slinger100 wrote:That may be. It would be a matter of the air taking the path of least resistance. The baro being set to .03 I would think that as the grates get covered with more ash it would get easier to pull more air from the secondary air which is unblocked by any ash. When i purchased the stove I did think it was odd that the secondaries were not adjustable. But if the baro is set to a constant draft it should pull the same no matter what the bimetallic primary is doing. So I'm guessing that if the primary is wide open and the grates are clean most of the air comes from there. As the stove reaches it's set temp and the primary closes the manometer doesn't change so the air has to be coming through the secondaries more. Does that help or make it worse? Lol
thanks for the additional info about your experience and point of view, it will be helpful to many looking into this phenom.
i agree with your sense that the ash load plays a considerable part in this and "the path of least resistance" has yet to be fully reconciled in this topic.
i will add just one other observed point about my set up. you state that "as the stove reaches it's set temp. and the primary closes the mano. doesn't change so the air has to be coming thru the secondaries more "
i have 2 MPD's in my set up so i can set the draft and not have by pass bleed or wind impact the stove box quite as much. what i have seen is that if i open the primary i can watch the mano. register a drop in the in stove neg. pressure. as the stove heats up to the new setting and the intake flap begins to close the neg. pressure can be seen to rise back to it's original set point by the time the flap is closed to about 1/8" as before.
since i also HAD a Baro. i can verify that this won't be visible in that case because the baro. will cover it.