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Top or rear flue exit?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Gasass, Mar 6, 2013.

  1. Gasass

    Gasass Member

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    We're considering purchasing a Woodstock Keystone and noticed it can be vented from the top or rear. All things being equal, does one draft better than the other? What are the pros and cons to both?

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  2. begreen

    begreen Mooderator Staff Member

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    Good question. In my experience with the Jotul Castine, top venting is better if possible. The shorter smoke path helps improve draft so that there is less chance of smoke spillage from the door and better mild weather performance. But I have not burned in a Keystone so I will leave it to those that have to follow through.
  3. lopiliberty

    lopiliberty Minister of Fire

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    If its vented out the rear you can use a T with a cleanout to make cleaning easier. That's how my old dutchwest was and when I cleaned the flue all I had to do was remove the bottom cap on the T place a bag around it and sweep. Eliminates all the creosote falling into the stove.
  4. begreen

    begreen Mooderator Staff Member

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    Good point, though pay attention to clearances if this is not in a fireplace. A telescoping pipe can do the same thing if need be. Slide it up and slip on a bag to catch the cleanings.
    Joful likes this.
  5. Gasass

    Gasass Member

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    How much does a 30 degree offset in the chimney pipe affect draft? I'm leaning towards top exit but may need to put an offset in. If that is the case, would a rear exit with a straight shot up be better? (From hearth to top of chimney is approximately 22')
    Thanks for your help!
  6. rideau

    rideau Minister of Fire

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    I have ICC pipe. If I slide mine up, it just falls down. I remove the adjustable piece, take it outside and clean it well, and attach a bag to the ceiling box. Works well.
  7. rideau

    rideau Minister of Fire

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    For expert advice, ask Woodstock. They know the keystone best and will give you the best advice in your particular setting. give them all the information about your set up, and what you want to achieve. For instance, top vent may let you get closer to the wall. Rear vent may slow draft a bit...or maybe not. Rear vent may leave more space on thes tovetop for cooking. They'll look different in the room.

    Woodstock will be quite happy to help you make the decision. And you can't get more expert advice.
  8. begreen

    begreen Mooderator Staff Member

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    If the stove is in a fireplace and rear-exit eliminates the offset, then I would go that route with a 22' liner up the chimney.
  9. fox9988

    fox9988 Minister of Fire

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    Quote from Todd:​
    Changed my install from a rear vent to top vent and it made a big difference. I was having sluggish draft and a little smoking during reloads but no more. Woodstock says don't worry about that rear vent 90, it's a typical install and doesn't effect the draft. Well I can tell you it effected mine and with the top vent the stove can be turned down lower, doesn't smoke, gets hotter and has a better looking fire. The old Fireview didn't act this way with the same setup but the Keystone seems to be a different animal. 3 90's can make a big difference in draft as far as I can see.​

    Me and the wife really wanted to leave the rear vent for that extra soapstone trivet panel but I'm liking the performance of the top vent much better. I have about a 2.5' horizontal run but it still seems better than the old 3 90 elbow setup I had before.​

    Now when I burn the stove at .5 it burns like it use to at a little below 1 but I still get the lazy flame for a longer period. The pipe temps have gone up about 50 degrees. Stove top temps seem to be a bit higher as well, 650 with little flame and staying over 500 for a good 3 hours or more. I'm liking it.​
    Attached Files:

    Blaze King Princess Parlor
    Woodstock Keystone
    Todd, Apr 15, 2011 Report Bookmark
    #24 Like Reply
  10. rideau

    rideau Minister of Fire

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    Interesting.

    He mentions 3 90s. I could see that being an issue. He is giving the draft a chance to get a bit established before it turns 90 and goes out the wall...

    Hope he'll chime in on this post.

    This OP is talking about going straight up once vented out the stove, so far less potential for issue with problematic draft.

    Hope Todd reported back to Woodstock with his results and details of his install, issues, and improved results with changes. Knowing Todd's great general helpfulness, I bet he has. That will allow them to give better advice for someone with a similar set up.
  11. Gasass

    Gasass Member

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    It will be a free standing corner install. The stove will be going in an addition we plan on building sometime this year, so I have some flexibility.
    My dilemma is keeping the chimney pipe close to the second floor exterior wall as it exits the one story addition roof. I want to build a chase around the chimney but dont want it too large. Ideally, we don't want the chase sticking out more than 24" +- from the exterior wall. With a rear exit, I'm pretty sure I can get a straight shot up and keep the chase size within reason. Top flue, I'll definitely need a slight offset. Hope that makes sense.
  12. Gasass

    Gasass Member

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    Thanks for the posted info. It is a little different install, as I will have one 90 rather than 3, but interesting. I'll have to search some of Todd's posts.
  13. Gasass

    Gasass Member

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    Spoke to them last week and they claim there is no difference. At some point, we're going to take a road trip to the factory to pick out our stove and I will bring the prints off the addition so they can see it on paper. It was a little tough explaining everything over the phone.
  14. fox9988

    fox9988 Minister of Fire

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  15. fox9988

    fox9988 Minister of Fire

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    I wouldn't worry about one 90, especially with 20+ ft of pipe (I have 16' top vent and great draft). Personally, I don't like the looks of an offset that is visible, otherwise I would have went with the Fireview. The Keystone does a great job and I have no regrets.
  16. Highbeam

    Highbeam Minister of Fire

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    I would go ahead and declare that top vent will always be a superior drafting application. Heat rises after all. Making the smoke run horizontal much farther and then turn the 90 can only be a negative. Shorter path, more direct path, less horizontal, are all what makes vertical superior.

    Rear vents are a compromise for fireplace installs.

    Sure, they will both work but if you want the best then top vent is it.

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