Barometric dampers and flue gas temps

[FixedGearFlyer]

We have a baro damper about 18 inches up-flue of our forced air wood furnace. In this morning's heavy winds, I'm watching the counter-weighted gate swing all the way open during some of the really heavy gusts (which are in the 60-some mph range! Wow!) and having conflicted feelings.

First, I'm glad that wind-induced draft isn't sucking the air through my firebox and over-firing my furnace in the basement while I sit in my first floor office. But, second, I'm wonder just how much creosote I get as a result of mixing room temp air with my flue gases before sending them up the chimney. We have a 7x7 square, clay-lined chimney that's about 34 feet tall. 10 of those feet are outside the insulated thermal envelope of the house. Between the baro and that long trip through the masonry, I'm sure the gas temps at the cap are below the creosote condensation point.

What say you, oh experienced and wise wood burners? Is a baro draft good or bad? Would we be better off with a cast draft key insert? I like the fact that the baro automatically does the adjusting, but am not such a fan of the drop in gas temps and accompanying creosote . . .

 

[vvvv]

temp of the fluegas would drop from dillution but the speed of the gas would increase? boiler room has woodburnewrs with baros installed. does your baro collect creosote?

 

[FixedGearFlyer]

The baro itself has picked up some very light, flaky creosote on the counter weight and back of the door, but nothing that a quick brushing won't remove. We've only done a dozen burns with it installed, so I'm more worried about the effects in the top 1/3 of our chimney and don't have enough of a track record with it to know if it's going to cause a lot of creosote up there.

 

[vvvv]

i'd leave the baro alone= if theres a power outage & baro isnt there to control the draft, furnace might overheat wihtout roomblower working. ideal chimifire siutation involves smoldering wood on a regular basis to coat the chimni & then setting off a blazing fire to ignite the creo. keep a wet roll or 2 of papertowels in a sealed plastic bag handy which is placed in stove during chimni fire to release steam up the flue & the baro should be blocked with al foil at the same time

 

[laynes69]

We burned with basically the exact same furnace for over 25 years here. Lots of creosote in the flue. When I bought the house from my parents 6 years ago I added a baro on our furnace. It did help with the burns, but not with the creosote. I removed the furnace the year before last and installed a EPA certified furnace. I still did get some creosote but not alot. I now have an insulated stainless steel liner in the chimney and of course a baro. I have put a face cord of cottonwood through our furnace since the end of september just burning nights and when needed. I worried about the baro cooling things too much also. But I found nothing in the chimney or at the baro in the flue. I guess where the creosote was coming from was an inproper chimney. With your 7x7 clay tile and the height, you will get cooling to the condensing point like we did. On top of that with a furnace that doesn't have secondary burn built into it you will get creosote. Keep the draft set higher with a max of .06" and that will help the baro to not open so much. That will allow for higher flue temps needed to help keep the chimney cleaner. I would leave it and clean things when needed. Down the road you may want to look into a liner thats insulated that will help keep those gasses hotter. You may not need one so play it by ear this year and keep an eye on things. You will get creosote, but burning hotter fires will help alot.