How to Use Both Wood & Coal in a Furnace

Split the wood small for use in a coal furnace. The fireboxes are smaller than used in wood furnaces and larger pieces of wood will smother the fire.

Start the wood fire with small kindling and add more pieces as the kindling begins to flame. Whether using a coal furnace or a wood furnace, leave plenty of room around the wood for air to circulate. Wood fires must be burned hot in a coal furnace. Coal puts out little to no creosote, unlike a slow, smoldering wood fire with large logs. For this reason, coal flues are smaller in diameter and will quickly become coated with creosote if a hot fire is not kept.

Shake the wood or coal ash down once a day with a coal furnace if it is a manual model. This deposits the ash in a protected container and keeps the fire hotter.

Keep to a consistent schedule when burning coal in a coal furnace. A properly maintained furnace will stay alight for an entire season. Shake the coal at least three times a day to remove the ash, and replace the burned coal with fresh on a regular basis to gain the most efficiency from the furnace.

Know the local codes for air pollution. Some municipalities forbid burning wood in any noncertified EPA burner. Coal furnaces do not require EPA certification so burning wood in one may be a prosecutable violation.