OAK and Power Outage

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by jimf, Nov 10, 2013.

  1. jimf

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    I have a Harman XXV with an OAK that extends horizontally from the house for about 18" (picture attached). We have been experiencing a good number of power outages lately. My question...with this setup, if I were to lose power with the stove running, would I expect to get a good deal of smoke in the house, or just a faint smell as the fire winds down? Thanks!
     

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  2. mithesaint

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    Your house has the same siding as mine. Nice color.

    OAK? Isn't that your exhaust? OAK stands for Outside Air Intake. Maybe I'm wrong, but that looks like an exhaust and not an OAK. If so, you could potentially get some smoke if the power dies while the stove is running. 3 feet of vertical would help with your draft and help prevent smoke in the house.
     
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  3. Bioburner

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    Hopefully only a small amount of smoke. The stove is supposed to be a close system. Think of getting a UPS and save on the stoves electronics.
     
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  4. moey

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    try it only one way to know.. If it starts smoking plug it back in so it doesnt massively stink up your house.
     
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  5. ChandlerR

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    Good morning Jim! It looks like a picture of your exhaust, not the air intake. As Bioburner said, the OAK is the inlet for the combustion air.
    Picture air used for combustion (not the air coming out of the stove) as a loop. Air comes in, aids combustion, then leaves through the exhaust. If you do not have an OAK, the air is drawn from the room that the stove is in. If you have an OAK, it is now a closed loop because all the air used for combustion is pulled from outside then exhausted through the exhaust pipe. In theory, no smoke would enter the house during a power failure. Because your exhaust points straight out, and you don't appear to have an OAK, some smoke may enter the house during a power failure if it's windy out. The wind could blow the smoke back into the stove through the pipe and it would exit from the combustion blower. With an OAK, the smoke would come out the OAK inlet.
    A UPS would allow you to shut the stove down properly or keep it running until a generator could be started. Hope this helps!
     
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  6. P38X2

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    That is the Harman OAK thimble. The OAK inlet is under the "roof" thingy directly above the pipe.
     
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  7. ChandlerR

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    Oh, ok..so this is what it looks like on the outside. I've seen pictures of it from the inside! Shows how much I know! Jim, as Roseanne Roseannadanna used to say....Never Mind!
     
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  8. P38X2

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    It's a pretty nice unit. Real clean.
     
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  9. jimf

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    Sorry all, it is the exhaust that's illustrated. Not nearly enough coffee this morning! :) It's the one-piece Harman thimble...the vents above the exhaust pipe are the air intakes.
     
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  10. ChandlerR

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    Sorry that my lack of real world experience didn't see that Jim. You should be good, I would think :)
     
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  11. briansol

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    if both your intake and exhaust are outside, the odds of getting smoke inside are virtually nill. its a loop to the outside through a fire.
     
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  12. mithesaint

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    My bad. Wasn't familiar with the Harman set up.
     
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  13. DBCOOPER

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    With my direct vent CB1200i I would get smoke back up thru the pellet chute and out of the hopper when the power failed. Pellets smouldering without combustion air makes for a nasty smelling smoke.
     
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  14. Sniz

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    speaking of a USB, any recommendations? all the one's I have found give ratings for winding a computer down. In order to wind the stove down it will need at least an hour or so and that's assuming you are there to shut it off.

    What are the thoughts on that?
     
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  15. SwineFlue

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    I believe Harmans can use a UPS to automatically shut down (running the combustion blower only) when the power goes out.
     
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  16. briansol

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    $$$$$$$$$$$$$$$$$$$$


    I have basically the biggest one available in non-rack form, and it goes about 50 min on medium.
    1500lcd syberpower pure sine.
     
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  17. mchasal

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    I wonder if one could wire a NO relay into the auger motor supply that would be powered by the mains, not through the UPS. Then, when power is lost, pellets stop feeding. You'd be essentially simulating running out of pellets and the stove should handle that gracefully.
     
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  18. briansol

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    I talked with an electronic buddy of mine... the idea was to use the usb output form the ups to trigger a thermostat call for temp reached, shut down more or less which would shut it down on my stove (my stove does hi/low for an hour, still no call then off/call, back on) but that wouldn't happen for an hour, and the ups would be long depleted. And then the warranty issue came up and I decided not to bother for a few years in case...

    Without knowing what kind of circuitry the aguer motor returns back to the control board, interrupting that may fry a board. And that's an expensive mistake.
     
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  19. #19 mchasal, Nov 12, 2013
    Last edited: Nov 12, 2013
    mchasal

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    Yeah, I thought about the thermostat approach, but my stove only has hi/lo or on/off, so it would have to be in on/off mode for it to work. The hybrid mode like you describe would work, but the delay is an issue.

    Good point, not sure how other stoves work, but the motor on mine doesn't have any feedback, just the AC lines running to it. In that case it wouldn't be any different than a motor failing open or a wire failing. But I can see how a more complex setup could cause issues. So, as an alternative, how about splicing the relay into the hopper safety switch circuit? That should have the same result and I don't think any of those are more complicated than a pushbutton switch? I suppose it's even possible to do a form of time delay relay so the shutdown wouldn't happen until the power's been out a few minutes.

    As for warranty issues, you could do the splicing with the factory style connections and have it fully pluggable.
     
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  20. DBCOOPER

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    What I did was get a short cycle relay. In the event of a power failure the thermostat circuit opens and the ups powers the shut down. It also starts a time delay which is variable and I have set for 10 minutes which is the maximum it can be set for. If there are no more power gliches in the 10 minutes then it will go back to normal operation.
     
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