Learning to Control Your Small Wood Stove
Operating a wood stove is a skill that requires patient experimentation to learn. Every stove will behave a little differently, since there are so many factors that influence the draft like flue configuration, elevation, weather, and fuel choice. Take some time to get to know your own stove and how the controls affect the fire.
In general, there are three types of air supplies on a stove. Primary air is fed to the bottom of the fire, secondary air is fed to the top of the fire, and a tertiary “air wash” may be fed separately or combined with the secondary air to keep the glass clean. Some less efficient stoves may also require a damper in the flue pipe to help reduce draft.
Wood fires burn from the top down, so it’s usually best to feed the fire mostly with air from the top, through the secondary air supply, and restrict the primary air once the fire is going. Restricting the primary air supply to a wood fire will help prevent the coals from burning out prematurely, and feeding lots of fresh air to the top of the fire box will generally make for a cleaner, more efficient burn. Coal fires, however, burn from the bottom up. If you’re using coal in your stove, you may want to restrict the secondary air flow to route the majority of the combustion air through the bottom of the coal bed.
HOW TO START A FIRE
To start a wood fire, you’ll need:
- Tinder. Materials that can easily be lit with a single match. Commercial fire starters or newsprint are popular options.
- Kindling. Dry pieces of wood that will easily catch fire from the tinder. About the thickness of a pencil.
- Fuel. Larger logs in various sizes. Properly cured hardwood works best. It’s helpful to have small, medium, and large sizes of fuel available so that you can choose the right size of fuel depending on the needs of your fire. Ideally, your fuel should be no longer than the width of your firebox.
- A source of flame. Matches, zippos, or aim-a-flame style lighters work well.
When starting a fire, you want to accomplish two things as quickly as possible:
- Get the flue system warm to get the draft moving. If you don’t get the flue warm enough fast enough, your stove will start spewing smoke out of its air intakes.
- Build a hot bed of coals. A common beginner mistake in starting a fire in a wood stove is to focus too much on the flames. Flames are nice, but coals are what make a fire self-sustaining. Use plenty of kindling to quickly burn down to a thick, hot bed of coals, and your fire will be burning cleanly and efficiently in no time.
Try various methods for starting fires to find what works best for you and your stove. We’ve found a few methods that tend to work very well for small stoves. Start with all of your air controls open 100%.
- “Full Log Cabin” Method: Lay several pieces of kindling parallel to one another on the bottom of your fire box, then lay several more on top, perpendicular to the first. Continue for 3 or 4 layers. Light a commercial firestarter and set it on top of the stack, then close the door almost all the way, leaving just a crack for extra air flow. Once the stack is caught, add more kindling on top and close the door.
- “Good news” method. Crumple 3 or 4 sheets of newsprint (preferably containing good news) to loosely cover a single layer on the bottom of the fire box. Lay several pieces of kindling parallel to one another on the bottom of your fire box, then lay several more perpendicular to the first. Continue for 3 or 4 layers, but not so much to compress the newsprint. Light the newsprint in several places, then close the door almost all the way, leaving just a crack for extra air flow. Once the stack is caught, add more kindling on top and close the door.
As the kindling starts to compact itself, add small pieces of fuel to the top of the fire. Progressively add larger pieces of fuel as you build a strong, hot coal bed. Once your fire is burning cleanly and efficiently, you can adjust the air controls to regulate the heat output of your stove. You should see little or no visible smoke coming from your chimney unless you’ve just added a new piece of wood. Thick plumes of dark smoke indicate an inefficient burn, and call for an adjustment to your technique.
Your priority for managing an efficient fire is to maintain your coal bed. If your coal bed burns out before your fuel is reduced to coals to replace it, then your logs are too large for the fire you’re burning. Use smaller logs to burn a hot and efficient fire, and keep a healthy coal bed going at the bottom of your fire box.
ADJUSTING THE TEMPERATURE
Adjusting the temperature of your wood stove requires a bit more manual participation than just turning a dial on a furnace. However, with a bit of practice, you'll become an expert in no time!
Adjusting the Air Controls
Opening air controls will give your fire more oxygen, and generally allow it to burn faster if enough fuel and heat is available. Closing the air controls will restrict the amount of oxygen available, which will slow down the fire.
Where you add air to the firebox makes a big difference in your burn.
Primary air enters through the coals at the bottom of the fire box. That helps the fire burn much hotter. But it also pulls more small ash particles through your flue system, which means more air pollution and more frequent chimney sweeping. Many stove manufacturers weld the primary air control shut on EPA approved models.
In general, you want your primary air control wide open when you're first starting a fire, and then partially or fully closed once your coal bed is established.
Secondary air enters at the top of the fire box to provide enough oxygen for all the products of combustion to fully burn. Feeding a wood fire primarily with secondary air helps your stove burn as cleanly and efficiently as possible.
Tertiary air, or "air wash," is a separate air supply located above the glass of the Dwarf stove. Its primary purpose is to create a blanket of fresh air to keep smoke away from the glass, so your glass stays clean. The air it adds is also available for combustion, so the position of the tertiary air control will affect your burn rate. We recommend keeping the tertiary air valve at least 50% open in most cases.
Take care not to choke the fire too much by closing your air controls too fast! A smoldering fire will produce lots of creosote, which can clog up your chimney or even cause a chimney fire. It's best to make gradual changes so that your fire has time to slow down rather than smolder.
Adjusting the Fuel
Aside from the type of fuel you're burning—hardwood, softwood, wet or dry—the size of your fuel will affect your burn rate. Smaller pieces will burn faster and hotter while larger pieces will burn slower and cooler.
When starting a fire, it's best to use lots of dry pencil-sized kindling to establish a healthy coal bed as early as possible. Once your kindling is burning, you can gradually increase your fuel size.
If your air controls are open but your stove isn't burning as hot as you want, you can increase the temperature by frequently feeding it smaller pieces of wood, rather than using larger logs.
On the other hand, if you want to keep your fire going but don't want as much heat, you can add one or two larger logs, and turn down the air controls.
Checking your Technique
Your goal should be to burn your stove as cleanly as possible, while maintaining the your desired heat level. This takes practice.
Two different users of the same stove, with the same fuel, can build a fire with the same heat output, but with one stove smoldering and belching thick clouds of black smoke and filling the chimney with creosote, while the other burns cleanly and efficiently with little to no visible smoke produced.
To check whether your fire is burning cleanly, take a look at the smoke at the top of your chimney. Once the stove is up to temperature, the smoke should be relatively thin or even invisible. You'll get some thicker smoke when you add a new log. But once the log is caught, it should go back to normal. If you have heavy clouds of thick, dark smoke, then you probably should adjust your technique or your fuel source.
GETTING THE LONGEST POSSIBLE BURN IN A SMALL STOVE
Small stove burn times are restricted by the firebox size. Too big of a fire box and you might be able to get a longer burn time, but you'll clog up your flue system and overheat your living space.
For the longest possible burn without stoking, try the “Upside-Down Fire” method. You should practice this method several times before attempting to do an “overnight burn,” since adding this much fuel to the fire box can cause an overfire if you don’t dial in your air controls properly. Place a solid layer of medium sized fuel on the bottom of your fire box, parallel to one another with no air space in between the pieces. Place another layer of fuel on top, perpendicular to the first. Continue until you near the center of the fire box, using small fuel for the final layer, ensuring there is no air space between the pieces of each individual layer. Add several layers of kindling on top, and light from above with a commercial firestarter. Leave the door cracked until the kindling is caught, then add more kindling if you have space and close the door. Once the fire is going, tighten up your air controls to control the rate of burn. If you’ve built your fire properly, your stove should burn hot and efficiently, slowly working its way down the pile, giving you the longest possible burn time.
If you need some help learning how to manage a fire in your small wood stove, or want to know what to expect when you install one, check out our free beginner's guide to wood stoves in small spaces, or contact us with questions.