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Tarm Owners-Secondary Air Adjustment Mechanism

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by 55Razor, Feb 20, 2008.

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  1. 55Razor

    55Razor Member

    Joined:
    Jan 23, 2008
    Messages:
    34
    Loc:
    St.Clair,Mich.
    When I'm tweaking my secondary air adjustment, there doesn't seem to be an appreciable difference in the "look" of the flame in the refractory tunnel from one end of the adjustment scale to the other. At least not what I would expect to see compared to the manual. Is this what you guys are seeing in yours? Also, can someone shed some light on the internal workings of this mechanism? Is it possible for this to become "dis-engaged", etc? It seems as though it's loose, or poorly attached...??? I've found that if I pull the lever down, and slide to adjust, I have to bring the lever gently up to the set position; if I just release it at that point, the airflow will be significantly less than when feather it into position. I found this out by experimenting with the boiler cooled down and monitorng the airflow in the refrac. slot by feel. This is starting to drive me cuckoo because I think this adjustment should be pretty straight-forward. Any observations are welcome. Thanks.

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  2. Jim Post

    Jim Post Member

    Joined:
    Oct 24, 2007
    Messages:
    134
    Loc:
    Southern WI
    I haven't noticed any up or down travel with my secondary air adjustment knob....It just slides left/right. I do notice a distinct difference in combustion tunnel flame depending on where I have the slider set. The drier the wood the more air required and the further left I keep the knob set. I try to get the combustion tunnel flame to just break over the front edge of the tunnel refractory as outlined in the tarm manual. HTH

    Stay Warm.
  3. kevin85

    kevin85 Member

    Joined:
    Jan 15, 2008
    Messages:
    87
    Loc:
    CT
    55Razor,
    I am with you. My lever has some play and I have never been able to see a difference between the flames. Therefore, I keep mine in the middle. I am anxious to see if anyone has an answer. My boiler is about 10-12 years old.
  4. Eric Johnson

    Eric Johnson Mod Emeritus

    Joined:
    Nov 18, 2005
    Messages:
    5,705
    Loc:
    Central NYS
    I noticed that when setting the secondary air adjustments on my EKO after getting it installed and running, I didn't get immediate gratification. I don't know why that would be. At first I thought I'd be able to fine-tune it by looking at the flame while making the air adjustment. You know, wrap the whole thing up in about 15 minutes. Instead, it seems to need to run for awhile for the change to take effect. This required more monitoring and adjusting over time than I would have liked, but once I got it dialed in, it ran just fine, which is to say, smokeless.
  5. 55Razor

    55Razor Member

    Joined:
    Jan 23, 2008
    Messages:
    34
    Loc:
    St.Clair,Mich.
    Olpotosi, you were right on! Using your "just slide it"method, instead of the "push down, slide to adjust , and raise" offered in the owners manual, was the ticket. The boiler was cooled off enough to test by feeling for airflow in the refrac. slot, so I tried each way. I actually found 2 things that were goofing me up. The first was the adjustment method, for sure, and the second was the scale sticker over the adjustment arm is off by a mile. When using your slide method, (1), I got good control with a marked difference in the air flow rates, and (2), I discovered that the scale applied to the housing above this arm is grossly out of calibration. What I thought before to be about 3/4 open is actually barely 1/4 open. Knowing all this now, I've re-started the boiler, and what a difference in the secondary combustion tunnel! That's what optimum gasification combustion should be! I get excited just watching it run. Thanks! Ray.
  6. jebatty

    jebatty Minister of Fire

    Joined:
    Jan 1, 2008
    Messages:
    4,165
    Loc:
    Northern MN
    I've been operating my Tarm Solo Plus 40 since Sept. Early on I had the same questions. This is my experience.

    1) Tarm has two air adjustments, the first being the draft fan with its own adjustable damper. This mostly controls the total air to the firebox and the gassification-secondary burn tunnel. I say "mostly" because the chimney draft also pulls some air through the draft fan air inlet, and depending on chimney draft, you may have to damper less or more to get the proper amount of total air. I have this damper adjusted to achieve 350-500 flue temp over the course of the burn. The burn might spike a little hotter, but usually is around 400 during most of the burn.

    2) The secondary air adjustment diverts more or less air from the draft fan between the firebox and the gassification-secondary burn tunnel. When the lever is all the way to the right, most air is fed to the firebox and a small amount of air is fed to the gassification-secondary burn tunnel. When the lever is all the way to the left, much less air is fed to the firebox and much more air is fed to the gassification-secondary burn tunnel.

    3) The reason you move the lever to the left for drier wood is because less air is needed in the firebox to maintain a burn producing sufficient wood gas to sustain gasification. Dry wood does not need as much air to burn, and if you feed too much air to dry wood, it burns too fast, produces too much gas, and the gasification is not complete, that is, unburned gas is going up the chimney. Wetter wood needs more primary air in the firebox to maintain a burn producing sufficient wood gas to sustain gasification. Thus the lever is moved to the right.

    4) I agree that the calibration may not bear much relationship to the actual diversion of air. Early on I tinkered with the control to try always to get the optimum burn. After awhile, I too just "set it in the middle and forget it." Occasionally, if I know a particular load of wood is fairly wet or really dry, I move the lever to the right of center for wetter wood and left of center for drier wood.

    5) I give more attention to the flue temp than to the exact position of the air adjustment lever, meaning that I position the lever to achieve the temps mentioned above, which in my case produces just about the maximum heat I can strip off the boiler through my hx with little or no cycling of the boiler. I certainly could burn in the 300-400 flue temp range, but for a variety of reasons I've opted for a little hotter burns.
  7. kevin85

    kevin85 Member

    Joined:
    Jan 15, 2008
    Messages:
    87
    Loc:
    CT
    Great info...I am planning to try everything listed above....now it finally makes sense to me. Thanks Jebatty & Eric.
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