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Vermont Castings "Defiant" vs Quadrafire "Isle Royale" vs Jotul "600 firelight"....

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Mr_Super-Hunky, May 22, 2007.

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  1. begreen

    begreen Mooderator Staff Member

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    Now that you've picked out the stove, download the manual from the VC website. It has detailed installation instructions and a nice graph that shows the effect of altitude on draft.

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  2. Corie

    Corie Minister of Fire

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    Yeah unfortunately eight inch pipe is EXPENSIVE, although Duravent is significantly cheaper than some other brands.


    Eight inch is also a little heavier too, making it all that much more fun to install.
  3. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    BeGreen:

    I downloaded the VC manual and according to fig 2., the proper height of chimney for 7600 ft is 25'. (we will be at 30'). It further explains that to large of a chimney (in diameter) will cause rapid heat loss and so it seems that the 6'' pipe may be a better choice??. Am I right?
  4. Corie

    Corie Minister of Fire

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    Yes, you'll have less heat loss from a 6 inch chimney based on surface area, since all other parts of the heat transfer equation would remain essentially equal between the two pipe diameters. As long as the volume of gas isn't choked by the 6 inch flue (and the manual indicated it isn't), its probably a better choice. Plus its cheaper.


    Of course when the manual is speaking about large chimney cross-sections, they're really talking about venting the stove into something like an 8x12 masonary flue, not the differences between the 6 and 8 inch flue.
  5. begreen

    begreen Mooderator Staff Member

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    The graph shows 6" flue performance. There isn't one for 8". So far I'm with Bart on this one, but Corie is the engineer. Corie, are your heat loss equations for double or single wall pipe?
  6. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    corrie/Begreen:

    I'm a little confused (which, for a newbie is par for the course!). I want to do what is right....the first time!. I can see how a larger diameter pipe will allow for more air flow (via less restriction), however, according to VC charts, a 6'' pipe at 7600 ft elevation should be 25'. Here's what I don't understand. If, according to the VC elev chart, 7600 ft should be 25' stack based on using a 6'' pipe; ....since we are using a 30' pipe (double wall simpson duratech), does that mean that we are *better* since we are 5' more than 25'?, or does that mean that we are *worse* because we are 5' over 25'?.

    Sorry for the technical questions but is anyone wanting a challenge??. I'm clueless!.
  7. begreen

    begreen Mooderator Staff Member

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    It's almost always better to be on the too much pipe side of the equation for a well behaved stove. Reducing draft with a damper is easy and cheap. Increasing draft can be a bigger problem.

    But I still want to wait for the engineer's heat loss calcs for 8" double wall pipe at 7600 ft. to see where that comes out.
  8. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    buster:

    The "heat loss" that you are referring to may be misunderstood from my description so I' will try to describe it clearer.

    The mfg sais that the temp of the air/gases rising up the pipe may actuallt be *cooler* using a 8'' pipe as opposed to a 6'' pipe. This is simply due to the larger volume of air space to now keep heated.

    I am trying to "read between the lines" on a lot of info and it can get confusing to say the least!. Since we will be burning primarily pine (creosote), I want to keep the pipe as hot as possible in order to prevent the creosote from precipitating onto the walls of the pipe due to cooler temps which a larger diameteripe may cause.

    At the same time, I also want to install the proper size piping diameter for a 30' height to get optimal drafting.

    According to the VC elevation diagram using 6'' pipe, 7600 feet should be around 25' of pipe; but we have 30. To compensate for the difference, I am trying to find out if I should go with a larger pipe (8) and possibly have cooler pipe temps, or should I stick with the 6''.

    Anyone know how drafting plays into this??
  9. MountainStoveGuy

    MountainStoveGuy New Member

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    Pine doenst contain any more creosote then any other wood, how wood is seasoned is what determins the creosote buildup in the chimney. Pine, IMO has less chance of creosote buildup due to the low density and a high combustion rate.

    Stick with the 6". 8" chimney is more forgiving at your altitude then someone at sea level, but your stove will perform better on a 6 inch flue. 30' is plenty of pipe for 6", i would be afraid of overdrafting the stove on 8". I have 24', 6" chimney at 9000' and my stove drafts perfectly. Remember, manufactures are going to be conservative with there recomendations.

    My last point would be that most modern stoves run on 6" flues, the trend seems to be going to smaller flues with every new generation of stove. When your stove wears out, i think you would be better prepared for a replacemnet with a 6" chimney in place, who knows, in 10 years the standard might be 5...

    here is a quote from http://www.mastersweep.com/wood.htm

    "Back in the early 1980's, tests were conducted to discover which kind of wood created the most creosote in a regular "open" fireplace. The results were surprising. Contrary to popular opinion, the hardwood's, like oak and madrone, created MORE creosote than the softwoods, like fir and pine. The reason for this, is that if the softwoods are dry, they create a hotter, more intense fire. The draft created by the hotter fire moves the air up the chimney faster! Because it is moving faster, the flue gas does not have as much time to condense as creosote inside the chimney. Also, because the flue gas is hotter: it does not cool down to the condensation point as quickly. On the contrary, the dense hardwood's tend to smolder more, so their flue gas temperature is cooler. Thus, more creosote is able to condense on the surface of the flue. So, saying that "fir builds up more creosote than oak" just isn't true! It is a misunderstanding to think that it's the pitch in wood which causes creosote. It's not the pitch that is the problem, it's the water IN the pitch. Once the water in the wood has evaporated, that pitch becomes high octane fuel! When dry, softwoods burn extremely hot! "
  10. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    WOW MountainStoveGuy!! What an enlightening response; you truly made my day!...really!!!

    If what you are saying is true..(and it makes perfect sense to me, rationally), this could possibly change a lot of peoples minds on what type of wood to burn.

    Although pine will burn much, much quicker, if the fuel is free and in plentiful supply all over your property (like mine), who can pass up free fuel!!

    I know it will take a LOT more wood, and a LOT more splitting (excuse for a nice log splitter!!), but my biggest concern was clogging up a new "cat" stove with crud as well as crudding up the chimney very fast.

    Now that I understand that a hotter fire is a cleaner fire (creosote wise)......and of course using seasoned wood, I feel much much better about burning pine in a new stove.

    Thanks for the info, you really made my day!!
  11. MountainStoveGuy

    MountainStoveGuy New Member

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    Actually pine grown at our elevations have much more density then pine grown at sea level. I burn about as much pine as our hardwood burners here burn in a given season. When i fill my non cat up with a load of wood i get at least 7 hours and more commony 8-10 hours on a burn cycle. I burn 4 cords a year to heat ~ 2000 square feet home with good insulation at 9000' feet. Not bad. You will get longer results with the cat stove, you just have to carefully watch the cat temp before you engage it.
    Glad i could help!
    MSG
  12. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Even though most of my property is red and white oak I burn a cord or so of Eastern yellow pine every year. In fact that is all that I will be burning in the Jotul in the office this year. Two cords are stacked and ready to go and I will be adding another cord or two this month. To go along with the five cords of oak.
  13. Corie

    Corie Minister of Fire

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    Back to the heat loss stuff for just a second. Using simple radial one-dimensional heat flow, assuming the inner temperature of the flue is the same, the insulation is the same, etc etc, you're going to lose more heat with an 8 inch pipe because it has a large external surface exposed to the cooler air. Also, an eight inch chimney will have a larger inner surface area but the flue gases will still contain roughly the same heat and you'll end up with that heat spread over a larger inner area on top of what I already mentioned.


    I can do the calculations for real with the two pipe sizes if you guys would really like to see the math. Using fourier's law and the simple approach above gives a pretty good idea of the difference based on the increased external area.


    The ONLY way I can see that the 8 inch pipe might present less heat loss is if the velocity dropped significantly below that of the 6 inch pipe. Then you could use the formula q (heat loss) = md * cp * (Tpipeoutlet - Tpipeinlet) and you'd see a decrease in heat loss IF the exit temperature of the gases was the same between 8 inch and 6 inch, which I doubt would be true.


    I guess I'm just beating around the same bush with that. Ultimately an 8 inch pipe will lose more heat when compared to an identical 6 inch pipe.
  14. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    He may be alright with the six inch for open door burning. I know that I burn the F3 sometimes with a screen and the 5.5 inch 30 footer with no problem. Usually over a bottle of an impertinet little cabernet after the tax return is put to bed in April.

    But it ain't trying to move anywhere near the air volume of an open door Defiant up the pipe.
  15. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    [quote author="Corie" date="1180844871

    I guess I'm just beating around the same bush with that. Ultimately an 8 inch pipe will lose more heat when compared to an identical 6 inch pipe.[/quote]


    Thanks corie for the detailed explanation. This is all good news as the 8'' pipe would have beed a lot more cash-o-la! Cheaper pipe that stays warmer (preventing creosote build up) works for me!
  16. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    Bart:

    I think we should have enough air due to the volume of area we have as well as the house having numerous air leaks and venting......I hope!
  17. Todd

    Todd Minister of Fire

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    I think you will be fine with 6". If it was me , I'd go with the 6", just because you have a 30' chimney. I have 22' with a 5.5 " liner, and when it gets really cold I think it drafts too good sometimes.
  18. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    BTW:

    Now that I've got the stove picked out and the pipe size..(6''), I have been told that the best brand of pipe is simpson "duratech" as opposed to their other line. Is it worth the extra money? or is all chimney pipe basically the same?
  19. begreen

    begreen Mooderator Staff Member

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    Simpson Dura-Vent is the company, DuraTech is the all fuel pipe system. Folks use the name interchangeably, but DuraTech is correct for the pipe. This is the same piping system we have installed. If you want to decode all the pieces, they have an online catalogue posted.

    http://www.duravent.com/?page=1.php
  20. Corie

    Corie Minister of Fire

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    I'd spend the money on the Dura-Tech. Besides it isn't really that expensive in the world of chimney products; I can think of quite a few other insulated brands that are as expensive or worse.
  21. Mr_Super-Hunky

    Mr_Super-Hunky New Member

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    Thanks for the simpson link BeGreen.
  22. RonB

    RonB Feeling the Heat

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    Hi MSG. I'm confused. Why would 30' of 8" draft better than 30' of 6".
  23. restorer

    restorer New Member

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    I am really confused, are we at the point of green paint drafts better than blue paint? Volume of air is a basic fact of moving air. If you need to move a lot of air, the bigger the tube the more air you move. In a stove if you move too much, you over burn (that's too fast, too hot). If you want efficiency you use the draft appropriate to the burn. That translates to the engine determines the size of the exhaust, not the huge exhaust needs an even bigger engine to work effectively. Regardless of profession or trade, if you move air you should understand the importance of having the right size flue for the source of the exhaust air. If you are too large in flue, you will not have adequate pressure to move your exhaust out. The best is the level of pressure that maximizes the movement of air, at the same time you don't want a ram jet to make the stack the place your fuel burns.

    All that said, has anyone seen anything about the actual temperature of a stove, or fuel source during a chimney fire??? My guess is it is less than the ambient temperature?
  24. scotty

    scotty Member

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    I'm an engineer and I'm not comfortable with VC's chart on chimney height versus altitude. It would be helpful to see how they arrived at their calculations.
    Hoping we can look into this a bit farther..... Scotty
  25. stoveguy13

    stoveguy13 Minister of Fire

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    are you talking about draft because draft is not thwe same thing as moving air threw duct work unless you have some sort of power vent hooked up moving the exhuast out of the stove is a function of the chimney that is created by tempeture dif. that is what creates draft and the a lareg pipe will not increas draft in alot of cases it will acctually lessen draft as the gas will cool quicker as they expand i belive corrie stated this before and he is dead on.
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