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Winter-time downdraft (suggestions welcomed)

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by ajthatch, Sep 10, 2006.

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  1. webbie

    webbie Seasoned Moderator Staff Member

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    Boxing in the chimney - in my opinion - will not solve the problem (It may help, but not fix). The air is being pulled down by negative pressure and you have to solve that....

    No, the interior double wall is not making the problem worse....

    In bad situations like this, I would usually see if the customer can install an interior T right near the wall. This allows you to open it, insert a piece of newspaper toward the chimney, and therefore have a better chance of reversing the chimney easily. Once reversed, Elks advice about a really hot startup will warm the chimney and keep it drafting.

    I wonder if a temp outside air hookup - just to test - would work. Like a piece of plywood with a 2" hole cut in it that inserted into a partially open window and then fed right to the stove air control. At least this might give you some indication if the air was off-balance.

    OH, you mention the force at which it comes down. If you install the T and then stuff a piece of newspaper in there balled up - that slows the downdraft a bit before you light it.....

    That makes me think that some kind of a solid turn damper would help also.....to slow or stop the reversing when the stove is not in use.

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  2. tradergordo

    tradergordo Minister of Fire

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    NO IDEA how you can say "chimney looks good and should work good" and also link to Gulland in the same post! ;)
    This guy has an evil outside chimney AND a basement install - two things that should be avoided if at all possible.

    From Selecting and Locating a Chimney
    "When it is cold outside, the warm air in the house wants to rise, just like hot exhaust rises in a chimney — this is called stack effect. Stack effect creates a slight low pressure area in the lower part of the house and a slight high pressure at the higher levels of the house. A neutral pressure plane (NPP) lies between the high and low pressure zones. If there is no fire in the stove or fireplace and the air in an outside chimney cools to below room temperature, the house becomes a better chimney than the chimney, and sucks cold, smelly air down the flue."

    I have no reason to believe that opening windows, punching more holes in your walls, or extending your chimney as it is will alleviate your problem, but then again, I'm not a professional installer... what I do know is that a good chimney makes draft even when no fire is burning.


  3. seaken

    seaken Minister of Fire

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    Okay, the way I read this post it seems that the main problem is a "downdraft" of cold air while the stove is idle. Once it get going it is fine. This is classic flow reversal caused by negative pressure in the basement, as outlined by Guland. All the tricks about getting the fire going aside, you need to look at solving the negative pressure problem. What is causing it? What will solve it? Honestly, from here there is not much chance that we will successfully diagnose what is causing your negative pressure, at least not in detail. Some of the common causes have been mentioned and referred to. What you really need is to have some local professionals who understand the issue come out and do a site visit and offer suggestions for solution. Bear in mind that this house pressurization issue is difficult to understand and many of us who are in the hearth business struggle with it. Some of us get it. Some of us don't. I would suggest that the dealer who helped you with that installation did not fully understand the issue. Or, maybe he/she tried to explain the issue but you decided to put in that outside basement chimney anyway. In any case, it's done now. So now what?

    If it were me, I would light the fire and never let it go out. If that is not practical for you, you may start by putting a door on your basement stairway. Then make sure there is plenty of make-up air (using one of those Condar thingies) near the furnace and utility room. A tight sealing damper can help but it is not a very practical device on that type of chimney. Maybe you can set up the pipe to be easily disconnected and re-connected so that you can block the flue when not in use. A PITA, but may be the only way to stop the down draft.

    Replacing the double-wall pipe won't affect the down draft issue. But it might slow the cold draft you are feeling coming from the slots in that pipe. The interior pipe is so cold that the room air is is being tempered as it passes through those slots.

    Sean
  4. elkimmeg

    elkimmeg Guest

    I believe you have a forced hot air heating system with all duct connections in the cellar? This has got me thinking, what if your return ducts are leaking or you installed a returns in the cellar? Floor joist pan bay returns are usually installed in a way that do leak quite a bit. They are never properly sealed. I have seen some without end cap seals using the fiberglass insulation as the only particial seal. All joints in your ducts, plemums, should be duct sealed. If the return side is leaking that means you are further drawing air from your basement, increasing negative pressure,drawing down that chimney. All leaking duct work effects the overall preformance of you primary heating system and could be part of your chimney problems.
  5. ajthatch

    ajthatch New Member

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    Well, if nothing else I have learned a few things from all of the information everyone provided. The stove was already in the house when we moved in some years ago and the shop where it came from is no longer in business. There are no other stove shops in the area (that I'm aware of) so I decided to post this and see what others thought.

    From what I gather, negative pressure is the cause of my troubles. Having an outside chimney contributes to this (via stack effect). My assumption that my furnace caused the negative draw probably wasn't completely correct. The furnace and other appliances may well contribute to it, but I don't think they are the root cause. I believe now that the cold outside temperatures created a stack effect which I associated with the furnace simply because it was running. This would help explain why the downdraft remained even when the furnace was turned off and no other fans/appliances were running. It also explains why I only notice this in the dead of winter (very cold out!) It sounds like I could try a number of things to help with this, but I'm guessing that without moving the stove/chimney that my chances for complete success aren't all that great.

    So, I think I will go with my current plan (and what I have done the past 2 years) - use the wood stove in the fall and early winter before the temperatures drop too far. Then, plug the chimney to keep out the draft and wait until early spring! Not what I had hoped, but it's better than just letting it set (and much cheaper than trying to move it). Thanks again for all of the information, I really appreciate it!
  6. webbie

    webbie Seasoned Moderator Staff Member

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    Yes, your unit is already in, so we can't talk about relocating, etc. - you now know enough to use it and try various things to see if it responds. Good Luck
  7. tradergordo

    tradergordo Minister of Fire

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    Yes, this is KEY information. If the problem occurs when nothing is running (furnace, fans, appliances) and gets worse when its very cold, it is absolutely a stack effect issue. If you really want to have and use a woodstove all winter, you shouldn't rule out relocating it or maybe even not relocating the stove but bringing the chimney inside. You already have almost all the hardware you'll need so its just a matter of the labor. Couldn't hurt to get an estimate (my guess would be anywhere from $500 to $1000 depending on where you live). The costs could easily be recouped over time from the energy savings if you decide to use the stove for primary heat. Although it doesn't sound to me like you really want to use the stove this way and maybe you don't want to deal with the extra hassle.
  8. Roospike

    Roospike New Member

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    Any information anybody on the out side pipe / boxing it in and insulation ? We talk about insulation for a liner in a chimney well what about the outside pipe being insulated and being boxed in ? ............. I'm sure the pipe running through the inside of the house is always going to be the better of the ideas but there are a lot of houses that are just not set up for it and dont have the room. I wouldnt think it would cost that much in framing for the outside pipe / insulation and to find a matching trim of the house . From the looks of ajthatch house if the pipe came inside and up without moving the stove its going to have to go through a bed room. I know the pipe can be boxed in i guess my question is more of insulation of the pipe with in the box .
  9. NFreiermuth

    NFreiermuth New Member

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    Just to add my two cents worth here:

    Maybe the older Kitchen and bathroom fans are missing the automatic flapper dampers, or just plain don't have them??? A few of those always stealing the hotter air from the living floors would definitely help exacerbate the problem. I recently had a friend who installed a high efficiency gas furnace a four years ago. It uses sealed outside combustion air. The hot water tank was never a problem until two winters ago, he installed an On-Demand gas water heater. To make a long story short, there were no more pilot lights and the bleeding of the hot water heating the chimney from the natural draft. What did we get for our increased efficiencies, voila' a frozen On-Demand water heater!!! How, If I didn't feel it for myself, I would have called him a liar!! It was falling down the chimney VERY fast. Is that the "Stack-Effect", yes, I think it it is.

    To solve his problem, he was told to either re-install a Hot Water tank, or use a power venter through the side wall. We decided to attck the problem head on and figure out where all of the infiltration was occuring. (Air falling down chimney must create air exiting dwelling from the top) Both the Kitchen exhuast fan and two bathroom fans had Bad dampers. The kitchen was held open from grease and the bathroom fans were held open from lint. Also, The powered attic ventillator, although not running, was a direct path for air out through the roof. I am assuming it was naturally pulling the air through ceiling fixtures (Recessed lighting, ceiling fans, etc.) He made a damper door for the attic ventillator, and when he turns it off for the winter, just installs the door. He has had no problems at all and it even drafts when not in use, hence "Good Chimney's make good Drafts"

    It will take some VERY serious and sound investigations, but this problem is probably repairable. The House didn't look too new to be one of the air-tight ones built to today's standards.

    For What it was worth.
  10. elkimmeg

    elkimmeg Guest

    If he had read his furnace installation manual,this situation should have been corrected. The 3 or 4" flue from the hot water heater can not generate enough heat to heat that 8/8 flue Again cross-sectional area code is in effect. The furnace manual would have instructed the installers of the furnace to address this issue. either a power venter of a 3 or 4" full liner is required to satisfy the gas heater venting requirements. Its part of every direct vent furnace manual to make it the responsibility of the furnace installer not to just leave only that gas vent to fend for its self. It is also addressed by code. I willing to bet the replacement burner was never
    permitted or inspected? Inspectors can not help you without knowing about it
  11. NFreiermuth

    NFreiermuth New Member

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    Sorry ELK

    Liner was installed, He did it right the first time.

    Also, the On-Demand uses a 5 Inch Liner, which is still in place

    Gosh, no wonder why nobody likes to talk to the inspectors.
    Always assuming the worst.
  12. Robbie

    Robbie Minister of Fire

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    I know almost nothing about these issues above, but it's such a nice looking stove installation. I wonder if a reverse air flow type damper in pipe above basement somewhere would help ? I forget what these are called but I have read about them, it sure would be worth a try looks like to me.

    And............if this did not work, why not a forced air motor to induce draft mounted near stove, looks like this would cure everything, I would never settle for a early spring and fall only usage if it were mine.

    These links were random, I'm sure the pros here know of many others,

    http://www.volko.com/Chimneyfan.htm

    http://www.tamtech.com/cape_damper.htm



    Robbie
  13. tradergordo

    tradergordo Minister of Fire

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    From the same place, they also have this electric draft inducer for woodstoves.

    Anyone have any experience with this type of product? I wonder how durable, reliable, and effective they are? You would be exposing those motors to some pretty serious heat and potentially clogging ash! But if they work, that sounds like a pretty simple solution that a lot of people might benefit from. Of course when you factor in the electric use, it may actually be an expensive long term solution depending on how much you use it.

  14. brian_in_idaho

    brian_in_idaho New Member

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    McMaster-Carr carries a "extreme temperature heat tape" that can handle up to 1400F, also a ceramic band heater (6 1/2 inch ID). I'm wondering if you could put either of these around your pipe where it exits the stove to generate enough heat to get your draft going the right way. And these are pretty cheap, around $50.

    http://www.mcmaster.com/

    Just a thought, no garantee.

    Bri
  15. elkimmeg

    elkimmeg Guest

    Note no mention of a permit or inspections. Had that been mentioned before I would not have posted
  16. suematteva

    suematteva New Member

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    Roospike,

    You see many installations like that up in Quebec, both with a boxed in chase and just the way the setup is pictured..

    believe it would help but the money question is it enough?

    Ours is in the basement and runs up through the 1 st level and 4-5 ft in the attic then out the roof..
  17. Roospike

    Roospike New Member

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    A little tad bit of information per linking . "Defining Perfection
    Ten characteristics of successful stove and fireplace systems / chimney. " " Do you have the perfect chimney set up ? " http://www.woodheat.org/planning/perfection.htm
  18. Roospike

    Roospike New Member

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  19. Roospike

    Roospike New Member

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