Flexburn

It's a waste of money...
It's a cat stove, with a removable cat. You have to let the stove go out, remove some fragile panels and then you can burn in non-cat mode. I have no idea what the 3rd stage would be. Maybe that's when your face turns red after you get the price for replacement parts!

I have the VC Encore flexburn, a brand new 2014 model. It is not required to remove the cat or anything else to burn in catalytic or direct mode. The cat only needs to be removed for periodic cleaning.

To change burn mode all you do is move a single lever one way or the other. It's that easy. The stove will run w/o the cat in place but there's no point in doing that.

The refractory material has been completely re-engineered. I wouldn't say its fragile. It's much like ceramic. VC has done much to improve the newer models.

OK_Bill said:

I have the VC Encore flexburn, a brand new 2014 model. It is not required to remove the cat or anything else to burn in catalytic or direct mode. The cat only needs to be removed for periodic cleaning.

To change burn mode all you do is move a single lever one way or the other. It's that easy. The stove will run w/o the cat in place but there's no point in doing that.

The refractory material has been completely re-engineered. I wouldn't say its fragile. It's much like ceramic. VC has done much to improve the newer models.

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That's not how the flex burn works. To run in non-cat mode, the cat must be removed. Running with the bypass open is simply that, bypassing all secondary combustion in order to heat the stove up.
I'm glad the stove is working out for you. Are you burning 24/7 with it?

No idea what the 3 burn thing is.

Probably:
1) Cat mode with the catalyst installed
2) Non-Cat mode with the catalyst removed
3) fireplace mode with the doors open, spark screen installed, and bypass open.

The stove is to be run with the bypass open constantly only when being used in fireplace mode however.

If you leave the bypass open for either of the more normal burning modes (cat or non-cat mode) you will overfire and damage the stove.

I have The Encore Flexburn. Despite the massive amount of negative criticism about VC the stove has been treating me exceptionally well for the past 3 years. I have had to replace the cat once under warranty...but i am hoping it is because I was burning with wet wood and had a couple over fire events due to my own negligence.

However, there are a few users on here with very negative experiences with the exact same stove (fragile refractory material, overfiring despite all attempts to slow the burn down, back puffing and dumping smoke into the house through the top loading plate).

So over-all the stove and the company get more negative feed back on this site than really any other brand and that probably is telling of something. I have the encore in my basement. I heat 100% 24/7 with wood and the stove has been a beast thus far. Happy with my purchase but I am always afraid the stove could develop problems like others have experienced.

Never mind i read the quote you are referring to "3-STAGE burn system that creates heat three times".

This sounds like a silly marketing ploy. I mean technically without the catalyst installed it is supposed to be creating a secondary combustion in the refractory box (however this is how the stove design got it's neverburn nickname from)...so maybe they are claiming that with the catalyst installed you are getting the catalyst burning, and sometimes still achieving secondary combustion like that which occurs without the catalyst installed, and then you obviously have the primary burn in the firebox. Either way it seems pretty silly.

Webby3650 you are correct - I'm really new to using wood as a fuel, and new to the forum. Although technically adept, I misread or under-studied the manual. The VC manual supports what you're saying: the manual addresses continuous burning in one of two modes: CAT or non-CAT. To burn non-cat, the element would have to be removed.

To answer your question, no I'm not running 24/7. Here in OKC, I'm just using the Encore as supplemental heat for when we get those cold arctic blasts that can drive temps well below freezing and make my heat pumps run nearly continuously. The rest of the time, its just sittin pretty on a nice hand laid stone hearth... something it does really well (I posted pics in the 2014-15 VC owners thread)

So now - this is the fun part - I see why folks are saying this is actually a 3-mode stove. With the damper closed, it can run in either CAT or non-CAT mode. Cool. And with the damper open, it's just an old fashioned wood stove with byproducts of combustion being drafted directly up the chimney.

I've been running it with the CAT in place, both with the damper open as well as with the damper closed. I've burned several fairly full loads of well seasoned blackjack oak in the Encore, with those being done 100% in what I'll call "direct" mode - that is, with the damper open and no hot stuff going through the cat/combustion chamber. Being a noob at this, I closely monitored those burns, and never had any trouble keeping temps down to around 600-650F or so measured on the griddle top. I also have an IR temp gun, so can monitor temps elsewhere and can verify the accuracy of the mag thermometer.

Of course, there's not much to be gained by burning this way, other than to make the fire look pretty with all the dancing flames ... when the stove operates so well in CAT mode with really nice long runs, very controlled temps, and combustor operation much cooler than if it was run in non-cat mode. (VC and other reputable sources claim the CAT can secondary burn at about 1/2 the temp of traditional O2 based secondary combustion)

Now the question is - should I burn wood in "direct" mode? That being where the damper is kept full open the whole time. I still can keep temps under control (650F max with primary air turned full down). Not an over fire by what I understand at all. Interestingly, the VC Encore manual doesn't directly speak about operation like this - it only addresses damper-open operation in an interim way. But, it also doesn't speak out against burning "direct" continuously... any thoughts about that??

Thanks again for your input. I do appreciate the help of those with (much) more experience.

- Bill

You dont want to burn this stove with the damper open unless you are reloading wood or running it with the doors open in fireplace mode with the spark screen.

You want that cat to be engaged to have the smoke being cleaned and reburned, that would mean burning with the damper closed and air shut down as much as possible after lighting off the cat.

Do you have a catalytic probe on the cat to tell you its temps?

Hey there Mellow - I only did a few initial burns with the damper opened the whole time. As I mentioned, there were no problems with those burns; they were just shorter lasting 5 hours or so. Now I'm burning in CAT mode (8 hours with same fuel load) which I can verify by observing the stack exhaust - which is absolutely devoid of smoke (or even steam). So the exhaust is clean as you say. Probably better for the chimney too. To date, I haven't operated the stove in "non-cat" mode, since I had an initial misunderstanding of what the manual was saying.

I do have a CAT probe on order from Condar. Hopefully I'll install it in the next 10 days or so (but- will that void my warranty?). I'm a technical operator at heart, so having combustor temps directly displayed is a nice thing to me, although VC doesn't make any provision for it.

Usually they have a port to stick the probe through, usually a screw is put into it till you use it, that would be a good question for VC.

Charles1981 said:

You dont want to burn this stove with the damper open unless you are reloading wood or running it with the doors open in fireplace mode with the spark screen.

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Maybe I don't want to do that... but VC specifically does not warn against it in the manual.

For more specific guidance, I emailed their tech support about this issue: operating the Encore with the damper open. Their response was that if operated that way:

" It could be, but yes wood load sizes and operating temperatures would have to closely scrutinized. Never closing the Bypass damper would mean you would never be operating the stove for heat and efficiency, as it is that action which activates the secondary burn system, allowing the high efficiency & heat levels and giving the extended burn time. Sort of defeats the purpose of having a stove like this."

So, Charles1981, I do agree with the basic sentiment of your guidance, but also note that its not an operational error to run the stove in direct mode as long as temps and wood load sizes are monitored closely. There's apparently more opportunity for the stove to over-fire if run this way - BUT its not prohibited. So it would be wrong to conclude that direct operation (damper open) will always lead to over-fire. Its just inefficient, and possibly less controllable. YMMV as always...

I can't leave the damper open > 30 minutes without temperatures reaching >800 griddle top and the refractory starting to glow. I have great draft, but regardless, you would have to sit by the stove and watch it 24/7. You can run the stove and any other stove any way you want but having to tend to something that closely to me defeats the entire purpose of burning with wood.

You can also do a slammer install, burn treated lumber, throw coal lumps into a wood stove ect. You just probably shouldn't.

I can definitely see some setups where the draft isn't as strong as others and the risk of over firing with an open damper is significantly mitigated, but again It seems extremely dangerous for both personal and stove safety.

Charles1981 - interesting how different your Encore burns -vs- mine. There certainly are lots of variables at play here. I'm very much in the early stages of my learning curve.

I appreciate your advise. The clear consensus here: from both yourself & other experienced members, as well as from VC tech support is that the Encore is designed to run with the damper closed; either with CAT in or not. For efficiency, and as you've pointed out - for safety.

Thx for helping me to get it right. I'll be burning in CAT mode.

Charles1981 said:

I can't leave the damper open > 30 minutes without temperatures reaching >800 griddle top and the refractory starting to glow.

Click to expand...

Out of curiosity, where is the primary air set? My downdraft stove generally will not overfire if primary air is fully shut, although flue temps can get excessive. Open the air and it's a whole different story.

The primary air shut limits draft some but not very much with the damper open.

The damper closed the stove runs great...and opening the damper for reloads is great because generally 15 minutes and the new wood is well caught, the griddle temp is 400-500 and the damper ready to be shut (I just always figured this was how the stove was supposed to operate). burn down to hot coals, open damper, add wood,wait for it to catch, close damper, shut down air slowly.

My system may just have excessive draft with the damper open but seems to be just perfect closed.

And damper = bypass plate in the VC world.

OK_Bill said:

its not an operational error to run the stove in direct mode as long as temps and wood load sizes are monitored closely. There's apparently more opportunity for the stove to over-fire if run this way.

Click to expand...

As I noted in the above reply, this probably also depends on where is the primary air is set, and ignores the fact that flue temps could get excessive even if the stove itself does not overfire. Do you monitor flue temps?

I have a different stove but with similar technology. When I open the air and don't close my bypass damper, the flue pipe can really start cooking in a hurry, well before the stove top temps take off.

Having the front door open, in fireplace mode, basically kills the intensity of the fire by letting in large amounts of cool room air, so greatly reduces the ability of the flue to overheat. If I burn with bypass open, I always make sure my primary air is nearly or fully shut.

Charles1981 said:

The primary air shut limits draft some but not very much with the damper open.

The damper closed the stove runs great...and opening the damper for reloads is great because generally 15 minutes and the new wood is well caught, the griddle temp is 400-500 and the damper ready to be shut (I just always figured this was how the stove was supposed to operate). burn down to hot coals, open damper, add wood,wait for it to catch, close damper, shut down air slowly.

My system may just have excessive draft with the damper open but seems to be just perfect closed.

And damper = bypass plate in the VC world.

Click to expand...

My stove runs pretty much the same, just seems to show more restraint if i shut the primary... could be a function of differences in both the stove design and how strongly our systems draft, but I should also mention that I never run the bypass open continuously with a full load, but only smaller loads when I'm running a quick fire to take the chill off.

If I think back a few years to when I last had a full load and forgot to shut the damper, I probably have seen that stove get pretty hot with the bypass open, even with low-to-no primary air. The amount of uncontrolled secondary air that pours into that firebox makes for a pretty good inferno when drafting directly up the flue.

Branchburner - I've shot the base of the flue pipe with my IR gun a few times. I do not have a dedicated flue temp probe installed.

During the initial burns I did with the damper open the whole time, I did note the flue temps were about the hottest thing on the stove. 700-750F. I was wondering how in the heck the paint didn't just flake off... but it didn't. Damn tough stuff. But you're absolutely right - I had no real idea of how hot the flue might get... I had no idea how the stove distributed heat... I had no idea really how the different burn modes worked. Thankfully, its a tough stove and I didn't hurt it even though the flue pipe did hit 750. The stove top was MUCH cooler. Now, in CAT mode, the flue is cooler and the stove body is hotter. The Encore extracts 87% efficiency out of the burn in CAT mode.

What I've learned is that when burning "direct" (damper open) the flue is exposed directly to the combustion effluents, and as you accurately point out, the flue is then at risk of over temp because the secondary (and tertiary) burns aren't taking place at all. Lots of BTU's getting transferred out the flue, rather than being absorbed by the 470+ pound stove body. That's grossly inefficient for sure, and possibly dangerous and/or damaging to the stove.

Today I went back and watched the videos of a VC rep explaining how the Flexburn technology works:

Video 1
Video 2 (and more discussion of Flexburn in this thread)

Earlier in this thread there were a couple comments expressing doubt and/or lack of understanding how VC achieves 3 burn stages with Flexburn. In these videos, the VC rep clearly explains how its done.

edit: fixed the link to Video 1

My stove has a rear burn chamber, but no cat. Wonder if the VC in cat-mode is really much better than other cat stoves... yes, the cat will re-burn at a lower temp whatever smoke is not burned in the rear burn chamber, but in the final analysis, is it really re-burning much more smoke than a cat stove that DOESN'T have that chamber?

It seems to me the "tertiary" burn is really just more secondary combustion by a different name, so I think that is where some doubt comes in. If you call a stove a "2-in-1" then 1+1 still =2, not 3. One form of secondary combustion combined with another form of it makes BETTER secondary combustion, not tertiary combustion.

Probably better referred to as a hybrid stove, as Woodstock calls it. The best feature of the hybrid stoves seems to be less heat up the stack, which I consider the drawback of my stove. I get a good, clean hot burn but I think the design of the stove mean a certain amount of heat loss beyond what would be sufficient to keep my flue free of creosote.

2 modes of operation: CAT and non-CAT.

3 burn stages: Primary / Secondary pre-CAT / Secondary post-CAT (if the CAT is installed - if not there's only 2 burn stages)

The "2 in 1" name references the 2 burn modes, not the 3 burn stages, as I see it.

Well you certainly found a gem of video there. I've looked for years for a good video describing how air flow actually moves around behind that refractory...

I kind of want to know more about that video... That certainly looks like a variation of the 2in1 system...but the video looks so old and the refractory doesn't quite fit together like my 2 in one.

Lol I also like how he is throwing that face plate cover around.... I handle that baby like its china with all the horror stories of people having to have it replaced 2-3-4 times just lightly touching it or reloading it.

regardless props to finding that video definite gem for all VC owners to watch.

I still think the burn system is bunch of junk. Just to many horror stories about the ceramic refractory melting, stoves over firing, face plates breaking, being nicknames the neverburn system (eek). That being said it is rather amazing how unique and how well it can work when it is working. Anyway just wish i I knew now what I did before I bought the stove and new absolutely nothing about stoves. I would have definitely gone with a different type.

The stove has completely paid for itself in just 2.5 years when you consider the cost of electric heating for my house. I am strongly considering purchasing a new stove in 4-8 years or whenever my Encore decides to crap its pants finally like it seems most do. Going to go with a hybrid like the Woodstock Progress or Ideal Steel, or maybe even just get a big cheap old tried and true burner like the NC30. Maybe even a Blaze King.

LOL

We should be neighbors...

I'm having a bit of fun with it.

OK_Bill said:

LOL

We should be neighbors...

I'm having a bit of fun with it.

Click to expand...

It is an intriguing combustion system. I've had fun tinkering with my encore. But mine was free! I built both a cat and a non cat combustion box for it out of skamol, the same material Jotul uses for their baffles. It might seem fun for you now and I hope it serves you well. Most people don't find it funny when I tell them it's going to be $800+ to fix a stove that's still new to them. We quit selling VC because of their "everburn" system, the numerous free service calls associated with it and the lack of support from VC. We only have a few 2in1s out there, they haven't had many problems so far.