Controlling the non-cat stove

[neumsky]

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.

Gotta know ...blue vommit??? Also...great stove!

 

[Ashful]

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

My Jotul is the catalytic predecessor to the big Firelight 600. Looks identical on the outside, but has a cat hiding in the back. I am very happy with it, and have been trying very hard to find another for the other half of the house. When you burn a 20 year old stove, there is an appreciable advantage to having two of the same unit. You can always steal parts off one to fix the other, if one breaks mid-season and parts are on backorder from Norway.

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...

Good to know. We have a lot in common!

So, going back to my prior statements, some right and some wrong:

1. A non-cat stove settles in for a nice long cruise, just like a cat stove, but at a higher cruising temp. By the time the secondaries go out, the creosote-producing compounds are typically depleted anyway.
2. There is some temperature swing associated with non-cat's, but Harman grossly exagerates the magnitude.
3. Some adjustment of primary air may be preferred to maintain even heat output, but is not really necessary in most circumstances. Can be "set and forget", like a cat stove.
4. Perhaps my one valid concern, the sizing of a non-cat stove relative to the room or house is more critical than a cat stove. Whereas a given mass of wood will always have a fixed BTUh, a cat stove offers far more control on the rate those BTU's are released.
5. Low heat output from a non-cat stove means smaller loads, and hence, somewhat shorter shoulder-season burn times than a similar cat stove. A minor point for most with central heating as backup, since the furnace won't have to work that hard pulling backup duty in the shoulder season.

Am I coming around?

 

[neumsky]

My Jotul is the catalytic predecessor to the big Firelight 600. Looks identical on the outside, but has a cat hiding in the back. I am very happy with it, and have been trying very hard to find another for the other half of the house. When you burn a 20 year old stove, there is an appreciable advantage to having two of the same unit. You can always steal parts off one to fix the other, if one breaks mid-season and parts are on backorder from Norway.



Good to know. We have a lot in common!

So, going back to my prior statements, some right and some wrong:

1. A non-cat stove settles in for a nice long cruise, just like a cat stove, but at a higher cruising temp. By the time the secondaries go out, the creosote-producing compounds are typically depleted anyway.
2. There is some temperature swing associated with non-cat's, but Harman grossly exagerates the magnitude.
3. Some adjustment of primary air may be preferred to maintain even heat output, but is not really necessary in most circumstances. Can be "set and forget", like a cat stove.
4. Perhaps my one valid concern, the sizing of a non-cat stove relative to the room or house is more critical than a cat stove. Whereas a given mass of wood will always have a fixed BTUh, a cat stove offers far more control on the rate those BTU's are released.
5. Low heat output from a non-cat stove means smaller loads, and hence, somewhat shorter shoulder-season burn times than a similar cat stove. A minor point for most with central heating as backup, since the furnace won't have to work that hard pulling backup duty in the shoulder season.

Am I coming around?

Sounds like you've pretty much nailed it! I do know when I spoke to BK a couple of years ago...they said there smallest stove was too big for my application...I've got an Oslo now...go figure!

 

[begreen]

I'd add that a stove with more mass will generally cause less room temp swing, cat or non-cat. It will be a slower to warm up and will continue to release heat even after the fire has died down. This is a characteristic of soapstone stoves and cast iron clad steel stoves.

 

[BrotherBart]

The best burn in a non-cat is when that "secondaries" light show is a non-event. Just let that secondary air injection pick off stray gasses up at the baffle in a nice even burn. If I get jets blowing in front of the tubes I screwed up. Wasted wood and heat. Not to mention the pucker factor when the thermo heads for the moon.

As far as the 1100 degree thing that is inside the firebox on a non-cat and in the cat chamber on a cat. Personally I like the heat distributed over the whole stove body. Not concentrated in the cat chamber and having to spread to the rest of the stove.

Just me.

 

[neumsky]

The best burn in a non-cat is when that "secondaries" light show is a non-event. Just let that secondary air injection pick off stray gasses up at the baffle in a nice even burn. If I get jets blowing in front of the tubes I screwed up. Wasted wood and heat. Not to mention the pucker factor when the thermo heads for the moon.

As far as the 1100 degree thing that is inside the firebox on a non-cat and in the cat chamber on a cat. Personally I like the heat distributed over the whole stove body. Not concentrated in the cat chamber and having to spread to the rest of the stove.

Just me.

BB what does that mean...jet blowing in from the front and stray gasses up in the baffle. You say you screwed up...how does this happen? Also...what your saying is is you prefer not using the cat on your cat model?

 

[BrotherBart]

BB what does that mean...jet blowing in from the front and stray gasses up in the baffle. You say you screwed up...how does this happen? Also...what your saying is is you prefer not using the cat on your cat model?

All I am saying is that I don't try for the intense secondary burn up in the baffle like a lot of people do. Will see what I mean when you put that stove to work.

 

[neumsky]

All I am saying is that I don't try for the intense secondary burn up in the baffle like a lot of people do. Will see what I mean when you put that stove to work.

Which stoves do you still have and your referring to a baffle such as??? I'm sure I only have tubes?

 

[BrotherBart]

Which stoves do you still have and your referring to a baffle such as??? I'm sure I only have tubes?

The baffle is the thing on top of the tubes. You have one. I still have all of them in the long list. I need to get rid of a few.

 

[neumsky]

The baffle is the thing on top of the tubes. You have one. I still have all of them in the long list. I need to get rid of a few.

Holy crap Batman...I'm jealous...and on the other note...yea...did not know if all had this baffle or not. We had a PE that had what I call a baffle.

 

[begreen]

A baffle is just a flame block that lengthens the flame path. It forces the flame to mix better with combustion air. Many stoves use a set of tubes with air holes under the baffle to introduce secondary air into the flame. The PE baffle is unique in that it fully encloses the secondary air manifold + baffle and insulation in a stainless steel baffle box that's removable as one unit.

 

[neumsky]

A baffle is just a flame block that lengthens the flame path. It forces the flame to mix better with combustion air. Many stoves use a set of tubes with air holes under the baffle to introduce secondary air into the flame. The PE baffle is unique in that it fully encloses the secondary air manifold + baffle and insulation in a stainless steel baffle box that's removable as one unit.

BG.. Is this something you've learned along the way... Or is there a book or video you or someone else enjoy's?

 

[BrotherBart]

Or is there a book or video you or someone else enjoy's?

It's called hearth.com.

 

[neumsky]

It's called hearth.com.

Good enough for me.

 

[begreen]

That's right. Craig has a lot of good articles here:
https://www.hearth.com/what/specific.php

John Gulland has good articles here:
http://www.woodheat.org/

and the Woodburner's Encyclopedia by Jay Sheldon is a worthy read for sure.

 

[neumsky]

That's right. Craig has a lot of good articles here:
https://www.hearth.com/what/specific.php

John Gulland has good articles here:
http://www.woodheat.org/

and the Woodburner's Encyclopedia by Jay Sheldon is a worthy read for sure.

Thank You...will look into both

 

[neumsky]

Ok...Craig...is the very info we have on hearth.com's site

 

[firefighterjake]

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.

I can never remember at what temp the secondary burn manifests itself . . . all I know is when the needle on my probe thermo in the double wall pipe gets into the "green zone" I slowly turn down the air on the Oslo . . . going down a bit by bit . . . until usually somewhere at the quarter mark to fully closed I get a nice, sustained, secondary burn . . . which lasts for a decent amount of time.

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.

I'm basically lazy at heart. Only time I fiddle with the air control is when I've started a fire or have done a reload and if the truth be told if the fire has been burning for awhile a lot of times I can get away with just adding wood, letting the fire take off with the air open all the way and then cutting back the air to the quarter mark or all the way shut in one move (vs. shutting it down in quarter mark increments) . . . after that I don't mess around with the air control as long as the secondary is going well.

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.

I would guess that most stoves -- cat or non-cat -- should be sized properly. I think a more important factor in heat output is how much wood you put in the stove, how often you reload and what you put in the stove for wood in terms of species, size of the splits and how much cubic space the fuel takes up (in which case size may or may not be a factor.) For example, in a few months I'll be putting in partial loads of my chunks, punks and uglies and for those first few fires I will just be doing the one fire . . . or maybe a single reload . . . and then letting the stove warm up the place. Later in the Winter I will be going 24/7 with the woodstove, using my prime wood and capitalizing on the space in the stove for longer burns.

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.

Possibly . . . depends on the size of the stove . . . insulation in the home . . . etc. Honestly, where I live, with my house and my needs I could not get by with just two loads a day.

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.

 

[neumsky]

That's right. Craig has a lot of good articles here:
https://www.hearth.com/what/specific.php

John Gulland has good articles here:
http://www.woodheat.org/

and the Woodburner's Encyclopedia by Jay Sheldon is a worthy read for sure.

Looks like the woodburners encyclopedia is out of print and it looks like you can get one if you can find one anywhere from 45 dollars to 115 dollars...whew...is this book that good...if so....why is it out of print?

 

[Highbeam]

The best burn in a non-cat is when that "secondaries" light show is a non-event. Just let that secondary air injection pick off stray gasses up at the baffle in a nice even burn. If I get jets blowing in front of the tubes I screwed up. Wasted wood and heat. Not to mention the pucker factor when the thermo heads for the moon.

Good stuff here. What can you or have you done to minimize the secondary show? What is the error that causes the run away stoves. In my observations, that huge secondary show is indeed from a rapid blow off of fuel gasses. If there is a trick or method that keeps the fuel in the log for a longer time then burn times may be extended. Certainly you have more control when the secondary fires are smaller.

It's a runaway because that larger secondary fire bakes the wood more which releases more wood gas faster which makes a bigger secondary fire, and on and on to a runaway. This is because in most stoves, the secondary air is at full throttle so this fire feeds itself.

The baffle does more than just create a longer path for smoke to travel. It is insulated to reflect and intensify heat in the area just above the fire, where the air tubes inject oxygen. This superheated area makes it easy for the fumes to ignite into a secondary fire.

 

[Todd]

Good stuff here. What can you or have you done to minimize the secondary show? What is the error that causes the run away stoves. In my observations, that huge secondary show is indeed from a rapid blow off of fuel gasses. If there is a trick or method that keeps the fuel in the log for a longer time then burn times may be extended. Certainly you have more control when the secondary fires are smaller.

It's a runaway because that larger secondary fire bakes the wood more which releases more wood gas faster which makes a bigger secondary fire, and on and on to a runaway. This is because in most stoves, the secondary air is at full throttle so this fire feeds itself.

The baffle does more than just create a longer path for smoke to travel. It is insulated to reflect and intensify heat in the area just above the fire, where the air tubes inject oxygen. This superheated area makes it easy for the fumes to ignite into a secondary fire.

Maybe a pipe damper can slow it down? The more that chimney starts to pull the more intense secondary air gets pulled in. Maybe even modifying the secondary intake so you have some control.

 

[BrotherBart]

Best thing I did was figure the difference between my 22 foot chimney and the 15 foot one the stove was designed for. Then blocked off that percentage of the secondary air intake. Made for a much more manageable stove and still no smoke with dry wood.

http://www.gulland.ca/florida_bungalow_syndrome.htm

 

[Highbeam]

So mods to reduce the draft and the intake setting are what you did to help keep the secondaries from going nuclear which wastes fuel. I don't have a problem with it but can agree that having an ideal chimney setup means good performance in all conditions and a little too good performance in ideal conditions like cold weather.

So the draft damper was born.

 

[BrotherBart]

No draft dampers here. I hate the things. For more reasons than the just the pain they are at chimney cleaning time. Like that air leak at both ends of the shaft.

 

[neumsky]

So mods to reduce the draft and the intake setting are what you did to help keep the secondaries from going nuclear which wastes fuel. I don't have a problem with it but can agree that having an ideal chimney setup means good performance in all conditions and a little too good performance in ideal conditions like cold weather.

So the draft damper was born.

I had issues with my PE with it wanting to runaway and so finally bought a damper...little piece of mind!