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Pellet stove technology

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Hammerjoe, Aug 24, 2006.

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  1. Hammerjoe

    Hammerjoe Member

    Joined:
    Aug 18, 2006
    Messages:
    125
    Loc:
    New Brunswick, Kanata
    Hi,

    I am a fairly new pellet stove user.

    I got my Harman Accentra this past march after ordering it in march.
    I love the pellets, they are easy to store, to carry and to feed the stove.
    I also love the automatization of the stove itself, basically it can work on its own and keep a constant temp with very little/none human intervention besides filling the hopper.

    Only drawback is that I find the Accentra design to be flawed regarding the ash conatiner, it should cover the whole bottom and not have that box in the middle, ashes get everywhere at the bottom and it is a pain to clean.

    The other negative factor I find about the stove is the technology used.
    It is impressive that the stove can work on its own, but I find that the user (me) still ahve alot of control on how the stove operates (I am talking about the control box).

    Because the stove is fully automatic, I shouldnt have the option to fiddle with the controls. It should detect the best settings and output most heat the most efficient way.
    Another thing is that the manual doesnt not explain how the changinf the settings affect the stove.

    The control box allows the stove to oeprate in either manual or auto mode and in any of these modes it also allows to either be controlled by a temp sensor or by constant internal stove temp, which both can be determined with the temp dial.

    Also fan speed and auger feed can be both set up.
    Now to throw into the mix and this is not explained in the manual, the stove can and will override the settings if its too hot, or the feeder is not fast enough, etc.

    So what is the point of having the choice if the stove will just override it whenever it feels like it?
    Better yet why just not leave the fan blower on max speed and the auger speed on 6 and let the stove do the rest?

    The settings used on my stove was auto mode, room temp, auger feed at 4 and fan blower speed middle setting.

    Are these the most efficient settings to keep a constant temp and burn less pellets?

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  2. Shane

    Shane Minister of Fire

    Joined:
    Nov 21, 2005
    Messages:
    1,830
    Loc:
    Casper Wyoming
    Generally pellet stoves run the most efficiently when up to operating temp and on high. You'll usually consume less pellets if you run them thermostatically and the stove shuts completely down after heat is no longer needed.
  3. moog5

    moog5 Member

    Joined:
    Dec 29, 2005
    Messages:
    79
    Loc:
    Shingle Springs, CA
    For a good explanation of how the stove and room temp modes on a Harman work, go to this thread

    http://www.hearth.com/econtent/index.php/forums/viewthread/964/

    and look for "pelletheats" threads. Or do a search, alot of people have explained this already.

    To get maximum efficiency, leave the stove on "room temp" mode and the igniter in the "Auto" mode. When you are in the room and want to keep warm, turn the stove up, when you go to bed and want to only keep the chill off, turn it down. Leave the blower on High, unless it's just too loud. If you run the stove on "stove temp" mode, the stove will try and maintain the exhaust at a constant temperature, not the room temperature. In Stove Temp mode, it may make your room hotter or cooler than you really desire. If it makes your room cooler than you desire, you will likely just turn the stove temp up, then there when the outside ambient temp heats up, your stove will still be trying to maintain its exhaust temperature, and at the same time burning and blowing out more heat into the room than is needed for the desired temperature.

    With respect to the "feed adjuster", follow the manual to set it. This will assure the stove completely burns the pellets, and doesn't shove them out of the burn pot. The stove is pretty darn smart, it just can't figure out on it's own what the quality and size of your pellets are. You need to give it this input with the feed adjuster setting. When you follow this procedure, you are essentially telling the stove to not ever deliver pellets at a rate which will shove them out of the burn pot. This is most likely going to occur when the stove is trying to crank out maximum heat. The feed adjuster tells the stove what the maximum amount of time the auger should stay on , but still not shove unburned pellets out of the burn pot. Unless the stove is shutting down, the auger is going to turn on every 60 seconds regardless of the need for deliverying heat. The length of time the auger will run will be dependent on the need for deliverying heat. When it needs to deliver alot of heat, it will stay on for about the same time it stayed on when you set it following the "feed ajuster setting instructions". When the stove needs to deliver only a little heat, the auger will run for a shorter duration each 60 seconds (the time is dependent on the need to deliver heat). If you notice that after a while some unburned pellets start getting close to, or actually get shoved out of the burn pot, it is probably a sign that the pellets aren't burning as fast as they did when you set the "feed adjuster". You can probably remedy this by giving the burn pot a could scraping, and cleaning the ash out from the area where the iginiter is, or even dial the "feed adjuster" down a tad bit.

    With respect to the room distribution blower, if you want the stove to operate as efficiently as possible, turn the blower on H (high), that way you will extract as much heat as possible before it gets blown out with the exhaust. Base on your tolerance to the noise, you may decide to adjust the blower down to a lower/quieter speed. The automatic temperature control in "room temp" or "stove temp" doesn't make any adjustments for efficiency, it just trying to maintain a temp. When your room gets warm enough, the blower will turn down on it's own, but at the same time the auger will be reduced to a low feed rate. When the blower reduces speed, more heat goes up the chimney, and loss of efficiency, but the but the only other choice would be to just let you stove shut itself off, a little sacrifice to keep the room at a constant temp.

    With respect to the Auto and Manual switch in "Room Temp" mode, to be as efficient as possible, leave it in the "Auto Igniter Mode". If you don't, your stove will continue to run even if your room is too hot. In "Manual Igniter mode", the only way it will turn off is when it runs out of pellets. In Room Temp mode, the stove will run automatically whether its in Auto or Manual iginiter mode, it just won't restart on its own in. This brings up the question "Why would you ever want to run the stove in Manual Igniter mode" . All I can figure is that if your iginiter goes out, you may not ever want the stove to shut down (because it won't start on it's own). In Manual Igniter mode, the stove will run like the older non automatic start pellet stoves, you have to start it with gel or paraffin chips, and turn it off manually when it gets too hot.

    With respect to the Auto and Manual switch in "Stove Temp" mode, per the manuals instructions, this would be the most inefficient way to run the stove. If the temp dial is set to 5 or less (~77F), the room distribution blower won't turn on and alot of heat is going to go right up the chiminey. The only reason I can see to run the stove in this mode is aesthetic reasons. Dialed down to 5 or less, the stove will burn like a free standing wood stove without a blower. If you have company over and want the stove have a good size flame, or not get the room too hot, or just be as quiet as possible, you won't want the room distribution blower to turn on. If the blower ever does come on in this mode, it's because your exhaust temp is higher than 350F (for safety reasons).

    In my xxv, the ash box also does not sit flush against the sides. I can tell you that based on past experience with other pellet stoves, having room to store alot of ash, and the ability to get rid of most of it by just dumping a box is a major convenience. The space between the side of the ash box and the inside walls of the stove helps ensure good flow of exhaust towards the exhaust port (I think).

    In summary, to be as efficient as possible, leave the stove set on "room temp" in the "auto igniter" modes, and the blower speed set as high as possible (or tolerate with respect to blower noise), and perform the necessary maintenance regularly
  4. drizler

    drizler Minister of Fire

    Joined:
    Nov 20, 2005
    Messages:
    948
    Loc:
    Chazy, NY 12921
    those adjustable controls may come in handy after while if you start burning other stuff like corn, pits, grass pellets ect. Otherwise just ignore them for the most part. Sounds like you are a bit overwelmed with the new stove. Believe me it will all be clear to you soon enough and its not much to digest. Don't wait to stock up on pellets as they have sold out and gone sky high in price the last couple seasons after December. Get yourself a programmable setback thermostat so the stove will come on early and heat the house up. Its well worth it as they aren't the fastest heaters out there so you gotta start early. That goes double if you set back to 55F like we do at night.
  5. moog5

    moog5 Member

    Joined:
    Dec 29, 2005
    Messages:
    79
    Loc:
    Shingle Springs, CA
    Hey Driz:

    It wasn't until a few weeks ago that I saw the thread about putting a set back thermostat in the loop with the room temp sensor. Sounds logical. In my case I leave the room temp at about 72. If I were to put a set back thermostat in the loop with the room temp sensor and I want the stove to keep the room at 72 or above, I undestand the logic for making sure the thermostat is set for higher than 72, I am just not clear how the stove will operate when the thermostat sets back to say 55F. I understand it will be just like disconnecting the room sensor (until it cools to 55F or lower). If I am in Room Temp mode and I disconnect the room sensor, are you sure that the stove just shuts itself off?


    I am also a little concernned that connecting and disconnecting this sensor (i.e what the thermostat essentially does) may somehow harm the electronics in the stove. If you can do this, I have to wonder why Harman just didn't include a set back thermostat with a room temp sensor in the first place.

    EDIT: My apologies Hammerjoe, I didn't mean to hijack your thread, so I will post the above question using a new thread.
  6. smirnov3

    smirnov3 Feeling the Heat

    Joined:
    Feb 7, 2006
    Messages:
    431
    Loc:
    Eastern Ma
    The simplest solution I saw (posted on Hearth.net a few days ago, FYI :) ) was to use a thermostat that makes / breaks the AC connection. so when the thermostat drops to 55 for the night, it effectivly 'unplugs' the stove. then, when the temp hits 55, it 'plugs' the stove back in.

    I don't know how good it is for the stove to be continuesly power cycled like that, though. It might be best to get a thermostat with a large hystoresis (ie ON at 55F, OFF at 60F)
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