Over draft

Re: Over draft

PostBy: Lightning On: Fri Dec 20, 2013 8:58 am

Yes I compassionately call that the yoyo effect. It was a miserable point in my life where I was forced up and down the basement stairs several times a day to adjust my primary combustion air control. The barometric fixed all of that hahaha.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix

Re: Over draft

PostBy: Sunny Boy On: Fri Dec 20, 2013 10:25 am

dustyashpan wrote:
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 :shock: ). 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.

Paul
Sunny Boy
 
Hand Fed Coal Boiler: Anthracite Industrial, domestic hot water heater
Baseburners & Antiques: Glenwood range 208, # 6 base heater, 2 Modern Oak 118.
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Re: Over draft

PostBy: dustyashpan On: Sat Dec 21, 2013 10:01 pm

ask any stove co. tech about overfire condition. first thing they say "its getting air from somewhere, look for leaks". every time I saw overfire condition was leaky stove. never overdraft from chimney. draft easily controlled with airtight design, main draft knob. baro & wind affect it some, not contantly daily chronic overfire. high baro makes car run better too. only slightly better. it dont add 100 hp every day. maybe 10 hp one day. chronic overfire condition is the setup, usually air leak somewhere.
dustyashpan
 
Hand Fed Coal Stove: Atlanta Homesteader, Harman
Baseburners & Antiques: Radiant Medal Dockash No.150 baseheater
Coal Size/Type: nut stove pea

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Re: Over draft

PostBy: dustyashpan On: Sat Dec 21, 2013 10:14 pm

Lightning wrote:Yes I compassionately call that the yoyo effect. It was a miserable point in my life where I was forced up and down the basement stairs several times a day to adjust my primary combustion air control. The barometric fixed all of that hahaha.



confused now-you said opening secondary above fire vents increased the poor draft in your stove & worked every time. now baro is miracle cure & dont even have to go downstairs near stove. which is it now ? would be interesting to see what your stove pulls on manometer with all drafts closed, mpd open, and baro closed. start there base reading. if its not zero manometer, guess what it leaks. mines been running no baro, no mpd, factory fixed slit above fire bleeds nonadjustable, no more than 3/4 turn open draft, for 20 winters. no downstairs, sits next to me in living room
dustyashpan
 
Hand Fed Coal Stove: Atlanta Homesteader, Harman
Baseburners & Antiques: Radiant Medal Dockash No.150 baseheater
Coal Size/Type: nut stove pea

Re: Over draft

PostBy: Lightning On: Sun Dec 22, 2013 10:49 am

I'm sorry but I'm not interested in pursuing a debate with someone who thinks a manometer measures volume instead of pressure. I think you need to rethink some of your basic physics principles. I don't have any further comment.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix

Re: Over draft

PostBy: bucksnort On: Sat Dec 28, 2013 9:47 am

Well I stalled a stainless steel chimney cap and it hasn't appeared to have much affect on the draft, as most said it wouldn't. However its probably a good thing to have anyway. Still waiting on the monometer I ordered to come in to get some draft readings...
bucksnort
 
Hand Fed Coal Stove: DS Machine Basement #4
Coal Size/Type: Hard Nut Coal
Stove/Furnace Make: DS Machine
Stove/Furnace Model: Basement #4

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