I'm planning on replacing my 2.1 cu ft wood stove (90's vintage) with a secondary burn style stove. It's installed in the basement which is 1600 sq ft unfinished and I use circulating fans to get the heat upstairs (also 1600 sq ft). If the temps are around 25 deg F or above I have no issues keeping the upstairs in the low to mid 70's (basement is in the 80's). Colder than that outside and I have to keep the wood stove fired up with a relatively good burn since it only has a 2-4 hour burn time. I'm looking at the Lopi Liberty (3.65 cu ft firebox) but I'm wondering if it is overkill for my application. Hard to get a Lopi Endeavor with a smaller firebox and I like being able to put longer pieces in stove which I was able to do with my present stove since it is a side load Hearthstone Heritage. Are there any issues with having a large firebox stove and only filling it partially full? I don't need the capacity all the time but when I do I would like the overhead. I'm not familiar with secondary air stove burn requirements and even with my present stove I rarely fill it full of wood. Do larger firebox stoves have different draft requirements? Any input?
Big stove, small fire, any problems?
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stoveliker
Minister of Fire
No, no issues that I know of. A fire of 3-4 splits should get the secondary burn tubes hot enough, I think.
However, if you would insulate the basement, you'll likely be fine for far lower outside temps. It's been estimated that 30 percent of the heat may be disappearing thru the walls.
Basements can have negative pressure issues, and newer stoves do need a good draft due to baffles (increasing impedance of exhaust flow).
If you're in the basement, your chimney is likely tall enough.
However, if you would insulate the basement, you'll likely be fine for far lower outside temps. It's been estimated that 30 percent of the heat may be disappearing thru the walls.
Basements can have negative pressure issues, and newer stoves do need a good draft due to baffles (increasing impedance of exhaust flow).
If you're in the basement, your chimney is likely tall enough.
Yeah, I kind of thought that if you are able to establish a draft you should be good to go. I've got a cast iron baffle in my present stove but no secondary air tubes. The Lopi has the secondary air tube with a thinner baffle on top of the tubes and some mat on top of that. It also has a bypass for startup when adding wood. I wouldn't think that setup would be much more restrictive than my present stove but it may be. I've talked to people with QuadraFire stoves with secondary air and they actually removed the tubes to get more area in the firebox. They didn't notice any difference in draft issues or burn. Now a cat stove is a different situation in regards to being more restrictive.
That's totally nuts. They are dramatically reducing the efficiency of the stove by doing that. That means more wood burned to make heat and a lot more smoke into the neighborhood. In a modern stove, when one closes down the primary air via the air control, a vacuum is created in the firebox that pulls air through the secondary tubes. This makes for a much more complete combustion of the wood gases which equates to a hotter fire, cleaner burn, and less wood burned for the equivalent heat.
Modern stoves need a bit more draft in order to pull the air through the secondary ducting, manifold, and then out the tubes. The amount varies with the stove design. Some stoves have a fairly direct feed to the secondary combustion holes and other stoves have a more circuitous path around the firebox. The purpose of the latter design is to better preheat the secondary air but they do required a bit stronger draft than the more direct secondary air supply.
The Liberty is a great stove. It should do the job well, but regardless of the stove, about a third of the heat generated is heading out the uninsulated basement walls. That's one cord of wood for every 3 burned which is a big waste of fuel. If the basement walls get insulated, then the Endeavor should be able to do the job, but the Liberty will go several hours longer between reloads due to the bigger firebox.
What is the current stove that is in the basement?
1994 vintage Hearthstone Heritage. I totally agree with losing heat out the basement walls. I'm not that concerned with the amount of wood I use as I cut my own and with 40+ acres of hardwood forest I can barely keep up with cutting up the dead trees. Would be nice to not have to re-fuel the stove as often though.
Turning the stove way down after insulating the basement would give you those longer reload times.
As someone who just insulated their basement (1/2 way done) I can tell you the difference is dramatic. Our homes are close in square feet as well.
Ashful
Minister of Fire
Stoveliker already said it right, but this bears reinforcement. You need enough BTU/hr rate to get and keep the secondary combustion going. On my Ashford 30’s this fails at 3 splits, is a “maybe” at 4 splits, but always succeeds at 5 splits. Don’t think your just going to chuck 2-3 splits into a big stove, and have a successful clean burn.
On a cold start maybe no, but not a problem on a reload. It depends on the size of the splits, species of wood & draft strength. On the 7am reload this morning, I put in two 7" doug fir splits and one 4". The secondary combustion was strong. (I almost did a video of it, it was so pretty.) Today is sunny and warming up so I didn't want too big of a fire by noon.
Ashful
Minister of Fire
Yes, I was talking about cold starts. I don't ever find myself in weather that's too warm for a full load, but also so cold that I'm doing hot reloads. It just doesn't happen, at least in this house, but every house and setup are different.
It got up to 50º today so I let the fire die out. This evening, for a test I tried a three 4" thick + one 2" split start. The stove was not stone cold. The top read about 125º. There were some leftover cold charcoal pieces from the morning fire. 15 minutes later I had the air turned down and secondary combustion with a 615º flue temp. Dry wood, kindling, and good draft let the stove get up to temp quickly.
Ashful
Minister of Fire
Cool! In my stoves, that would be just barely enough wood to get the cat up to temperature for light-off, and I'd be waiting awhile for it to get there. Since I've had a few failures to launch on just three splits over the years, I've made a "4 splits minimum" rule, which always works unless they're real small.
Poindexter
Minister of Fire
The short answer is you can build a small fire in a big stove, but you cannot build a big fire in a small stove.
My limit is about a third of the firebox full of shorts and uglies. That is plenty to get my catalytic combustor up to the active zone and have a good hot burn long enough to take the chill off the house before the fire goes out.
I would call the two videos from begreen roughly a quarter of a load.
My limit is about a third of the firebox full of shorts and uglies. That is plenty to get my catalytic combustor up to the active zone and have a good hot burn long enough to take the chill off the house before the fire goes out.
I would call the two videos from begreen roughly a quarter of a load.
Ashful
Minister of Fire
Lol… some of my posts from ten years ago sound the same. Spend a few years cutting, hauling, bucking, splitting, stacking, moving, and loading 10-14 cords per year. Your tune will change, if for no other reason than age and joint damage, I can almost promise you.
Ashful
Minister of Fire
Hey begreen, how do you know that you’re hitting and then maintaining secondary burn in that stove?
I'm only cutting around 5-7 cords per year and have been for over 30 years. I'm cutting the wood to keep my forest in fairly decent condition and would probably still cut wood even if I didn't burn it. I even give away a couple of cords to my brother-in-law. It is a lot of work that takes a lot of time but it is also good exercise with an element of danger in it. It definitely is true that more heat is generated making wood than burning it. I'm just looking at replacing my current stove and maybe upgrade to something bigger so I don't have to load it so often, even though it is somewhat satisfying to burn the wood you have stuck so much labor in cutting.
With the pre EPA rule stove I have now I generally have it as low of burn as it can go without getting smoke in the house once I get a good draft going. Even though my basement is uninsulated on the inside it is buried in the ground and has 2" of pink board on the outside. It definitely would be warmer if I would finish the walls but I'm already able to maintain temps in the 85 deg F range in the basement. I have some fans to get the heat upstairs (as well as the furnace fan) with temps in the 70's unless it is windy and below 15 F. Actually feels refreshing to go upstairs after spending time in the hotter basement.
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