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Encore Non-Cat Overfires

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by cmcramer, Feb 19, 2007.

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  1. begreen

    begreen Mooderator Staff Member

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    I read through the VC manual which is excellent in many respects. Yet, although there is a section on draft, it never addresses overdraft. Like there is only poor draft and normal draft, but over draft doesn't exist. This seems to be a glaring omission considering overdraft can lead to overfiring which may void the warranty. It puts the owner in a Catch22 circumstance. As a comparison, the Harman Oakwood manual, for a very similarly designed stove, has a specific paragraph for overdraft conditions. Lopi doesn't have a specific section on draft like VC and Harman, but does include a separate paragraph on overfiring the stove:

    Over-Firing the Stove
    This stove was designed to operate at a high temperature. But due to differences in vent configuration,
    fuel, and draft, this appliance can be operated at an excessive temperature. If the stove top or other area
    starts to glow red
    , you are over-firing the stove. Shut the air control down to low and allow the stove to
    cool before proceeding.

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  2. marc nichols

    marc nichols New Member

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    I have a VC Encore dealer installed in late November 2006. The thread is very interesting. My dealer rep is due out tomorrow for a second inspection. I don't know if my problem is the same, but I am unable to control stove top measured temp with the thermostate lever. In an updraft mode, I can easily get to 550 deg though I usually close the damper close to 500. From then on, the temp slowly decreases to around 390 or slightly lower with on a few quarter sections on hot coals. Changing the position of the thermostat and waiting 30-45 minutes has no discernable effect.

    We are at 3000 ft altitude and have an double wall 8" chimney pipe (required for open door burning with VC screen in place). The chimney is @ 25' in height. The install manual has a graph for 6" chimneys buit nothing for 8" though I would think my local dealer understands needs here. I am burning year old oak that is probably not adequately cured and I would expect the stove to therefore be incapable of maximum efficiency and temperatures. But, I would expect some control.

    Does anyone have insight to this? Recommendations? What stove top temperature (RR corner is where I have been measuring) minimum and maximum would be typical? Does anyone have actual measurement ranges when in the efficiency mode and a reasonable load of wood aboard?

    I just found this site. It's a wonderful resource.

    Thanks

    marcn@wildblue.net
  3. MountainStoveGuy

    MountainStoveGuy New Member

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    25' of 8", once hot, will pull twice as hard as 25' of 6". You problem sounds very similar to the original poster.
    My guess on how your stove operates on 8 inch would be something like this.
    Load the fireplace, start up should be difficult.
    One the draft is established, your intial load of wood burns up within the hour.
    you reload the stove, turn it down, and the second load of wood burns up in a hour or two. There would not be much noticable difference betwee the air wide open and the air shut down.
    If this sounds like you, your loosing lots of efficiency, and your stove is overdrafting. Do you have access to a flow meter to check draft?
  4. cmcramer

    cmcramer Member

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    Hey MountainStoveGuy: You don’t have to send me that free kindling. Plus, I’m telling everyone I see today that you’re the smartest stove guy I know…

    Installed manual damper 20” from flue collar. Left it oriented at ‘noon’, or 0 degrees. Wanted to see if this alone would have any effect. Started a fire.

    Later, with surface temp up to 500 degrees and a good thick bed of hot coals, filled firebox to near capacity – but not quite - with maple. Primary air at lowest, Everburn engaged. After an hour, temp was 625 and part of the rear cast iron was glowing dull red. Glow lasted 20-30 minutes before subsiding. But only a part of the back glowed this time…..and a duller red than before.

    Next re-load, surface at about 475 degrees, with damper now turned to about 30 degrees…or 1:00 on a clock dial. Two hours later, surface temp peaked at about 610, no red glow at all.

    These are preliminary findings, of course, from my first two real hot burn cycles. But it sure looks to me like the damper is reducing my DANG OVERDRAFT! I will continue to watch very carefully as this stove goes through its burn cycles over the next few days and weeks. I’ll be sure to report back on this thread.

    Truth be told, I’d never even heard of ‘overdraft’ before this discussion. When I first bought a house/woodstove in early 80’s, all the discussion was about LACK of draft and how to get MORE. There’s a whole generation of woodstove owners ready to update their 20-30 year old stoves who will need to be educated about these new cat / non-cat stoves and their new requirements. Once I get the damper dialed in so that it prevents glowing red cast iron but does not prevent a good draft for fire starting and good hot burn cycles.....this non-cat stove will be just fine.

    Side notes: (1) Everburn rumble much less noticeable with manual damper set at 30 degrees. (2) Originally, I just estimated my chimney at 30 feet, not knowing this was critical. It’s actually 25-26 feet, if that make a difference.

    Now, about my warantee....and that pesky letter on CFM letterhead that says glowing red cast iron is not a problem.................

    Thank you, again, to everyone who help me through this woodstove issue.
  5. elkimmeg

    elkimmeg Guest

    MSG it appears Marc has the opposite problem he is dampering down too quickly and not establishing that 2 to 3" bed of hot coals first His case is not over drafting but not estamlishing a good bed of coals and charing of the wood he is loosing ground after dampering.

    Marc you have to wait longer its ok to see 650 degrees before dampering down infact your manual warns of going above 750.
    The other key is to establish the bed of coals and rake them to around the everburn shoe center rear
  6. marc nichols

    marc nichols New Member

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    I don't have access to a draft meter but perhaps the installer rep will have one with tomorrow. I'll try calling them first thing and suggest that. I just reloaded and left in updraft for 10 min. I moved the stove top thermometer reading 430 to the center just behind the top loading plate and it quickly went to 500 and a little. So, temps were generally higher than I thought. I closed the dmper and this time left the thermostat on full hi. After 15 min, the temp is up @20 deg but I'm sure things haven't normalized yet.

    I had broached the idea of a damper with my installer several weeks ago. They were not adverse to installation but wanted me to try different loading and burning proceedures first which have been fruitless. After reading posts about VC's clear recommendation not to install a damper, I am concerned with warranty issues. IF this stove is overdrafting, I'm sure the damper would control that. However, I don't know what secondary effects it may have on the EBT combustion process and I can't measure what is going on at that level of the stove.

    Does anyone offer a thermometer that works on double wall pipe so that I can accurately measure exhaust temp?

    This is my third wood stove and second VC. I'm really dissapointed. They should not be so fiddley to operate. If this thing is "normal" , it doesn't belong in a home. I can't say I'm a wiz at these things, but after years of operating them and being a trained firefighter by trade, one would think I have the basic understanding necessary for good judgement here.

    20 minutes now and temp is 550. I'm going to try and throttle it back. Still have only a few pieces on a good bed of coals/

    Again, thank you for any input on this thread.
  7. marc nichols

    marc nichols New Member

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    per master of fire:

    Apreciate your input but; my stove has been burning for @18 hours and has a very well established bed of coals. After reloading, the VC manual says " close the damper and set the air control lever for for the desired heat input" (this is after allowing the stove to regain thermal momentum) "when the surface temperature reaches 450 degrees F, adjust the air control for the amount of heat you desire.

    Please look at my most recent post for more detail. Accordingly, I fired well above VC recommendations for the system to operate properly when moved to the EBT mode.

    As to stirring the coals, what would be the advantage of top loading if one must open the front anyway? And secondly, how would one do that efficiently with several pieces burning on top of the coals. And most importantly, why should this be necessary for the operation of something so intrinsically simple as a wood stove. If this is what a current VC non-cat requires, it is woefully under engineered and not customer friendly.

    I find it disconcerting that two knowledgeable people with the same info can arrive at such divergent conclusions. Wood stoves are not rocket science and should not become so. Unfortunately, I haven't figured this out either and here we are...
  8. begreen

    begreen Mooderator Staff Member

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    I have the Condar 3-19 on my double wall stack.
    http://www.condar.com/meters.html
  9. MountainStoveGuy

    MountainStoveGuy New Member

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    i have a general rule of thumb, any chimney on a main level of a home, 20' and over should have a damper installed. The exceptions to this rule are catalytic stoves, and stoves installed in a low pressure area like a basement. Im pretty familer how a 25' 8 inch chimney works, i have one in my showroom. Noting i put on it works like its inteded without the use of a damper. Its not rocket sicene, but it is scientific, but with the unique nature of every install, its more like art.
    does any of the sypmtoms i put forth in my last post apply to you?
    Mind you that my chimney setup here at the shop is at 5500' altitude, and it still pulls way to hard. 14'-16' is ideal hight at lower altitudes, and lower then 14 and you have to add pipe, any higher then 16' you might need to add a damper, and at 20' there is usually no question that a damper is needed. Once again, these are just generic rules that i use, every installation is different.

    CMC, im delighted that the damper worked for you. Happy burning!
  10. elkimmeg

    elkimmeg Guest

    marc Your manual recomends to monitor center griddle top temps
  11. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    His manual also says:

    "Overfiring may cause a house fire, or can result in permanent damage
    to the stove and to the catalytic combustor."

    What is that all about?
  12. elkimmeg

    elkimmeg Guest

    As to stirring the coals, what would be the advantage of top loading if one must open the front anyway? And secondly, how would one do that efficiently with several pieces burning on top of the coals. And most importantly, why should this be necessary for the operation of something so intrinsically simple as a wood stove. If this is what a current VC non-cat requires, it is woefully under engineered and not customer friendly.

    Marc I have the cat encore which still works simmilar to yours I use a poker or fireplace tool shovel Stiring the coals removes the fly ash accumulation with in the coal bed mix this fly ash actually acts as insulation between the coals . The combintion about piling the coals infron of the everburn shoe, was told to me by the maneger of engineering at VC.
    Goose and I were both told this during the entire everburn demonstration. When we did the plant opperations tour .
    This information ( piling the coals around the everburn shoe has been posted numerous times here.
    Smoke is drawn over the coals and super heated before it reaches the secondary combustion chamber threw air is injected from the holes in the shoe further heating the smoke as it passes into the secondary combustion chamber.
    That is how the technology works.
    Most stoves we are told to rake the pile to the front to enhance the airwash system, the Everburn stoves it is opposite to enhance the everburn secondary burning.
    It takes 1200 degrees for smoke to combust and your hotest part of the srove is the active coal bed
  13. elkimmeg

    elkimmeg Guest

    BB that disclaimer is part of almost every manual printed
  14. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    A statement about ruining the cat in a non-cat stove in almost every manual? I dun tink sooo Lucy.
  15. elkimmeg

    elkimmeg Guest

    You have never seen one manual cover more than one model appliance or tool?
  16. Gooserider

    Gooserider Mod Emeritus

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    I have, but usually the manuals that cover multiple appliances SAY they are for multiple appliances, list the relevant numbers, and so forth... This is presumably one of those proofreading "Thinko's" but the manual in question (I have hardcopy) SAYS on the front cover, Encore NON-Cat stove, model 1450, and nothing else, but also has the warning about damaging the cat that was quoted earlier - it's on the bottom of page 24, near the end of the operation section. What I would suspect is that a lot of the text in the VC manuals is "boilerplate" that doesn't change much, and they missed fixing it here.

    It's not a fatal error but it is sort of an amusing / embarassing one. :red:

    Gooserider
  17. MountainStoveGuy

    MountainStoveGuy New Member

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    i was hoping to see Vermont follow up with this thread... :(
  18. cmcramer

    cmcramer Member

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    Me Too!

    You can be sure I will follow up with VC - in writing - as soon as I give my dealerthe 2-3 weeks he asked for so a VC Rep can contact me. I believe an extended warrantee is called for here.
  19. begreen

    begreen Mooderator Staff Member

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    And perhaps a few replacement parts would be in order.

    Have you done a draft test yet with the manometer? What is the draft reading with the damper wide open? How far can you close the damper and yet still maintain good draft (.1")?
  20. TMonter

    TMonter Minister of Fire

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    The overdraft issue seems to be a glaring oversight on VC's part, but to be fair a lot of other manufacturers also seem to miss it. I know my Quadrafire 3100i manual says nothing about too much draft in the chimney.

    Perhaps this is something we should ask all stove manufacturers to address in their manual.
  21. cmcramer

    cmcramer Member

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    BeGreen -

    Does "manometer" = "air velocity meter" = " "draft guage" ?? I did not buy one, opting instead for manual damper with trial and error. So far, my fire has started fine and my 30 degree damper setting seems to stop my stove at just below glowing red. I'll continue trial and error until I have a good fell for damper settings.

    Based on MountainStoveGuy, Elk, and others....sounds like with 25 straight feet of 8 inch stainless chimney, lack of draft will not be a problem. So I am concentrating on the upper end: how much damper do I engage to eliminate glowing, but not alter other burn characteristics, like start-up.

    In your opinion, what are the chances I have done permanent damage to my cast iron such that its life span will be significantly shortened? Let's say I had 15 overfires...each lasting 30-45 minutes....blood red or a little hotter.

    Other opinions?
  22. tradergordo

    tradergordo Minister of Fire

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    Where the heck were the pro's when I said ON PAGE 2 of this thread:

    "We don’t know if he has an excessive draft problem (he described a 31+ foot (flue+chimney) straight up exhaust - that sounds suspect to me!"

    ?

    :) Oh well, I'm glad the problem is solved now!
  23. begreen

    begreen Mooderator Staff Member

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    Yes. If you can get the dealerto come out with a guage it may strengthen your case. Particularly if the draft readings are very high without the damper.

    The best results are likely to have the stack damper open when starting the stove. Then closed as much as possible without negatively affecting the secondary burn in the stove. Try 45 degree angle for the damper after she gets going good. Do this for a few burns and see how it behaves at that setting.

    That's a topic I'd take up with the dealer. It's a little confusing from the posts, is it one part that is red or several? If the heat shield was glowing red, how red was the part behind it? The rear shield needs to come off and a close inspection on all affected parts should follow. If anything is white or cracked, I'd insist on replacement. But maybe inspection will show all being ok. As mentioned earlier, car exhaust manifolds can get red hot each time they run in some vehicles. Whatever, I would like it in writing that the warranty is intact if there is ever a failure with this part.
  24. marc nichols

    marc nichols New Member

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    Well, my dealer rep showed up this morning; a different fellow from the first time. This guy was quite knowledgeable about the design of this stove and clearly well versed in the dynamics of fire, fuel and air flow.

    To make a long story short, he confirmed that we could not control the burn rate at all with the thermostat lever, all systems were working and there were no gross leaks. His conclusion was that the system was over drafting. You may recall this unit has an 8" x25' pipe. He planned to call his distributor and VC directly for suggestions. Two ideas were discussed: a damper above the stove and a controllable cold air intake for testing purposes. Based on discussions here, I doubt that VC will condone either. However, it is their responsibility to make this system function. Otherwise, they can have it back no expense to me. And...you all will know that the design is in this way challenged and VC stepped up or.... didn't. As I see it, the sticky problem they have is that the stove is certified as it is specified.

    BTW, with my thermometer center mounted just to the rear of the top loading plate, and a moderate load of Oak, the temperature runs 400- 500 deg. depending on how long the load has burned down. Relative to a proper running set up, I don't know where this lies in the normal range of operation for this stove. Does anyone have numbers?
  25. elkimmeg

    elkimmeg Guest

    center griddle top temps should run between 400 and 650 though the manual does indicate 750 but I never try to run it that high

    The manual also indicated the ranges as high low and mediun the prior manuals for older Encores do indicate the range by temp.
    I will look them up and post them here.

    Readings in the 350-500°F (175-260°C) range
    indicate low to medium heat output.
    • 500-600°F (260-315°C) readings indicate me-
    dium heat output.
    • Readings of 600-750°F (315-400°C) indicate
    high heat output. Operating your Encore continuously
    at griddle temperatures of 750°F (385°C)
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