Barometric Damper on Harman SF-160 ideas

[longboarder2]

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

 

[laynes69]

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?

 

[longboarder2]

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.

 

[katman]

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.

 

[longboarder2]

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.

 

[maple1]

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.