How to Use a Victorian-Era Furnace
Chimneys are strange objects. Most people believe they know how chimneys work, until they try to use one. You can test your understanding by answering this simple question: imagine you are smoking a cigarette in front of the door of a tall building. Instead of rising straight above your head, the smoke will go sideways into the building and exit at the top. Why does it take this indirect path, when it is going to end up in the same place?
Before getting into the answer, here are the practical issues:
Lighting Procedure
What you’ll need to get started:
[ ]cardboard[ ]kindling (anfeuerholz)[ ]coal[ ]ash pail[ ]lighter or matches
- Leave the ashes from the previous day, unless the ash pan is so full that it blocks air flow.
- Clear the grill of ashes, letting the ash fall into the ash pan.
- Start a paper fire.
- Start a wood fire with the paper fire. If you can arrange the kindling in a criss-cross fashion, they will ignite better. On warm days, you need more kindling than usual. Keep the top door closed and the bottom door open until the fire is strong.
- Start a coal fire from the wood fire. Don’t crush the wood fire with the coal bricks. It’s best to build a little coal house around the wood fire.
- Remove ashes as described in the ashes section.
- Close the main door after the fire seems strong with no risk of dying out. Leave the sliding door open.
- When the coal is no longer producing white smoke, close the sliding door. If you leave the sliding door open, your fire will burn out very quickly. A good fire will otherwise last 8 to 12 hours.
- If you are lighting a furnace in a cold room, it can take up to 12 hours for the room to feel warm. The reason is that the brick walls and the material between the floors will absorb the heat first. Once your fire dies out, your room can remain warm up to 12 hours because the walls are releasing their stored energy. Fazit: plan ahead.
There is zen to lighting fires, and the zen of lighting a fire is this:
Seek not to dominate fire. Liberate air flow. For when you have achieved airflow, fire shall come.
Maintaining procedure
You can extend the life of your fire by adding coal during the burn.
Before you open the top door to look inside, open the bottom door for five to ten seconds. The worry is that white smoke should have accumulated in the tinderbox due to poor airflow. Be that the case, by opening the top door, you give the smoke an exit path. Open the bottom door first, let the smoke evacuate through the chimney, then open the top door to look inside.
If your fire is hot, you can throw on a coal brick and shut all doors immediately. The high temperature means that the new brick will ignite quickly and the white smoke will be carried away.
If your fire is weak, or if you put on a lot of coal, then the white smoke will not be evacuated effectively. You must leave either the main door or the sliding door open, depending on temperature and amount of new coal.
When your furnace is operating normally, there ought to be no smell. If your furnace stinks, it means it is not evacuating the air properly. This can arise because the temperature outside is relatively warm. In this case, open the sliding door. When the temperature outside is less than 10° cooler than inside, and you are near the top of the building, you might have to leave the sliding door open during the entirely of the burn.
You must close all doors after the white smoke is gone, otherwise your fire will burn out quickly. Set a timer.
If you are not using your furnace, keep all doors closed. A chimney is specifically designed to evacuate warm air from your house, regardless of whether there is a fire.
Relighting procedure
The next morning, there might be some embers left, so a wood fire is not necessary. However, simply dumping on more coal might fail.
Coal is ignited not with flame, but rather with heat. You can interrogate your intuition by imagining trying to light a frozen coal brick with a cigarette lighter. On the other hand, if you put a coal brick in a baking oven, it will spontaneously ignite once it’s warm enough.
If you dump a pile of coal on a feeble bed of embers, the heat might be transferred to the entire mass of coal without heating it enough to ignite it.
Cover the embers with a single layer of coal. Use pieces of coal instead of entire bricks, if there aren’t enough embers.
If you leave the door open, the embers might burn out before they have transferred their heat. In the case of a weak bed of embers, leave all doors closed for 15 minutes. This will give the ember enough time to transfer its heat to the edge of a coal brick. Then, by opening the sliding door, you can increase the airflow enough to fully ignite the coal brick.
When the first brick is ignited, put on as much coal as you want.
Close the sliding door after the new coal heap s glowing.
There is a situation when throwing on a pile of new coal does not kill the fire: when two brick have faces that meet at a heat source. The set up is this: two of the coal bricks have facing sides, and there is an ember below them. Their bottom edges ignite. The heat from one side heats the opposing side, which facilitates further ignition. As the air between the faces heats, it flows up very quickly, which brings more air into the tinderbox. The additional air increases ignition. This virtuous circle is enough to eventually ignite the heap. That is why throwing a pile of coal on feeble embers often fails, but sometimes succeeds.
Removing ashes
- When you hear the rush of air drawn in by the fire, it’s time to empty the previous day’s ashes. Dump the ash pan into the ash bin directly in front of the furnace door. The rush of air will draw the dust cloud into the furnace. Try to cover the door with the ash pan so that all dust is sucked in. If you empty the dust pan in any other way, a cloud of dust shall arise and settle on all the furniture. In this case, seppuku is the only honorable response.
- Set the ash pail aside for a few hours. If you dump it in the trash bin immediately, embers hidden within the ashes might start a fire in the trash bin. This causes the neighborhood to burn down.
- The correct trash bin is the black bin on wheels (Restmüll). If the Restmüll bin is not in the courtyard, it is on the sidewalk in front of the house.
- Coal ashes may not be put in the compost bin. They are toxic. Wood ash from non-treated wood may go in the compost, but most wood around here has varnish or paint, so put this also in the restmüll.
Coal
- When the coal is hot, it releases white toxic smoke. This smoke is re-ignitable.
- When the coal is ignited (glowing), it is mostly odorless.
It is important during the first phase to keep the airflow as high as possible, in order to keep the smoke moving toward the chimney exit. Otherwise, it might exit into the room. The smoke is toxic and the ridicule from fellow residents isn’t much better.
Another possibility is that the smoke should build up inside the furnace, where a spark could reignite it. The result could be anything from a popping sound to the detonation of the furnace. Don’t worry, you hear only the first one.
Furnaces
There are three types of furnaces in the house:
- Stove-type metal furnaces: can burn both wood and coal as primary fuel sources.
- Kachelöfen: These are tiled furnaces whose interiors are all clay and brick. These may also burn both wood and coal.
- Kohleöfen: These are metal furnaces in a tile shell. They may only burn coal. The tops of the tinderboxes (Brennkammer) are subject to expansion and cracking under the high temperatures produced by a wood fire. Once cracked, they leak smoke into the room. The good news is that the smoking procedure will keep your body intact and natural-looking for decades.
Physics
Here are some relationships you need to understand:
- air flow is proportional to chimney height. This means it is easier to light a furnace on the ground floor than on the top floor. The higher air flow is evident on a cold day: the furnaces on the ground floor whistle even when they are not in operation, but the top floor furnaces do not.
- Air flow is proportional to the difference in temperature between the tinderbox and the outside air at the chimney exit. This means that it is easier to light a furnace on a cold day than on a warm day. It also means that on a warm day, the wood fire must be hotter in order to start the coal fire.
- Air flow is inversely proportional to the diameter of the smallest section of the system. Typically, this is the furnace door. When the door is closed, the air flow is restricted, which is obvious, but what is not obvious is that on a warm day, you might have to run the furnace with the secondary door left open. If your fire is burning on a bed of ash, the ash is a constriction, which means you might again have to burn with the secondary door left open, or add more fuel to increase the temperature.