If you’re new to wood burner ownership, struggle to get it going, or experience dirtying of the glass then the below should be off help.
The first thing to check is the installation. This should have been done by a qualified tradesperson, meaning that the flue size and location allows the stove to draw enough air and expel the burnt gases.
Assuming the above is okay then the next critical issue is fuel.
Why does wood burn? Probably not something you’ve really given much thought too, luckily some boffins already have, hopefully the following is reasonably simple to follow
As the temperature of a log rises in a fire it eventually gets to the point where flammable gases are driven off (gasification) – it’s these gases that burn and give off the heat.
A wet log can’t heat up very quickly. That is because it takes a lot of energy (heat) just to drive off the excess moisture before it can start to get hot enough to properly gasify.
That moisture and unburnt gas is the dense white smoke you see coming out of a chimney. That will also condense inside your stove and flue as tar deposits
If when you burn your wood water is bubbling out of it then it is far too wet. Ideally, it should below 20% to meet current national standards, but the odd bit over this is not going to be a major problem. Keep your wood dry by storing it undercover, ideally store a bit inside prior to use to drive of any moisture it has gained over a wet winter (the relative humidity of the atmosphere outside in the winter is usually very high). Be very careful about storing it next to your stove for obvious reasons - there should be at least 20-30cm gap between the logs and the stove. Also, bear in mind that different tree species will have different characteristics. Birch, Sycamore and Ash will burn and split easier than Oak, but will also burn quicker and give out less heat. Willow and many conifers will spit when burnt, so not good for open fires. Horse Chestnut doesn’t burn that well even when dry. Hornbeam burns well, but is extremely difficult to split. Alder is good firewood but it must be split and stored undercover soon after felling otherwise it will quickly rot. And you thought it was all logs were the same!
Lighting the fire is the next bit.
Make sure your kindling is nice and dry. You can usually find enough smaller bits of wood amongst your firewood delivery to make some kindling. If not buy some kindling, or buy a small hatchet. Using a hatchet can be dangerous and so only use if you confident to do so. Only attempt to split smaller bits of wood and make sure it is straight-grained and there are no knots in it. You should not have to forcefully swing the hatchet up and down as if your life depends on it, as this will lead to an accident.
There are lots of really useful videos on You Tube showing the principles of stove lighting like this one and this one so there’s no need to go into huge detail here. However, the following few pointers should useful Before you start an essential bit of kit is a flue thermometer to measure the temperature of the combustions gases. One of the main points often missed is that the stove and the flue themselves will absorb a lot of heat during the lighting process, so don’t shut your stove vents down as soon as you see a few flames, as the stove will be still be sucking heat from the gasification process. At this point, don’t worry if your flue temperatures are a little bit higher than ideal. It is not going to cause a problem for the short while it takes your stove to warm up, but do remember to shut it down!
A good measure of your firewood is to take a look at what comes out of the top of your chimney. When initially started you should see some light grey smoke, but after around 5-10 minutes the stove and flue should be up to operating temperature and then shouldn’t see anything more than a heat haze, or at worst a little bit of very light grey smoke when you put a couple of new logs on. Chimneys pouring out dense white/grey smoke are because of burning wet wood. This will not only cause dangerous tar deposits on the flue and the inside of the stove, but also be a source of air pollution.
Keeping it going
Once up to temperature (as shown by the flue thermometer) you should only need the minimum of draft, to keep it going. The flames should just be lazily licking around the inside of the stove, not roaring like a blast furnace. If you constantly need a lot of draft to keep it going, your wood is very likely too wet. Of course, if the stove has nearly out then you may need a good draft to get the last embers to catch the logs you’ve just put in. In this case if it is nearly out then chucking that lump of Oak on, that you can only just get through the door, isn’t going to work (think of the energy needed to get it up to gasification temperature) , choose some smaller quicker burning pieces to get it going again.