Expert: Paul Karthaeuser - 2/1/2012

Question
QUESTION: Hi I have a small building that I have recently put a Great West Metal air tight portable wood heater like the one in the picture and I'm having troubles with it. After I make a fire in it I can't control how it burns. Once I get a good fire in it and then close the draft off about half way the fire will die down and if I open the top to put more wood in it will make a poof and blow smoke and flames out at me. Also when I have a fire going and open the draft all the way the fire will roar so bad that the whole stove will vibrate and when the draft is fully closed the fire dies down completely then after a short time it will make another poof and blow the cover off the stove and flls the building with smoke and I'm scared to use it. My stove pipe is run straight through the roof with no elbows and is about three feet above the roof which is flat and at the top of the pipe I have an H shaped cap. I took notice that when there is no fire in it and when I put my hand inside the stove there is a fair amount of air coming down the pipe into the stove. Would you be able to tell me how I can have this stove so that it doesn't "blow up" on me when I use it. Any help is greatly appreciated.
Thanks

ANSWER: Trevor,
The first thing that comes to mind based on your description of the problem is pressure related issues.  That is to say that the building in question sounds like it is in a negative pressure situation.  The fact that the stove/chimney pipe is down drafting when not in use is indicative of a building that is under a negative pressure situation.  The building is trying to equalize itself by pulling air down the chimney to create a balanced pressure inside the building.  A simple test of this theory is to open the stove door and check with your hand to feel if air is down drafting into the stove, if it is then open a window or door partially that is opposite the stove, preferably in the same room.  You should not need to open the window or door much.  Next go back to the stove and put your hand inside and see if the chimney is drafting normally now.  Has the airflow reversed itself and is now flowing up the chimney?  Alternatively you can tape strips of newspaper to the front of the stove door opening with the door of the stove open and watch them fluttering into the room and when you open the window or door in the room to the outside atmosphere watch the strips of newspaper reverse themselves and flutter into the stove.  If this is the case it means that the building is exhausting more air through vents, attic fans, bathroom fans or anywhere the building exhausts air than the building is bringing in and the easiest and largest place for that building to bring air in to balance itself is usually the chimney.  The corrective action is to bring in more air to the building for combustion or leave a window slightly cracked open when using the stove.

That is one issue hopefully explained. I would replace the cap with a more conventional cap that is less restrictive to venting the flue gases(smoke.  Believe it or not those "H" style caps are very restrictive to the venting system and may as well be the equivalent to more than one 90 degree elbow in the venting system.  

I think that if you do the above mentioned things you will see a dramatic change in how your stove operates and will have much more control over how the fire burns.  Your problems are all related to the lack of air in that building with which to burn the stove.  Try the simple test above and next time you use the stove do it with the window slightly open and then make your adjustments to the draft/combustion air openings on the stove.

Please feel free to ask any follow up questions you like and I would love to hear from you once you have done the above trouble shooting measures.  I hope this has been helpful and educational.  Thank you.

Paul

---------- FOLLOW-UP ----------

QUESTION: Hi I tried what you had mentioned about opening a window and checking for draft coming down the chimney and there is really no difference from windows being open or closed. There is still a fair bit of air coming through the stove pipe. I even tried with all the windows open but there was no difference. I also tried it with the building door opened and closed and when the door is open there is alot of air coming through the stove pipe and when the door is closed it still draws air down. Would it make a difference if I use a T pipe and put an elbow on it?

Thanks

ANSWER: Trevor,

I'm sorry this was not the answer to the problem.  I was fairly convinced this was the source of the problem. Sometimes it's very difficult to diagnose a problem from such distance without the benefit of inspection-on site.  But I will continue to try and help you if you like.

Could you email me a few pictures?  Maybe one or two outside looking up at the chimney pipe and roof and one or two of the set up inside the building of the stove and connected piping?  This may help me.  Send to paul@thechimneyguys.com  Please put them all in a zip file if you could.

In re-reading your initial question I focused on the word SMALL building.  How small is small?  One story?

Another comment... when you open the lid to re-fuel the stove are you just cracking the lid slowly and allowing some air to enter and then lifting the lid off?  It's never a good idea to just open the lid like you would the front door of your house as that tends to create a momentary back draft situation spilling smoke from the stove.

Let me take a look at a few pictures and go from there.  Thanks.

Paul

---------- FOLLOW-UP ----------

QUESTION: Hi I sent you some pictures earlier today and hopefuly they came through for you. When I go to put more wood in it I usually open the front dratf all the way and then put wood in. But usually when I open the draft all the way the fire starts roaring like crazy and the stove vibrates and shakes. And if I leave the draft about halfway open and lift the lid slowly it will poof and send flames and a ball of smoke out at me. Even when the draft is completley closed after a short time it will make a poof and pop the lid up and fill the building full of smoke.

Answer
Trevor,

Please check the email that you sent me the pictures from as I responded to you in length after having seen all the pictures.  Also check your spam/trash mail folder just in case it ended up there by accident.  If you did not get this email let me know and I will re-send my response to you.  Thank you.

Paul