Tell me how to get the longest burn time...

[jkazak]

I have a Lopi Liberty and a Hearthstone Manchester. I use Locust / Mulberry and on occasion I dig into a stash of Osage Orange I acquired. All wood has been seasoned 2-3 years.

The Manchester retains heat overnight and most often I can restart a fire off the coals if I get to it within 10-hours but the Liberty....not so much.

Door gaskets are tight and both stoves are in good order. I know they are two different animals. The Liberty will heat up / cool down faster and its ventilation system is much easier to work a fire with. Once the soapstone gets chugging it radiates a good amount of heat for a long time. One time - with a primo stuffing of Hickory I was able to restart the fire after 16-hours. No joke.

So what's your best method of getting the longest heating time from your stove(s)..?
One thing I should mention is the Liberty has a factory blower fan while the Manchester has an external fan next to it blowing the air out of the Alcove...which may make the difference.

 

[begreen]

Are the flue heights the same on both stoves or different?

 

[jkazak]

The flue on the Liberty is a good 10 feet longer...hadn't thought of that... it's in the basement with the Hearthstone on the main floor

 

[begreen]

The Liberty may benefit from some draft reduction with a flue damper.

 

[Woody Stover]

Both of those stoves like to run...you might try cutting the air as soon and as much as possible, without killing the re-burn. If the Manchester takes longer to get up to heat, you could burn a couple 'sacrificial' splits to do that, then load the main load. But it's hard to think that you are burning all that much wood coming up to temp in a non-cat, like I was in the Buck 91 cat...
The flue damper that begreen suggested sounds like it's gotta be an improvement.

 

[kennyp2339]

Hmmmm, both seem like great tube stoves, I think between turning down the primary air down faster and possible installing a key damper on the lopi you might be able to squeeze more time out of loads, but don't sacrifice secondary reburn, if you install the key damper and sudden loose secondary's then fineness the key damper until you get re burn again, also get true stove top thermometers of a good ir gun and monitor temps (might be harder on the soap stone) to make sure your not sending up to much heat out the chimney or burning to low.

 

[jkazak]

Thanks guys for the thoughts...!
Maybe I'm expecting too much from these stoves. I like to see at least 400-degree top stove temps from my IR gun - otherwise it seems the outside temps creep inside. My beautiful log home just isn't that draft free. I'm sure that's a big differential.
So there has to be enough air supply to keep the stove temps up - but that cuts into burn time.

 

[begreen]

Save the biggest, thickest splits for the Liberty. Close down the air quickly, as soon as secondary burn starts.

 

[Woody Stover]

log home just isn't that draft free.

Yessir, I feel your pain. Not sure how modern your log house might be, but here the wind gets between the logs and the wall covering (looks to be equivalent to a double layer of drywall.) There's no insulation so the heat is sucked away through the wall covering. I also haven't sealed up all the outlets yet, or ceiling light penetrations. It gets tough to keep up when we get teens and wind...temps in here can drop to 66. I need to tighten up because there's really no alternative rear-vented cat stove that's a bit bigger, yet will easily fit in my fireplace.

 

[Donk4kyv]

Save the biggest, thickest splits for the Liberty. Close down the air quickly, as soon as secondary burn starts.

The problem I have with my stove, cutting down the air quickly, is that the firebox fills with smoke from the smouldering wood, then the smoke ignites with a small explosion, puffing smoke out past the door seals and stovepipe connections and stinking up the house. It doesn't do that if I leave the air turned up about 1/3 the way, but that burns up the load of wood faster. I never could get much more than 4-5 hours of burn with a full load in that stove, and I usually add wood every 3 hours or so.

 

[begreen]

Yes, backpuffing is a common problem with downdraft stoves. They are particular about draft and need dry wood. How tall is the flue system on the Oakwood?

 

[jkazak]

The last couple of nights I've been using some (big) 20-25lb splits of hedge in the Liberty and they last a good amount of time keeping the stove nice and warm with minimul supply air. But I still have to keep the air slightly open to keep the wood flaming.

I don't babysit the stove enough to perfect a technique I guess....the other night I threw in a few big pieces of Elm and they started to "run away" on me so I closed the supply air completely and they threw off quite a bit of heat for a long time...just kind of smoldering with the secondaries flaming up consistently. Hmmmmm.....

 

[Woody Stover]

have to keep the air slightly open to keep the wood flaming....the other night I threw in a few big pieces of Elm and they started to "run away" on me so I closed the supply air completely and they threw off quite a bit of heat for a long time...just kind of smoldering with the secondaries flaming up consistently. Hmmmmm.....

Yeah, that could be the problem; As I understand tube stoves, the wood doesn't have to be flaming...as long as the secondary is eating the smoke, it's all good. That could really stretch the burn. I don't think you even need flame off the secondary to burn clean, but I could be wrong. Just experiment, then go out and look at what's coming out of the stack. If there's no smoke, you're good.

 

[begreen]

There may be no flame or little flame on the wood, but I look for some flame under the baffle. It can be lazy or wraithlike, but it is present.

 

[bioman]

I would try a key damper, should help.

 

[Donk4kyv]

Yes, backpuffing is a common problem with downdraft stoves. They are particular about draft and need dry wood. How tall is the flue system on the Oakwood?

25 ft, 6" stainless steel. The stovepipe runs horizontally from the stove about 5 feet to reach the bottom of the vertical flue. This is one of the recommended configurations shown in the owner's manual; the outlet for the stovepipe can be bolted into place either to run vertically or horizontally. I get a good enough draught that a piece of newspaper burns like a blowtorch when I light it to pre-heat the flue for a cold start. It was not practical to run the stovepipe vertically up from the stove, and I have often wondered if the horizontal outlet exacerbates the back-puffing problem.

 

[begreen]

25 ft, 6" stainless steel. The stovepipe runs horizontally from the stove about 5 feet to reach the bottom of the vertical flue

That horizontal run is very long and likely the problem. Try pitching it uphill toward the chimney as much as possible.

 

[jebatty]

Don't forget that a load of wood in a particular stove only has a mostly fixed btu heat content availability. Longer burn time means less heat over a longer period, and shorter burn time means more heat over a shorter period. Total heat is about the same.

 

[Chimney Smoke]

Chasing longer burn times with a tube stove is also more likely to result in lower temps and more creosote. Pick some reasonable stove and flue temps and try to keep them there on every reload, you'll probably end up with a lot less mess to clean up. Even with 3 year seasoned hardwood my air is usually not closed more than about 80%.

 

[Donk4kyv]

That horizontal run is very long and likely the problem. Try pitching it uphill toward the chimney as much as possible.

That would be impossible with my configuration, without a major demolition of the wall and mantelpiece. That horizontal stove pipe is the minimum possible length that would maintain the required clearance between the back of the stove and the wall behind it, plus the required clearance between the other side of the wall and the flue. If that configuration wouldn't work, they shouldn't have shown it as a suggested installation in the user manual, and the stove shouldn't have been designed to allow the stovepipe to come out of the back of the stove horizontally.

 

[Donk4kyv]

I stand corrected; brain fart. I just measured the horizontal run, and it is only about 24", not 5 feet.