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Enviro Mini – House full of smoke

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by LI-Mini-Owner, Jan 30, 2008.

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  1. LI-Mini-Owner

    LI-Mini-Owner Member

    Joined:
    Nov 22, 2007
    Messages:
    143
    Loc:
    Long Island, NY
    I awoke last night to sound of our smoke detector and a living room filled with smoke. No blowers on, nor any lights at all on the control panel, but a smoking fire in the burn pot, leaking out door seal. I was not thinking straight cause I just woke up, and just concentrated on clearing the house of smoke while the fire died down. I was convinced that something had gone haywire with the control system.

    In the morning I pieced together what happened, and was able to duplicate the conditions again to confirm my theory. As a result, I can’t believe the control system was designed this way. I’d like the opinion of any folks on the forum as to how their brand of stove operates in this scenario. (First let me say that my stove is vented straight out the side of the house, then up 6 feet, terminating with 2 45-degree elbows to pitch slightly downward. This normally gives plenty of natural draft to clear fire box in case of a power failure, but not in this case).

    I have the stove connected to an auto-set-back thermostat, set to turn down to 65 degrees at 10:30 PM, and back up to 70 degrees in the morning.

    I run the stove in two modes, depending on how cold it is out, The first mode is for cold days, where the stove cycles from highest output to lowest, depending on if the thermostat is calling for heat. The second mode, which I was running in last night shuts the stove completely down when the thermostat is not calling for heat, and goes through an ignition cycle when its time for heat. This mode is for warmer weather when it would be too hot in the house even with the stove on its low setting.

    Well last night, shortly before 10:30 the stove must have started an ignition cycle. The fire started, but before any heat could build up, the thermostat kicked into 65 degree mode. The combustion blower shut down, and without any heat built up there was no natural draft, and the smoke came flowing out.

    The root cause of the problem IMO is that the presence of a “fire” is detected by a heat sensor (not a visual flame sensor like is typical on oil burners). If the heat sensor does not think there is a fire, when you turn the thermostat down it shuts off the combustion blower. My real gripe is that they could have designed the controls to err on the side of caution, and keep the blower running for say 10 minutes IF the thermostat opens AND the ignition cycle is still in-progress (heat sensor trip point not yet reached).

    I can’t believe this is my 3rd season and this is the first time by chance that the set-back kicked in shortly after the fire started.

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  2. hearthtools

    hearthtools Moderator Emeritus

    Joined:
    Jan 6, 2006
    Messages:
    2,019
    Loc:
    Oakhurst, California, USA, Earth
    Im not sure if the thermostat Shut down cycle was the problem.

    The board is timed to go into a 30 minute KEEP FIRE MODE AND WAIT (low feed rate) before it will going into shut down.
    this is to prevent Repeeted cycles in warm homes. The stove will go to a Low feed rate and wait to see if the thermostat calls for heat again
    if it does not call for heat in 30 minutes then the stove will shut off.

    I COULD BE WRONG AND YOU MAY HAVE A BAD CONTROL BOARD.

    My explanation of what MAY have happened below. Im not say this is what happened but this is what I have seen happen before.

    What have seen in the MINI and most other enviro stoves in ON and OFF thermostat is that IF the burn pot has a build up of clinkers the burn pot
    the stove will take a long time to start or to get into a full Burning mode due to the fact that not enough air is flowing through the burn pot.

    Your stove might have ran into the 10 minute start up mode but never go hot enough for the PROOF of fire limit switch to kick in and keep the Combustion blower going.

    When the 10 minutes start up cycle was done the control board shut off power directly to the blower and was relying on the Low limit switch to take over.
    But the low limit switch never closed to keep the blower running because the fire realy never got going good enough.

    You may of had a Load of Pellets in the burn pot and just enough embers to smolder because of the Build up of crap in the burn pot.

    I could see this happening more in a MINI because the burn pot is so damned small.

    Just my 2 Cents and why I dont like my enviro customers to run the stove in ON and OFF thermostat mode.
    If you dont keep an EYE on the build up of clinkers in the burn pot the stove will fault out More often.

    HI LOW MODE is a much more reliable mode unless you have a stove like the OMEGA that has a Self cleaning burn pot to churn up the Clinkers int he burn pot.
  3. LI-Mini-Owner

    LI-Mini-Owner Member

    Joined:
    Nov 22, 2007
    Messages:
    143
    Loc:
    Long Island, NY
    Rod - Thanks for the reply. As far as clinkers go, I had just cleaned and scraped the pot liner that evening. Here is the test I ran to duplicate the problem. In the on/off mode, I turned the thermostat up, and waited for the fire to catch. 30 seconds after it started I turned the thermostat down. As soon as I did the combustion blower stopped.

    I wonnder if my controller board has an older software revision then what's out there now. (it does not have a hi/low vs on/off switch like I;ve seen on pictures of new Minis - instead it has jumper on the board).
  4. hearthtools

    hearthtools Moderator Emeritus

    Joined:
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    Loc:
    Oakhurst, California, USA, Earth
    Call your dealer and have them call Al at Enviro and ask about that senerio
    All email them just what you said on the last post.

    Like I said you could have a bad board.
  5. LI-Mini-Owner

    LI-Mini-Owner Member

    Joined:
    Nov 22, 2007
    Messages:
    143
    Loc:
    Long Island, NY
    Well I contacted my dealer who spoke to Al at the Enviro factory. He confirmed that my stove is functioning "as designed". It can take several minutes after the fire catches until the heat sensor detects that a flame is present. If during that time you turn down the thermostat, the combustion blower will shut off. Smoke it then free to leak out of the stove (since there is not enought latent heat for a natural draft).

    They have changed the design on new stoves so that the exaust blower will continue to run in this condition, but it will cost me like $ 400 for a new board, bracket, and cover. Kind of sucks that safety improvement is not offered for free, I would think that Enviro would not want this liability hanging out there.

    BTW - My dealer said that all other brands of stoves hes has except one behave the same as mine in this condition.
  6. BIGISLANDHIKERS

    BIGISLANDHIKERS Feeling the Heat

    Joined:
    Sep 12, 2007
    Messages:
    316
    I had a similar situation with my Mt Vernon AE. Last night it almost ran out of fuel. The flame was almost out. I added fuel and went back to bed. About an hour later I awoke to the house full of smoke. Smoke was pouring out the ashpan door and no fans were running. I believe what happened is that pellets made it to the pot but the stove got a mininmum firepot temp error, dumped the smoldering pellets inot the ashpan where they continued to burn. The ashpan door was closed but there was just too much smoke.

    BIH
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