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How to extend your stove's burn times

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by precaud, Jan 2, 2011.

  1. precaud

    precaud Minister of Fire

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    One of the most frequent questions posted on this forum is "How can I get longer burn times from my stove?" I've shared my success in dealing with this in response to these posts, but apart from a few individuals who have "gotten it", it doesn't seem to sink in. All it requires is a small modification to your stove, a slight change in burn habits, and a little experimentation to "dial things in". So last night I decided to use my stove the "usual" way (i.e. unmodified) just to demonstrate again that my approach works. First, some basics.

    When someone says they want longer burn times, that usually means they want enough red hot coals in the morning to do a "warm restart" without having to build a fire from scratch. Rake the coals forward, put in a fresh load of splits/rounds (maybe a couple sticks of kindling under them, maybe not), and in a few minutes, away it goes. Morning after morning, reliably. That is the goal.

    The thesis is simple: The most effective way to get control of burn times is to get control of the air sources in your stove. Period.

    The problem is, almost every modern stove has air sources that run wide open all the time, giving plenty of air to the coals to burn down overnight. More air = coals burn down more quickly. Less air = coals last longer. The solution is to examine each stove, identify where these "always open" air inlets are located, and come up with simple and effective ways of controlling them. This only needs to be done once for each stove. Findings can be posted in this thread. I'll show some ways I've done this to some of my stoves, as examples of where to look and how to make simple controls.

    Back to the comparison. Last night there was a movie on later than I usually stay up, which gave me a good excuse to do this. My normal procedure is:
    1. Start the last load of the evening so that the flames will die out right around bed time.
    2. When the flames die, close down the secondary air.
    3. Close down the primary air ALMOST all the way. Go to bed.
    4. Wake up in the morning, open the air controls, and within minutes have plenty of live coals for an easy warm start.

    My normal bed time is 10pm, so with the Quad 2100, I start my last load somewhere in the 7-8pm range, depending on how big a load it is. Normal wake up time is 5-6am. That's 10-11 hour burn times. Reliably.

    Last night I used the stove like it would be used without the secondary air controls.
    1. Load up the stove about 40 minutes before going to bed.
    2. Adjust controls to get the burn established and then burning stable at a low burn rate. Go to bed.
    3. Wake up in the morning to find not enough live coals for a warm restart.

    Last night, the last load was at 10:30pm, I woke at 6am to find very few live coals in the firebox. That's less than 7.5 hours burn time.

    This approach works. It can significantly extend the burn time for ANY EPA stove.

    Later today I'll post some examples showing where to look for the air inlets and how to fashion simple shutoff controls.

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  2. Todd

    Todd Minister of Fire

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    Or you could just buy a cat stove since they require less air to burn clean. :coolgrin: I'd be careful messing with the secondary air, could lead to more ceosote if you burned that way too often or wood wasn't dry enough.
  3. Big Al

    Big Al New Member

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    Can't wait to see it. You metioned this yesterday in my thread and I'm all over that idea. I'm sure there'll be others who'll jump at it too as well as some who won't want to mess with thier stoves. I'm guessing the factory didn't put such controls in because they wanted to dumb things down for average user. Also there'd be a potetial of folks misusung the controls and smoking up the air.
  4. precaud

    precaud Minister of Fire

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    Details of the first example, for a Morso 2110, are posted here:
    http://www.hearth.com/econtent/index.php/wiki/Add_secondary_air_control_to_stove_Morso_2110/

    I did eventually grind the handle down so it looked more graceful and painted it black. Unless they knew what to look for, noone would ever notice it.

    Todd, this thread isn't about stoves with cats. And this technique doesn't "mess with" the secondary air while the flames are burning. So both of your comments are irrelevant. This thread is for folks who want to extend the burn time of the non-cat EPA stove they have.
  5. JustWood

    JustWood Minister of Fire

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    I've had the same results with my stove.
    I had some short pieces of square tool steel laying around that I experimented with. The small pieces allows a very fine tune.
    Less than ideal seasoned wood is not recomended.
  6. begreen

    begreen Mooderator Staff Member

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    I've been observing long fires too now that winter is here. Seems that you can only cut down the air supply so far, if the goal is a long burn and... heat. It's hard to get the real long burn unless you give up some heating. The primary factor for altering that equation in our stove appears to be - change the wood.

    With the onset of cold weather I switched from doug fir to cherry. The difference is dramatic. With the fir, I get quick heat, average 6 hrs meaningful heat and no coal and very little ash to speak of once the load has burned down. With the cherry, I am getting big lingering coal beds and a lot more ash. There are lots of good coals 10hrs later without doing anything different.
  7. oldspark

    oldspark Guest

    Hell I do not even know what I'm doing and I can get 10 or more hours out of the summit.
  8. precaud

    precaud Minister of Fire

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    Here's another example, for the Quadrafire 2100M ACT. The secondary air passes through channels running down each side of the stove. (The side panels are not removable so I can't take a photo.) Each channel makes a 90º turn at the bottom of the firebox and into the inside of the pedestal. The first photo shows what they look like (sorry for the blurry pic). It would have been slick to be able to operate the cutoffs for both inlets from a single control, but that was way more complicated than I wanted to get into at the time. So I opted for separate controls for each side. There is enough of a gap between the inlet and the pedestal for a thin sheet of metal to slide smoothly within. I found a corner piece of thin stainless steel, cut two pieces out of it, trimmed them down to size, drilled a hole toward the end of the flat section and inserted a long screw for an operating handle. Push the handle in when operating the stove, and pull it out when the flames die to close the secondary. Simple but effective.

    Like many stoves, the Quad primary air control does not close all the way, so its primary air control needed a small change too The last photo shows the primary air inlet and control, located just under the ash lip. That Philips screwhead you see is the stop for the air control. It was simple matter to remove it, restoring full range to the primary air control. It just so happens that, when pulled out all the way, there is a sliver of an opening on it, just perfect for a small amount of "bleed" air for the doghouse to keep the coals alive but not burn them down.

    These simple mods increased the burn time from about 7 hours to 12-14 hours.

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  9. precaud

    precaud Minister of Fire

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    From what I have seen, the primary and secondary air on the PE super and summit fireboxes are both fed from the same air channel and controlled by the same air control. So this mod/technique is not applicable to PE stoves. There may be others like this, but to my knowledge, they are unique in this respect. It takes a lot more engineering work to dial in proper amounts of air for each source from a single control. So you guys will figure out another way.

    But then again, not many PE owners struggle with this issue. :)

    EDIT: and we see already, PE owners chiming in, saying just that!
  10. Roxburyeric

    Roxburyeric Member

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    I don't understand why you would go to this trouble. Just buy an old smoke dragon and save some money. Also why do you let your stove burn out before bed? I load up the stove about 15 minutes before bed and dial it down to as closed as it will go, giving me lots of heat even after I go to bed, and I still get easy starts with hot coals 10 hours later, with no mods to the stove.
  11. precaud

    precaud Minister of Fire

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    OK Rox, I'll bite. Why do you live in a house where you have to dump heat into it while you sleep? What a waste of wood.

    I guess every constructive thread has to tolerate its share of irrelevant posts. Sigh.
  12. begreen

    begreen Mooderator Staff Member

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    Try a pure softwood diet. Hardwood is really nice to have around. Rare enough here that I have to hoard it.
  13. Roxburyeric

    Roxburyeric Member

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    Every house is different. Don't you heat you house if the evening? I wasn't trying to be an @#%%^ - I just read on here about the old smoke dragons shutting down all the air and it it seems like that is what you are doing with your modifications.
  14. begreen

    begreen Mooderator Staff Member

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    Not really. If you notice that he posted that he is cutting off the secondary air - after the flames stop. At the charcoal stage the wood has stopped outgassing. There's no smoke at that stage, even in a non-EPA stove. The point about heat is true though. If you need it, the fire may need more air.
  15. oldspark

    oldspark Guest

    Expalin that one to me, the secondary air is under the ash pan separate from the primary air unless I am missing something.
  16. oldspark

    oldspark Guest

    My wood has not been that hard in years. On a more serious note I doubt I could get a long burn on softwood. Cherry is supposed to be a good coaling wood though.
  17. precaud

    precaud Minister of Fire

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    Spark, I believe that's the "doghouse" air, not the secondary. The Summit cutaway I saw showed pri and sec air fed from the same channel.

    Also, the PE secondary design puts very little air into the firebox proper. Most of it goes into the chamber above the baffle. That's quite different from, say, the more common arrangement with burn tubes arranged front to back.

    PS - the burn times I'm describing are with pinon pine. Not hardwoods.
  18. oldspark

    oldspark Guest

    The hole in the back of the stove feeds the baffle.
  19. Battenkiller

    Battenkiller Minister of Fire

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    Although I applaud folks who are clever enough to modify their stoves and dial them in better, when it comes right down to it, you are always faced with this choice. If you cut the air back, you will get a slower burn rate and a longer burn time, but less total heat. If you burn less seasoned wood at night, you will get a slower burn rate and longer burn time... but again, less total heat. If you want a longer burn time without sacrificing total heat output throughout the night, you have no choice but to use your best seasoned, densest wood for the overnight burn and letting it have the air it needs to burn the entire charge by morning. We folks in the frozen north have no problem seeing and accepting this. No fun waking up to coals when the house is cold.
  20. begreen

    begreen Mooderator Staff Member

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    ??? what hole, the oak connection?
  21. oldspark

    oldspark Guest

    No the square one in the back when you take off the ash pan.
  22. oldspark

    oldspark Guest

    I am confused, there is a square hole in the back that lines up with the channel that goes up to the baffle, I was thinking this feeds the secondary air to the baffle, is this the case?
  23. begreen

    begreen Mooderator Staff Member

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    Interesting. Spark, the stove is hot right now and I have to head out and take my son back to college. Will check it out, you could be right.
  24. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    I bet there is. That is the way the 30-NC secondary manifold is fed.
  25. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Keep it coming precaud. I for one find it an interesting thread.

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