You just bought a stack of "smokeless" ovals and you're staring at your stove. Can you actually throw coal in a log burner without melting the thing? Honestly, it depends entirely on whether you actually have a "log burner" or a multi-fuel stove. People use the terms interchangeably. They shouldn't. If you’ve got a dedicated wood burner—the kind with a flat firebox floor and no grate—dumping coal in there is a recipe for a very expensive disaster.
Wood likes to burn on a bed of ash. It needs air from above to stay happy. Coal is the opposite. It needs air from underneath to breathe, or it just sits there smoldering and producing nasty gases. If your stove doesn't have a raised grate and an ashpan, you're essentially suffocating the fuel while simultaneously overheating the base of your appliance.
The Brutal Truth About Grates and Airflow
Most people realize too late that coal burns much hotter than wood. We're talking about a significant difference in caloric value. If you have a cast-iron stove designed specifically for timber, the intense, localized heat of a coal fire can warp the internal baffle plates or even crack the firebricks. It's not a "maybe." It happens.
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Multi-fuel stoves are built for this. They have a riddling grate—a series of metal bars you can wiggle with a lever—that allows the ash to drop into a pan below. This keeps the airway clear. When you're burning coal in a log burner that's actually a multi-fuel model, you need to open the bottom air vents. Wood wants the top vents; coal wants the bottom ones. Simple, but easy to mess up if you're used to just tossing logs on a fire.
Let's talk about "House Coal." In the UK and many parts of Europe, selling traditional house coal for domestic heating is now actually illegal or heavily restricted due to the Air Quality Regulations 2020. You’ve likely seen the "Ready to Burn" logos. If you try to use old-school bituminous coal, you’re going to produce a thick, yellow-grey smoke that coats your chimney in flammable creosote faster than you can say "chimney fire."
Why Smokeless Fuel Isn't Just Marketing Fluff
Anthracite is the king of coal. It’s a natural, hard, shiny rock that is almost pure carbon. It burns with a tiny blue flame and creates almost no smoke. But it's finicky. It takes forever to light. Most people nowadays use manufactured smokeless ovals—basically anthracite dust squeezed together with a binder.
These ovals are actually pretty great for overnight burns. If you’ve ever tried to keep a wood fire going until 7:00 AM, you know the struggle. You wake up to a cold room and a pile of grey dust. Coal stays in for the long haul.
However, there is a chemical downside. Coal contains sulfur. When that sulfur mixes with any moisture in your chimney, it creates a mild sulfuric acid. This eats through stainless steel chimney liners over time. If you’re burning coal, you absolutely must get your chimney swept more often than if you were just burning kiln-dried oak. HETAS (Heating Equipment Testing and Approval Scheme) generally recommends at least twice a year for coal users.
The "Slumbering" Mistake
A lot of folks like to "slumber" their stove. They pack it full of coal, shut the vents tight, and go to bed. Don't do this. It’s tempting, sure. But starving a coal fire of oxygen creates carbon monoxide. If your door seal (that rope gasket) is even slightly perished, you’re leaking an odorless killer into your living room. Plus, the low temperature means the fuel doesn't burn completely, leading to "clinkers"—those nasty, glass-like lumps of fused ash that stick to your grate and are a nightmare to chip off.
Mixing Wood and Coal: The "Don't Do It" Myth
You’ll hear "purists" tell you never to mix the two. They’re halfway right. If you put a heavy log on top of a fresh pile of coal, the moisture from the wood (even "dry" wood has about 15-20% water) can react with the sulfur in the coal. This creates a nasty, corrosive soot.
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But, practically speaking? A lot of people use a bit of kindling to get the coal going. That’s fine. Just don't make a habit of a 50/50 split all night. Pick a lane. If it's a chilly evening and you want a pretty flame, stick to wood. If it's -5°C outside and you need the stove to act like a radiator for the next ten hours, go with smokeless ovals.
Technical Specs and Warning Signs
Check your manual. I know, nobody does that. But look for the "CE" plate or the data badge on the back of the stove. It will explicitly state what fuels it's tested for.
- Distorted Grate: If the metal bars in your stove start looking like a Salvador Dalí painting, you're burning the coal too hot or not clearing the ashpan.
- White Deposits: If the inside of your glass is getting a stubborn, white cloudy film, that’s often a sign of chemical over-firing from mineral fuels.
- The Smell: Burning coal has a distinct, sulfurous "old train station" smell. If you can smell that inside your house, your flue draw is failing or your seals are gone.
Basically, if you have a modern, EcoDesign Ready stove, it's a high-performance machine. You wouldn't put diesel in a Ferrari. Most of these high-efficiency stoves are actually tuned specifically for wood. They use "secondary" and "tertiary" air washes to burn off the gases released by the wood. Coal doesn't benefit from this tech as much because it doesn't "gasify" the same way.
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Actionable Steps for a Better Burn
Stop buying the cheap bags of "mixed" fuel from the petrol station. They're usually full of petroleum coke (petcoke). Petcoke is the "forbidden fruit" of the stove world. It burns incredibly hot—so hot it can actually melt the cast iron grate right out of your stove. It’s often used in industrial furnaces, not your cozy living room.
- Identify your appliance: No grate? No coal. Ever.
- Empty the ashpan: Coal needs air from the bottom. If the ashpan is full, the air is blocked, the grate overheats, and it will sag and fail.
- Use a thermometer: Get a magnetic stove pipe thermometer. For coal, you want to stay in the "Best Operation" zone. If you're pushing into the "Overheat" zone, you're damaging the internal welds.
- Check your liner: If you have a 316-grade stainless steel liner, coal will eat it in a few years. If you plan on burning coal regularly, you need a 904-grade liner, which is much more resistant to those acidic deposits.
- The "Top Down" Method: Surprisingly, this works for coal too. Put your large ovals on the bottom, kindling on top, and a firelighter on the very top. It heats the chimney faster and creates a better draw, which reduces smoke during the startup phase.
Burning coal in a log burner—or rather, a multi-fuel stove—is about management. It's not a "set and forget" fuel despite its long burn time. Keep the ashpan clear, keep the bottom vent cracked, and for the love of your chimney, stay away from the unapproved house coal.