How to sustain coal combustion in a recalcitrant multi fuel stove?

Visiting

I have a German 10kW steel multi-fuel stove (ST-AD Komfort 11) with a long clean flue liner and am failing hopelessly in getting coal to stay hot enough to maintain combustion.

I begin by building a big wood fire filling the entire firebox and when, after 15 minutes, it looks about as hot as it's going to get and the body of the stove is hot all over I start to balance coal on the wood's hottest areas. I then close the door, shut the top vents and open the bottom vents. I repeat this, adding coal over 15 minutes, until there are perhaps 15 lumps on the grate or balanced on burning pieces of wood. All seems ok for some minutes but tho initially the coal is glowing red with a gentle dancing flame the coals gradually fade and die over the following 45 minutes or so.

Despite many attempts I cannot get the coal to produce enough heat to sustain combustion. Having watched a sea of brightly burning coal on open fires and heard reports from others of their effortless experiences with it I am at a complete loss as to what to try next.

I routinely burn wood effectively but my inability to burn coal is leaving me quite exasperated, and cold.

A._Badger

Without seeing your fire it's hard to do more than guess but two thoughts occur to me.

The first is that if by 'coal' you mean conventional house coal, then it's almost certain that you shouldn't be using it on this stove. Coal produces a lot of soot and pretty soon your stove's passageways and the flue will become blocked by it. Most (thought not all) stove makers say you should use smokeless fuel instead, for this reason.

That won't account for your burning problems, though, and, in fact, coal would be easier to get started than smokeless, so clearly there is a problem here. My guess is that either you have insufficient draft, or you are simply not building a large enough fire.

Assuming your chimney has been kept clean and the stove seems in good order, try building a bigger fire and see how that goes. You may well need to add fuel after the first half an hour or so - add enough to really get it glowing.

If that doesn't work, I would suggest you call in a professional sweep and ask his advice. In my experience they tend to be very knowledgeable about fires and stoves in general, not just about chimneys.

Hope that's at least a little help.

Visiting

Thanks Badger.

I am using smokeless anthracite. The flue is clean.

From your observations I suspect that insufficient draft is quite possible due to a lack of coal on the grate. There is plenty of draft whilst there is wood burning in the stove but it is markedly reduced after the wood has burned away and there's just the coal left gently simmering.

Today, instead of adding coal to a wood fire, I'll try starting out with a grate well filled with coal and then building a wood fire around and over it.

ariba10

To get something like that going you need to make sure there is a good airflow from below the Fire bed.

As little as possible above the fire, until the fire is established.

suki1964

Anthracite is a mare to get burning .
My mum uses it and her stove is always sooting up as like you she cant get the stove hot enough to maintain a good burn

My work around is phurnicite. When you get your kindling started, chuck on half a scuttle of that and open all vents once thats all red and flaming, start closing the vents till you get low or no flames . Then on top with the antracite. The stove will be hot enough to burn it . You might need to open vents for a while on every re fill,

I use the anthricte more as a damper , keeping the fire going for long periods without the need to refuel and use the smokeless ovels to get going

Visiting

My latest experiment was to direct a blowtorch at a small pile of anthracite placed directly over the circular holed air-supplying cast iron plate at the base of the stove. After some minutes I had a couple of pieces glowing red/white and figured that if only I could build-up on that. So I shut down the torch and shut the door with lower vents fully open.

The red glow quickly died and the anthracite was back to black within thirty seconds. I am beginning to think that my supplier sold me a bag of granite.

wrightk

i dont really use anthracite anymore as i find it has a lot more negatives than positives for us. if i ever do get any i always mix it as suki says with smokeless ovoids (or eggs as i call them). The ovoids will give you the benefits of getting the fire going quickly, the anthracite will keep it in longer.

If you do have to burn it on its own, i found that it helps to build it up in layers, ie paper kindling coal, let it catch for a while then kindling and more coal, and loads of air from under the grate


cheers

A._Badger

Visiting wrote: »

My latest experiment was to direct a blowtorch at a small pile of anthracite placed directly over the circular holed air-supplying cast iron plate at the base of the stove. After some minutes I had a couple of pieces glowing red/white and figured that if only I could build-up on that. So I shut down the torch and shut the door with lower vents fully open.

The red glow quickly died and the anthracite was back to black within thirty seconds. I am beginning to think that my supplier sold me a bag of granite.

I don't use anthracite for that very reason. It's simply too variable, in my experience - always hard to light and often not very good to burn.