As I said, it's a guess, but I based it on the appearance that the worst warping is near the bypass opening, and not as much above the rear tube. I'll grant you that the bypass area is inherently more prone to warping since it's less reinforced, and we don't have a good pic of the entire firebox to see other potential damage. But his subsequent description of his startup procedure would support the theory that it's not an overfire when running..he has the air closed 90%. Sure, an overfire when cruising could still happen in some cases, even at 10% air. But he said he has the door open when bringing the stove to temp, and doesn't shut it until the pipe meter is to the "wasting fuel" range.
It sounds like he's using a Condar WoodSaver. I'm using the same meter on my SIL's stove, and I'm already cutting air and looking for secondary action when it gets to the bottom of the "best operation" zone. Running the meter that high with the door open, the area around the bypass is getting absolutely hammered by huge flame, like a blast furnace, so I still think it's a pretty good guess I made.
But I agree that if the operator doesn't overdo it, you can safely have the air wide open for a while without damaging the stove. I just don't see the point of doing that for more than a few minutes, to get the load burning..not to bring the stove up to temp. I'd rather run medium flame and give the interior of the stove time to absorb the flame heat, instead of running it wide open and sucking the flame around the baffle and up the flue. I don't think the stove will heat up much faster, if
any faster, running it wide open, so why risk chimney or stove damage by doing so, when it can get away from you quickly?
It probably burns through more wood as well. It's concentrating the heat in fewer areas instead of distributing the heat more evenly as a more moderate fire does. I think it results in more stress on the stove over the long haul.
That's just the way I think about it. You may think differently, and that's fine. You also swap out stoves every five years, so maybe you're less concerned with how long a stove lasts. To each, his own, when it comes to how they want to run their stove.
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So where does the flue meter settle in, a while after you've cut the air to 10%?