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Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by BurningIsLove, Nov 16, 2007.
Regarding air flow to the shoe...has anyone tried cutting some splits short and running a load N/S ?
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Had a decent weekend burning my stove and I learned a couple things that I thought might be helpful to others.
I had excellent success getting an everburn fire by starting it using a lot of pallet wood. I used the thin strips to get a small bed of coals then added the thicker inside pieces of the pallet to create sort of a "pallet wood goulash". Once that was going well, I made sure there were some half burnt pieces in front of the reburner and loaded up with small splits and opened the primary air. After the splits were charred I closed it all up and had a really loud everburn rumble that kept going for at least an hour or more and I got a 6+ hour burn from that load.
NOTE: While preparing my "pallet wood goulash" I had to keep the primary air closed so things would not get too hot. When I added splits I opened it up fully which produced a really hot bed of coals which the reburner liked based on the noise it was making
Another thing I learned this weekend is that if you dont have coals within 4 inches of the reburner your not gonna keep it going. I had an instance this weekend where wood in front of the reburner was consumed but the logs above failed to drop down...when they did the everburn rumble came back by itself. I made it a point to stack wood in front of the reburner in a manner that allows it to drop straight down without getting hung up. I noticed several times this weekend that when the pile would shift I would get a fresh loud rumble and a the temps would go up for a few minutes.
Another thing that seemed to help me since my wood is not very dry was to split it into smaller pieces (2-5 inch). With each new load I would add a biobrick or a couple thick pieces of pallet wood to provide some fuel to help dry things out.
All of this everburn stuff is making me hungry. I'm glad I don't have my DW anymore because I never would have been able to find the time to go to culinary school to learn how to operate it properly...
I just went down to the basement and looked up my chimney with a mirror and it's still very clean. I have gone through a good 1 1/2 cords of wood so far with my Oakwood and I think it's burning cleaner than I thought after looking at the chimney.
That's quite good, BJ.
With older stoves, I have seen folks really muck up their chimneys with that amount of wood!
We can't forget that there are many levels of burning "clean".....or I should say, many levels of burning dirty!
The old "creosote hogs", IHMO, were more than just bad stoves - in fact, some of them were not too bad. It was the combination of chimney, operator, wood AND stove (lack of education about the subject) which caused the first rash of chimney fires.
So, if nothing else, this and other similar threads are helping folks to pay attention to how their stoves are burning.
Forgive my noob perspective but I suppose it's possible that I don't know if the "Everburn" (hereafter referred to as downdraft as per a previous post) is actually working on my VC Encore NC but I can tell you what it does and why I believe it is working. I too get the stove, as measured via stove top thermo only, up to about 450 before engaging the damper. I always do so with the primary air wide open and only after I have vigorous flames (if I didn't I wouldn't get to 450 to begin with, at least on the initial loading). I get the usual wooshing sound that eventually dies down. Just because I don't hear it after that however, doesn't mean it isn't working. In fact I suspect it still is because the behavior of the fire is quite different than when the bypass is not engaged. When it isn't engaged, there is a much more bright orange (I'm assuming due to the oxygen rich nature of the fire) and much less of a tendency to produce coals as quickly. I suspect that the wooshing sound has to do with the changing flow rate of the smoke as it burns and the subsequent change in temperature/flow characteristics, but that's just conjecture on my part.
I agree with Elk's post on about the second page of this thread where he states that he believes the real problem may be that many people simply aren't using their stove properly (no offense intended). I also agree that it may be very dependent upon the variables of each installation but I can tell you that mine is far from ideal. I have a 45 degree shot straight out of my stove to the wall to a 6" Excel chimney which runs straight up the outside of our house (about 21' high) and only about 10 feet or so away from a nearby tree. That having been said, I'm sure that some of these problems might be QA related on the part of VC. All I can attest to is that I personally don't have this issue.
What I'm actually interested in are the burn times. When I purchased this stove, only about 2 weeks ago, I was sure that just like automotive gas mileage among other areas, the manufacturers overrated heating areas, heat output in BTUs, etc. What I wasn't really prepared for however, was what I consider to be a severe overrating in burn time.
I'm burning Norway Maple, seasoned 1 year. Although I don't have a moisture meter yet, by the condition of the wood, I believe it to be sufficiently dry (yes this isn't a valid scientific method but I'm at least in the ballpark). I can't get anything close to the 9-10 hour burn times VC states is possible.
My technique is to get the stove up to temp, engage the damper, and after a few minutes, 10 at most, turn the primary air all the way down. It turns into a bed of coals very nicely, and puts out an appreciable amount of heat, burning steadily for about 4 hours. At the end of that time, I've got only about a half inch or so of coals left. Plenty to stoke up a new fire easily and rapidly (certainly not anywhere near enough to achieve the secondary downdraft type of burn without a sufficient preparation period). But I tend to like to sleep more than 4 hours a night without getting up to tend a fire. If I wait until about 5 hours, it's almost just like a cold start except the stove temp is till at least 100 degrees or so and the stack is warm so it's not necessary to restart the draft, that is I don't have to prime the chimney since it's still somewhat warm. I was wondering if anyone has experienced this short burn time, and if so, have you managed to fix it? Any input would be greatly appreciated.
I'm reasonably sure that I don't have an overdraft condition as I'm actually using a 6" ID insulated chimney with the 6" adapter (not the oval to round kind) and stove-pipe as opposed to the 8" that comes standard on this stove. Just like an internal combustion engine, a stove is also really just a glorified pump so the more it's throttled/choked on the back or front side, the less it should put out, and the longer it should last (in terms of burn time). I suppose it's possible that I'm simply not loading it high enough as I don't like to stack wood up until just under the griddle top. I suppose it's possible that another small log on top could make a little difference but not 2+ hours.
By the way, I have two friends at work who burn old non-EPA rated stoves and from their experiences, I honestly believe that the downdraft type of burn really results in a much more consistent burn with a mildly decaying temperature profile. Although I haven't instrumented my stove with thermocouples yet, I believe that this is in sharp contrast to their experiences where their stove top temperatures seem to fluctuate wildly from really hot (I can't get my stovetop temp over 550) to relatively cold.
FWIW, I load my Encore CAT model 2550 to just below the griddle - I try to see how much I can get in and still close the lid! This will give me a 10+ hour burn with the stove at minimum air, with the CAT engaged, ranging down to about 6 hours if I'm cranking the stove hard.
My DEFIANT NC stove was the biggest mistake I ever made, just because I believed VC's marketing hype. After two months of EVERBURN my chimney was caked with stage 3 creosote (shiny black) in the top 6 feet of the stack and I had gone through twice the wood of my DEFIANT CAT stove. I was so dissapointed with VC that I went out and purchased a Hearthstone Mansfield. The Mansfield has operated flawlessly since installation, uses half the wood that the VC CAT stoves do and is providing a nice clean burn while keeping the house very comfortabl (70's) with no effort.
I hope everyone who has a VC stove does not have my terrible experience with the Everburn; as far as I am concerned it was a very expensive ($2400+) mistake. I had VC CAT stoves and they are great; but I will never do business with VC again and don't recommend them because they put this product out.
Good luck to those who can get it to work correctly: but you have no idea what you are missing with stoves that actually work simply and use a lot less wood while doing it.
After much review my take on what makes them work is if you just happen to have the proper balance of draft to enable the air siphon for the secondary burn to function as designed. BUT, chimneys vary from house to house; so results are going to be mixed. Eventually this will affect sales and VC will pull back or modify the design in use now; that will render these units obsolete. Glad I've taken the hit now and don't have to live with it any longer.
Also, this will be my last post about the VC NC stoves, I've said all I have to say about it. I will be happy to help anyone who has one but am not going to present my thoughts beyond saying these devices are not recommended by me.
Norway maple is not the best wood. I use the same stove, but burn year old ash / beech, I can get 6.5 hour burn with nice bed of coals left to re-lite new wood.
Much less than advertised....that's for sure. And, no, I do not think I have have an air leak....although others sure do!
When damperd down and with minimal air....all I see in the firebox are the 'dancing northern lights' type of bluish flame. Wouldn't an air leak result in some orange flame?
Smang, welcome to the forum. To both of you guys that just asked about burntimes, let me just say that I do think the VC published number is misleading, however I can say that I can now consistently get solid 8 hour burns with nice big coal bed and usable heat at the end of those 8 hours, and I can stretch that to 10 hours with a smaller coal bed at the end but still good enough. It took more than a full year to figure this out along with tips from another owner.
First, you really MUST do the dollar bill test, ALL along every square inch of all gaskets. These stoves are notorious for having gasket problems straight from the factory or after the initial burns. Fix any problems by replacing gaskets, adding silicone sealant, and/or tightening door latches. You won't get 10 hour burns with air leaks.
Second, seasoned hardwood is an absolute must. Smang you said your wood was seasoned for a year, but was it split over a year ago? Has it been under cover for a year? For what its worth, I found that my wood this year which was stored in a woodshed with no sides burns considerably better than my wood did last year which was covered with tarps over the top. I think having a nice big air space over the top helps.
Third - you need a big red hot coal bed. It has to be 2-3 inches thick and covering most of the bottom of the stove. You are going to rake this toward the shoe (back center). You can pile it right up there, but first clear all the ash away from the shoe and the air holes along the bottom back of the firebox (by raking everything temporarily forward and sweeping away the ash). The stovetop, as measured around the flue collar, should be 550+F (internal flue temp should be 700+), if its not, then add some small wood and/or crack the ash pan door to bring the temp up before proceeding.
Fourth - fill the firebox with wood, starting with smaller splits on the bottom. If you use pallet wood, put a piece right on top of the coals in front of the shoe. Add big splits on top, as much as you can get in. Then fill in any gaps that are left with smaller wood, 2-4 inch diameter unsplit branches are great. Fill right to the top of the firebox (which isn't the griddle I might add, there is a double top on these stoves).
Fifth - IMMEDIATELY CLOSE THE DAMPER AND CUT THE AIR BACK 100%.
If your wood is good, it will start everburning immediately, you will hear it. For me this procedure pretty much guarantees an 8-10 hour burn every time, with a big coal bed and usable heat still being produced in the morning. It is then ready for new everburning within 15-20 minutes after a reload. My upstairs bedroom is still 70 degrees in the morning (8 hours later) even with temps in the teens outside.
Like I said, it took me a long time to figure this all out. Last year I thought I had to let all the wood get engulfed in flame before dampering down, but that is a guaranteed way to get a 6 hour burn. I found myself getting up in the middle of the night to add wood. That is all a thing of the past now.
My morning routine is that I come down stairs immediately after I get out of bed in the morning, I add wood, if the coal bed is big, I just keep it undampered and air up, if coal bed is smaller, I also crack the ash pan door. Then I go take a shower, get dressed, etc. 15-20 minutes go by from when I reloaded, and its back up to critical mass temps and ready for dampering down again (but usually with air at least 20%). This routine has been working very well for me for several weeks now and I feel like I've finally got this stove mastered even though I still think its not a very user friendly design and I probably wouldn't recommend this model to friends and family. That said, I'm heating my house well, and with less wood and longer burntimes than a couple of my friends with other designs of stove. So who knows, maybe the story isn't over yet on everburn, but I can't help but feel this design will just frusterate most people.
I can't emphasize enough how critically important it is to have very dry wood. I stack about a day's worth of wood around the stove, so that it gets "kiln dried" so to speak. I think this makes a difference.
Hey Trader and all,
I cc'd the below from another thread post, which I did earlier.
I have the greatest respect for Trader's efforts to help all user's of this device get the most out of it. He has developed a way of dealing with the monster that keeps it at bay and , I think, gets the best performace out of it.
The other thread is concerned with burn times. I was getting a bit more than the 6 hours that post talks about; I could often get up to 9-10 hours with lots of coals left and heat still being produced. I think that poster is dealing with over draft vs. design point.
YES, and that is exactly what I fear. The can’t see it, the CAT stove is the best product that they have, the only one in fact. So when they stop selling it, the will be done.
Don’t let them tell you this is normal. Even if you have to call CFM customer service over and over, it is a possibility they will give you a CAT stove to replace the NC. . The dealers and CFM do have some interest in having people think its OK to have to manage the stove; but having to babysit a stove constantly is rediculous.
I sincerely hope you are able to get this thing working for you; at least to the point that you can heat with it and it doesn’t take too much of your time. BUT, you really have to keep an eye on the smoke coming out the stack because it equals creosote.
As Craig emphasized, you need to get your draft as close to the factory design point to have this thing work optimally.
After speaking with the dealer, doing some thinking and searching on this issue, and doing a bit of reading I decided to check a couple of areas and experiment a little since I have a few days off. Since the stove is hot and I can't currently do the dollar bill trick, I got a good fire going and then closed the damper and throttled the stove back. I then took a lit match and moved it around the outside of the door in the vicinity of the door to stove interface gap. I could clearly see a difference in the flame at some locations around the door. A smoke tester would be more ideal for this but itconfirmed my suspicions, brought about by trader's post, that there might be an air leak or two around the door (particularly since they removed the doors when the brought the stove into my basement). As can be expected, the match flame changed from calm burning to erratic as I approached areas I suspect to be leaking air. I suspect that either the gasket is defective or more likely, that the door merely needs to be adjusted to obtain a better seal. This makes sense since A) the doors were removed and installed cold and B) when things are heated they expand which could further exacerbate any leaks. In addition what I did was to check the air intake hole on the bottom rear of the stove. When the primary air was fully open, I could feel a large volume of air rushing in obviously, but when it was closed, I could still fill a large flow rate of air, although not as much as with the primary air wide open, entering through this hole. This is in fact the point of this opening as the stove has to get oxygen to burn with the fuel from somewhere. I then stacked a series of ceramic plates up to block this hole until I had gone too far (as judged by my inability to have any effect on the flame via the primary air flow adjustment lever) at which point I backed off a bit. Essentially I wound up choking the fire, albeit relatively briefly, by starving it of enough oxygen to burn properly (although it never went out it just died down a bit and I was unable to effect it via adjusting the input air). I noticed that after I backed off, and reduced the air flow restriction that I had induced, the primary air flow lever provided more instantaneous response of adjustment. I then went outside to check the exhaust coming out of the stack. There was little difference that I could detect from when there was no obstruction in the air inlet. With the damper engaged and the primary air throttled completely back, there was only a very little bit of smoke coming out while the stove top was at a temperature of 380 degrees F. It wasn't fully loaded or I suspect it would have been higher. Furthermore, I seemed to be able to induce the downdraft burn at a lower temperature and it lasted for much longer and didn't stop making the wooshing sound nearly as soon as I thought it did previously. Or at least I didn't notice it if it did.
So what I'm thinking is that the mechanism that adjusts the air is out of alignment or adjustment. I won't be able to do anything with it immediately but at my first available opportunity, I will try to adjust it to reduce the air as I've obviously been burning in an overly oxygen rich environment. I wonder if this is a common malady with these stoves and merely an adjustment that needs to be made on the part of many users? An unfortunate circumstance, given the high price of these stoves, but not one that is the burden that many people on this forum have made it out to be (at least making an adjustment to the air inlet mechanism isn't a big deal to me if I can do it once and be done with it).
Today, while I'm awake and in the immediate vicinity, will be my first test of this and its effect on burn times. I'm really hoping that it will help me increase the burn times to at least 6 or so hours as that will be a much more manageable time frame for me to have to feed this stove. That is hopefully I won't have to wake up every four hours to do so.
One last comment regarding my wood. Yes, it has been split for a year. I finished splitting the wood by the end of January and it has been up on pallets with a tarp that only slightly covers a little bit of the sides. So in other words, with the exception of the top layer of wood which is covered by a tarp, the old adage applies in that "the spaces between the wood are only large enough for the mouse to run through (and I do kill mice in the wood pile continuously) but not enough for the cat who's chasing him!" Furthermore, I received my moisture meter yesterday and all that wood (i.e. one year seasoned maple) is registering between 19 and 20% as opposed to the fresh pine that I'm still splitting which is 30% or more. I hope to do exactly as you mentioned trader, and build a semi-permanent cover where I can remove the tarps and allow more air to circulate over the top layers of wood.
Finally, although it is not the holy grail of hard woods (this, I think, belongs to shagbark hickory or apple) there is no way that the difference in energy densities between ash, hickory, and maple can account for a lack of achieving a burn time closer to 8 hours than 4. Yes it could make some difference but not that much so I seriously doubt that is the issue. I suspect that fuel air ratio and flow rates have much more to do with burn times than energy density.
Thanks for the input trader, especially on the stacking for a more optimal burn. I'll post again later, hopefully with positive results.
Your wood sounds OK. I just burn a mix of hardwoods (Ash, oak, maple, hickory, yellow poplar). But a high BTU hardwood can burn about a 1/3 longer than a low BTU hardwood, that's the difference between 6 and 8 hours right there. Regarding moisture content - one thing you can try, if even just as a one time test, is to put a bunch of big splits around your stove for a few days (up to a week) to super-dry them. Then see if this makes any difference when you burn it. But it sounds like you are OK there. The air leak thing is a biggie. I doubt there is any problem with your air control mechanism, and the rear bottom air inlet is for secondary combustion, I would not mess with that. If you want the 8-10 hour burn you really do need to pack it tight with wood... based on the temps you mentioned, I think you are not burning the stove hot enough personally, anything in the 300 range stovetop is not going to give you good secondary combustion (if any at all).
Hi SMang & all,
We really have to define "burn time". I believe some of us read it differently. When my griddle temp is 450 & flue (outside) temp is 275 & there are hardly any coals left, it is then time to reload. And that is usually 5-6 hrs. Today I am trying well seasoned elm (3yrs), I loaded the stove up at 3pm with it. It's six pm (est) now my griddle reading 600 & flue 325. At this rate I believe I have about 2-3 hrs before reload.
Couple of members here suggested that overdraft might be my problem...well if that is the case I should not be getting yellowish/blue dancing flames at this state of the burn (3 hrs in). Also, when I engage the damper I cut air to 95% closed I loose all the flame for at least 1hr. (pretty boring fire my wife claims). If I had overdraft I would be seeing lots of flame right....
Primary air is controlling a flap over the front windows, when the stove cools down, look up above the windows with a flashlight and you will see the flap moving. It is a direct linkage from the lever to the flap. This is fed by the air input hole in the back bottom.
Secondary air is a direct input from the same air input hole in the back, the amount of air that comes in once the large damper is closed is controlled by the amount of draft your chimney has, too little hard to get the secondary to go or continue. Too much draft and hard to keep the burn rate down resulting in less burn time. These are not adjustable at all. At least not without major modification to the air siphon mechanism on the secondary burn; which will void any useless warranty that CFM provides.
If you have too much draft, you can slow it down a bit with a damper; that's about it.
What was the chimney height used with the nc defiant? I believe you did not have enough draft to engage everburn. If the ideal VC testing conditions called for a 15' chimney why do the installers play with that height i.e. mine is 21' & my installer claims..it is perfect height!!
btw it is 5.5hrs after I reloaded with well seasoned elm my flue temp reads 200 & griddle 475 with some coals left...enough to restart! Craig mentioned earlier (or maybe in a different post) that he get 8hrs + from his acclaim with 30% smaller firebox! Something is just not right...I am tempted to remove a 4' chimney section & see what happens
I had the same chimney with the Defiant NC, but, for the Mansfield I lined it with a 6" SS liner. (For the Defiant I was running into the clay 8X12 flue which worked like a champ for the Defiant CAT stove) I was going to line it with 8" for the Defiant (that is what is optimum) but since I hated the Defiant anyway I decided to do it all at once.
From what I could tell VC seems to have used the 15-16 foot stack at 8" as the design point. The draft is pulling on the Everburn siphoning air in through those holes in the refractory assembly. Too much draft, more pull, less burn time. BUT most likely clean and hot.
I would definately try removing a section to see if it slows it down for you and still engages the Everburn consistently.
Someone here said that putting a rock in the flue pipe might work...I am not sure if I feel comfortable with such method. Time to reload!
I think a couple of folks said that...And Craig verified it. That's a cheap way to go. A small damper plate would be too. But, I like take off a section and see what happens.
I will try the rock first, then once we get a warn spell (-10f outside at the moment) I will remove a 4' section..it looks like a pretty easy job.
The only concern with removing a section of fluepipe is if that would leave you in violation of the Codes on height requirement - specifically the 10-3-2 rule (3' above the roof penetration point, 2' above anything within a 10' radius) - This is usually the minimum needed to get a clean drawing chimney and it is rare to see a chimney built taller than needed to comply with this rule unless there is a specific other reason to do so. Shortening the stack is likely to cause other drafting issues, so I would be far more inclined to try the "rock in flue" method, or install a damper plate before removing a pipe section.
Thanks Goose, I will check the distances once it warms up. Again, thanks it seems like you're always looking out for everyone here in terms of "code" it's good!
I'd rather try a flue damper than a "rock in the flue". But really those are last resort options in my opinion. And I doubt shortening your chimney will make a big difference. Strong draft is usually a good thing, and short burn times are more often the result of an air leak and/or sub-optimal operation of the stove.
I don't know if I was clear in my recent procedure post. With these down drafting stoves, if you operate them right, the horizontal flame path allows only the bottom of the wood load to burn. When you are dampered down, you should see very little flame activity, sometimes you'll see no flame activity at all, just an orange glow, and if you've got wood piled up towards the front, you might not even see the orange glow! Someone posted the comment, "a boring fire" - YES, it is supposed to be if you are operating it right. This is the key to long burn times. If you want a lively fire, you can operate it with the damper open (but the fuel will disappear fast).
From an old VC manual: "The logs on top are dried by heat, and fall into the flame area as those below are consumed. Thus a full wood load can provide heat all night long. The use of horizontal combustion allows for us to place the fuel in a magazine where the fueling of the fire is automatically accomplished by gravity".
You should try to keep the coal bed big, this will keep the momentum going for easy clean burns on any reloads. The secondary combustion chambers have to be seriously hot to work optimally (producing no visible emissions). If necessary, reloads can be done in two steps - a few small splits on the coals, undampered for 15-20 minutes to get things rolling (very hot) followed by the addition of fresh (bigger) splits on top of that when it reaches the point that you know you can damper down and get good secondary combustion. This keeps the top of your fuel load (the magazine) from being consumed all at once, and ensures a long burn time. You can stuff in huge logs for the top, which will get you the longest burn times, basically there is no such thing as "too big" a split, as long as you can manage to get it though the door and into the firebox! But if the huge split(s) are not very dry, they are just going to smolder and possibly even put out your fire.
That is exactly what I get (btw how do you quote here?) the boring fire! For the first two hrs or so I can not see a thing in the firebox (black). The secondary is going because I can hear it, no smoke at the stack & the flue (outside) temp sits at a nice 500-600. After about two hrs I start to see glow at the back of the box, some small flame on either side of the firebox & the rumble is much quieter. At times the rumble will get too quiet & I will see those fireball explosions in the firebox & on occasion a puff of smoke through the griddle...time to open the air a bit. Burn time still max 6hrs!
OK - well it sounds like you are on the right track. Does NOT sound like you have an air leak. I doubt its an overdraft problem either. I think the issue is either the wood, or the way you are operating the stove. Have you tried loading it the way I described? Put some small splits on, let it burn undampered for 20-30 minutes, get it super hot, then load it as full as you can, with the biggest splits you can fit though the door, stuff it full, and then IMMEDIATELY damper down and cut the air to zero. If you still only get a 6 hour burn, I'd say its probably due to low BTU wood although I guess it could be some kind of overdraft issue in which case a flue damper might help.