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NC-30 Smoke Spillage

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by BCC_Burner, Oct 16, 2013.

  1. BCC_Burner

    BCC_Burner Member

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    So I finally got my NC-30 hooked up and running last Thursday. First break in fire resulted in lots of smoke from the paint, but the draw was strong and I got no smoke spillage when reloading.
    I was out of town until Sunday night, so I didn't do any more burning until then. Sunday night's fire was a little slower starting than the first one, but still, good draw once established and little to no smoke spillage.

    Monday night I had a moderate amount of smoke spilling, but I could mitigate it by cracking the door for about 30 seconds before swinging it open.

    Last night, however, I was getting a serious volume of smoke pouring into my place on each reload, regardless of how slowly I opened the door. With the door closed, the fire seemed to be burning well, no backpuffing or visible smoke filling the firebox and some nice secondary action with the damper 1/2-2/3rd's closed.

    I should also add that I don't think my problem is temp related. It was around 41 degrees when I started the fire last night, and dropped down to about 25 by the time I went to bed. This morning I encountered the same problem at 20 degrees outside temp.

    I am in a rental property, so my options for major alterations are basically nill. However, I can think of a few steps that will improve my draft given my less than ideal situation.

    I have 42 inches of vertical [single wall] stovepipe into a 90*, then a 20 inch horizontal run through a thimble, into the "T." From the "T" to the top of the stack is only around 12 feet, but it is an insulated 5.5" Flex King liner. I know this is far less than chimney than ideal, but I can't go adding enough height that I will need to brace it, as my lease prohibits that sort of modification. It looks like I could go with a 2 foot extension on the chimney without needing additional bracing affixed to the roof.

    I am also planning to replace the 90* with two 45*'s in an attempt to keep flue gas speeds up from the stove to the chimney.

    So, will going from a 90* to two 45*'s and adding 2 feet to my chimney enhance the draft? My location is reasonably sheltered from the wind, but it is in the bottom of a relatively deep, narrow canyon, so I can be fighting general downdrafts on a regular basis.

    I am really impressed with how the stove burns and heats so far, a vast improvement over the previous woodstove I was using, but I would really like to minimize smoke spillage. I stinks having to throw the windows and door open for 15 minutes after a reload to air the place out. Thanks for the advice.
    Last edited: Oct 16, 2013

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  2. mudr

    mudr Member

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    My less than experienced guess is the following: Colder outside temps and adding height will be your biggest friend. The two 45s might help, but, not as much as the aforementioned factors.

    Im running a 30 for the first time this year. I guess I was spoiled with my Drolet Myriad at my old house, it had the bypass damper which really helped this time of year to prevent spillage.
  3. begreen

    begreen Mooderator Staff Member

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    I think you have both a short chimney and your altitude working against you. This will probably take changing out the single-wall to double-wall with the 45's and extending the chimney as much as possible. I would try a 36" extension if possible and make sure the top plate is secured well.

    Was it windy yesterday night?
  4. BCC_Burner

    BCC_Burner Member

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    Dead calm air last night and this morning. Will a 36'' extension need bracing? It seems like it would. Adding 24'' as a percentage increase is pretty substantial given the length of my chimney. I originally looked into doing double wall stove pipe but it's really not in the budget right now.
  5. begreen

    begreen Mooderator Staff Member

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    High altitude needs more pipe. Get a couple 24" lengths of cheap galvanized round pipe and shove one in there on a calm day and try it out. If the smoke spilling is still bad, add the second length and test again.
  6. Sprinter

    Sprinter Minister of Fire

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    Here's a pretty good article that explains chimney height as it relates to altitude, offset bends, etc. Altitude is pretty big factor.

    http://www.rumford.com/draft.html
    begreen likes this.
  7. BCC_Burner

    BCC_Burner Member

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    I know altitude plays a pretty big part in things. I'm trying to minimize this problem within the constraints of being in a rental property and not having a large budget. I would love to anchor 8 feet of Class A to the top of the existing chimney, but reality doesn't allow it.
  8. Bluerubi

    Bluerubi Member

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    Not ideal, but couldn't a powered fan be a decent solution since it's a rental? Could be easily removed when it's time to move out, and no major changes to the existing structure.
  9. begreen

    begreen Mooderator Staff Member

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    Yes, I was thinking of a draft inducer too like the draw collar. Definitely not ideal but it might work, though not cheap. A freer breathing stove is another possibility, but again at additional cost.
  10. BCC_Burner

    BCC_Burner Member

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    It's puzzling to me that the stove seems to burn very well during normal, door closed operation, but the draft is still this weak.
  11. begreen

    begreen Mooderator Staff Member

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    Sounds like it is on the threshold if you are getting decent secondary combustion with the door closed. If so there is hope that the less expensive solutions will work. Have you tried opening a nearby window a little and see if that helps reduce smoke spillage with the door open?

    Also, try opening the air control all the way, wait a minute and then open the door slowly.
  12. BCC_Burner

    BCC_Burner Member

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    I do get great, albeit short lived (30-60 minutes) secondary combustion with a half a load of beetle killed pine, then it settles into a lazy flame with flickering secondaries.

    Last night I threw in a few smallish hardwood uglies (2 pieces of oak, 1 elm, 1 black locust) in with the damper open and slowly turned it down. Got great secondaries with the damper about 65% closed for an hour or so before I retired to bed, and they were still going. When I got up 7.5 hours later I still had a nice bed of coals that allowed me to start a small fire this morning using a handful of bark and some small splits. That took off after smoldering for 3-5 minutes with the door closed and the primary wide open, but once again spilled smoke upon the pre-work reload.
    Last edited: Oct 16, 2013
  13. begreen

    begreen Mooderator Staff Member

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    Sounds like there's hope. Get the 45's on there and try the extension.
  14. Sprinter

    Sprinter Minister of Fire

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    If you open a nearby window before you open the stove's door, does that help at all? Some houses are so tight that the stove can't breathe well unless it has outside combustion air. Even if the stove is doing okay with the door closed, maybe the additional demand for air causes the spillage when the door opens. Just musing.
  15. oldspark

    oldspark Guest

    Well if the smoke spillage is happening went the stack temp is low (reload) that could explain why it is happening at that point in time, less temp in the flue=less draw.
  16. stoveguy2esw

    stoveguy2esw Minister of Fire

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    could be a negative pressure issue with a marginal flue it can act inconsistant depending on indoor perssure as well as the temp differential between the flue and the ambient ourdoor temps.

    also you could have effects with negative pressure caused by other appliances, for instance if your clothes dryer is running it can pull a fair amount of air from the house this lowers the indoor pressure a bit if the house is tight. with a marginal flue this could be the difference between drafting or spilling smoke.

    if this were to "cure" the problem an OAK would be the lasting fix

    try opening a window af ew minutes before cracking the door
  17. BCC_Burner

    BCC_Burner Member

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    Opening a window or door might help slightly, but not in a huge way, still got spillage. The house is on the drafty side just as it is.

    No dryer installed yet, no exhaust fans running either. I think some of it has to do with temperature and pressure gradients where I live. My house is very well sheltered by tall pine trees, so unless the wind is blowing I get little air movement across the top of my stack.

    I am in a canyon bottom that is about 1/2-3/4 of a mile wide, with peaks on all sides that reach up to 10,000-11,500 feet. Especially on clear, calm evenings, like last night, where there is substantial snow cover up high I imagine we must get strong down drafts coming off the peaks and settling the cold into the bottom. Had an outdoor temp drop of about 12-14 degrees in one hour last night around nightfall.

    I was thinking it might be stack temp related, but I did a reload while the stove was still hot last night (stove top around 600) just to see, and still got spillage.

    Calling the stove shop to order my 45's on my lunch break today. Looks like I have a weekend project.
    Last edited: Oct 16, 2013
  18. BCC_Burner

    BCC_Burner Member

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    I will be installing the two 45's this afternoon when I get home from work. I imagine this will help as it will reduce my horizontal run from 22 to about 8 inches.

    I determined what was causing the smoke spillage and increasingly poor burns though. My landlord installed the chimney liner and cap, which I hadn't been up on the roof to inspect closely until this weekend. The chimney cap I have has 3/4 inch holes to prevent critters from getting inside. For whatever reason, the landlord wrapped this in 3 layers of 1/8 inch mesh, and 2 more layers of what appears to be almost as fine as window screen material. Needless to say, this ultra fine mesh was significantly blocked. After removing the small gauge mesh the stove burned much better even with the 90 degree bend inside, little to no smoke spillage.

    I'm excited to see if the straighter shot to the thimble will improve things a little bit more.
  19. begreen

    begreen Mooderator Staff Member

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    Yea, that's good news. Maybe he was trying to keep out wasps from nesting?
  20. BCC_Burner

    BCC_Burner Member

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    That's a possibility, but boy did that give me a headache over the last week or so. I spent yesterday afternoon listening to NPR and starting contentedly into the non backpuffing flames.
    PapaDave likes this.
  21. Highbeam

    Highbeam Minister of Fire

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    As an owner, he probably thought that if one spark screen is safe that three would be safer.
  22. BCC_Burner

    BCC_Burner Member

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    Based on how he planned to do the install prior to me insisting on an insulated liner, I don't think safety factors too highly into his thought process. I had to do some limbing of an adjacent tree too because the branches were fully enveloping the chimney cap after he finished the install.

    He said it didn't pose a fire risk because the tree is still alive and too wet to burn. !!!
  23. Sprinter

    Sprinter Minister of Fire

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    That will do it! Glad you found something concrete. The decreased horizontal run and 45's should help a lot also.
  24. Soundchasm

    Soundchasm Feeling the Heat

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    So in Dayton, if I dig a 1,000 foot hole to put my stove in, I won't need to install a 4' chimney extension?;lol
  25. Sprinter

    Sprinter Minister of Fire

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    Make it big enough and it could be an awesome echo chamber for your recording...

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