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Sizing stove through oil usage.

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by jslinger, Jan 27, 2013.

  1. jslinger

    jslinger Member

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    I am pretty new here, and was wondering if picking the right pellet stove is as easy as observing usage of your current fuel source?
    Example:
    I currently have an oil boiler. Over the last week, during the cold snap, we have averaged burning around 3 gallons per day. Based on the assumption that there are 119,000 BTU's in a gallon of oil, based on a boiler with 85% efficiency, that equals 357,000 BUT's per day. If a pound of pellets contains 6,000 BTU's, based on a stove with 75% efficiency, that means I need to burn 60 pounds of pellets per day to equal the output of the oil boiler. Or a stove that is capable of putting out roughly 15,000 BTU's per hour.
    Is it this simple? Or is there more I need to consider?

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  2. jtakeman

    jtakeman Minister of Fire

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    Careful most of the stoves are rated as gross BTU output. You will need to deduct the efficiency loss of the unit. Some have over rated their units a bit too. Also don't rate right at the BTU, Give yourself a buffer for the really cold days. A safe bet is to have at least 25 to 35% of the unit in reserve JIC.

    Some also use the BTU's of the furnace to get them close.
  3. DexterDay

    DexterDay Guest

    To make sure you get it right, pellets contain 8,000 BTU per Lb. So you will need less lbs per day than you think :)

    Which amounts to 45 lbs a day.. But in this cold snap, I don't know if that is right?

    Avg use is 2 bags a day when cold... Some use 3.

    How large is your house? Single story? Sq ft?
  4. jslinger

    jslinger Member

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    I accounted for the BTU loss for a stove with 75% efficiency. That is how I came to 6,000 BTU's. Two story, 1050 sq ft 1st floor, and 750 on the second.
  5. heat seeker

    heat seeker Minister of Fire

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    Be careful, that may be just the burn efficiency, not the overall efficiency. The burner guys don't tell you that so you'll be more impressed, IMO.
    SwineFlue likes this.
  6. SwineFlue

    SwineFlue Minister of Fire

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    True (and very good to keep in mind), but it's better than trying to use square footage ratings that are based on a "well-insulated house in a mild climate".
  7. jtakeman

    jtakeman Minister of Fire

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    Not all stoves will hit these numbers(75%). They do not rate them just by convection. Its a combination of 3 IIRC(electric-thermal and combustion). So if one is down(thermal or convection) you can actually be below your numbers. Plus the manufactures tend to over rate them. So add a buffer or lower your percentage to 50 to 60%.maybe? Also the auger systems aren't dead accurate at feeding the required pounds per hour as consistent as one thinks. They tend to vary due to slippage and such. Keep a safe distance so your not on the ragged edge or you will need assistance once it get really cold.......

    I'm only slightly bigger sqft wise and I use 2+ bags in the cold. But my stove is capable of 3+ no problem. Just trying to keep you from being undersized. An undersized stove will make the owner not very happy in the cold.
  8. DexterDay

    DexterDay Guest

    Oh. Sorry. I still think your gonna need more than 1.5 bags a day (especially the coldest days).

    I think a 50,000 BTU unit would work well. Always better to have more and not need it, than need it and not have it. Plus the unit will last longer if your not running Full tilt every day.
  9. jslinger

    jslinger Member

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    I am torn between the P43 and the P61A.
  10. jtakeman

    jtakeman Minister of Fire

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    If you want to be sure and oil free? Go with the P61a. If you don't mind burning a touch of oil if the temps drop really low? The P43 will do OK.

    Ideally a 50K or 55K unit would be the target IMHO. Isn't the XXV 50K?
  11. DexterDay

    DexterDay Guest

    Yep. Im with Jay.

    61 WILL DO IT. The 43 may? Based on your #'s it should.

    But remember. These are space heaters. Getting heat upstairs may prove to be difficult.
  12. jslinger

    jslinger Member

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    We never turn the heat on upstairs. There is typically a 2* loss from the first floor to the second. Floor plan is pretty open down stairs.
  13. movemaine

    movemaine Feeling the Heat

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    yeah, you could go for the XXV or Advance, as they are in the 50k btu range. But based on your numbers, I still think a 43 would carry you - but the XXV is also attractive (doesn't suffer from big black box syndrome)
  14. jslinger

    jslinger Member

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    i like the look of the XXV, but it is hard to justify spending that much more, when I could go for the 61, and get more stove for less money.
    Thanks for the input.
  15. boo boo

    boo boo Feeling the Heat

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    Your dealer should let you know
    I was looking at the p61 and my dealer said the p43 would do the job and it has
    2 floors and 1800 sq feet semi open first floor three beds on second
    ask your dealer
    Also if you used only 3 gallons of oil a day during that cold snap you dont have much heat loss that seamed low to me. My boiler uses .75 gallons of oil per running hour
  16. jslinger

    jslinger Member

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    My dealer said I would be ok with the P43, but he said my house is on the threshold of being too big.
    I agree. My oil usage did seem a bit low. That number was an estimate. We just got filled up, and in the last 80 days, have used just under 200 gallons.
    That includes heating water. My fiance takes a bath every single day, so that didn't help.
    When it was -5*, I would turn the heat down to 55* at 9pm. By the time we went to bed, at 10:30, the temperature only dropped 1.5*.
    I am going to call the dealer today, and ask him if he would recommend going with the P61A.
  17. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    There are a couple of gotchas doing the sizing that way.

    The first is it leaves no head room for record cold and the temperature drop that will take place every time you shut the stove down for cleaning. Let alone both happening at the same time (trust me it can happen).

    You want your heat loss covered on the day of your lowest temperature at the mid point of your stoves firing rates. If you size the stove to meet your consumption exactly then you'll be fine some of the time but not all of the time.

    Ask anyone on here that hates to turn their stove off to clean it when it is cold out or talk to those who have trouble heating during the coldest part of the winter.
  18. boo boo

    boo boo Feeling the Heat

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    You will be happy with with either stove and the p61 should be a good stove for you. My brother in law has that stove and loves it. You will only be heating water with the oil like I do and I love it. Pellet burning is a great heat and like most people say why didnt I do this sooner

    Good luck and and post up when you get it running
  19. moey

    moey Minister of Fire

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    Wow 3 gallons? I suspect I would be closer to 4-5 gallons during last weeks cold snap, but I have never actually used my oil heat as the only source. Go with a bigger model or accept you'll have to turn you oil heat on at times. My setup struggles below 10 degrees more because of the layout then stove BTU though.
  20. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    If I was to turn my t-stat down to 55 at night my oil eater wouldn't burn much either which is another thing you don't want to try with a stove just sized to your current usage. Your usage pattern will change that's another given.
  21. jtakeman

    jtakeman Minister of Fire

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    The dealer knows, Ha thats a good one! hehe. Sorry can't control myself sometimes! Bad pellet burner bad! ;em

    But a "warm" one! ;)
    moey likes this.
  22. jslinger

    jslinger Member

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    So I shouldn't trust my dealer's opinion? He did come do an in home consultation.
    He is in Florida right now, and he will hopefully be calling me soon.
  23. jtakeman

    jtakeman Minister of Fire

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    Most look at a sheet and say yep! Its within the square footage of the stove so it works! No acounts for variance/layout/heatloss and yadda yadda.

    If ya trust him run with it!~ But don't say we didn't try to steer ya to just slightly larger JIC! Again just enough is fine until the cold sets in and the heat loss rises. Moving heat up a floor is hard enough all by itself. Add the extra heat loss and all bets are off.

    These things are space heaters. Not really meant to heat the whole house. Unless you plan ahead and take the go big or be cold route!
  24. boo boo

    boo boo Feeling the Heat

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    Hay my dealer was great. Went over the floor layout with two possible locations. Showed me his spair parts list he had in stock along with the parts room.. 10% off the stove and delivery to the spot where I wanted it. The downfall was his eyes followed my wife around more than I wanted but if it got the deal done Im ok with that
  25. moey

    moey Minister of Fire

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    He/She is a salesperson at the end of the day take their comments and then form your own opinion and then ask more questions.
    DexterDay likes this.

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