A coal stove differs from a wood stove in three ways: it feeds air up through a grate rather than across a flat hearth, it is built to survive a hotter and more corrosive fire, and it has larger ash handling. A stove made only for wood can be damaged or burn unevenly if you simply load it with coal, so check the liner, the air path and the flue first.
Part of Coal Surface Mining
How stoves built for coal differ from wood stoves in air supply, firebox materials and ash handling, and what to change before burning coal in a wood stove.
The Three Differences
Air path. Wood is mostly burned as gas rising off hot logs, and a wood stove often has a solid hearth with air entering above or at the side. Coal burns as a glowing bed that needs air from below (the parent article: “Coal requires air from below”). Without a grate and an ash pan, ash packs around the fuel and smothers the fire.
Heat and materials. The parent notes coal burns hotter than wood. Plain steel plate firebox walls can warp or burn through at coal-fire temperatures, which is why coal stoves use cast iron or firebrick. Brick liner also protects against the heat from a deep glowing bed in contact with the walls.
Ash and corrosion. Coal leaves 5-15% of its weight as ash (parent), more than wood does, so the pan must be larger and emptied often. Sulphur in the coal makes acidic flue gas that condenses in a cool flue and corrodes the metal. A coal flue wants to run hot enough to carry the gas out and be cleaned more often.
| Feature | Wood stove | Coal stove |
|---|---|---|
| Air | Across hearth, secondary air above | Up through grate |
| Bed | Shallow, burns off quickly | Deep glowing bed |
| Firebox | Steel plate may suffice | Cast iron or firebrick |
| Ash | Small amounts | Large amounts, pan |
| Flue | Creosote hazard | Acidic condensate, soot |
Method: Converting A Wood Stove To Try Coal
Step 1: Check the firebox walls. If they are thin steel with no liner, line them with firebrick or do not burn coal in it.
Step 2: Fit a grate and a pan. Raise the fuel bed on a grate so that air reaches it from below and ash drops out.
Step 3: Start with small loads. Watch for red-hot metal, warping and the smell of burning paint.
Step 4: Check the flue and clearances. The stove runs hotter, so check the clearances and the flue joints (Chimney & Stove Safety).
Common Mistakes
- Burning coal on a solid hearth in a stove built for wood.
- Using a cast-iron stove cold-to-hot too fast. Cast iron cracks under thermal shock; warm up gradually.
- Not cleaning the flue.
Safety
An overheated stove sets walls and floors alight
A stove running at coal temperatures can ignite nearby combustibles by radiation alone. Increase the clearances, shield the walls, and make sure the flue is sound. Carbon monoxide can leak from cracked castings and unsealed joints: check them every season (Carbon Monoxide Risks).
What’s Next
- Learn next: Clinker Management — what the grate has to deal with
- Combine with: Burning Coal Effectively — operating the stove