Can I get the catalytic in an Encore to work with just a small fire?

[SonOfEru]

You might ask why do I have a stove that could be bigger than I should have, but it's a very long story. If you want to you could look at my first thread asking some questions about it

https://www.hearth.com/talk/threads...1992-defiant-encore-0028.166615/#post-2233611

But here's my question now.

I got a 1992 VC Defiant Encore from a friend, put it in on Saturday. He had only used it about 5 years before getting a furnace. I have a space of about 700 sq ft to heat, the rest of the house runs on the central heat. My old stove was a 1988 Encore, and I only ran small fires in it, never more than about 1/4 to 1/3 of a full load. The catalytic had been removed [long story] and it had warped where the damper plate closes, so it didnt have full control of the fire path. But small fires were ok to keep the heat up. I am retired so I could just keep an eye on it and drop one or two logs on when it needed.

So now I have an Encore with a damper that closes nicely, and the catalytic seems to still work. But I wonder how it will work with small fires. I have been observing it as I run it according to the manual - open the damper, load the wood, give it full air, let the stovetop temp get up to 450, close the damper, run it with full air to get the catalytic up to heat, then adjust the air down to where you want it.

What follows may seem obvious to you who know, but let me run through it

So I can see the catalytic kicking in - I can see through the passage into it, and it starts to glow red. I figure that is definitive. Then when I set the incoming air down, the flame in the firebox settles down, of course, and the red glow continues. But only for a while. After sometimes less than a minute, the red glow fades away.

I figured maybe there was just not enough unburned gases getting to it and the flame of the cat wasnt enough to sustain itself. I have tried a larger load, and indeed the red glow was sustained. After maybe 10 minutes of minimum air there was no flame at all in the firebox but the glow was there.

It was also odd to see that every minute or so a thin layer of flame appeared ABOVE the cat, and then it touched off the smoke in the firebox, with a "whooomf".

So, once the cat fires up does it need a minimum amount of combustible gases to keep going? It seems obviously yes, but even with a small load there were surely unburned gases getting to it, there were logs that were only in the firebox for a short while, they weren't down to just coals at all.

I am reluctant to put too large a load in, nervous that even with the incoming air all the way down it will roast me out of the house. I have very very dry wood - I put it in the cellar after drying in the field all summer, then leave it for a full year before using it. It burns enthusiastically so I worry about a full load running away with it and overfiring disastrously. And I also wonder about the "whoomf" effect. If a big load was putting of a big amount of combustibles would the whooomf get bigger and hurt something?

So the question is also this - with a larger load of extremely dry wood, can the incoming air control keep the heat output at a continuous low level? Or is the catalytic heat output proportional to the size of the load?

Sorry for the length but it feels like there are a lot of factors to bring into the questions

Thanks

 

[bholler]

You are having backpuffs they are pretty common with these older vc stoves. It is usually caused by shutting down to much poor draft or wood not being dry enough. Have you checked the moisture content of your wood? A cellar typicaly is a pretty poor location to dry your wood. Also what height size and type chimney do you have?

 

[SonOfEru]

You are having backpuffs they are pretty common with these older vc stoves. It is usually caused by shutting down to much poor draft or wood not being dry enough. Have you checked the moisture content of your wood? A cellar typicaly is a pretty poor location to dry your wood. Also what height size and type chimney do you have?

I think the cellar is pretty dry. It's a new house, they put the black gunk on the outside to seal the concrete. I can feel the difference in this years wood and last year's - lighter, the sound of knocking on it is sharper, things like that. Someone once told me you can tell when wood is really dry by holding the log up and lighting it with a match. If it's really dry it will catch fire and stay lit, which my 2-year wood does. Also if I put a stick of this year's wood in the fire it hisses just a bit but the 2-year wood does not.

The exit of the stove is a foot from the chimney thimble, one section of 8" pipe, one of those adapters that starts oval and goes to round. It's a new chimney of course, the stove has its own flue, and the chimney would be about 25 feet up from the stove, I guess. It has always been extremely clean - burning the small fires in the old stove made for no creosote at all. Just gray dust that I cleaned out once a year.

 

[bholler]

I think the cellar is pretty dry. It's a new house, they put the black gunk on the outside to seal the concrete. I can feel the difference in this years wood and last year's - lighter, the sound of knocking on it is sharper, things like that. Someone once told me you can tell when wood is really dry by holding the log up and lighting it with a match. If it's really dry it will catch fire and stay lit, which my 2-year wood does. Also if I put a stick of this year's wood in the fire it hisses just a bit but the 2-year wood does not.

The exit of the stove is a foot from the chimney thimble, one section of 8" pipe, one of those adapters that starts oval and goes to round. It's a new chimney of course, the stove has its own flue, and the chimney would be about 25 feet up from the stove, I guess. It has always been extremely clean - burning the small fires in the old stove made for no creosote at all. Just gray dust that I cleaned out once a year.

I would get a moisture meter to check the wood. Also check cleanout door etc to make sure you dont have air lesking in somewhere decreasing your draft.

But really you may just be discovering some of the issues with these stoves that gave vc a bad name in the industry.

 

[SonOfEru]

I would get a moisture meter to check the wood. Also check cleanout door etc to make sure you dont have air lesking in somewhere decreasing your draft.

But really you may just be discovering some of the issues with these stoves that gave vc a bad name in the industry.

You're not the first to say VC isnt the greatest. Maybe in its day, but ...

I went recently to a local stove store with some of my questions and I started out explaining my situation and that I was looking for advice, and the guy said - sell it and get a new one, forget about catalytic.

So ...

 

[bholler]

You're not the first to say VC isnt the greatest. Maybe in its day, but ...

I went recently to a local stove store with some of my questions and I started out explaining my situation and that I was looking for advice, and the guy said - sell it and get a new one, forget about catalytic.

So ...

No that stove wasnt very good in its day either. It is not a problem with the cat there are some very good cat stoves out there it is a problem with the design of the stove

 

[Ashful]

He was wrong to malign catalytic technology, most of today’s best performing stoves are catalytic (eg Blaze King and Woodstock). However, it took manufacturers a while to get it right, and that’s part of your issue, here.

First, the combustor, if in good condition, will actively reburn your emissions (aka “stay active”) at any temperature above 500F. But it will only visibly glow at temperatures above 1000F, so most of the time it’s active, it’s not actually glowing. The best way to determine activity is with a cat probe thermometer, but folks have also made due judging by their chimney smoke emissions (is it black?).

To directly answer your other question, it is a little more difficult to keep the cat active on very small loads. Depending on how many hours are on that cat (over 10,000 hours?), that could be your biggest single issue.

So, in theory, there’s no reason you can’t load her full, and just turn way down. After all, that’s the primary advantage of a cat stove. However, you appear to have a back-puffing issue that will hamper this effort.

Bholler is right that wet wood can aggravate a backpuffing setup, but that’s just an aggravating factor and not the true cause of it. It is typically caused by weak draft combined with low burn rates, which allows combustibles (wood gas) to collect in the firebox more quickly than make-up air allows them to pass out thru the combustor. It’s an oscillatory phenomenon.

How tall is your chimney, and what’s the construction?

 

[SonOfEru]

How tall is your chimney, and what’s the construction?

Without tape ruling it, I would say 20-25 feet from the stove to the top. A pretty standard cape with chimney, and as I said it's pretty new, 20 years now.



It's founded in the cellar below of course, and that's where the cleanout is.

It's an 8" tile, the stove has its own flue.

I have never seen black smoke, with the old stove or the new, or anything but white and light gray. More often you cant see much of anything. And there has never been any creosote. I do think the wood is very good [I cut it myself, so that's a prideful statement. And I clean it myself, my own brushes].

I dont have another chimney to compare to, but I always figured I have good draft. Is there a way to measure it?

 

[Ashful]

It’s an interior chimney, so that’s good. Clay tile can take a while to warm up, so the draft may be poor in the early part of a new fire, but I’d expect it to improve as it heats up.

Yes, you can measure draft with a manometer, and there have been a lot of those discussions on this forum recently. Someone ID’d one that works nicely, and can be picked up on Amazon for $30’ish. I prefer the Dwyer Magnehelic, and bought one on eBay for $38. The challenge with either is finding one that’s accurate at the low numbers produced by a chimney (typically around 0.05” water column (WC), so you’ll want 0.01” WC graduations).

I suspect the wood is fine. I had the same back-puffing issues on one of my 1990’ish Jotul Firelight 12 catalytic stoves, and they were definitely worse when my wood was not dry, but they never completely went away even when I had dry wood. I now have a Blaze King catalytic installed on the same chimney, with no such issues, those older cat stoves are just more fussy.

My solution was pretty simple, I just avoided burning on days with any high temp above 40F, and never turned it down far enough to cause the back-puffing issue. My rule with that stove, and several others have echoed the same with their older Woodstock’s, was to always make sure there was some small flame in the firebox. It would only back-puff if I turned it down far enough to kill the flame. For me, that meant running that stove with the air set around 10%, not all the way closed.

One last thought, you can buy a manometer and check draft, but it might be a waste of money. Put otherwise, if it measures low, are you prepared to do something to improve it? I’d just try to run the stove as it is, and if you can’t make it behave, consider reselling it and upgrading.

 

[bholler]

He was wrong to malign catalytic technology, most of today’s best performing stoves are catalytic (eg Blaze King and Woodstock). However, it took manufacturers a while to get it right, and that’s part of your issue, here.

First, the combustor, if in good condition, will actively reburn your emissions (aka “stay active”) at any temperature above 500F. But it will only visibly glow at temperatures above 1000F, so most of the time it’s active, it’s not actually glowing. The best way to determine activity is with a cat probe thermometer, but folks have also made due judging by their chimney smoke emissions (is it black?).

To directly answer your other question, it is a little more difficult to keep the cat active on very small loads. Depending on how many hours are on that cat (over 10,000 hours?), that could be your biggest single issue.

So, in theory, there’s no reason you can’t load her full, and just turn way down. After all, that’s the primary advantage of a cat stove. However, you appear to have a back-puffing issue that will hamper this effort.

Bholler is right that wet wood can aggravate a backpuffing setup, but that’s just an aggravating factor and not the true cause of it. It is typically caused by weak draft combined with low burn rates, which allows combustibles (wood gas) to collect in the firebox more quickly than make-up air allows them to pass out thru the combustor. It’s an oscillatory phenomenon.

How tall is your chimney, and what’s the construction?

I agree with everything you said other than the statement the best performers ate cat stoves. That depends entirely upon your performance needs. If you need long low burns you are absolutly correct. If you need high btus not so much.

 

[jetsam]

Why say "the stove is going to heat 700sf and the furnace is going to do the rest"?

Get a couple box fans going and load 'er up, give the furnace a day off.

(Also, from what I've read, you may want to consider switching stoves. You could sell the encore to someone who wants a decorative stove, and buy a much better stove with the money. A new NC13 is $700 on homedepot.com right now, and someone usually has a sale and sells them even cheaper in the spring.)

If you want a stove that can burn very low to heat 700sf, your choices are:

1) Fork out for a good catalytic stove like a Blaze King. Disadvantage: cost, may still be too much for 700sf on warm days.
2) Buy a tube stove (like the NC13 I mentioned) and burn small, short fires in it. Disadvantage: uneven house temperatures, short fires, may be way too much for 700sf on warm days.
3) Get by on what you have. Disadvantage: Known issues with stove. Buying a new NC13 may actually be cheaper than a free VC over the stove's lifetime. Also too much for 700sf on warm days.

Any of the above can keep you warm!

 

[SonOfEru]

Why say "the stove is going to heat 700sf and the furnace is going to do the rest"?

Get a couple box fans going and load 'er up, give the furnace a day off.

(Also, from what I've read, you may want to consider switching stoves. You could sell the encore to someone who wants a decorative stove, and buy a much better stove with the money. A new NC13 is $700 on homedepot.com right now, and someone usually has a sale and sells them even cheaper in the spring.)

If you want a stove that can burn very low to heat 700sf, your choices are:

1) Fork out for a good catalytic stove like a Blaze King. Disadvantage: cost, may still be too much for 700sf on warm days.
2) Buy a tube stove (like the NC13 I mentioned) and burn small, short fires in it. Disadvantage: uneven house temperatures, short fires, may be way too much for 700sf on warm days.
3) Get by on what you have. Disadvantage: Known issues with stove. Buying a new NC13 may actually be cheaper than a free VC over the stove's lifetime. Also too much for 700sf on warm days.

Any of the above can keep you warm!

Well, the factor I havent touched is one that I really can't do anything about. I live with my wife and will to the end.

I love her dearly, and I am fully reconciled to the issues involved. She just cares about things I dont care about and vice versa. Sometimes I say that together we make almost a whole person.

I would of course get fans set up, I've thought about it a lot, but she wouldn't have it. You see the photo I posted, it's a very nice looking house and a fairly good copy of an old style of cape. She's really into it, and the insides of the house are beautifully designed and furnished, all to her credit not mine. I admire the house for sure but I'm a practical guy and she's ... well, not very practical. Or rather the idea of practical is not at the top of her list of care factors. I care about how things work and she cares about how things look. I would do things or not do them because of cost savings or lessening the work of living here, but those factors are immaterial to her - the look is all that counts.

And I dont think I could get her to consider a stove change. She doesnt like the bits of bark on the floor near the stove but she loves the look of the Encore. It is quite graceful and fits right in with the decor.

So the stove contributes to heating the rest of the house, it does flow around corners and up the stairs enough to matter but I do rely on the thermostats in the other areas to keep them up to warm.

I dont know if you're married, but if you are you probably would agree with the old saying "Love is blind but marriage is a great eye-opener."

 

[begreen]

Well, if she's happy you can live with an 85ºF house and dance around naked. Maybe open a window and get dressed when the family visits.

 

[SonOfEru]

So what it's coming down to at this point is:

On not-so-cold days I will probably just keep a small fire going, one stick at a time as needed, and let it burn with good air and no damper. I fear that if I damp it the cat wont do much and I will be creating a creosote factory, even if it's a small scale one. Might as well let it burn bright and clean and just accept that some energy is going out the chimney.

When it's colder I will run it through the cat, and hope that Ashful is correct in saying

the combustor, if in good condition, will actively reburn your emissions (aka “stay active”) at any temperature above 500F.

And by the way, am I correct that references to "500" mean the temp at the stovetop? Or does it mean the temp inside the cat, where I cant observ it?

I wont see if any creosote has happened until I clean it in the spring. I'm too old now [69] to want to climb up on the roof to look at this time of year, with ice and snow up there. I used to be fearless about that kind of thing but after a fall I've become willing to wait on some things.

And I figure the colder it is the more I can dare to load the stove. I'm waiting for cold now [it's been a warm spell since I installed it], for a chance to see if the heat output will stay low with a bigger load, with the incoming air control turned down. I have some experimenting to do.

 

[Ashful]

And by the way, am I correct that references to "500" mean the temp at the stovetop? Or does it mean the temp inside the cat, where I cant observ it?

The 500F number is typically measured as the exhaust temp directly downstream of the catalytic combustor on other stoves, but reading the Encore manual I just Googled (not sure it's the right one), it appears VC already figured all of this out and translated it to stove-top thermometer temps for you:

For example, when the thermometer registers at least 450°F (230°C) on the stove top after start-up you know the stove is hot enough and it may be time to close the damper if a sufficient ember bed has also been established. Note that the stove will warm up much sooner than the chimney, though; a warm chimney is the key to easy, effective stove operation. Please review the "Draft Management" section of this manual to see how the size, type, and location of your chimney will affect your stove operation. When thermometer readings drop below 350°F. (175°C) it’s time to adjust the air control for a higher burn rate or to reload the stove. A temperature reading over 650°F. (340°C) is a sign to reduce the air supply to slow the burn rate.

There's no way this is going to be as fast or accurate as measuring with a catalytic probe thermometer, as other stove manufacturers recommend and supply provisions for, but it's probably reasonably effective guidelines.

BTW... I like Jetsam's suggestions.

 

[SonOfEru]

Well, if she's happy you can live with an 85ºF house and dance around naked. Maybe open a window and get dressed when the family visits.

<giggle>

 

[SonOfEru]

The 500F number is typically measured as the exhaust temp directly downstream of the catalytic combustor on other stoves, but reading the Encore manual I just Googled (not sure it's the right one), it appears VC already figured all of this out and translated it to stove-top thermometer temps for you:


There's no way this is going to be as fast or accurate as measuring with a catalytic probe thermometer, as other stove manufacturers recommend and supply provisions for, but it's probably reasonably effective guidelines.

BTW... I like Jetsam's suggestions.

I dont know where I would put a catalytic probe thermometer, it's all cast iron until you get to the exit from the stove, which would mean a flue pipe thermometer. That's a good ways away from the cat itself.

 

[au2183]

The Encore is a pretty stove, no doubt. Has your wife actually looked at many other stoves? Given where you live, why not take her on a little adventure to West Lebanon to look at what Woodstock Soapstone has to offer. I think she could fall in love when either a Keystone or a Palladian, and you’ll have a stove that will be both beautiful and functional at the same time. Not only that, it will pay for itself within a few short years if you’ve a mind to use it.
I’m paired with the same type one wife and I’ve learned hours to deal with that in most situations so she feels like it was all her idea. We’ve been married almost 38 years and I’ve learned a thing or two, much like you, but sometimes I just refuse to waste the money on something of inferior quality just because it looks good. Safety and utility come first, especially with something like a wood stove, but in this case their are quite a few options that fit that description. Fortunately for you, some of the very best are quite close to you, and they are the best people to do business with. I told my wife on the 3 hour drive from our house in Maine a couple weeks ago, and we’re buying a Fireview.
We used to have a Resolute in red enamel. Beautiful stove but it ate a lot of wood. I’m too old and lame to tend a stove like that now. The Fireview will replace our pellet stove. It’s been good, but it’s not wood heat, and those 40 lbs bags are too much for either of us, not to mention the dust everywhere. Your wife would hate that, mine does.
Good luck to you neighbor!

 

[au2183]

Nice screen name btw. Tolkien is great

 

[SonOfEru]

Nice screen name btw. Tolkien is great

Wow, you got it!

 

[SonOfEru]

The Encore is a pretty stove, no doubt. Has your wife actually looked at many other stoves? Given where you live, why not take her on a little adventure to West Lebanon to look at what Woodstock Soapstone has to offer. I think she could fall in love when either a Keystone or a Palladian, and you’ll have a stove that will be both beautiful and functional at the same time. Not only that, it will pay for itself within a few short years if you’ve a mind to use it.
I’m paired with the same type one wife and I’ve learned hours to deal with that in most situations so she feels like it was all her idea. We’ve been married almost 38 years and I’ve learned a thing or two, much like you, but sometimes I just refuse to waste the money on something of inferior quality just because it looks good. Safety and utility come first, especially with something like a wood stove, but in this case their are quite a few options that fit that description. Fortunately for you, some of the very best are quite close to you, and they are the best people to do business with. I told my wife on the 3 hour drive from our house in Maine a couple weeks ago, and we’re buying a Fireview.
We used to have a Resolute in red enamel. Beautiful stove but it ate a lot of wood. I’m too old and lame to tend a stove like that now. The Fireview will replace our pellet stove. It’s been good, but it’s not wood heat, and those 40 lbs bags are too much for either of us, not to mention the dust everywhere. Your wife would hate that, mine does.
Good luck to you neighbor!

Well, I am at a point of considering options. I have cut my own wood for 40 years now and at 69 I wonder how long I will want to do that. I have a friend who is 91 and he still does his own wood, with tractor and winch and splitter and all that but me? I dunno.

I also have a pellet stove in the workshop down below, and I can still do the 40's but that too ...

So any choice of a further investment has to consider how long I want to do wood. Not sure I would plunk down the bread for a new stove at this point if this one can be made to behave.

 

[au2183]

Well, I am at a point of considering options. I have cut my own wood for 40 years now and at 69 I wonder how long I will want to do that. I have a friend who is 91 and he still does his own wood, with tractor and winch and splitter and all that but me? I dunno.

I also have a pellet stove in the workshop down below, and I can still do the 40's but that too ...

So any choice of a further investment has to consider how long I want to do wood. Not sure I would plunk down the bread for a new stove at this point if this one can be made to behave.

I hear you on both points. You have a decade on me but I’ve been physically disabled for the past decade and it’s making it difficult to do these sorts of things, but I’ve also determined that it’s best to keep moving and do what I can do or I’ll soon lose even that capability. I applaud your friend of 91 and I hope to be there myself someday. Independence is key to a long happy life imho and I’m as independent as they come lol.

One question about your chimney setup. It’s 20’ total, but what is the heist from your stove outlet to the top of the flue? That’s the figure that determines draft, not including what’s below the level of your stove thimble. So on your 20’ chimney from the basement to the top you may only be using 12 or 13’ from the first floor up, which is too short to create a good draft. Or did I misunderstand your measurements?

I’m a big Tolkien fan!

 

[bholler]

I hear you on both points. You have a decade on me but I’ve been physically disabled for the past decade and it’s making it difficult to do these sorts of things, but I’ve also determined that it’s best to keep moving and do what I can do or I’ll soon lose even that capability. I applaud your friend of 91 and I hope to be there myself someday. Independence is key to a long happy life imho and I’m as independent as they come lol.

One question about your chimney setup. It’s 20’ total, but what is the heist from your stove outlet to the top of the flue? That’s the figure that determines draft, not including what’s below the level of your stove thimble. So on your 20’ chimney from the basement to the top you may only be using 12 or 13’ from the first floor up, which is too short to create a good draft. Or did I misunderstand your measurements?

I’m a big Tolkien fan!

He said 20' from stove to top of chimney. Which sounds about right for a cape.

 

[SonOfEru]

I hear you on both points. You have a decade on me but I’ve been physically disabled for the past decade and it’s making it difficult to do these sorts of things, but I’ve also determined that it’s best to keep moving and do what I can do or I’ll soon lose even that capability. I applaud your friend of 91 and I hope to be there myself someday. Independence is key to a long happy life imho and I’m as independent as they come lol.

One question about your chimney setup. It’s 20’ total, but what is the heist from your stove outlet to the top of the flue? That’s the figure that determines draft, not including what’s below the level of your stove thimble. So on your 20’ chimney from the basement to the top you may only be using 12 or 13’ from the first floor up, which is too short to create a good draft. Or did I misunderstand your measurements?

I’m a big Tolkien fan!

The 20-25 ft figure is from the flue to the top.

And only real Tolkien fans would know the Ainulindalë - of "Eru, the One, who in Arda is called Ilúvatar".

As Eru is called "Father of All" I like to call myself Son of Eru.

And yes Tolkien is quite something, I have found nothing like his work. It intrigues me that he presents the tale of Creation as coming from Light and Music. Many mystics have said the same.

 

[begreen]

What you've told us so far is that running the stove on low sometimes causes the cat to stall and then puffback. The remedy for this may be as simple as giving the fire a bit more air. Have you done partial loadings to see how the stove does? If it continues to be cranky at a low setting or with partial loading then change out the stove. At this age what else are you going to spend your money on? Hopefully you'll be around for the next 10 yrs and as you get older you will appreciate the bone warming heat even more.