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Stove Temp vs Room Temp

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by jdege, Nov 15, 2011.

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  1. aaronnoel

    aaronnoel Member

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    I will for sure try out stove temp manual in the dead of winter, as I'm always wanting to save pellets, but I don't understand one thing, how low will the stove go down to when on manual and the stove is at it's set temp? It seems to me that it will only go down as low as low fan on #1 so I don't see how that can save on pellets.

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  2. jdege

    jdege Member

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    I have tried running the stove on Room Temp Manual and the outside and top are getting warm/hot to the touch which was not the case in Room Temp Auto. Is this just a function of the stove running non stop but nit need ing non stop heat or do the stoves just run hot to the touch when on continuous run?
  3. forya

    forya Member

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    Room Temp for me. I extended the probe wires to a good spot and run it at 72. I am on my 3rd year burning and have not replaced my igniter yet. I do have a MAP torch just in case It does go, and my Heat pump/Electric heat is set at 64 in case it doesn't light at night. When it gets real cold it really doesn't cycle on and off though.
  4. Trickyrick

    Trickyrick Feeling the Heat

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    What happens is the distribution fan turns off and the stove is still running so it "heats up". It is fine but it is a waste of heat.
  5. lbcynya

    lbcynya Feeling the Heat

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    Stove distribution fan doesn't turn off on room temp, switch set to manual (unless it's on mantenance burn in which the distribution fan will over cool the stove and reduce efficiency). How is a hot stove a waste of heat? That's not wasted energy, just stored energy which will dissipate into the room at some point.

    My XXV get's nice and hot to the touch, love it.
  6. tinkabranc

    tinkabranc Minister of Fire

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    I only run the stove in room temp during the shoulder seasons and switch it over to
    stove temp mid season.

    Seems to keep the house a more comfortable temp and less wear and tear on the ignitor.
  7. Trickyrick

    Trickyrick Feeling the Heat

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    If the distribution fan isnt running then more BTUs are going out the exhaust. That is wasted heat.

    I agree the distribution fan doesnt turn off in manual but in room temp it does. that will allow the top and front to heat up and because you do not have turbulent flow through the exchanger you are wasting heat.
  8. lbcynya

    lbcynya Feeling the Heat

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    My fan doesn't shut off on room temp, switch to manual... I would presume the fan is motor controlled by the esp temp over anything else...
  9. lessoil

    lessoil Minister of Fire

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    Curious about what happens to room temperatures in stove mode when outside temp swings
    from lets say -10 to +20. If you are comfortable with a certain setting at -10 and do not
    change it, does it get too warm at +20? Do you have to re-adjust??
  10. thedude110

    thedude110 Feeling the Heat

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    It would be helpful if Harman would release an honest, pro-con chart of the two modes.
  11. lessoil

    lessoil Minister of Fire

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    Yes a chart would be nice.


    Here is what I have seen.
    A Harman Tech at a seminar (2009) stated that Room Temp was more efficient.
    We had a new control board installed this past Summer.
    I have noticed the following:
    1) Startup is slower ie a much more gradual fire ramp up
    2)When stove shuts down the auger does not run at all. It used to feed a small
    amount to help keep fire from moving toward bin.
    3) Does not keep temp on setpoint like the old board. More fluctuation.

    **Igniter burned out last month. Original 13 fin from 2008**

    So now I am running stove in Room Temp but with the igniter in manual. (This mode is in the book)
    Another forum member pointed this out to me.
    This seems to keep the temp more stable and also keeps the fire going. Saves on igniter use.
  12. lbcynya

    lbcynya Feeling the Heat

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    How your stove works - The facts are pretty straightforward, but how you get people to properly interpret the facts is the hard part.

    It's your toy, run it the way you want as long as you understand what's going on behind the scenes!

    Everything noted below is based on me seeing what the stove is doing via the Harman diagnostic tool during the various operation methods. I get to see feed rates, max feed rates, current ESP temps, ESP set temps, room sensor temperatures, room sensor target temperatures, knob positions, switch positions, etc.


    Here are the facts:

    Stove temp - 100% driven the the ESP (temperature probe in stove exhaust flow). Temp dial corresponds to a fixed ESP temperature. For simplicity, let's assume a setting of 3 = 300 degrees ESP temp. The stove will ramp feed up/down to always be as close to 300 degrees as possible. In stove temp the stove doesn't care what the room temp is, only the ESP temp. The room might be 60 or 90 degrees doesn't matter, all it cares about is maintaining an ESP temp of 300.

    The stove will not shut off in stove temp regardless of whether the igniter switch is set to auto or manual.

    Stove temp, switch to manual - I call this fireplace mode. Distribution fan will not turn on unless the temp knob is set to 5 or higher. This is designed to give a nice fire, but not a ton of heat in the room. Most goes up the chimney.

    Stove temp, switch to auto - distribution fan operates normally to push heat into the room, regardless of stove or room temperature. There is a caveat to this, if you have your room temp set to 1 (very low) then the distribution blower might shut off because the ESP temperature is below the lowest setting allowed for the distribution blower to run.

    ____________________________________________________________________________________________________


    Room Temp - The stove is 100% driven by the room temp sensor. The stove will automatically adjust feed and ESP temp to achieve the room temp set point. Once the set point is reached, the stove will slowly throttle up/down to maintain temperature. If it's 20 degrees outside, your heat load is high and the stove will feed more pellets to get the ESP temp hot enough to maintain room temperature set point. If it's 60 degrees outside, the stove will feed as little as possible and keep as low an ESP temp as possible to maintain room temperature.

    Igniter switch to manual, stove will go into maintenance burn in between calls for heat - prevents igniter cycling, might use a few more pellets in this mode...maybe...

    Igniter switch to auto, stove will initiate the shut down process in between calls for heat - igniter could cycle several times per day, depends on set point and heat load. If there is a call for heat during the shutdown process, the stove will start feeding pellets provided that the ESP temperature didn't go below the low limit. So, on really cold days, the stove might not shut off, even if it's on auto.

    So there's the facts, interpret away... :)

    ______________________________________________________________________________________________________

    And more...

    Feed Rates - Feed rate us controlled by the stove ESP. The stove will select a feed rate based on the actual temperature and target call for heat. The larger the temperature delta (actual room temp vs. target room temp), the greater the feed rate will be. 10 degrees would be a large delta and the stove would feed to reach max ESP temp of about 500 degrees depending on stove model. A 2 degree delta might only result in a feed rate of 20 seconds per minute even though the feed rate max dial is set to 4 (or 40 seconds per minute). The stove can vary the feed rate between 2.5 seconds per minute and the max feed rate you set. A feed rate of 6 would represent continuous feeding if the ESP wasn't seeing sufficient temperatures to satisfy the call for heat.

    Feed rates can lead to incomplete combustion comes in 2 forms -
    1. Pellets spilling over the edge of the burn pot before they are reduced to ash.
    2. Smoke.

    Relative to #1 - when you run the stove wide open, the burning pellets should come no closer than 1 inch from the edge of the burn pot. You should have burning pellets and about 1†of ash before the edge. If pellets are bulging and close to the edge, you might not turn them to ash before spilling over the edge, wasting energy. If the burn line is too close, dial the feed rate back a bit, may by 1/2 of a number (i.e. 3.5 to 3). The stove doesn't run wide open once everything is up to temp, so this is only for scenarios where, for instance, the room is 65 and you want it 75 degrees. When up to temp the stove will regulate itself form 5 seconds per minute of feed up to the limit you set.

    Relative to #2 - smoke is also a sign of incomplete combustion, meaning that there is more fuel than air supplied by the combustion blower. This too should be evaluated when the stove is running WIDE OPEN. At night with a flashlight, you’ll always see smoke… During the day, smoke is rated based on opacity or how easily you can see through it. Startup might be 50% opacity or fairly heavy smoke. If you are 10% or less (barely visible), that’s reasonable and you aren't really wasting anything. If you have to struggle to see it, you’re probably good. If you can easily see smoke and your flame is HUGE, try dialing back feed rate a bit to bring the air/fuel mix back into a more efficient range. Once again, dialing it back by 1/2 of a number (ie 3.5 to 3).

    In most cases, you don’t want to be below 3 or above 4. You’ll also want to recalibrate after changing brands of pellets since the blend and size of pellet will cause it to burn/feed differently.

    Setting your feed rate too low doesn't save pellets and stove performance will suffer. Setting your feed rate too low is like putting a brick underneath the gas pedal of your car. Don't be tempted to set your feed rate too low.
  13. PJPellet

    PJPellet Minister of Fire

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    This is a very accurate explanation.
    I have been fiddling with different settings on my P43. I have found I like room temp the best. I have found that for my installation and house that leaving the stove in room temp always, then putting the stove into manual when the temp gets below 35* works great. Above 35* I flip it to automatic and it starts and stops as you would expect. I put it in manual below 35* because I noticed that the stove would go into shutdown but before the combustion blower finally stopped the stove would need to re-ignite. I love the way room temp works, and the only reason I even flip the switch to manual at that certain temp is to save on the ignitor. All of this being said I still fiddle and play. Bottom line for me is room temp in automatic works the best at my house. It burns the least pellets and keeps the house at an even temperature. Love it.
  14. lbcynya

    lbcynya Feeling the Heat

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    Thanks PJ!

    (Moved content to post 36, since this is the link referenced in my signature.)
  15. referee38

    referee38 Member

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    I have a harman P-43 and was wondering about the best place for the sensor and from what I am reading I should have it away from the stove to get the best results. This is what I wanted to do so thatnks for helping with that.
    Ed
  16. lbcynya

    lbcynya Feeling the Heat

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    Unfortunately, there's no good way other than the method I outlined above. Mine is happiest directly under the stove exhaust outlet. Corner install, basement, on tile floor over cement floor. You might need to move yours elsewhere, on a wall, etc. If it's on the floor, you shouldn't have to move it too far from the stove. You can extend the room probe up to 25 feet using thermostat wire. Just depends on your layout. Best to try and find someplace easy and close before you go extending things.

    Second thought, you could use an IR temp gun to take surface temperatures around the stove area to find the temp that equals what you have set on the temp dial. Let the stove run for several hours or a day to let everything find equilibrium before trying to find the sweet spot.

    Attached Files:

  17. Harman Lover 007

    Harman Lover 007 Minister of Fire

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    Dude, that is the best explanation I have ever heard for the operation of a Harman and it is exactly how I understood it to be....thanks.
  18. 76brian

    76brian Feeling the Heat

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    This is why I bought a cheap digital thermometer and placed it exactly where the room temp sensor is. Now I know precisely what the sensor is reading, and can interpret how to set the dial on the stove. I don't find the dial to be all that accurate, but it's close enough that it's easy to adjust based on what I see at the sensor.

    All in all, I find "Room Temp" keeps that thermometer within a degree or two of what the stove is set to. It's not bad really... the slight difference could simply be a small variation in component values and the fact it's an analog control. Digital at the stove would be a great improvement though.

    Thanks for the explanation, will clear things up for many I am sure!
  19. Oink Oink

    Oink Oink Member

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    Can anyone explain how the feed rate plays into all of this?
  20. Harman Lover 007

    Harman Lover 007 Minister of Fire

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    As I have said many times here in the past year, the feed rate on a Harman is a "set it and forget it" adjustment. My P61A is set at 3. The feed rate adjustment is a setting that controls the maximum rate that your stove will feed pellets when, and only when, the stove calls for it. Do a search on Harman feed rate.
  21. Oink Oink

    Oink Oink Member

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    So this is my strategy: Set the feed rate at 3.5 and forget it.

    In the middle of the winter room temp using manual, so that the igniter doesn't have to be used heavily.
    Shoulder seasons room temp set on auto, to save on pellets.

    Good strategy?
  22. subsailor

    subsailor Minister of Fire

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    Acorrding to my dealer, the feed rate only applies when in room temp. Not a factor in stove temp.
  23. Harman Lover 007

    Harman Lover 007 Minister of Fire

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    Well he doesn't know the product line he sells very well then. The proper way to set the feed rate in the first place is done in Stove Temp mode. It's in your owners manual.
  24. Marg

    Marg New Member

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    So it does not matter if you use Stove Temp on Auto? On Manual can you run it on Stove Temp or Room Temp?

    Marg
  25. Marg

    Marg New Member

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    Stove Temp mode on Auto or Manual to set right feed rate?

    Marg
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