I agree with this as when I increased the draft on my Intrepid flexburn last month by renewing the stovepipe and sealing it better the performance improved significantly. I also started to run the stove hotter which helped alot. The Intrepid has a different downdraft design than the Encore (which I had at one time) but believe would have the same effect. My Intrepid is happy at around 900f for the cat and 400 STT. At 900f cat temp there is virtually no smoke out the chimney. As said at 600 I don't think the cat is lit or barely. Just to say the cats in these VC stoves are for tertiary treatment after the secondaries. So it's possible most of the smoke is consumed in the combuster before it even gets to the cat. This may explain cat temps not much higher than STT and little smoke coming out the chimney. It's clear to me tye VC stoves run way better on the hot side then trying to make it simmer over night on a low setting. Just my thoughts on it though.
2022/23 VC Owner thread
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An Encore flexburn I had 3 years ago or so had this problem. Thought it was the cover wasn't made right so I bought another cover. Same problem. So the problem wasn't the cover it is the combuster frame isn't right. Just put a piece of sheet metal formed to go over the cover in that spot and it stayed in place. Sold that stove to a co-worker after that and he had no problem with the fix. The stove was new but I would have to drag it back to the dealer myself so that didn't happen. I've heard of others with that problem. If not under warranty I don't think it's worth the trouble and cost to tear the stove down to put a new combuster frame in for this issue but that problem is a PITA.
My 2 Cents.....
- I have never had the cat cover fall out, but I did have one crack in the first year. VC replaced it under warranty and the new cover was thicker than the old one. No problems since.
- Is this a new problem? If so I would check for cracks or things moving around in the refractory area. If not a new problem I would contact your dealer for a warranty claim.... assuming it is still under warranty. VC has accepted several warranty claims from me in the past (all refractory related) with no issue. Took 3 months to get parts but other than that they were good.
- The covers are loose by design, refractory gets really hot so you want to leave some room for thermal growth. Yours is obviously too loose for some reason. Your gap at the top seems larger than mine, and uneven on left and right sides....
- The plate rests on a ledge at the bottom on either side, maybe try installing some shims in there to life the cover up? Not sure how long they will stay there. Maybe bend up some sheet metal so they stay in place? Assuming you can't find an obvious cause....
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- Hotter will certainly keep the glass cleaner.... no doubt. I went through the same learning curve when I first bought mine. I cleaned the glass every day.... no more, a thick hot bed of coals and lots of air usually works pretty well, but not always.
- Glad you are happy with the stove and it running good. But if you do not have a cat temp monitor how do you know..... I need at least my cat temp probe, but it can be maddening..... Ignorance is bliss, till something breaks. You definitely do not need a data logger if the stove runs well.... I only got mine to try and figure out what was going on. On a well running unit it is pretty boring.....
Good info...thanks. The CAT cover was always looser than I would have liked, but never fell out before. I don't see any cracks. I will talk to my dealer about it and see what my options are...we have had it less than a year right now (early February 22). I am picking up my BK Ashford once the fan kit gets in sometime next month and am hoping to install it in May...but that depends on spring snow and some other factors in the mtns. It can be shoulder season at elevation (cabin is at 9700) all summer and cabin stays cold so I should get plenty of burns in this summer. One of the reasons we went with the BK was due to stories from you and others about the Defiant and other VCs with run away CAT temps. Supposedly you can't do that with the BK's or it is less likely. I really liked the Defiant fire box size, top loading, our Encore runs great and dealer had one in stock...but I thought two VC's might be pushing our luck. I am looking forward to comparing the two and will update how my experience goes with the BK Ashford vs VC Encore.
We do have the standard coil CAT probe on the Encore, just not a digital probe so we only go by the operate catalyst painted section on the VC provided CAT probe to gauge the CAT operation (I am planning to upgrade b/c I like data, but don't love the aesthetics of lots of wires/digital readouts). I will order a stove pipe probe thermometer (coil as well) and install that soon and most likely will install a digital setup with alarms for next season...especially since the wife loves the idea of alarms. I suppose a wireless setup is available, just won't be cheap. As long as the stove/CAT is running well and I don't overheat in the stovepipe, I can deal with CAT replacement every few years...so ignorance is bliss right now using my VC provided CAT probe.
We tried shimming the bottom of the CAT cover and that will work but what we were using wasn't stable enough and the door gasket worked to hold the cover solid for now. I will probably fashion some metal pieces to see if I can raise it up a bit or use some kiln shelf ceramic if I can keep it in place (wife is a potter). Seems like Kevin W. used metal shim on his Encore in previous post and it worked just fine. Even if VC provides a solution for the cover issue we will be mostly out of fire season here in TX in 3 months...maybe a shoulder season fire every now and then...so the temp fix will be permanent for this season.
Nothing is cracked and it seems we can hold the cover in place fairly well with the right shims and the stove works great when cover stays on...so overall we can't complain too much. I would love for it to be a simple solution like a new cover, but that might be too hopeful. It's worth seeing what VC will do, if anything, since we should still be under warranty. I will provide an update with what VC says. I appreciate the input.
Thanks...I think I will do something similar. Still under warranty so I will try that too.
Not sure there is a way to compare Ashford to Defiant/encore. Totally different stoves behaviour wise. One is set it and forget it (almost too boring), the other is like a “high maintenance girlfriend” always looking for attention😝
Woodsplitter67
Minister of Fire
Id get it up past the T a littil where you can see.. and. look at the temperature.. even though you have height.. heat/smoke don't want to do horizontal runs and 90s
Woodsplitter67
Minister of Fire
Your stove may be stalling a bit due to the way its coming out of the back of the stove.. a thermometer may Confirm this
Next time I have it up and running good I'll take a couple temps with the IR thermometer.
A lot of people seem to think that this may be a draft issue it very well may be. When the stove was installed they did a piss poor job and I had to have them back out to fix it. That "fix" included them running a bead of caulking or cement or whatever around where the flue collar meets the stove pipe. That obviously dried and cracked off with use last year. I just ordered some flat gasket material on Amazon that I am going to replace what's left of their "fix" that with. I have checked it a couple times and haven't noticed air being pulled in, but that sure would explain a draft issue.
Woodsplitter67
Minister of Fire
This is what im thinking.. draft is weak and stalling the stove but to be on the safe side its best to check.. I would Put the gasket in.. Clean cat and stove so no ash will fly into the cat. Id get the stove up to temp, cat engaged and take stove pipe temps and cat temps at the same time like every 5 minutes. for a bit
Let me try to guess which one is which...... pretty sure I got this one.
I would love to hear your side by side compare.... or was that it. hahaha
Does the BK come with an ashpan? If not do you miss it? One of the great features with a VC I think.
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Well.... I managed to get the stove into meltdown mode again.
- This was a 3/4 load 3-4 bigger splits, stove was pretty cold, minimal coals.
- When I engaged the cat the griddle was on the low side, but the exhaust gas was hot. Lately I have been throttling the air down when exhaust gas hits 400, I wait for the griddle to come up to 400-450 then I engage the cat. I did not do that this time, might be the reason.....
- Cat rocketed right up to 1300, right away I knew it was going to be trouble. I can also hear a difference. It is like a turbulent combustion noise.
- Cut the air down to 60%, lately this seemed to be the right air setting for 1200 on the cat. Not this time.
- at 1400 I cut air down to 10% and temp responded, but then it slowly crept up to 1400 again and started to launch.
- Cut air down to 0% all the way back, temp dropped for a short time then crept up again.
- Tried to reduce the draft with my key damper and again temp dropped initially and then continued climbing.
- Closed key damper all the way and temps actually went up aggressively. I think the air flow dropped to the point where I was trapping all the heat in the stove and everything was just heat soaking. I opened up the damper and temps came right back down and seemed to stabilize.
- After that the burn went well, I could see bursts of lazy intermittent blue flames through the glass, but not to the point where it was pushing smoke out. Threw off a lot of heat.
- The griddle temps were a bit lower than what I typically see during a controlled but are typical of what i see during one of these runaway burns.
- When I get these kind of burns some things seem to be consistently occurring:
- Reducing airflow yields a short term drop in temps but they always creep back up.
- Griddle temps are cooler than "normal"
- Glass is smoked
- The initial state of the burn seems to set the course for the whole burn. Very hard to recover once the cat is raging. Even opening the bypass damper is inconsistent in bringing things back in line.
- When I get these kind of burns some things seem to be consistently occurring:
- Going forward I am going to try to:
- Hold exhaust temps to 400 -450 during warm up by reducing primary air (to control the draft)
- Wait for griddle to come up to 400 -450 before engaging the cat.
What do the flames look like after you engage the cat? Sounds like maybe these stoves need to keep more flame in the box before turning it down to a lower burn rate? I’ve never had a VC but burned other cat stoves and I remember times when I shut the air down to low too soon the cat seemed to gorge itself on smoke and sometimes temps were closing in on that danger range. Many times all it took was a slight air adjustment to get more flame back in the box for the cat temps to come down.
How long does this whole process take to get to a set and forget setting? Sometimes it took me 30+ minutes even with a Blaze King. I think they even recommend burning on a higher setting for 30 min before turning down? Maybe more time in the bypass mode at a lower air setting before engaging? Not sure, just trying to help. I’d like to see you guys figure this out.
How long does this whole process take to get to a set and forget setting? Sometimes it took me 30+ minutes even with a Blaze King. I think they even recommend burning on a higher setting for 30 min before turning down? Maybe more time in the bypass mode at a lower air setting before engaging? Not sure, just trying to help. I’d like to see you guys figure this out.
yeah your line of thinking here is precisely what I am thinking.....
Typically after engaging the cat on "bad" burns the yellow flames almost completely go away. Usually I just have an orange glow at the bottom. If I leave it alone I eventually get bluish flame that will intermittently runaround the firebox above the wood, it reminds me of the aurora borealis..... I think it is just wood off gassing that does not have enough oxygen to burn right away, eventually enough oxygen comes in and it lights off, consumes all the oxygen and then dies out. It repeats every 60 seconds or so, it varies. If it gets strong enough I will get puffing.
Certainly I have had times where increasing the air got some flame back in the firebox and cat temps came down. Usually it eventually starts creeping back up again, unless the wood is almost all done off gassing and coaling up. During these "bad" burns I never get to a "set and forget" setting until the wood is done off gassing and I got just a bunch of coals. Depending on the load size I will be messing with draft, air setting and sometimes opening the bypass for up to 2 hours....
On "good burns" I can set the air maybe once or twice in the first 30 min and it is fine, usually these are smaller loads.
As you suggested, I am going to try running longer in bypass and see what that gives me. As I recall my VC manual recommends running in bypass till the wood is "charred" and then throw in the cat.
It feels to me like there is an imbalance between the primary burn (too low) and secondary burn (too high) when the stove gets in these moods.... Precisely what you are suggesting.
Quite the effort and analysis there. I applaud your efforts. I got fed up, ripped everything out and just gave up trying to play the game. I now just know how best to run MY stove in MY situation. I get the heat that it is meant to produce, Im not creating creosote, my glass is fairly clear - on par with what I see others having on a good day. I keep the coals chonky and keep my load ups to about 1/2-3/4 and usually dont try to put large pieces inside. If I do, it would only be one with all others being on the medium side. I like to throw smaller pieces in the middle, and I criss cross a piece or two.
Woodsplitter67
Minister of Fire
Your creating creosote.. you should give up completely.. wood burning is not for you.. sell the stove and look for other options regarding heating before you have another chimney fire.. You can capitalize the word my all you want. its obvious.. you run with out the cat.. your stove is to big for your room.. you turn the air down.. you make creosote..
Thanks for the applause..... hahaha. That's great you found a process that works for you and your setup, I am still searching for something repeatable. I had a good burn last night, with a pretty full load, not sure why.... I need to review the temp data and will post for everybody's amusement.
Todays edition of "As the Stove Burns"
First burn was pretty wild, a lot of messing around with draft and air settings, all trying to keep the cat under 1500. about 2 hours in it finally settled down with my key damper and air full closed, let it coast there fro the rest of the day.
Second burn was a smaller load on a bed of coals, reduced air to 50% at 1000 and left it alone, key damper full open.
Third burn was a nearly full load, but not packed, again on a bed of coals, reduced air to 50% at 1000, key damper full open. Left it alone.
Some key differences I pointed out below:
Hoping for a blue sky day so I can check smoke, hard to tell as it has been overcast all week.
Seems like the initial start of a burn sets the tone for the whole run, if things are off it is really hard to bring it back. If things are good it just cruises with no adjustments needed.
First burn was pretty wild, a lot of messing around with draft and air settings, all trying to keep the cat under 1500. about 2 hours in it finally settled down with my key damper and air full closed, let it coast there fro the rest of the day.
Second burn was a smaller load on a bed of coals, reduced air to 50% at 1000 and left it alone, key damper full open.
Third burn was a nearly full load, but not packed, again on a bed of coals, reduced air to 50% at 1000, key damper full open. Left it alone.
Some key differences I pointed out below:
- First burn was from stone cold, 2 good burns had a bed of coals and stove was warm, 300 - 350 on the griddle
- First burn flue temps were hotter for longer, probably had a lot of draft, readings were elevated .09- .12
- Griddle temps were a lot hotter during the good burns, 400 - 600 vs 350 - 400
Hoping for a blue sky day so I can check smoke, hard to tell as it has been overcast all week.
Seems like the initial start of a burn sets the tone for the whole run, if things are off it is really hard to bring it back. If things are good it just cruises with no adjustments needed.
Got a very nice burn going this morning, full load. I will post plots later this afternoon.
Have been noticing that after the cat falls off I am left with a lot of coals lately. Do you guys see this on a full load?
I am sure if I open the air up it will heat back up but I do not need the heat right now....
Pic is not great but best I could do. Coals are stacked almost up to the top of the glass.
- Cat is done at 623
- STT = 431
- flue gas = 235
- Air set to 40%, have not touched it in hours....
- No smoke or steam from stack
- Still throwing plenty of heat....
- Right side was burning colder for some reason, notice the smoked glass.
Have been noticing that after the cat falls off I am left with a lot of coals lately. Do you guys see this on a full load?
I am sure if I open the air up it will heat back up but I do not need the heat right now....
Pic is not great but best I could do. Coals are stacked almost up to the top of the glass.
- Cat is done at 623
- STT = 431
- flue gas = 235
- Air set to 40%, have not touched it in hours....
- No smoke or steam from stack
- Still throwing plenty of heat....
- Right side was burning colder for some reason, notice the smoked glass.
@arnermd Your graphs are great. On your cat temps they seem to peak and then steadily drop off a lot. Granted I'm not graphing but when I check my cat temps they seem to stay steady for hours. Last night about 3/4 load after burning all day and with the air cut back the cat settled about 1350 and stayed there for hours before easing to about 1250 when I went to bed.
This is a challenge to see what it's going to take to get the mixture just right in 3 adjustments or less. Getting to the point where I need to use my weather station to plot my adjustments. I can say I've only aborted the mission once and bypassed the cat when I wanted to go to bed and not fool with it any longer. Now I reload earlier so I can be sure I've got it where I want it.
This is a challenge to see what it's going to take to get the mixture just right in 3 adjustments or less. Getting to the point where I need to use my weather station to plot my adjustments. I can say I've only aborted the mission once and bypassed the cat when I wanted to go to bed and not fool with it any longer. Now I reload earlier so I can be sure I've got it where I want it.
I agree they seem to tail off to quick. I think that started when I reduced the draft.... need to go back and check. Nice to have legacy data.
Sounds like you got your process just about dialed in, 1350 - 1250 sounds great. We should hand out certificates of merit. Still working on mine, slow learner.
The post-superKey burns show flue temperature clearly tracking with catalyst temp (still with a huge delta T). I do think you’ll get a fair amount of natural convection as your cast iron heats up, I just can’t figure how the pre-key setup could precisely keep up with heat transfer demands at the higher catalyst temps and hold flue temps. Would imply a very intelligently designed heat exchanger….
I actually got my first stable burn today. I’ve been working through mostly ancient maple (>8 years seasoned) in my first season but put a couple more recently cut chunks of locust (maybe 1/3 load) on hot bed of coals. Got about 3 hours between 1050 and 950. My first flat top burn. Most others looked like yours with a peak and immediate monotonic decay. Today, I swear I could see the secondary air controller trying to hold temperature. Looked like a slow response feedback loop on the Auber. If the mechanism of extended constant catalyst temp burns is secondary air control, I would assume it has to be draft based. If I went back to your 4 options for the Florida bungalow document, the author’s last resort was intake mods. I’m wondering if you could get the outside air kit (hopefully cheap) and put an also hopefully cheap key damper (or even ball valve). Still using inside air but possibly, you could maintain design intent split between primary and secondary, just managing the total flow on input side.
However. I think you’re on the verge of a totally workable setup with the super-damper in the exhaust pipe. Can’t wait to see more data to try and figure out how these things work.
Data from this mornings burn, still cooking down the heavy coal bed as I write this. Stove is still putting out some heat but almost done.
I would say this burn went very well.
So....
I would say this burn went very well.
- Full load, not tightly packed but I did sneak some shorties in vertically on the left and right side.
- Started with a pretty thin bed of coals.
- With cat bypassed I had air at 100%
- As the flue temp came up I kept dialing the air down to hold flue temp at 400. Notice the corrections on flue temp before I threw in the cat.... that was me dialing the air down.
- This is very different from the way my stove used to run, with the cat bypassed I could not control temps with primary air control. Even with air full closed the flue and STT would just climb to 600+. When I modified the damper (reduced the draft) it changed this behavior.
- Very early on (10 years ago now) I contacted VC about the lack of temp control in bypass and they said don't run it that way.... I suspect what they should have told me was, your draft is too strong.
- When STT hit 400 I engaged the cat and opened the air up to 100%
- As the cat came up I dialed it back several times landing at 40% open. Have not touched anything since then
So....
- I am very pleased with this burn. It did not go as long as I expected but it did throw a lot of heat. Reducing air even further will certainly help extend the burn time.
- I also did not burn real solid wood, it was plenty dry but a little light. This wood I got from my neighbor who let it sit on ground for 2-3 years before he decided he was too lazy to do anything with it and asked me if I wanted it. I have had it split and under cover for 18 months.
- Cat temps were kind of flattish..... for a while. Progress. Seemed to want to hover around 1000.... little low but I will take it. I did check for smoke and it looked like all white steam to me, and not much of it.
- Will be curious to see if lower outside temps try to push the 1000F cat temps up as the draft increases.....
- If not I may try to fine tune it and add back in some draft. That's for later.
- Temps were responsive to temp adjustments which is really what I have been longing for. If the stove responds to my input I am calling it a good burn. Everything else is gravy at this point....
- Glass is fairly clean, I got some coking on the right side but this fire started on the left side, so I think that explains it.
- I also have a pretty deep layer of ash (2-3") on top of the grate, that may have helped too. I am going to knock it down to the pan tonight and see what the effect is.
Woodsplitter67
Minister of Fire
Woodsplitter67
Minister of Fire
You look like you have a monster experiment going on, did you already have this gear hanging around the house
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