VC Encore secondary air intake

[phishinphree]

Hi all.

Bought an encore 2040-cat-c last week. The thing wants to over-fire if given even the smallest amount of air. Thought we were doing good getting a VC due to their reputation but it seems their stoves are garbage these days and I'm learning that after the purchase. If anyone is looking for one in the Bangor, ME area, I'll cut you a great deal.

I'm not new to burning wood. My last stove, a Jotul 3 was decent but past its prime.

Anyway, to get to the point, heres a photo of the primary and secondary air intake. Should there be a cover or any restriction over the secondary intake? It looks unfinished and I feel like it might be so ready to over-fire because its missing a cover or something which would restrict airflow. Does anyone else have an encore who wouldn't mind confirming theirs looks the same? From what I can tell, the flexburn model should be identical except the cat is optional.

 

[gthomas785]

I have the same stove. Yes all of the pieces are there. If it's overfiring it's probably due to excessive draft; these stoves are sensitive to the amount of draft from the chimney. Also check for air leaks around the door and griddle which can be another reason for overfiring.

 

[gthomas785]

Also, how do you define over-firing? If you're seeing the cat temperature gauge going to the top of its operating range, that's normal for a new catalyst and will actually be worse if you close the air intake too much.

 

[phishinphree]

Thank you for confirming I'm not missing parts. I've noticed when I close it down, the cat temp will often spike as more combustion occurs there than in the firebox. It has never exceeded the normal range as indicated on the included probe.

The stove top over-fires. On my first burn after the break-ins, I hit 900 on the griddle. Manual says over 650 is too much although that is a change from the 2040 flex which listed 750. I've had it a week and once I have it going with a bed of coals, I add wood, give it some air. Griddle temps drop due to the cold wood then rise. If I'm not quick to shut it down completely, the griddle temps get into the 700s. The cat varies from the low range of active to high in that range when I close it up. I get dirty glass due to the lack of primary combustion and notice it burns up all the wood within a 4-6" radius of the air holes in the refractory at the back much quicker than the rest. Seems to me the air is skewed very much towards the secondary and not pulling in enough for primary burn. If I turn it up, it gives me more primary burn but griddle temps go through the roof.

Chimney is 6" square masonry, middle of the house, 16' from stove top (basement) to chimney top. 1 story house with full basement. Built 1986.

I've heard some will plug a few of the secondary air holes in the refractory section. Also I've seen mention if "epa" air holes near the legs that some will cover. Do you know where exactly they are located? I'll check gaskets later today but with the lack of flames in the firebox when I close it up, I don't suspect that's an issue.

 

[gthomas785]

It sounds like you could benefit from a flue damper.
I haven't gone searching for the epa holes on my 2040, but I know on the 2550 they are located behind the front legs. The 2040 may be the same.
Have you also checked the ash door gasket for leaks? Even a tiny amount of air getting in under the coal bed will cause some major overfire.

 

[Woodsplitter67]

Are you checking the griddle temp with a bimetal thermometer or an IR gun

 

[phishinphree]

I have 4 ways to measure temp on the griddle top. A new rutland bimetal which is 200-300 degrees low, and old bimetal which I believe to be most accurate. I tried an IR gun but because the griddle is shiney, an IR gun won't be accurate and reads low. IR guns don't work well on reflective surfaces. If I read the black cast iron an inch away from the griddle with it, it reads 300 deg higher than the griddle itself. Finally I have a bare thermocouple which if placed under the magnet on one of the bimetal thermometers, it agrees with the old bimetal within 10 or 20 degrees.

I'm getting a new digital k type thermocouple probe today along with a digital unit so I can monitor the stack and cat as well as provide a third independent measurement on the griddle.

 

[Woodsplitter67]

The Bimetal thermometers and really not accurate. I have one on mine and I just have it there for a reference. when the Bimetal is at 500 my stove is more like 650 ish and I doubt check then close my damper.
I don't think that your stove is getting to 900.. Are you see anything glowing when the stove is getting that high. How active are the flames.. You may have to much draft What does the box look like when this is happening. You may have a couple things going on not jut one.. strong draft and wrong STT reading.
I read your first post I believe your statement is complete wrong. These stoves are good heaters, beautiful, and put out long even heat. All to many times the stove issues are user error or the setup is poor. You have a different stove, it's not a jotul.. and if you try to run it like one your probably going to have some difficulty with the VC.
Also your better off asking a mod to move this to the VC Forum

 

[phishinphree]

No doubt the VC makes some nice looking stoves. Although it the basement now, we purchased with the anticipation of moving it to a new home in a few years into a living room where it can be admired.
I get that some people love their VC and this isn't my first. A house I rented years ago had an old defiant that I loved. it must be hard to design a stove that'll work equally well on a 10 foot external brick chimney as a relined 3 story interior chimney. All while making the EPA happy. I don't feel my situation is uncommon and on that scale, pretty much in the middle of the range in expected draft strengths. My house isn't hermetically sealed like they build these days, but its also not a drafty 1700's farm house. Again, I'm somewhere in the middle.

When its overfiring, the flames are almost non-existent (wispy and few and far between) and the stove is shut down less than 1/4 to 1/4 at most. I can see the glow of the secondary through the top of the cat access cover. After an hour or two, the lack of air washing the glass causes them to blacken pretty decently. I really feel like the balance of air going into the secondary is out of wack with that going into the primary. When it was hitting 850-900, it would back puff when I closed it down all the way. I now understand I should have opened the bypass and the doors which seemed counter-intuitive at the time.

Any thoughts on partially covering the secondary air intake? I'd rather control the possible excessive draft from there then drop the cash on a new double wall pipe section and push the stove further into the room just to troubleshoot.

 

[gthomas785]

The secondary air is meant to create a lean mixture going into the catalyst. Any excess of air going into the secondary intake should increase cat temps and result in a cleaner exhaust, but it wouldn't increase the heat output by much. The primary air is what controls the burn rate and ultimately, the heat output. If you can verify your temperature measurements and are sure it is overfiring, I'd be looking for air leaks into the main firebox not the secondary intake.

Now, I've had a suspicion that due to where the secondary air enters the firebox, it would be possible for a leaky bypass damper to allow secondary air into the main firebox and overfire the stove. I've never seen this though, just a hunch that it would be possible.

One last thing, you mentioned your windows going black. I've never had that problem except when I was burning damp wood. And by damp, I mean red oak that was seasoned for a year instead of 2-3. How have you seasoned your wood? Although it may seem counterintuitive, damp wood can lead to many of the symptoms you described due to excessive smoke production from a cool primary burn.

 

[Woodsplitter67]

No doubt the VC makes some nice looking stoves. Although it the basement now, we purchased with the anticipation of moving it to a new home in a few years into a living room where it can be admired.
I get that some people love their VC and this isn't my first. A house I rented years ago had an old defiant that I loved. it must be hard to design a stove that'll work equally well on a 10 foot external brick chimney as a relined 3 story interior chimney. All while making the EPA happy. I don't feel my situation is uncommon and on that scale, pretty much in the middle of the range in expected draft strengths. My house isn't hermetically sealed like they build these days, but its also not a drafty 1700's farm house. Again, I'm somewhere in the middle.

When its overfiring, the flames are almost non-existent (wispy and few and far between) and the stove is shut down less than 1/4 to 1/4 at most. I can see the glow of the secondary through the top of the cat access cover. After an hour or two, the lack of air washing the glass causes them to blacken pretty decently. I really feel like the balance of air going into the secondary is out of wack with that going into the primary. When it was hitting 850-900, it would back puff when I closed it down all the way. I now understand I should have opened the bypass and the doors which seemed counter-intuitive at the time.

Any thoughts on partially covering the secondary air intake? I'd rather control the possible excessive draft from there then drop the cash on a new double wall pipe section and push the stove further into the room just to troubleshoot.

If your stove is cut down with the air to .25 and you have wispy flames your stove top would no way be near 900. The back puffing is from your wood off gassing and the lack of draft to pull out the gasses. I can fully load my stove .. cut the air all the way back and never get a back puff.. my STT will never go past 450 With a full load of wood and the air all the way down. Blocing your primary air will only reduce your draft even more.. When your cutting your air back that lazy flame is a sign of control. the black glass is a sign that you have cut the air back to much for the amount of wood you have in the stove or lack of draft.. Back puffing is user error the operator is cutting back the air during or having week draft. You mentioned that your stove in now in the basement.. basement installation it tough due to the negative pressure of the basement.. draft is sometimes weak at best even though you have plenty of chimney.. There are many on here that have basement installs with other brand stoves and during reloads have smoke pouring out of the doors or on a cold start struggle to get a fire going. You stated that you have years of experience with wood burning You do realize that your putting a down draft stove in a basement.. right..

 

[Crash525]

Hello, late for the reply here. I have a vermont castings encore 2040 with the cat. I had problems with mine over firing earlier this year. I used it twice before I realized when I went through it that the thermostat cable was pinched and the air control door was stuck wide open. I purchased it new. They fixed it and it works better now but I think I have an air leak somewhere now. Its a beautiful stove but I cant get it to work right for the life of me.

 

[RandyBoBandy]

I don’t have a 2040 but I have read about some using stainless steel sheet metal screw to plug some of the secondary air holes. Is there 5 holes? I think someone on here plugged 3 out of the five and it seemed to make a significant difference. I also agree with a lot of what woody is saying. Seems impossible to have a GT temp of 900 if there is no real active fire in the firebox. Also if it was 900 degrees in the firebox there’s no way your glass would be black. My glass only turns black when I’m burning less than ideal wood. My stove really doesn’t like 20%mc. Something in the 16-18 is ideal for my situation. Instead of locating and blocking the epa holes behind the legs just leave about 2” of ash in the firebox. I’m not convinced you have an air leak or I would think you would see more flame in the box. Once the GT hits 450 try engaging the cat and start turning down your primary in increments. Back puffing accuse often when you shut the primary down to fast or in to big of increments. I have a short stack and if I’m not attentive to a good turn down I can experience back puffing.

 

[NewGuy132]

I just started running my Intrepid last week but this is what I have noticed. The first few days I was running on kindling and biobricks.

I get the stove lit with some kindling and a biobrick. Wait for it to burn down a bit and add another one. Wait for STT to hit 500. I noticed that the hottest part of the stove top is dead center right behind the griddle. My griddle never gets nearly as hot as the stove top(this could be because I have an enamel stove and an IR gun). Once we are around 550 or so I flip the damper and set the air to around 40%. After a couple minutes of the woosh sound that stops. I get lazy flames for a while and they stop at some point. My STT drops to around 450. The cat probe ready in the active zone, but never climbs more that 25% of the way in to the active zone.

I did get a couple back puffs, but after looking and playing with it I realized that I was setting the air too low. Have to be close to 50% open to not get them. To me it does seem that the secondary is getting all of the air. As soon as I open the damper to add another piece I have flames again. To me it is just a learning curve that I am getting used to. My glass is also fairly dark. At one point I had a good hot fire going and it cleared up a bit, but the doors are getting bad again. I think I'm not running it hot enough personally, but I'm new to this so I am slowly ramping it up.

 

[Crash525]

I don’t have a 2040 but I have read about some using stainless steel sheet metal screw to plug some of the secondary air holes. Is there 5 holes? I think someone on here plugged 3 out of the five and it seemed to make a significant difference. I also agree with a lot of what woody is saying. Seems impossible to have a GT temp of 900 if there is no real active fire in the firebox. Also if it was 900 degrees in the firebox there’s no way your glass would be black. My glass only turns black when I’m burning less than ideal wood. My stove really doesn’t like 20%mc. Something in the 16-18 is ideal for my situation. Instead of locating and blocking the epa holes behind the legs just leave about 2” of ash in the firebox. I’m not convinced you have an air leak or I would think you would see more flame in the box. Once the GT hits 450 try engaging the cat and start turning down your primary in increments. Back puffing accuse often when you shut the primary down to fast or in to big of increments. I have a short stack and if I’m not attentive to a good turn down I can experience back puffing.

I fired mine up again the other day. It was running fine for a while then as the wood was burning down the temps on the griddle thermometer went from a nice 400-425F to 700 then 0ver 750F without any warning. All the while the air control was almost completely shut and the damper was shut. I had to open the damper and and then it still took a while to cool off. There was about 1/4 of wood in it if not less. I cant say mine got up to 900 but it was pretty darn hot. I dont have any issue with back puffing and my glass does have soot on it and it didnt burn off.