I don't have a damper but I'm thinking of putting one in. My pipe is about 20 feet of single-wall. Every time I start a new load of wood, it will "take off" and burn out of control until I move the thermostat down below 1.75. Even at 2, the stove will run far too hot and burn through wood at a rapid clip. I see a lot of smoke coming out the stack until I get the firebox under control. Smoke = unburned fuel and means you aren't getting as much heat from your wood as you should be. Others on this board have theorized that the smoke happens during overdraft because the gases fly through the cat too fast to fully burn up. This seems logical, and I've observed that my cat doesn't glow full orange until I get the draft under control.
My BK Princess manual recommends a draft of 0.05" wc *operated on high*. You said you measured 0.07" on the lowest setting.The draft is not a constant value, it depends on the average flue temperature which obviously depends on the rate you are burning fuel in the firebox. So in your case it definitely sounds like an overdraft situation to me. There's a chart at
this link that shows how draft related to chimney height and gas temperature.
My theory for my stovepipe situation is that it overdrafts when the fire is hot, and actually underdrafts when the fire is low (due to my single wall pipe that bleeds off a lot of heat from the flue gases). I installed a manometer to check this. It reads as high as 0.09" when when I'm starting up a new load. When I throttle down the thermostat to get things under control, it settles in around 0.05". If I set the thermostat to #1 and let it go, in the morning it's often down to 0.02". Theory seems to check out. In my case I think I need a shorter double-wall pipe, or a damper (damper seems like the more cost effective option!).
It sounds to me like you have the same problem but to a greater degree since your pipe is double-wall and will thus generate even more draft per foot of rise.
Here's what I've been doing to cope with my non-ideal draft situation and get decent burn times without too much smoke:
1. Thermostat to #3 (highest) for kindling the new fire, and close the bypass as soon as the load is burning well.
2. As soon as the cat is into the "active" zone, I slowly turn the thermostat knob down until the flames go from a fast flicker to a slower licking/rolling. This is usually somewhere around 1.5 depending on the load of wood.
3. Let it run at that setting for 30-60 minutes until the cat temp is maxed out. Check that the draft is about 0.05-0.06"
4. Turn down to the "slow burn" setting I want, typically 1.0-1.25
I was originally following BK's procedure of running on high for the first 30-60 and then turning down by .5's to the desired setting. This worked, but I was wasting a lot of fuel during the first hour or two as the stove was overdrafting and spewing unburned smoke out the chimney. Stovetop never got much over 600F but it would probably overfire if left to run on 3.0 or even 2.0.
If anyone else is having similar draft problems, I'd like to know how you solved it and/or if this procedure works for you too. The main downside to my procedure is that it smokes the glass up pretty bad. All four corners are blacked out.
Does anyone run their princess with a damper in the flue? I remember seeing pics of one being removed from a twin princess to mine and would like some info on how well it worked. I have a 7 inch dia. pipe by 20- 25 feet double wall insulated selkirk thru the middle of the house. Then necked down to 6 inch leading to 2 x 45s spaced out for max flow down into my stove. My problem is i cant run this thing past 1.5 or it trys to overfire and overheat my flue. Like i can only run it with the damper completely shut or it takes off and il have an infirno. Tonight i set the thermo just under '2', and after half hour/ hour my Cat was at 5oclock closing in on 6, and my flu was at 800deg plus and not coming down with a roaring fire. Thats with the blowers not running. And it will stay this way all night long. And when i go down in the AM i find a pile of dormant coals 2 inches high above the door and a lukewarm stovetop. After only 8 hrs or so... Iv been told its drawing too hard but with the thermo shut its pulling .07 at a very low setting. As soon as it opens she takes off on me, making me think its overdrafting thus the damper. Iv already tightened my door and bypass.
Im having no luck with BK service in BC (Canada) and my dealer is being a knob. I would really really appreciate some info and HELP as im ready to pull the plug and put my ol Smoke dragon back into servie. Thanks
It is interesting to hear how everyone works these steel boxes.
Right now it would be helpful to compare some numbers though.
