs an air supply from below. Therefore , the primary airflow intake is below and its manually adjustable Primary Regulator Control outside (usually, somewhere near the bottom of the stove door & is normally either a sliding slat or turning knob/disc) is used to burn it effectively.
Wood doesn’t need this additional air supply below therefore , wood burners come with only a ‘flat bottom‘ . This limits the air supply to the fuel, resulting in a slower burn and you will see they ONLY have a top secondary air flow intake with manually adjustable Secondary Regulator Control.
**** The adjustable multifuel grate in the picture below shows it can be both raised (top) allowing upwards air flow or it can be flattened (bottom) stopping upwards air flow from below. ****
You will find that wood burns faster on a multifuel stove than on a normal wood-burning stove because of the extra oxygen and air flow from below.
So what do I want to buy then?
In short , what to buy depends on what you are going to burn? If you’re thinking of using wood as your main fuel then it’s best to buy a wood-burning stove. By buying a multi-fuel stove, you are already almost committed to coal being your main fuel (but keeping the option open to burn wood if need be, albeit at a lower efficiency) and wood as an option.
Therefore , for the reasons already mentioned above , smokeless coal is your prime candidate fuel for a multi fuel stove. So you will be considering Anthracite, as well as a host of brand name alternatives such as Taybrite and Phurnacite.
However , as you will see in our article on stainless steel liners there are some drawbacks to using these smokeless fuels.
Things to keep in mind::
1. Normal house coal is cheaper but too dirty for stoves
2. Smokeless is expensive and more corrosive but burns clean enough & is better to use in stoves than bituminous
3. Unless you have a free source of weathered hard woods then having a multifuel means using smokeless coal IS the option.
4. Don’t ever use wood and coal together at same time, water in wood dissolves sulphur in coal creating sulphurous acid !! ALL coal has sulphur , some worse than others.
5. Best to have a china hat/cowl to deflect water ingress. All lum/flue dampness causes sulphurous acid corrosion, esp with smokeless fuel
6. Smaller (within stove capacity) hotter hardwood fires are cleaner and don’t ruin baffle-plates or warp stoves
7. Read about liners on this site, 316 SS for wood and 906 for Anthracites NB/ sulphur ~ halogen corrosives
8. In olden days damper plates were used to control burning[often slumbering Tutt Tutt!!] by choking the fumes exhaust rather than the air intake itself reducing combustion. This is dangerous due to the accumulation of toxins rather than reducing their creation in combustion control itself.
Using a wood [you see SRC only ! Flat Grate] only stove:-
You would be controlling the flames ONLY by the Secondary air flow intake [see picture 1 above] by manually adjusting the Secondary Regulator Control. Correct settings would be seen as curling yellow flames emanating from the mixture of gases combusting above the fuel on the grate.
Using a multi [you see PRC & SRC Raised Grate] fuel stove:-
You would control the main flames by using the Primary Regulator Control [see picture 1 above] then adjust further also with more tighter control to satisfactory conditions by the SRC [see picture 1 above]. Visually blue/orange flames would be seen below and yellow ones above the fuel.