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"Losing heat up the flue"

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by nola mike, Dec 29, 2011.

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  1. LLigetfa

    LLigetfa Minister of Fire

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    Many stoves have an unregulated stream of primary air blasting at the base of the fire. It is usually located front and centre below the door. Some call it the doghouse. I don't recall who it was but someone from one of the stove makers called it the zipper I think because it make the fire zippy.

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  2. woodmiser

    woodmiser New Member

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    I've always heard that inlet referred to as the doghouse. Both of my stoves are regulated there. What stoves use an unregulated doghouse?
  3. oldspark

    oldspark Guest

    LLigetfa-did you ever try a flue damper?
  4. begreen

    begreen Mooderator Staff Member

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    I lose heat up the chimney, intentionally. And as a result have never had a chimney fire with an EPA stove.

    Had a flue damper in the DVL pipe on the T6 for a season, but I removed it. I found that although it slowed the fire a little it was at the expense of poorer secondary combustion which I could see as visible smoke out of the flue cap. YMMV, every flue/house/terrain/climate combo is different.
  5. LLigetfa

    LLigetfa Minister of Fire

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    My RSF is an insert so the class A pipe connects directly to it. There is really no convenient place to put a flue damper. In my former home I contemplated placing a firebrick on top of the baffle to reduce the size of the opening but was concerned about possible smoke leakage when the door was opened. To reduce the draft a little, I put vents in the chimney chase to promote convection air flow and extract some of the heat. It helped.

    In my current home the flue is much shorter and so I don't have too much draft. Here, I double chased the chimney with radiation shield so that it would retain more heat to service the draft.
  6. oldspark

    oldspark Guest

    I still have high flue temps using the damper and my secondaries are better so I find it interesting you had the opposite results, just last week with a wicked south wind I had a 725 flue temp using the damper.
  7. oldspark

    oldspark Guest

    Are you saying a flue damper is going to help cause a chimney fire, thats just wrong cause its how you run the stove.
  8. Oldhippie

    Oldhippie Minister of Fire

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    Ah, thank you.. between "slammer", and now "zipper air" the lingo is difficult to translate.
  9. LLigetfa

    LLigetfa Minister of Fire

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    Agreed! I advocate leaving enough heat to service the flue. If you have too much going up the flue you could use single-wall smoke pipe to extract some of it or a vented class A chase. If you don't have enough, switch to double-wall or seal (insulate) the chase.

    Too often folks want to increase the efficiency as if they were running an uber efficient gas furnace. Wood stoves are supposed to be non-condensing. In another thread someone with a double-barrel stove is trying to heat a greenhouse and is condensing because too much heat is extracted.

    Burn dry wood, burn it hot, and accept that some heat needs to go up the flue.
  10. begreen

    begreen Mooderator Staff Member

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    No, I didn't say anything like that. What I said was that in some cases a flue damper is a necessity to reduce draft. Read it again and you will see I am referring back to the OP's question. That is one wants a certain amount of heat to be heading up the flue. It is not heat "lost". A cold chimney that allows the flue gases to condense can be a contributing factor to creosote accumulation. And that can lead to chimney fires if left to accumulate, then ignited by a robust start to a new fire. Whether it is dampered or not is a separate issue depending on the aforementioned conditions which vary depending on the installation.
  11. gyrfalcon

    gyrfalcon Minister of Fire

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    Geez, yes. So did you figure out what a "slammer" is? If so, please tell.
  12. oldspark

    oldspark Guest

    What he is saying is that some of the posts on here are confusing and to that I agree with, said that all along and still see it to this day, the post before yours just did it again, accept what going up the flue, YRMV and that is poor advice my friend.
  13. LLigetfa

    LLigetfa Minister of Fire

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    That there is old school. Many EPA stove makers advise not to put in a damper. Even if you put one in, they come in different sizes with a variety of cutout sizes. Then it's not all about size but how you use it.

    In the old days we would buy an oversized damper that was too big to turn 360. We would "tune" it by the size of the cutout. We would sometimes hang a weight from the handle to make sure it stayed full open or full closed depending on how the stove was loaded.
  14. begreen

    begreen Mooderator Staff Member

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    Slammer = an insert that is installed with no flue connection. Instead it relies on the insert's surround to seal off air infiltration and smoke leakage. This type of installation is no longer permissible in many areas.
  15. woodmiser

    woodmiser New Member

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    I thought a slammer was a short flue pipe connected to an unlined chimney? Might even have a blockoff plate.
  16. oldspark

    oldspark Guest

    Who do you think you are talking to? Been there done that, heated the house for a little over 30 years with no back up, my set up needs the damper and its not old school, its knowing what you are doing and getting your system to work right, my summit now works like it is supposed to with the damper, I am not the only one reporting this. Read some more of the post about it, dismissing some things as old school is incorrect. You need a damper if you draft is too strong period, my Nashua worked better that the summit with out the flue, I for the first time am burning less wood then with the old stove.
  17. Oldhippie

    Oldhippie Minister of Fire

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    I checked with my buddies, and they said "That's where to cops put you if you've had too much to drink and can't drive home. Then they throw you in the slammer." They're usually right about most things.

    I dunno how that relates to wood stoves, but I guess somehow it does.

    Okay, back to the topic at hand. :)
  18. gyrfalcon

    gyrfalcon Minister of Fire

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    Well, that's what I thought, but then talking about a "slammer install" gave me visions of shoving some miscreant up the chimney, but it didn't seem like that's what they were talking about after all, unfortunately.
  19. begreen

    begreen Mooderator Staff Member

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    I think that is usually referred to as a stub-in. You are correct, it should be done with a damper-sealing block-off plate.
  20. gyrfalcon

    gyrfalcon Minister of Fire

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    Got it. Thank you, sir. I can see why that would no longer be permissible. Beyond me why anybody would want to take chances with this stuff in their homes, but what do I know.
  21. woodmiser

    woodmiser New Member

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    A chimney system is basically unregulated. Sure you would want a perfect chimney design that meets the needs of the home and the stove. You could tailor the chimney in the design phase to accommodate. Most stoves are not installed onto a perfect setup.

    Adding a damper is giving some regulation in the cases where you have a chimney that you cannot economically change. Also some stoves... like soapstone in particular, tend to heat up better with a bit of regulation. One of, if not the premier class A chimney companies (Excel ICC-RSF) sells a double wall damper assy as part of it's premier stove pipe system. I don't think old school is applicable.
  22. Huntindog1

    Huntindog1 Minister of Fire

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    As reference when my damper is closed my flue pipe temp about 10 to 12 inches above stove is at 400.

    With these efficient stoves if the temps in the top of the stove stay up and you see secondaries going then creosote shouldnt be an issue.

    Its the burning of the smoke gases that leaves very little to build up in the chimney.

    In the old stoves of the past when you damper it down the smoke condensates at the top of the the chimney once it cools down and forms creosote.
  23. jharkin

    jharkin Minister of Fire

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    Digging this one up to the top again, just because I had a thought. Maybe its already been done but one thing that might be useful to us all is to add a page to the FAQs on this great sight that has a stove terminology cross reference by manufacturer. Reading threads like this it seems a lot of confusion arises because different manufacturers use different terms for the same function, and/or the same term for different functions.

    Air intakes are a great example - Every stove has one, some have multiple. Some are user controllable, some are fixed, some are thermostatically controlled and non adjustable, others are thermostatically controlled and manually adjustable. Some stove makers call them an "air control", some a "draft control", some an "air damper" some a "heat output control" and so on.

    Some examples

    My Encore has 3 (three) air intakes:
    - the Primary air intake that feeds the airwash and regulates the burn. This is user controllable and has a bimetallic coil damper.
    - An auxiliary intake in the ashpan. This is fixed and just the minimal air to keep the fire burning when the primary is closed
    - A secondary air intake feeding the catalyst. This is thermostatically controlled by a bimetallic coil but not user set (it can be adjusted once)

    VC Dutchwest stoves have the same air sources but I believe on some or all of them the cat secondary air is manually controlled.

    Blaze king cat stoves also have a user controlled air inlet with a bimettalic thermostat. I think they call it a draft control? Not sure if they have secondary air...

    Woodstock I believe also calls the air inlet a draft control.

    Non cat stoves always have at least a user controlled primary and a (usually fixed?) secondary for the burn tubes. I see that these have all kinds of names from draft to air to "zipper air"

    And some stoves even have an extra start up air.

    . . .

    Another example of terminology mix up are bypasses. All cat stoves and some non cats have a bypass to control when the secondary combustion system is engaged. Most manufacturers tend to call these a bypass, but Vermont Castings calls it a damper. But its not the same as a butterfly flue damper. or an air control damper.

    . . .

    So when somebody says damper - they might mean butterfly flue damper, or a VC catalyst bypass damper, or even an air control.
    Ans similarly the word draft might mean the draw of the chimney, or the air control.
    etc...

    Clear as mud, eh?
  24. Oldhippie

    Oldhippie Minister of Fire

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    Great idea! The thought crossed my mind yesterday that there may be a "terminology definition page" within the voluminous Q/As etc.. but I couldn't find "slammer" on a search.
  25. LLigetfa

    LLigetfa Minister of Fire

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    In school, there are laws or rules that over time lose their immutable status and no longer can go unchallenged. It doesn't mean the rule has been proven wrong or that it no longer applies, just that it is no longer immutable. Within the context of oldspark, his rule was stated as if it were immutable which is old school.

    I understand that a chimney system may operate outside the parameters the stove was designed around and that it may need to be mitigated. Many stove makers also recognize that as well. Some put it in writing while others make a case-by-case exception. Some stove makers provide technical specs WRT min and max flue height or draw.

    I'm just saying there is no one-rule-fits-all as oldspark appears to imply.
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