Anyone with an oakwood & top flue discharge..

[SIERRADMAX]

Have trouble maintaining stack temps with a loaded stove? I haven't been able to fully load the stove before going to bed without a constant threat of excess temps in the stove pipe. It seems draft pulls flames up into the pipe and I've seen temps upwards of 800 degrees.

 

[branchburner]

I assume you are talking bypass closed. I have rear discharge, and with secondary combustion in that back chamber there is a lot of heat -- but sounds like you are over-drafting. Is the stack a straight run up, and how high? What are you loading the stove with, and what is burn time for a full load?

Also, if you don't already, I would suggest monitoring the temps on the back of the stove to see what your burn chamber is running when the flue is running 800 w/ bypass closed.

 

[SIERRADMAX]

Here's a picture of my hearth. I have a probe thermometer 18" above the stove just before the 45 degree bend.
(broken image removed)

I've been playing around with the bypass being open and closed. With the bypass closed and a good bed of coals, I get a good amount of buildup on the glass so for the most part, I've been running the stove with bypass open, primary air damper closed (all the way to the left) and a flue damper partially closed. All 2 year seasoned oak & maple. VERY low moisture content.

I have a feeling that the secondary chamber needs to be cleaned out but is the oakwood only designed for long, fully loaded burns in secondary combustion?

 

[branchburner]

is the oakwood only designed for long, fully loaded burns in secondary combustion?

You got it.

With bypass open, flue temps DO get very high. When starting/reloading I will often burn as you do, with bypass open and primary between 0-50% open, but only for a short time (or for a really small fire meant to take the edge off a cool but not cold day). Secondary will not do well without a good deep bed of coals an/or a few minutes of the new load firing up.

A few minutes before shutting the bypass to get secondary combustion, once the new load is cranking, I will open the primary to 75-100%. The flue temp will quickly rise towards that 800F mark, and when it does, I shut the bypass, leaving primary open for a few minutes. As the flue temp drops, I shut the air back in steps: 75 to 50 to 25% over 5-10 minutes.

I am only certain the secondary is burning well by observing a temp rise on the back burn chamber and drop in flue temps. If the secondary is not kicking in, flue temps will stay high and the the rear of the stove will stay low.

My glass is dirtiest when burning with bypass open and air closed. If you are getting dirty glass with bypass closed, it probably means the secondary is not engaging or not staying engaged.

How old is the stove?