Barometric Damper on Harman SF-160 ideas

i am running a harman sf-160 as an add-on to my existing oil boiler. things have been going well---not burning much oil. my current issue with the unit is that i feel like i am burning a lot of wood way too fast and it does not last thru the night.

the 160 is a smokedragon--no secondary burn. myself and a few other harman users have been comiserating here on the forum with similar problems---so far i have put metal plates in the firebox to block off the back third of the grates--this and a coffee can full of chestnut coal have helped me maintain some embers through the night. i have the draft knobs on the loading door closed tight and the air door on the bottom open about half way---still flying through the wood (adding logs every 30 to 45 min.. even here in "not so cold NJ" i am looking at going thru between 4 and 5 cords from thanxsgiving to feb.

the usually useless tech dept. at harman suggested installing a barometric damper on the smokepipe about 12-18" above the collar. my only experience/knowledge about barometric dampers is that they exist and i have one on my oil boiler. i have about 5' of smokepipe coming up from the back of the boiler--an elbow, then 4' of pipe which turns into 7" all fuel, leading to a "t", then up 30' to the top of the stack. when i open the ash pan door on the bottom of the unit, i get wicked draft, like a jet!

they suggested that maybe i burn too much wood because i have too much draft and the barometric damper would equalize the draft between the unit and flue.

any opinions or advice would be appreciated. thanks

Yes, a barometric damper will slow your draft, and make things work more efficiently. Your pushing too much heat up the flue. Have you been measuring flue temperatures?

when the fire is going with a few logs on it, the flue temp stays around 300-350. as the fire dies down, the flue temp goes down to around 250 and usually bottoms out around 200. once the water temp goes down below 150. i add some wood and get her rollin again. i do a 500+ burnout at least once every two days and usually once a day. the chimney sweep looked in the unit and at what came out of the flue and said keep up the good work.

i stuck my draft meter in one of the draft knobs on the loading door and was at .07 over the fire. plan on checking in the flue pipe tomorrow---anticipating a lot of draft there.

it does sound like you are sending way too much heat up the chimney. I have a baro on my coal stove but when I used a wood stove I preferred a manual damper.

i stuck my draft meter in the draft knob on the laoding door yesterday---.07 over the fire. haven't done one in the pipe yet, but the .07 ofver the fire seems high---i have no point of reference.

Was that measurement done when there was a fire burning?

I would find out what Harman specs for flue draft for your unit, then check your flue draft (with a fire going) with a guage, then go from there.

A barometric damper might quite likely improve things for you, that is a pretty big chimney - hard to tell without some good measuring & comparing with specs though. When used in a 'smoke dragon', they will likely also cause a creosote buildup around their opening, so will need checking & cleaning fairly often until you get a handle on its habits for that - but the flip side of that is that it is usually fairly easy to clean that area by just pushing the damper flap open & scraping (i.e no pipe disassembly needed).

Just for some comparison, my chimney is also 30 ft. high (the 7" double insulated 'factory stainless' type), all inside (except for the last 3 feet), and with a cap (no screen). I have a draft guage hooked up all the time. The stove pipe section is just screwed together, seams are not sealed. With a fire going, and no wind, and my baro closed, I easily get & maintain about 0.1-0.12" of draft (it is almost zero with a cold boiler). My hottest fires can go 0.12-0.14. If you've got any wind at the top of your chimney, all bets are off without a baro - I can hold my baro closed & see the draft approach 0.3" when it's blowy out. That would suck a ton of heat out of your unit.