bucksnort wrote:I am having problems with my chimney drafting too hard and pulling the heat out of my stove and up the pipe. !
chimneys dont pull too hard, its some stoves leak too much. vacuum cleaner pulls hard too, put hand over hose, it stops pulling cuz its shut, your hand is valve. thats the draft knobs. should be able to shut any stove right down, if not its leakin air. fix air leaks & you can control it. gotta be airtight. otherwise its a car with gas pedal stuck 1/2 way down. will go faster but wont idle.
Primary and secondary damper settings can vary air feed into an air-tight stove without changing the physical opening size of those dampers, because air is compressible and will speed up or slow down to deal with the pressure drops. All that has to change is the air pressure those dampers see on either, or both sides and the air flow through them changes.
To use your car engine analogy, the engine only runs at half throttle because of the air pressure before and after. If you suck the air out of where your 1/2 throttle car engine is running , or stick a potato up the tail pipe, I guarantee that motor will die. And if you remove restrictions in the exhaust system, it will run faster without throttle change (race motor exhaust vs cat converter + mufflers).
And because air is compressible, and will change speed through a fixed opening with changes in pressure drop, wind gust changes in draft of a chimney will affect an air tight stove too.
Think what would happen if you could hook a large vacuum cleaner to the top of the chimney for your air-tight stove (other then your electric bill would sky rocket
). Or, do the same by just put a fan close in front of the primary damper opening of an air-tight and see what happens. With a fixed setting, the stove can not adjust for differences in air pressure in the room verses in the chimney.
But the baro can.