The multi-fuel part simply means that the stove can also burn solid fuel like smokeless briquettes or coal. If it is multi-fuel then it will have a grate and typically a riddling mechanism (a way of shaking the ash and embers into the ash pan below the grate). You can often buy a multi-fuel ‘kit’ for a standard wood burner thus converting it into a multi-fuel stove. If you are going to burn solid fuel then you must understand that it is quite different to wood in the way that it burns.
Our stoves pages contain models that are either wood burning only or multi-fuel. If you are unsure which model you might need please get in touch with us to discuss your requirements.
Wood burns best when the air supply is provide from on top of the wood, usually by a pre-heated mechanism. This air supply is usually called the secondary air supply on modern wood burners. The primary or underneath air supply should be closed apart from when first lighting the fire.
If the stove has a grate then this should be shut to stop embers falling into the ash pan. The embers or coals are an integral part of the wood burning process and should be allowed to build up underneath partially burnt wood.
New wood should then be layered on top and a good burst of air provided to properly ignite this new fuel, this might be for 15 minutes or so. Once the new wood is burning well, the air supply can be reduced but not so much that the flames disappear – always have some flames within the firebox. This is what tells you that the combustion gases are being burnt off. Ideally, the firebox should be completely loaded with wood each time you re-fuel.
Then over time, the middle to bottom layer of this sandwich will slowly turn to charcoal because the air supply to the underneath of the fuel is limited by the new wood. The top layer of wood will burn down slowly (because the air inlet is partially closed) and when this wood has turned to glowing coals, new wood can be placed on top. Since charcoal needs less air to burn than fresh wood, a fire containing charcoal as a base allows the combustion process to slow down and helps to stabilise the cycles of burning and re-fueling.
Slow or fast
The loading and laying of wood inside your wood burner permits different types of fires, from quick fast fires to long slow burn ones but remember, never let the fire smoulder as this is wasting a lot of wood energy in the form of smoke and this is what will coat your chimney with creosote and tar. If you want a longer burning fire then stack the wood tightly inside the firebox, if you want a faster fire then stack the wood with larger air spaces between the logs.
Keep the ash
Modern wood burners are surprisingly efficient to new owners, especially if they are used to burning solid fuel on an open fire. They produce very little ash compared to solid fuel such as coal or smokeless briquettes. The ash underneath the embers provides a insulating bed for the heat of the embers and should not be removed between fires. Ideally there should be a bed of about 1 inch or so of ash. If you have a multi-fuel stove that you mostly burn wood on but your grate cannot be closed then try to block the grate by compressing the ash using a piece of wood or even adding a piece of fire brick to block the slats. This will stop embers from falling through during the wood burning process.
Burning Solid Fuel
Solid fuel prefers to have a stream of cold air coming from underneath the fire and directly into it. This airflow is often referred to as the primary airflow in a stove and usually is controlled by a slider or opening near the ash pit on the front of the stove. Solid fuel is best burnt in a narrow firebox so that the solid fuel briquettes can build up on top of each other. Ash and embers should be riddled regularly, allowing the cool air to enter so that grate bars do not overheat. Be warned that solid fuel can burn a lot hotter than wood and if you over-air the fuel there is a chance you will warp parts of the stove. Once there is a nice bed of glowing solid fuel, air flow should be restricted so that the gases in the heart of the stove transmit maximum heat to the body of the stove rather can escaping too quickly up the chimney. The secondary air supply should be closed for burning solid fuel, apart from perhaps a trickle to keep the flue gases moving if the primary air supply if closed down (overnight burning for example).
Use a stove thermometer to learn about how your stove warms up (and cools down!). Learn to manage fuel better by understanding your stove’s burning cycle. All wood burners are different and it takes a bit of time to get to grips with them so don’t be put off. We think part of the fun of wood burners is learning how they react to different types of wood and properly managing refueling. If you think you are getting through too much fuel it may be your technique. Review the information above on wood fuel.
Mind the air
One of the common reasons why people use too much wood is that they leave the secondary air supply open too long or perhaps don’t refuel with enough wood. This over-supply of oxygen to the wood causes it to burn vigorously and give an intense blast of heat but it also carries a lot of the hot gases out of the stove and up the chimney. The wood will burn down quickly and the stove will require refueling more often. By reducing the air supply, the wood can be allowed to turn to charcoal (see above), this uses less air to burn and the stove will reach its optimum temperature. Our friends are often surprised at how hot our wood burner at home gets even though there isn’t a roaring furnace inside!