New VC Encore Backpuffing

[Shinook]

I recently had a VC Encore installed new and am having some issues with it backpuffing, it's preventing us from using the stove now that temps are dropping and I wanted to reach out to get some help since we're new to this.

When I close the damper and reduce the air, it's the most noticeable and occurs with greater consistency. It did it bad enough last night to lift the griddle and you could hear it, but normally it's just visible. It's much more noticeable when the thermostat is closed down even a tiny bit, but I've had it do it full "open" (hottest) also but not as much. It doesn't happen when the damper is opened up, only closed with the cat engaged. I've tried reducing the temp very slowly several times, but it still happens. I've read other posts that suggest leaving the damper partly open, but the manual indicates the damper is an either all open or all closed affair, attempting to crack it a bit just results in it falling open, so that doesn't seem to work even when I tried, it will either only stay closed or open.

The manual states when this happens to open the damper to cool it down, which makes 0 sense because it actually heats the whole thing up, so that isn't much help either. It gets too hot for our use case and burns the wood faster, obviously.

Our install uses 6in straight pipe and a fresh air draw from outside. There is no blockage in the catalyst or chimney, it's all new and I looked to verify. Our wood is well dried, around 12-15% when I measure moisture down the center after splitting a piece. It seems to occur mostly after the wood has burned a bit and doesn't seem to matter if it's to the front or rear of the stove. I also verified the holes in the rear aren't blocked.

I noticed last night that it appears to only happen when there is no visible flame on the wood, it seems like the flame is being pulled into the rear chamber and reduced on the logs when the damper is closed, the logs just have glowing embers on them visually. When I open the damper, the flame pops back up. When there is an active flame off the logs then it doesn't occur, the problem is how do I keep that going overnight to prevent this from happening? With the damper closed, the size of the flame cuts down almost entirely and becomes inconsistent, I've yet to see the logs remain visually lit with the damper closed for any period of time and when it is there, it's usually small and to one side of the stove but dies after 30min or so.

I understand this is due to off gasses developing but not being burned or drafted out at a fast enough rate, but I'm not sure what to do about it.

Thanks for the help.

 

[Megunticook]

I own an older Encore so a bit different but same basic idea.

Hard to say for sure but it sounds as if you may be closing the damper prematurely. Do you know the temperature of the catalyst and/or the griddle top when you flip the damper?

Let's eliminate that as a possible cause first before venturing down other possible avenues. Could be a lot of things.

 

[Shinook]

I own an older Encore so a bit different but same basic idea.

Hard to say for sure but it sounds as if you may be closing the damper prematurely. Do you know the temperature of the catalyst and/or the griddle top when you flip the damper?

Let's eliminate that as a possible cause first before venturing down other possible avenues. Could be a lot of things.

I've been closing it after the griddle temp hits 450 or higher, last night I left it open a bit longer and it was around 550-575 before I closed it off. When I reload it, I open the damper and thermostat entirely, put a few logs in (I've not filled it past halfway yet), let everything catch for a while then close the damper followed by temp. I usually wait a few minutes after to start dialing the temp back. Usually the logs are pretty well charred by the time it starts backpuffing

Cat temp shows in range of the catalyst (it doesn't show actual temps just a marker where it's active) and griddle temp is at least 450 but the few times we've fired it, it was closer to or above 500 before we closed it off.

 

[Megunticook]

What happens if you keep the primary air inlet control fully open after closing the damper? Did your original post say you still had a backpuff with the primary air inlet fully open?

The backpuffing suggests your firebox is starved for oxygen. When you close the damper to engage the catalyst you should still see some flames in the firebox, depending on where you set the primary air inlet. I generally have small "lazy" flames when I'm dialed in (usually the primary air control is half closed in my case). If there's no flame at all either there's not enough air, the fuel's not fully dry, or your draft is compromised somehow.

How tall is your chimney by the way?

Have you checked to confirm your outside air inlet isn't obstructed?

 

[Shinook]

What happens if you keep the primary air inlet control fully open after closing the damper? Did your original post say you still had a backpuff with the primary air inlet fully open?

The backpuffing suggests your firebox is starved for oxygen. When you close the damper to engage the catalyst you should still see some flames in the firebox, depending on where you set the primary air inlet. I generally have small "lazy" flames when I'm dialed in (usually the primary air control is half closed in my case). If there's no flame at all either there's not enough air, the fuel's not fully dry, or your draft is compromised somehow.

How tall is your chimney by the way?

Have you checked to confirm your outside air inlet isn't obstructed?

Opening the primary air inlet all the way reduces it but doesn't stop it. In last nights case, it started a visible flame and seemed to cut it down, but the previous time I fired it, it didn't have any effect until I opened the damper for several minutes, then shut the damper again and left it open all the way.

I'll have to check the height of the chimney, I'm not 100% sure. Is there an ideal length?

I'll double check the outside air inlet but I did check it a few days ago and it was clear. It also seems to pull enough air in when the air inlet is fully open or the damper is open, would it be more sensitive to blockages when the damper is closed? There is a screen over it but it seems to be pulling air in other circumstances fine.

 

[Eman85]

Welcome to the world of Vermont Castings!, not trying to be funny as we all have had them belch smoke raising the griddle.
If it's not cold out the draft isn't as good and it can cause the problem, NC hasn't been that cold unless you're in the mountains and it really hasn't been cold there yet. Every day every burn can be a little different. A digital probe for the catalyst and a stove pipe thermometer can help. If you look at the VC posts you'll find plenty of back puffs and a lot of monitoring temps.

 

[Shinook]

Welcome to the world of Vermont Castings!, not trying to be funny as we all have had them belch smoke raising the griddle.
If it's not cold out the draft isn't as good and it can cause the problem, NC hasn't been that cold unless you're in the mountains and it really hasn't been cold there yet. Every day every burn can be a little different. A digital probe for the catalyst and a stove pipe thermometer can help. If you look at the VC posts you'll find plenty of back puffs and a lot of monitoring temps.

Thanks, I'm in the mountains, temps got to around 40f last night. Other times I've used it, outside temps were in the 40-45 range.

Is there an outside temp where draft is the most ideal?

 

[Megunticook]

Opening the primary air inlet all the way reduces it but doesn't stop it. In last nights case, it started a visible flame and seemed to cut it down, but the previous time I fired it, it didn't have any effect until I opened the damper for several minutes, then shut the damper again and left it open all the way.

I'll have to check the height of the chimney, I'm not 100% sure. Is there an ideal length?

I'll double check the outside air inlet but I did check it a few days ago and it was clear. It also seems to pull enough air in when the air inlet is fully open or the damper is open, would it be more sensitive to blockages when the damper is closed? There is a screen over it but it seems to be pulling air in other circumstances fine.

I believe VC says 15' minimum on the chimney, at least for the Encore 2550 which is what I have. Check your manual. I have more like 28' feet here at my house, 8" flue, so that's a fairly strong draft especially when it's cold outside.

What size is your outside air inlet duct?

You visually checked your catalyst for fly ash or any other sort of obstruction? I found that to be a regular issue with the Steel Cat when I ran one of those for several years.

 

[Megunticook]

we all have had them belch smoke raising the griddle.

To be fair to VC, I'm not sure I've ever seen my stove do this. Sure, I've foolishly raised the griddle when the damper was engaged, but that's on me. And I've had smoke come out the stove once when there was a screen blocked by fly ash and several other times during warm/extreme low pressure/windy weather. But not sure I'd say having a VC "belch" smoke like IP describes is normal behavior.

 

[Shinook]

I did check the catalyst for debris, I remove it every time the stove is cool the next morning and clean it off, so far haven't found anything on it.

The outside inlet duct appears to be 4 inches looking at the screen. It's slightly larger than the pipe coming from the stove, it looks like they wrapped it with some kind of ducting tape to seal it into the larger outlet.

Chimney is 8ft inside the house, looks to be another 1-2 feet in the attic, and another 3-4ft on the roof. I don't have a ladder large enough to get on the roof and I hate heights, so I'm estimating the latter two parts. It looks like the manual states a minimum of 16ft, so that might be part of the problem.

 

[Eman85]

The colder the better it will draft, and a short chimney makes it tougher to draft. My weather is close to yours, I'm in the TN mountains, and I haven't even lit my stove yet as it's been too warm. Today is the first cold day we've had so far.

 

[Shinook]

The colder the better it will draft, and a short chimney makes it tougher to draft. My weather is close to yours, I'm in the TN mountains, and I haven't even lit my stove yet as it's been too warm. Today is the first cold day we've had so far.

I'm gonna call and see if they can address it or add length to it.

We fired it up a few nights ago when it dropped down into the 40s, I did it to follow the breakin instructions and figured it was cold enough. The week or so after that, it was way too warm to run it even in the dead of night, but this week we're down into the 20s for a night or two so I figured it was good timing to try and run it longer, but at this point I'm not really comfortable doing it with the amount of backpuffing we're getting.

 

[Megunticook]

I did check the catalyst for debris, I remove it every time the stove is cool the next morning and clean it off, so far haven't found anything on it.

The outside inlet duct appears to be 4 inches looking at the screen. It's slightly larger than the pipe coming from the stove, it looks like they wrapped it with some kind of ducting tape to seal it into the larger outlet.

Chimney is 8ft inside the house, looks to be another 1-2 feet in the attic, and another 3-4ft on the roof. I don't have a ladder large enough to get on the roof and I hate heights, so I'm estimating the latter two parts. It looks like the manual states a minimum of 16ft, so that might be part of the problem.

Yes, I would think especially on a low-pressure day with temps in the forties or fifties that setup might not draw very well. Would be curious what happens if you temporarily unhook the outside air inlet and let the stove breathe from the room air. Potentially introduces other issues esp. if you have a tight house or are running any kind of fans inside. But might be worth a try. I don't really think that's the issue, just freestyling on possible solutions.

Does the new Encore still have the secondary air inlet that's thermostatically controlled? Don't suppose that could be malfunctioning or blocked. Worth a check.

 

[Shinook]

Yes, I would think especially on a low-pressure day with temps in the forties or fifties that setup might not draw very well. Would be curious what happens if you temporarily unhook the outside air inlet and let the stove breathe from the room air. Potentially introduces other issues esp. if you have a tight house or are running any kind of fans inside. But might be worth a try. I don't really think that's the issue, just freestyling on possible solutions.

Does the new Encore still have the secondary air inlet that's thermostatically controlled? Don't suppose that could be malfunctioning or blocked. Worth a check.

We do run some interior fans, the house isn't mega tight but it's probably tight enough to be a problem. I could try to unhook it and see if the backpuffing stops and open a door or something. The grate covering the intake does seem a bit restrictive so I can pull that off temporarily too and see if it fixes anything, I just figured it would've been an issue with the setting on high also if it was too restricted.

I think the Encore is thermostatically controlled. I considered that also but being blunt, I don't wanna disassemble it and be blamed if they find a problem 2 weeks after the install, so I may let that be their task

 

[Megunticook]

The secondary air inlet is visible on the back of the stove--at least on the 2550. No need to disassemble anything.

You could also observe the operation of the primary air inlet on the stove when you unhook the duct.

But this seems like a draft issue.