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More smoke with Catalytic element engaged

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Randal, Jan 29, 2006.

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  1. Randal

    Randal New Member

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    We have recently installed a Vermont Castings Defiant stove and are having an issue where there seems to be significantly more smoke with the damper closed and the catalyst engaged, than with the damper open and the catalyst off. Any suggestions as to what could cause this?

    Thanks in advance.

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  2. got wood?

    got wood? New Member

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    how hot are you running the stove before you engage the cat? They need a while to heat up before they offer efficiency.

    are you using fully seasoned wood (grey color, sound like drumsticks when whacked together, cracks on the ends)?
  3. Randal

    Randal New Member

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    I let it get to 450-500 (gridle temp) and the wood is fairly well seasoned.

    I am right in thinking that even if the wood was not well seasoned, there should still be less smoke with the catalyst engaged?

    Thanks again...
  4. Todd

    Todd Minister of Fire

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    Is it a used stove? Catalyst might be old.
  5. got wood?

    got wood? New Member

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    that should be hot enough...and I do believe you are correct that if the cat is hot enough, there should be less smoke (I've got a non-cat so I can't say with authority). How about the gaskets? Are they in decent shape?
  6. Sandor

    Sandor Minister of Fire

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    Have you cleaned the cat lately? (if the stove is used)

    I'm sure when your engaging the cat, the fire is being choked and the fire starts smoking.

    Also, if the stove is new, try leaving the damper more open to see if u get a clean burn..... play around with it some until you get if figured out. Just keep an eye on the thermometer.
  7. MountainStoveGuy

    MountainStoveGuy Minister of Fire

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    If the stove is new, it only takes one low temp engage to plug it. I would make shure the cat is clean. Also, you might install a flue temp thermometer. A few other points to look at, is how well is the stove drafting? how many elbows do you have? is the chimney on the outside of the building? Is the chimney tall enough? You need fairly good draw to make that cat work properly as well.
    RYan
  8. DavidV

    DavidV New Member

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    I would suspect the wood (wet) or the temp not being high enough. What kind of CAT is it. Condor requires 600 degrees to fire off if I am correct. Surface temp doesn't jive exactly with the temp of the cat and 450-500 surface(front surface) would probably give you close to what you need. If you have green or wet wood you probly have a clogged cat and like MountainStoveGUy said, only takes one time to clog it. I feel your pain. my first year with my cat stove was a pain. big learning curve. Love it now though.
  9. wvstriper

    wvstriper Member

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    Where do you have your air control lever set? Often (depending on draft), if you engage the cat and then close down the air damper the temp will drop, rendering the cat ineffective. I suspect, as others have posted, that your fuel may be a little on the damp side. Try keeping the air damper open longer. Don't trust the thermostat to always regulate the fire for you though. Keep an eye one it for a few burns until you get a feel for the wood you are burning. Remember, if you use wood from multiple sources, then it will probably be dryer/wetter from load to load.
  10. Mo Heat

    Mo Heat Mod Emeritus

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    Even with 450 - 500 griddle temp, the cat (and perhaps the sides and bottom of the stove) may not have come up to light-off temp yet. It usually takes around an hour, plus or minus a half hour, depending on... lots of things.

    While you are learning, let it burn 1.5 hours before engaging the cat. If I suspected my cat was a bit dirty, I'd try to burn it clean before disassembling things (PITB). I might let a first medium sized load of wood go to coals, add more wood to build a second medium sized load, get that load going good (don't rush it :), then engage the cat. Probably around 1.5 hours before cat light-off.

    Once the cat is engaged, temps needs to climb from 500*F to 1000*F before the cat is actually at operating temperature (~1000*F - 1700*F) and consuming smoke efficiently. This can take another few minutes or more depending on... many things. Don't rush things your first season of learning. You will love that cat stove your second year after you learn to light it off consistently. Better to engage it later and keep the cat cleaner.

    I prefer a digital probe cat chamber thermometer. Takes all the guess work away. Costs a hundred bucks, though. With a free standing stove, you might be able to use one of those analog dial jobs (~$20+-$5) just stuck in the back if you can see behind the stove. I think it's worth it. Less anxiety. Better performance. Critical temp feedback. Improved overall firing at all phases of a load's burn. Easy to keep cat at optimal operating temps. More heat. No danger of thermal shock (POP!). Less wood consumed. On and on. I wouldn't operate a cat stove without one!

    Personally, I start my fires cleanly (little smoke on start-up), using a modified top down method (Mo's canyon between splits technique :). It takes longer to get things going, but there's almost never much smoke, even before the cat lights off. That way, I'm in no hurry, thermal expansion rate is moderated for new fires (less stress on stove), cat has plenty of time to heat up, and there's little pollution (smoke) before cat light-off.

    If you didn't cut and season your own wood, or test it with a moisture meter, you are burning blind and may have damp wood. Happens to me more than I care to think about. Wood Men stories abound.

    Good luck.
  11. Eric Johnson

    Eric Johnson Mod Emeritus

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    That's pretty good advice, Mo. Well said.

    I guess I can't do a top-down start on my boiler because it goes 24/7 for the entire heating season. So I always have a bed of coals sitting on the grates (blower moves air up through the grates). And that means that my stack temps are usually 500 or above (as measured by an internal stack thermo). Does that sound like a good environment for a cat to operate? I disengage the cat when loading the boiler and will leave it open if the stack temp is around 500. When I go back out to engage it, say an hour later, the stack is always up over 1,000--usually closer to 1,500.
  12. Todd

    Todd Minister of Fire

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    Hey Mo,
    What about an internal stack thermometer? Would that be close enough to the cat temp? My new Fireview has a hole in the exhaust collar for a cat prob thermometer, but I would have to look around the back of the stove to get a reading. I was figuring if I put a probe thermometer into the front of the stove pipe about 6-12" above the exhaust collar, it would read about the same temp?
  13. Eric Johnson

    Eric Johnson Mod Emeritus

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    I was wondering about that too, Todd. Currently my probe thermo is below the cat element. I guess I thought I should know what the temp was just below the cat to know when to engage it. However, the reading above the cat would tell me not only when it's hot enough to engage, but what the resultant stack temp is. Just too lazy to go out there and drill a new hole, I guess. Do you think the higher temps would damage the thermometer?
  14. Todd

    Todd Minister of Fire

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    The probe thermo I was looking at reads up to 1700 deg! I heard a cat starts to get damaged at temps above 1600, so I think the thermometer would be ok?

    It seems to me that the temp may be a little lower in the stove pipe than right at the cat, but with a little trial and error you should be able to figure what temp works best for you?
  15. Mo Heat

    Mo Heat Mod Emeritus

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    Ideal is said to be a probe on both the intake side of the cat, and the exhaust side, too. But you'd need a budget like the space program for that. Two digital probe setups would be near $200! I guess you could just have two $25 probes and alternately hook them to one digital indicator, but that seems like a hassle switching them back and forth, and the plug seems fragile. The analog ones would be much cheaper, but you've got to poke your head around the back in most cases, to read them.

    Next best is said to be one cat probe therm on the exhaust side (within a inch or two of the cat element). This will tell you more what is going on with the cat. Has it lit off? What is the exhaust temp (and therefore close to the cat element temp). And perhaps most importantly, what is the cat temp after I have just loaded fresh, relatively cool wood? I never engage my cat on new loads unless it is below 1,000*F. In practice, I usually wait until the cat exhaust temp drops to 800 - 900*F before I load more wood. This way, there is little danger of thermal shocking the cat. The most likely way to damage it according to Condar.

    Intake side temps only help with initial light off temps (as far as I can see).

    I've recorded exhaust side cat temps as high as 2,100*F. 1,800*F for short periods is common, so you may fry a normal stack thermometer, depending on its scale. Condar cats are approved for continuous operation at 1,700*F with transient spikes at higher temps acceptable (just not too long or with too rapid temp changes).

    Mo Heat
  16. Eric Johnson

    Eric Johnson Mod Emeritus

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    I've got a Condor analog. But since my element is suspended in a regular section of black stovepipe, it disengages when I rotate it 90 degrees, just like a conventional cast-iron damper. As such, I can't get it closer than 4 inches to the surface of either side. But I can view it from the front.
  17. webbie

    webbie Seasoned Moderator Staff Member

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    Make sure it is smoke and not steam (white)....

    Assuming stove is new:
    Wood?
    More coals in stove before you engage
    More draft needed in chimney

    Assuming stove is old:
    Cat is bad or covered with ash
    chimney and wood also.

    Keep in mind that these stoves are tested by EPA as EASY to operate, in fact almost impossible to make them not work correctly, so it should not take a lot of trouble to make a new one work correctly.

    This model does need decent draft!
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