Thought this might be an appropriate thread to share some observations I've had over the last couple of days:
Had to take the combustor out a few days ago because it was not functioning, but still need to heat the house and haven't been able to get to the store yet for distilled water and vinegar to clean it out. So I've been running the stove without the combustor, and I think I've found out why people love soapstone stoves. It's not primarily for the soft heat or the way they give off stored heat after the fire dies down. It's because the soapstone firebox, once it is up to room-heating temperature, is hot all the way through and very resistant to changes in temperature. Once that thermometer on top says 500, I can close the vent down to around 1, give or take a little, and I get the same slow, steady burn I get with the combustor in place. The stove doesn't have to be full, and the burn doesn't have to be rapid to maintain this temperature, and when the stovetop is at least 450 I don't see or smell anything coming from the chimney. Even the flue pipe temperatures I'm seeing (325-375 measured 1 inch from the back of the stove) are about the same as what I was getting with the combustor. Besides that, although 3 or 4 days is not enough to draw any broad conclusions, I don't feel as though I am putting wood in there any more often than I did before. Here's the thing that's making my head spin, though: I am sure I'm getting substantially more heat out of this thing. If that's true, then it must be going through at least a little more wood, but that's a trade-off I'd make since I always wish for more heat output when it's really cold.
Since this sounds distinctly like I'm saying Woodstock has wasted all of their time and money designing systems that decrease the performance of their stoves, let me try to clarify the conclusions I'm drawing:
1. Without the combustor, the stove can be operated in a way that generates little in the way of noticeable emissions, though I have no doubt that chemical analysis of the exhaust would reveal much that is not seen or smelled from my front yard. Meeting the EPA's strict standards in a way that is predictable is the bar they have to clear in order to sell stoves.
2. This design, which has the combustor located inside the top of the firebox at the beginning of the smoke exit path, cannot be made to function when the wood is not dry enough. In order to maximize the contribution of the combustor, it is necessary for the wood to burn very slowly and make a lot of smoke. In order for wood in this state to continue burning for hours without losing temperature and eventually going out, it must have very little moisture. Wood can appear very dry but still have a moist interior, which will shut down the burn once the outer (dry) part has burned away. Attempting to stabilize the temperature of such wood by increasing the draft, even if the increase is fairly modest, seems to clog the combustor with ash or creosote. Extremely dry wood, on the other hand, will just sit there and glow until it's all gone, even with almost no air (once the firebox is hot).
3. I don't know if the people at Woodstock could have communicated to me the actual importance of burning very dry wood. They certainly did emphasize it, but I took it as just another principle of woodburning. It is obvious that every bit of moisture that evaporates from the wood in your stove takes away heat that would otherwise go into your house. My experience suggests that with this stove, you actually cannot burn wood that is above a certain threshold of moisture unless you do not use the combustor.
I'm not unhappy with my stove; in fact, since I discovered just how well it works even without its modern technology, I'm more confident than ever in my ability to heat my house with it indefinitely. But now I know that if I want to use the combustor, I need to gain better control over my wood supply.
By the way, even the length of burn I can get is the same. I loaded it last night at around 9:30 or so, and when I came down at 7:30 this morning there was a big pile of glowing embers in there. No kindling necessary.
Adam
PS: Just noticed that I left out what stove I'm using- it's a 2010 Fireview.