Forced-air wood burning furnaces are fascinating machines. They consist of several systems that work together to deliver much-needed heat, all while venting out hazardous byproducts to ensure a warm, safe home.
If you’re a prospective wood furnace owner, it’s natural to have questions about how these systems work. After all, this is the thing that’s going to help you stave off the winter cold; the more you know about how they work, the better.
At HY-C, we manufacture wood burning furnaces. Obviously, that means we know plenty about how they work. But we also know the common questions that new or soon-to-be furnace owners ask to ensure that buying a furnace is right for them.
And we want to cover them here.
In this guide, we’ll outline and answer some of the most frequently asked questions about forced-air wood furnaces.
Whether you’re considering buying a wood burning furnace for the first time or you’re a veteran wood burner with a question that’s been nagging you for a while, we’re going to address as much as we can here to ensure you enjoy an informed, stress-free wood burning experience.
Wood Burning Furnace FAQs
Are Indoor Wood Furnaces Safe?
As long as the furnace is installed properly and operated according to the manufacturer’s standards, then yes — indoor wood burning furnaces are perfectly safe to use.
But that doesn’t mean they’re without risks.
For instance, it’s vital to adhere to your furnace’s clearances to combustibles (i.e., the distances from which certain parts of the furnace need to be kept from flammable materials). Also, if you burn firewood that’s not properly seasoned, you could wind up with creosote in your chimney.
Accidentally dropping hot coals or embers when opening the furnace door is always possible, too, which is why it’s important to utilize the right kind of stove board around your furnace.
To avoid all of these pitfalls, be sure to read your furnace’s owner’s manual to ensure you’re operating it safely and properly.
What’s the Difference between a Wood Burning Stove and a Wood Burning Furnace?
The primary difference between a wood stove and a wood furnace comes down to the way they deliver their heat.
Wood stoves radiate their heat to the living area. Wood burns in the firebox and the produced heat simply spreads to the surroundings.
Wood furnaces, on the other hand, connect to your home’s HVAC system. A blower motor on the unit blows hot air from the heat exchanger into your ductwork and out through your registers, delivering hot air to each individual room in the home.
Does a Wood Furnace Need a Chimney?
Yes, a wood burning furnace absolutely needs a chimney. Burning wood fuel produces smoke, and all of that smoke needs to be vented out of the furnace so it doesn’t end up in the home. Connecting the furnace to a chimney is the only way to operate it safely.
Do I Have to Line my Wood Furnace’s Chimney?
One of the best ways to revitalize an old masonry chimney is to add a stainless steel chimney liner to it. The process is pricey, but lining a chimney can help to alleviate draft issues and ensure the safe operation of your unit.
That said, if you’re connecting your wood furnace to a masonry chimney, you don’t necessarily have to have it lined (although we do highly recommend adding a 6-inch stainless steel liner to any masonry chimney that’s servicing a forced-air wood furnace).
If you choose not to line your chimney, then at the very least, you need to have it inspected by a chimney sweep and approved for use with your furnace before starting any fires.
What is the Life Expectancy of a Wood Furnace?
This is a complicated question with an answer that’s highly variable.
For instance, if you overfire your furnace, neglect regular maintenance, burn unseasoned firewood, or skip out on cleaning its chimney, your wood furnace won’t have a very long life.
But if you follow the operating and maintenance procedures outlined in your furnace’s owner’s manual, you could very well experience 20 or more years of service life from your appliance.
How Often Do You Have to Fill a Wood Furnace?
Again, the answer to this question varies based on several factors, like:
- How well (or poorly) your house is insulated
- The temperature outside
- Your thermostat setting
Generally speaking, though, you can expect to add more wood to your furnace two or three times a day.
Can You Leave a Wood Furnace Unattended?
Yes, you can leave a fire burning in your furnace and go about your day. Just be sure that the firebox and ash pan doors are closed and sealed tightly and that the clearance-to-combustible distances around the unit are met at all times.
What is the Best Wood to Burn in a Wood Furnace?
While the best firewood to burn is a matter of debate, generally speaking, it’s good to burn oak, black locust, and maple in a furnace due to these species’ high heat output. Each of these types of firewood produce over 25 million BTUs per cord of wood.
Even more generally, it’s better to burn hardwoods rather than softwoods in a wood furnace. Hardwoods both put out more heat and produce less smoke.
How do I Make My Wood Furnace Last All Night?
There are a few things you can do to extend your furnace’s burn times so you can avoid waking up to a cold house.
First, load your furnace right before bed. This will ensure that the unit has plenty of fresh fuel to burn as you sleep.
Second, set your thermostat temperature as low as you can handle. If your thermostat is set to 72 °F, it will burn through its wood fuel much more quickly than if it were set at 66 °F. The lower you set the thermostat, the longer the burn times you can expect.
Finally, be sure you’re using properly seasoned firewood. Using firewood with a moisture level below 20% will result in a more efficient burn, allowing you to get more heat per log (and go longer between reloads in the process).
Can a Wood Furnace Get Too Hot?
Yes, wood furnaces can burn too hot. This is especially possible during a power outage when the distribution fan is unable to blow heat out of the firebox. Furnaces also get too hot when their ash pan doors are left open, allowing excess air into the firebox to create a very intense fire.
A furnace that burns too hot can crack or become warped, both of which may cause it to become unsafe to use. To prevent these problems, keep a backup generator around in case of power outages and never operate your furnace with the ash pan door open.
Can You Put Too Much Wood in a Furnace?
It’s very difficult to overload a furnace. Their fireboxes are designed to burn and break down large quantities of wood, filtering out soot, ash, and other solid byproducts into the ash pan.
You can feel pretty comfortable loading your furnace fully, especially if you’re trying to achieve a consistent temperature in the home while you sleep.
Is a Wood Furnace Right for You?
This has been a look at some of the most commonly asked questions about owning and operating a wood burning furnace. If you’re looking at this list ahead of a possible furnace purchase, you may still be wondering whether a wood furnace is right for you.
Luckily, we’ve created a guide that covers just that. It will help you to qualify (or disqualify) yourself so you can decide whether or not you’re ready to jump into the world of wood heating.
And if you’re confident that you’re ready to buy a unit for your home, you can use our product locator to find a Fire Chief furnace near you.
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