Controlling the non-cat stove

[Ashful]

So, this is an honest question from a cat stove owner to all the experienced non-cat stovers out there. It's not a "cat vs. non-cat" debate, or any attempt to insult or compare one technology to the other. It's a simple, "I'd like to buy one of those pretty non-cat stoves, but don't understand how the heck one heats a house with those things," kind of question.

I've never burned a non-cat stove, but here's a list of information I've collected or deduced, correct or assumed. Please tell me where I'm right, and where I'm wrong!

1. Non-cat stoves must be burned with the firebox temp at or above 1100*F to keep the secondary burn active. If firebox temperatures fall below 1100F, the secondary burn fails. It's not clear how much creosote one is producing after the secondaries go out of ignition.

2. The famous Harmon Firedome graph:



To someone who's never operated a non-cat, it sure appears your stove is going to hit 10x it's "cruising temperature" in the first 1/3 of the burn. It also appears that maybe the secondary burn lasts only half the burn cycle.

3. A non-cat stove requires the operator to adjust the air control several times during the burn cycle to minimize temperature swings, and maintain the longest possible secondary burn.

4. Due to the high temperatures produced in the first half of the burn cycle, non-cat stoves must be properly sized (not too big or too small) for an application.

5. If one's goal is to load the stove twice a day and keep an empty house at a relatively cool 62*F for 20 hours per day, then heating to 68*F or 70*F for 4 hours each evening, a non-cat stove may not be up to the challenge.

Again, I'm hoping that I'm wrong on nearly all of these statements, but they were gathered (or perhaps incorrectly inferred) by things said here by those more experienced than I.

 

[Ashful]

Doh! I posted in the Wood Shed. Idiot.

 

[BrowningBAR]

Didn't you already post this some time ago?

As a non-cat owner with to cat stoves, there is little difference between operating the two types of technologies. You adjust the air once the fire is burnt in, much like a cat stove. The only difference is that you are locking it in at a higher temp. You leave the air controls alone throughout the burncycle and then open up the air at the end to burn down the coals, much like as you do in a cat stove.

 

[dafattkidd]

These are reasonable questions, but i think you're overthinking it a bit. My firebox is oversized for my house. I control the heat output directly with the amount of wood I put in the stove. So having a larger stove doesn't mean cooking yourself out of the house necessarily. I think the temp swings in non cats are a bit greater than the cats but it's pretty much set it and forget it. We heat 24/7 with wood and load my stove probably more like 3-4 times a day but we keep the house warmer than what you stated, and we don't usually pack the stove 100%. Hope that helps.

 

[begreen]

The infamous "firedome" graph might be a better term. Already discussed in a prior thread. The non-cat scenario is a bit exaggerated to say the least.

 

[certified106]

The infamous "firedome" graph might be a better term. Already discussed in a prior thread. The non-cat scenario is a bit exaggerated to say the least.

+1! That graph is definitely exagerated

 

[Ashful]

Didn't you already post this some time ago?

Not that I'm aware of. I posted a thread a while back asking about the basic differences between cat and non-cat stoves, from which some of the above statements were taken, but this thread has nothing to do with cat stoves (nor FireDome, nor any other technology other than typical non-cat stoves).

 

[neumsky]

Is it not also true that the cat is running at a higher temp longer, than the non cat stove? My stove top temp requires approx. 300 degrees for my secondary to run and thats where I like it up to 400. Adjustment takes place and it sits there while I stoke it with wood. I have no idea what the internal temp is.

 

[Prof]

Keep in mind that wood off gases more early in the burn cycle. When the secondaries stop, it is usually due to the gas being exhausted (assuming you don't dampen the stove down too far, burn wet wood, etc.). At this point, there is little left to create creosote--since as things cool down, there isn't much to condense on the cooler surfaces. I wish I had scientific literature to reference here, but the best I have is anecdotal support. I burn 24/7 and get less than 16 ounces of creosote per season. I've never had a cat stove to compare this to, but that much creosote doesn't concern me.

On a different note, I'm going to build a house in a couple years and have been doing extensive research on what stove is best for me in the new place. I've been drawn to cat stoves for the performance (i.e. being able to burn low and slow for a long time). That said, I'm likely going to get another noncat. Simply put, I'm addicted to the secondary burns--it's mesmerizing!

 

[neumsky]

Keep in mind that wood off gases more early in the burn cycle. When the secondaries stop, it is usually due to the gas being exhausted (assuming you don't dampen the stove down too far, burn wet wood, etc.). At this point, there is little left to create creosote--since as things cool down, there isn't much to condense on the cooler surfaces. I wish I had scientific literature to reference here, but the best I have is anecdotal support. I burn 24/7 and get less than 16 ounces of creosote per season. I've never had a cat stove to compare this to, but that much creosote doesn't concern me.


On a different note, I'm going to build a house in a couple years and have been doing extensive research on what stove is best for me in the new place. I've been drawn to cat stoves for the performance (i.e. being able to burn low and slow for a long time). That said, I'm likely going to get another noncat. Simply put, I'm addicted to the secondary burns--it's mesmerizing!

Is it a general consensus I'm hearing then that the view is not as spectacular with a cat?

 

[clemsonfor]

My cat stove will have secondary burns for several hours.

 

[Todd]

Maybe I was doing something wrong but I've burned many EPA non cats and it seemed like I was always tweaking the air control to find that sweet low burn spot. There wasn't many times where it was just set and forget unless I was burning at a higher rate, I always had more success controlling the output of my non cats by the amount of wood in the stove verses a full load and air control.

I also never thought the non cat tube stoves had the better looking fire. To me it almost looks unnatural like a gas grill. I get plenty of slow lazy floating secondary flames when I want them, just depends on where my air is set.

 

[jeff_t]

To me it almost looks unnatural like a gas grill.

 

[begreen]

Not that I'm aware of. I posted a thread a while back asking about the basic differences between cat and non-cat stoves, from which some of the above statements were taken, but this thread has nothing to do with cat stoves (nor FireDome, nor any other technology other than typical non-cat stoves).

https://www.hearth.com/talk/threads/cat-vs-non-cat-pros-and-cons.87312/page-3#post-1133554

Here's another graph for ya, equally deceptive, but true.

 

[Ashful]

Is it a general consensus I'm hearing then that the view is not as spectacular with a cat?

No flames when burning low and slow with the primary air shut down, which is the desired mode of operation for a lot of cat stovers. I can't speak for anyone else, but if I open up the primary air control and burn my stove hot, then I see the same pretty flames I see from any other fire.

Maybe I was doing something wrong but I've burned many EPA non cats and it seemed like I was always tweaking the air control to find that sweet low burn spot. There wasn't many times where it was just set and forget unless I was burning at a higher rate...

This is my primary concern with going non-cat. Was Todd doing something wrong?

Here's another graph for ya, equally deceptive, but true.

Point taken, begreen, but you seem to be taking my attempt at getting to the bottom of this issue as an assault on your stove. I'm the guy who really wants to buy a non-cat (most of them are a heck of a lot prettier), but just doesn't want to regret making the wrong choice.

In my case, the wrong choice has nothing to do with having to spend money to replace a stove two years after installation, and everything to do with turning the wife off on woodburning, should we end up with a stove that's any less than "phenominally easy" to control. If I buy a VC cat stove, and it behaves well but falls apart in two years, no biggie. That's easily chalked up to a junk stove, and maybe the BK Ashford will be available by then as a replacement. If I get a stove that routinely roasts us out of the house, has wide temperature swings, requires frequent small loads to keep temperature at a moderate level in the shoulder seasons, she'll be done with burning inside one season. I imagine anyone who's been married can understand.

 

[Highbeam]

So, this is an honest question from a cat stove owner to all the experienced non-cat stovers out there. It's not a "cat vs. non-cat" debate, or any attempt to insult or compare one technology to the other. It's a simple, "I'd like to buy one of those pretty non-cat stoves, but don't understand how the heck one heats a house with those things," kind of question.

I've never burned a non-cat stove, but here's a list of information I've collected or deduced, correct or assumed. Please tell me where I'm right, and where I'm wrong!

1. Non-cat stoves must be burned with the firebox temp at or above 1100*F to keep the secondary burn active. If firebox temperatures fall below 1100F, the secondary burn fails. It's not clear how much creosote one is producing after the secondaries go out of ignition.

2. The famous Harmon Firedome graph:

View attachment 71329

To someone who's never operated a non-cat, it sure appears your stove is going to hit 10x it's "cruising temperature" in the first 1/3 of the burn. It also appears that maybe the secondary burn lasts only half the burn cycle.

3. A non-cat stove requires the operator to adjust the air control several times during the burn cycle to minimize temperature swings, and maintain the longest possible secondary burn.

4. Due to the high temperatures produced in the first half of the burn cycle, non-cat stoves must be properly sized (not too big or too small) for an application.

5. If one's goal is to load the stove twice a day and keep an empty house at a relatively cool 62*F for 20 hours per day, then heating to 68*F or 70*F for 4 hours each evening, a non-cat stove may not be up to the challenge.

Again, I'm hoping that I'm wrong on nearly all of these statements, but they were gathered (or perhaps incorrectly inferred) by things said here by those more experienced than I.

1) While the 1100 degrees is required for secondary combustion that temp is right there under the baffle in the fire. Fire burns hot and the 1100 temp in the flames corresponds to a wide range of stove temps. Unless you have really wet wood, you would have a hard time burning a fire that wasn't at least 1100 degrees. It just happens.

2) True, the non-cat will have a more peaky cycle. Hotter in the beginning and a long cool down. Heat output from combustion is not linear through the cycle. This is one reason that stone stoves, or even cast iron stoves, are so popular. They abosrb that high early output and release it during the lower output times. Both technologies release about the same btu overall, the non-cats just do it with an explosion.

3) Not in my experience. You are overthinking this secondary burn. It is automatic. Burn it in, and lower the intake setting in a couple of steps to a final setting and you're done. This is where we get to be nerds, you can either fiddle with it constantly or just let it run. Some people insist on constantly fiddling with things. I fiddle more in the early season and just let it run later on in the season. With the EPA required minimum setting you really can't screw this up. Even the low low setting will result in complete combustion and nothing but ash in the morning. I have not been able to "snuff" a fire by shutting off the air too early. It might smoke more but it will clean up automatically.

4) This is the real weakness. You don't get much control of output, it is either hot or hotter. Stove size is important to regulate heat ouput but so is fuel load and time between loadings. Burn time is a real odd duck with non-cats, the bigger stoves burn longer but not that much longer. Cat stoves win here.

5) That's a pretty tall order. You might want a pellet stove. Part of the charm of a non-cat woodstove is the heat cycles.

 

[Seasoned Oak]

Maybe I was doing something wrong but I've burned many EPA non cats and it seemed like I was always tweaking the air control to find that sweet low burn spot. There wasn't many times where it was just set and forget unless I was burning at a higher rate, I always had more success controlling the output of my non cats by the amount of wood in the stove verses a full load and air control.

I also never thought the non cat tube stoves had the better looking fire. To me it almost looks unnatural like a gas grill. I get plenty of slow lazy floating secondary flames when I want them, just depends on where my air is set.

I have 2 different non-cat stoves , downdraft secondaries look completely different than say a NC-30. Downdraft secondaries are definitely much nicer and more natural.

 

[begreen]

Point taken, begreen, but you seem to be taking my attempt at getting to the bottom of this issue as an assault on your stove. I'm the guy who really wants to buy a non-cat (most of them are a heck of a lot prettier), but just doesn't want to regret making the wrong choice.

The point is that the firedome graph is just marketing, not trying to promote one stove over another. I don't think that bogus marketing has a place in this discussion. It just confuses things.

FWIW, my wife fought getting a big stove for years. She now runs the T6 regularly, day after day and loves the stove. We don't see more than about 74F in the living room. Bottom line is that it's very possible to overanalyze getting a stove to death. One can not predict human habits. If your wife is cold and wants to burn to be warm, she will. And she will learn to run the stove because she wants to. My only advice has been to keep it simple.

 

[Ashful]

My only advice has been to keep it simple.

Definitely! Something I've never been good about.

5) That's a pretty tall order. You might want a pellet stove. Part of the charm of a non-cat woodstove is the heat cycles.

Wow! Thanks for all the info. In terms of item 5, I can adjust the heating schedule to suit the technology. Since that part of the house is empty at least 100 hours out of each 168 hour week, I was just driving at the fact that there is an opportunity to burn very low for the majority of the time, only requiring high heat output at select times. No need to keep the joint at 70*F when we're upstairs asleep or away from home.

 

[neumsky]

Maybe I was doing something wrong but I've burned many EPA non cats and it seemed like I was always tweaking the air control to find that sweet low burn spot. There wasn't many times where it was just set and forget unless I was burning at a higher rate, I always had more success controlling the output of my non cats by the amount of wood in the stove verses a full load and air control.

I also never thought the non cat tube stoves had the better looking fire. To me it almost looks unnatural like a gas grill. I get plenty of slow lazy floating secondary flames when I want them, just depends on where my air is set.

Todd my jotul has the low & slow lazy floating secondary flames as well as our PE Spectrum did. Beats the old Dragon Burners of old, doesn't it? What a beautiful site!

 

[neumsky]

Definitely! Something I've never been good about.



Wow! Thanks for all the info. In terms of item 5, I can adjust the heating schedule to suit the technology. Since that part of the house is empty at least 100 hours out of each 168 hour week, I was just driving at the fact that there is an opportunity to burn very low for the majority of the time, only requiring high heat output at select times. No need to keep the joint at 70*F when we're upstairs asleep or away from home.

Joful...are you not happy with the Jotul? is it a cat or noncat model...does Jotul make a cat model?

 

[Highbeam]

Since that part of the house is empty at least 100 hours out of each 168 hour week, I was just driving at the fact that there is an opportunity to burn very low for the majority of the time, only requiring high heat output at select times. No need to keep the joint at 70*F when we're upstairs asleep or away from home.

Even though there is no need to keep the joint at 70 all the time, it might make life easier. The extra wood is not significant but the extra effort of trying to jack around with temps can drive you nuts. We generally accept a room temp between 65 and 78 as being normal during our 9-10 month burning season whether we're home or not. I have wood coming out of my ears, it's not about firewood, this isn't like a propane tank where I have to conserve fuel.

 

[neumsky]

Even though there is no need to keep the joint at 70 all the time, it might make life easier. The extra wood is not significant but the extra effort of trying to jack around with temps can drive you nuts. We generally accept a room temp between 65 and 78 as being normal during our 9-10 month burning season whether we're home or not. I have wood coming out of my ears, it's not about firewood, this isn't like a propane tank where I have to conserve fuel.

We have tv's in other rooms lol

 

[Blue Vomit]

In my case, the wrong choice has nothing to do with having to spend money to replace a stove two years after installation, and everything to do with turning the wife off on woodburning, should we end up with a stove that's any less than "phenominally easy" to control. If I buy a VC cat stove, and it behaves well but falls apart in two years, no biggie. That's easily chalked up to a junk stove, and maybe the BK Ashford will be available by then as a replacement. If I get a stove that routinely roasts us out of the house, has wide temperature swings, requires frequent small loads to keep temperature at a moderate level in the shoulder seasons, she'll be done with burning inside one season. I imagine anyone who's been married can understand.

The wife running the stove when I am gone was a huge part of the decision when we purchased the Oslo. She doesnt have much interest in wood burning and that doesnt bother me at all. She has enough to worry about with the kids, dog, laundry, house, cooking, etc. I wanted her to be able to throw some wood in, close the door, set the air in a few minutes, and wait till I get home without worry. I picked the Oslo beacuse it has a chit simple, near bulletproof, forgiving reputation, and it looks great. I know she's not going to do everything perfect and I dont expect her to. I'm also pretty confident she's not going to hurt that bad boy either. The Oslo isnt exactly delicate.

 

[SteveKG]

Maybe I'm about to learn something here. I've been heating exclusively with wood since the mid-70s. All my stoves are and have been non-cat. I know nothing about using a cat stove. One of our stoves is "airtight" and the others are not. Or, not really.

Anyway, the deal is, I build and light a fire in a stove, adjust the air intake a couple of times as the initial fire burns toward and reaches a reasonably steady state, and that's it. Occasionally, I add a piece or two of firewood. Every couple weeks, clean out the ash bin.

If I need to increase the heat output of the stove, add more wood. If the stove is putting out more heat than I want or need, I close down the air intake some and don't add more wood.

I can't imagine anything easier. Perhaps a pellet stove, but as with cats, I know nothing about them except what I've read.