Post
by Ky Speedracer » Mon. Nov. 23, 2015 9:30 am
Edit; just a heads up, this is a long read, sorry. But I'm not sure I could have written it differently without leaving out necessary detail...
Here's an update on my secondary air project:
I've been burning on and off for 11 days now. I say on and off because I had to let it go out a couple of days last week due to the outside temps last Tuesday and Wednesday (highs in the 70s and lows in the 50s).
I've been burning anthracite for the most part with a little bit mixed in (that's another thread I need to update...lol).
Based on my experiences so far, the design of my secondary tubes pulling air from the primary air is NOT ideal. It works, but it's very temperamental. There is a very fine line for when and how it works.
With anthracite, I originally couldn't tell when and if it was working. I spent the first couple of days fiddling with the ash door and the load door trying to get the fresh anthracite going. I used a lot of combinations of doors half open, partially open, one closed and one open, secondary tubes open, with doors closed, etc.
Here's the best combination I've found so far; shake-down, leave ash pan door wide open, secondary tubes closed and load door closed. Allow the coal bed to get really hot. Then add a layer of anthracite. Dig a hole through the fresh ant coal to get some flame. Open the secondary air tubes completely up, open the primary control all the way and then shut the load door completely.
At first I get a single "blow torch" looking flame coming up from the hole that goes down through the new coal into the hot coal bed. This was pretty much what I would have expected. Nothing remarkable...but after about 5 minutes I started noticing the ghostly looking blue flames soaring around up in the TOP of the firebox right underneath the baffle plate. They were really hypnotizing...
In another 4 or 5 minutes the ant coal bed ignites and looks pretty typical. BUT, what I hadn't noticed the first couple of times is that I have a completely different fire burning up above the coal bed at the baffle plate...I don't mean a few random flames, it's a a separate fire burning there. I've tried to get pictures of the two different fires burning but the picture doesn't really show a distinguishable difference between the two fires.
If I close the secondary tubes off, the upper fire goes away. With the secondary tubes half open the only difference I see is the fire on top of the coal bed gets taller.
If I leave the tubes completely open for about twenty or thirty minutes the entire firebox turns into one great big gorgeous fire. It's really spectacular. But ironically, it doesn't seem to translate into a lot of additional heat. ??? The stack temp will climb. I've seen it get up to 240 or so. But the stove temp is 250 or 260. If I mess with the secondary controls It basically puts out the upper 2/3rds of the fire box.
Another interesting thing is with this setup, I rarely get anything that looks like the "blow torch" look coming out of the secondary air holes that I've seen pics and videos of that some of you all have posted. I sometimes see that a little in the first part of the burn. Then, at least this is my assumption, as the secondary tubes start to heat up, the semi blow-torchy looking flames start kind of releasing and and head up towards the baffle plate and keep burning for a several seconds. Then shortly after that is when the upper fire begins really burning.
As the fire burns for 45 minutes to and hour it settles down and looks like any other ant fire I've seen.
At that point is when I turn off the secondary air tubes. After the secondary tubes are off, the stack temp goes way down but the stove temp climbs way UP.
In order to get any benefit of the secondary tubes with my setup, I have to leave the primary control wide open. When they're closed, you have to quickly shut the primary air down to 1 to 2 turns open or the stove temp starts to go crazy.
As for bit coal, I can pretty much just leave the secondary tubes completely open and control the entire fire with the primary air control. The bit fire is very stable with these tubes. Again I don't get the blow torch look coming out of the air holes in the secondary tubes... I basically just get a firebox full of flame that isn't crazy hot. After and hour or two when all the volitales have burned off I shut off the air tubes and burn as normal.
Due to my setup, I have to always open and close the ash pan door to make adjustments.
My next goal is to cut a couple off holes in the area between the load door and the ash pan door and turn the tubes out there. That way I can make adjustments easier and can take advantage of the difference in pressure between the inside of the firebox and the outside of the firebox. Not just the difference between below the grates and above the grates...