EPA Ratings and Wood Usage/Heat Output?

[XmasTreefarmer]

I'm planning on replacing my old 1979 VC Defiant with a Jotul Oslo. Yes, after all of the posts about how much wood they burn and how little heat they produce, I'm still on it. I might be one of the slower members of the forum! Here's the setup and then my question:

I see numerous posts about how a BK will use 1/3 less wood than many stoves - including the Oslo. There are also many posts about how the Oslo, "eats a lot of wood". There have even been posts that say that the Oslo really produces very little heat! As you can imagine, I'd be pretty unhappy with a stove that burns a lot of wood and produces very little heat!

The Oslo has an HHV of 74% - a BK Princess has an HHV of 81%. That's a difference of 7%. That BK is doing some good stuff there, but it's only a 7% difference. How can that translate to using 1/3 less wood?

Trying to understand why I can't use the HHV ratings to get an idea of how efficient the stove is in terms of wood usage and how much heat it will put out from a given load of wood.

 

[Jan Pijpelink]

I am confused, I need a drink.

 

[Highbeam]

I went from a noncat to a bk and saved way more wood than the efficiency ratings would indicate. Maybe a 25% reduction. The difference is burn rate control, long burn times, and how efficiency is measured.

I can heat my house exactly as hot as I want it without wasting fuel by overheating. It burns so long that I don’t have to keep restarting new fires and wasting startup wood. At low burn rates, where it burns most of the time, the efficiency is even higher.

I burn a big noncat in my shop also. That thing just hogs the fuel!

I believe efficiency is tested at steady state so it ignores all the wasted warm up fuel. With a well behaved cat stove you just keep it warm.

Don’t worry too much about efficiency. We all burn 4-5 cords per year.

 

[XmasTreefarmer]

I went from a noncat to a bk and saved way more wood than the efficiency ratings would indicate. Maybe a 25% reduction. The difference is burn rate control, long burn times, and how efficiency is measured.

I can heat my house exactly as hot as I want it without wasting fuel by overheating. It burns so long that I don’t have to keep restarting new fires and wasting startup wood. At low burn rates, where it burns most of the time, the efficiency is even higher.

I burn a big noncat in my shop also. That thing just hogs the fuel!

I believe efficiency is tested at steady state so it ignores all the wasted warm up fuel. With a well behaved cat stove you just keep it warm.

Don’t worry too much about efficiency. We all burn 4-5 cords per year.

Ah ha! Thank you Highbeam - this is making sense to me finally! I can see now how a more even burning cat stove could save that "wasted wood" from restarts and overheating. And your point that the cat stoves can be down in the lower burn rates where the higher LHV rating is, picks up even more percentage points! Got it. Very insightful and understandable! And to think as a new member just a few months ago I didn't even know what HHV or LHV was! LOL!

 

[jotul8e2]

I have an Oslo - this is my ninth season.

A stove is not just a stove, it is part of a larger system that includes the species of wood burned, the combustion air supply, the flue, the relationship of the flue to the roof, and of course the physical space in which it sets. As a result generalities about any particular stove are always difficult.

My Oslo installation is very efficient. It routinely heats far more space than Jotul advertises. It is easy to work with and requires very little maintenance. I burn 24/7 for about three months and somewhat less for two more and use only about two to two and a half cords per year.

What the Oslo does NOT do is throttle back during warmer temperatures. A cat stove can do that, at least to a point. The advertised difference in efficiency may well be true, and no I would not make a decision based solely on seven percentage points difference in claimed efficiency. But is is also true that the ability to cut the burn rate back will provide more effective efficiency by reducing consumption when you do not need as much heat. As a corollary you also get better comfort by reducing the range of temperatures.

 

[Highbeam]

Ah ha! Thank you Highbeam - this is making sense to me finally! I can see now how a more even burning cat stove could save that "wasted wood" from restarts and overheating. And your point that the cat stoves can be down in the lower burn rates where the higher LHV rating is, picks up even more percentage points! Got it. Very insightful and understandable! And to think as a new member just a few months ago I didn't even know what HHV or LHV was! LOL!

On the HHV vs. LHV I’m not sure it’s just whether you’re on low vs. on high but one includes water. You want to use the 81% number.

The cat stoves get really clean and efficient on low.

 

[illini81]

Many noncat owners use their "backup" heating system when temperatures are > about 45. In these temperatures, you have to get creative with how you run your noncat stove, which increases the work involved. In addition to making your life easier, using your backup system in the warmest part of the shoulder season shouldn't have a huge impact on your heating bill, since the system isn't having to work very hard to maintain house temps.

Below about 45, it is not difficult to run a noncat without overheating your house (this is my experience, and from what I've read it is shared by many others, although of course probably not true for everyone - dependent on stove and house). As temperatures continue to get colder, the way you run a cat stove (in terms of frequency of loading) becomes more and more similar to the way you run a noncat.

In my opinion, if you use backup heat during the warmest parts of the shoulder season, the significant advantage of a cat stove disappears, and the difference is just that 7% difference you point to. Of course, if you'd like 100% of your heat to come from wood, this isn't an option. Also, if you live in a very mild climate where the temperature is > 45 for much of the winter, the advantages of a cat stove are a bigger factor.

 

[Woody Stover]

A rule of thumb I've seen is that compared to your old Defiant, a modern tube stove might only use 2/3 the wood and a cat stove might save you up to 1/2. But then there is the cost of replacing the cat every few years. If you go through a lot of cords and buy your wood, you should get back your cat money and then some. If you cut your own wood, you can put a value on your time, fuel and equipment wear and tear, and factor that in..

 

[jetsam]

What the Oslo does NOT do is throttle back during warmer temperatures. A cat stove can do that, at least to a point.

Yeah, but the point is about 65°F if you have the right stove. It's 60 today and I am burning right through it. I'll probably reload about this time tomorrow.

 

[XmasTreefarmer]

Many noncat owners use their "backup" heating system when temperatures are > about 45. In these temperatures, you have to get creative with how you run your noncat stove, which increases the work involved. In addition to making your life easier, using your backup system in the warmest part of the shoulder season shouldn't have a huge impact on your heating bill, since the system isn't having to work very hard to maintain house temps.

Below about 45, it is not difficult to run a noncat without overheating your house (this is my experience, and from what I've read it is shared by many others, although of course probably not true for everyone - dependent on stove and house). As temperatures continue to get colder, the way you run a cat stove (in terms of frequency of loading) becomes more and more similar to the way you run a noncat.

In my opinion, if you use backup heat during the warmest parts of the shoulder season, the significant advantage of a cat stove disappears, and the difference is just that 7% difference you point to. Of course, if you'd like 100% of your heat to come from wood, this isn't an option. Also, if you live in a very mild climate where the temperature is > 45 for much of the winter, the advantages of a cat stove are a bigger factor.

Thanks Illini. Your comments helped me to get a better handle on things. Especially how outside temperature affects what I'll call the cat stove "advantage". I can see how that sort of "disappears" a bit as it gets colder outside.

Like most of us I guess, I have to work a bit harder when the temps are above 40 degrees. Once we get down to the 20's or lower here in Southern WI, it gets much easier to burn my trusty old Defiant. I burn it all day and then load it up a bit before I go to bed and I have coals in the morning. For much of the heating season, I don't do that and just let the fire go out at some point in the day depending on the outside temp. Starting a fire in the morning has been part of my routine for the last 30 years or so and I must say I enjoy it.

I do like to "not run" my LP furnace - it's just the principle of not using LP if I don't have to - I like the financial savings, but even more I like the feeling of independence and the feel of wood heat. A person has to have heated with wood to understand the difference between furnace heat and wood heat. Some of my favorite fires of the year are my Spring and Fall "3 piecers". I could just run the furnace a bit, but instead I built a small fire with just 3 splits. It burns, drives some moisture out of the house, gets the house up to temp and I just let it go out.

All of this help I'm getting from members like you is getting me closer and closer to being able to make the right decision for me. Back in my 20's I burned an old sheet metal stove that was in a house I was renting. Then for 10 years I was moving every few years and didn't heat with wood. Then for the last 30 years I've been burning my old Defiant that I bought new in 1979. As you can see I don't swap stuff very often (to say the least), so I'd like to make this purchase my last wood stove and am really working to define what's important to me and then matching a stove to that. Thanks again for your insights.

 

[XmasTreefarmer]

A rule of thumb I've seen is that compared to your old Defiant, a modern tube stove might only use 2/3 the wood and a cat stove might save you up to 1/2. But then there is the cost of replacing the cat every few years. If you go through a lot of cords and buy your wood, you should get back your cat money and then some. If you cut your own wood, you can put a value on your time, fuel and equipment wear and tear, and factor that in..

Woody - A good way to look at it. I'm seeing this decision on a new stove as having basically 2 main parts: 1. Saving wood. I cut all of my own wood here on the farm. I'm very fortunate to have my wood available to me right here. I burn mostly Red Oak, Hickory, Red Elm, and some Ironwood. I burn 4 full cords each year heating exclusively with wood - sometimes a bit less in a warmer Winter and a bit more in a colder one. I've been hoping that I *might* get a 1/4 reduction in my wood use - going down to just 3 cords a year would be nice. I like making wood, but wouldn't mind not making quite as much! 2. Less fire starting/more even heat - I see now how a cat stove would give me that. As it turns out, I don't think that is high on my priority list. I am trying to do the "right" thing here - I really don't want to "miss the boat" and not get the best stove for my needs. Thank you.

 

[Woody Stover]

Yeah, but the point is about 65°F if you have the right stove. It's 60 today and I am burning right through it. I'll probably reload about this time tomorrow.

2. Less fire starting/more even heat - I see now how a cat stove would give me that. As it turns out, I don't think that is high on my priority list. I am trying to do the "right" thing here - I really don't want to "miss the boat" and not get the best stove for my needs.

I'm with ya on point 2. If it's 60 out, I'm letting the stove go and I'll "probably reload about this time tomorrow" anyway. If I don't have enough coals left to load onto, no big deal to start a fire...might even do a top-down load.
You're right to take your time, read and learn more, then make your decision later when you are confident that you are making a choice you'll be happy with over the long haul.

 

[illini81]

Sounds like you're really thinking this through, and enjoying the researching phase of the buying process. It'll be fun to see what you end up with. I'm curious - have you considered the Pacific Energy T6?

 

[Woody Stover]

I'm curious - have you considered the Pacific Energy T6?

They are supposed to burn long for secondary burn stoves. I guess it will depend what dealers are within range. I'd want to look at a stove in person first if possible.

 

[Highbeam]

Lots of good stoves to choose from. I have both a cat for the house and a big noncat for my shop which is actually bigger!

 

[Poindexter]

I think you will end up happy with your choice because you a) have experience and b) are asking the right questions.

I think the LHV/HHV numbers are useful in that the test conditions are the same for every stove, but no one actually lives in that house. So they are useless numbers to apply to your application, but useful to compare stove to stove.

I have operated many smoke dragons over the years, wrangled an EPA non cat for one season, have a cat stove in the house now, and within the limits of never say never, I would not willingly choose to go back to heating my house with a non cat.

Like Highbeam above, if I had a detached shop I was only spending time in on weekends, yup, I would drop a big old non cat in there and heat that area right up Saturday AM. If I was working out there full time I would put a cat stove in my shop too.

I can relate to the 3 split fire thing in the right season, the warm end of what is still shoulder season. I can load my cold stove about one third full, get it going, get the combustor engaged, leave it on full throttle for 30 minutes as called for in the manual, leave it on high and it will burn out in a couple hours. Then I have 500# of warm steel sitting on the hearth until tomorrow night, and a warm snuggly wife.

The upside to cat stoves is the higher flexibility. An EPA cert non cat will reburn or secondary burn the smoke particles down into low emission land efficiently, but the secondary burn chamber is going to be up around 1400dF or so. A cat stove will do the same low emissions, but with that little platinum coated brick of a combustor stable at 600 or 700 dF.

The down side to the cat stoves is the added complexity, extra parts, blah blah.

I burn about 8 cords annually. I replace my combustor about every two years, about 8-10k active hours. There are folks here getting 12 and even 16k active hours out of a combustor; I work mine like a rented mule. Honestly, compared to an EPA cert non cat I am burning enough less wood to drop $200 on a replacement cat every single year and still come out ahead just on wood usage, with the wider dynamic range of the cat stove just gravy.

The hardest part of running a cat stove, for me, was leaving the darn loading door closed. I spent hours and hours and hours with my grandpa in his shop, opening the loading door every 20-30 minutes and poking at the coal bed to get it just so. I cherish those memories, but the skill is detrimental to cat stove operation. The hardest thing for me to do was to put down the poker and walk away for 12 hours at a time.

If a non cat can meet your needs they are simpler stoves, fewer parts, and less stuff to break. My cat stove isn't quite as dependable as an anvil, but it is plenty more dependable than my Toyota.

 

[ratsrepus]

once you go cat, you'll never go back. At least that's my way of thinking. After 40 years and I cant remember how many stoves. I got my first cat stove. Remarkable

 

[XmasTreefarmer]

I think you will end up happy with your choice because you a) have experience and b) are asking the right questions.

I think the LHV/HHV numbers are useful in that the test conditions are the same for every stove, but no one actually lives in that house. So they are useless numbers to apply to your application, but useful to compare stove to stove.

I have operated many smoke dragons over the years, wrangled an EPA non cat for one season, have a cat stove in the house now, and within the limits of never say never, I would not willingly choose to go back to heating my house with a non cat.

Like Highbeam above, if I had a detached shop I was only spending time in on weekends, yup, I would drop a big old non cat in there and heat that area right up Saturday AM. If I was working out there full time I would put a cat stove in my shop too.

I can relate to the 3 split fire thing in the right season, the warm end of what is still shoulder season. I can load my cold stove about one third full, get it going, get the combustor engaged, leave it on full throttle for 30 minutes as called for in the manual, leave it on high and it will burn out in a couple hours. Then I have 500# of warm steel sitting on the hearth until tomorrow night, and a warm snuggly wife.

The upside to cat stoves is the higher flexibility. An EPA cert non cat will reburn or secondary burn the smoke particles down into low emission land efficiently, but the secondary burn chamber is going to be up around 1400dF or so. A cat stove will do the same low emissions, but with that little platinum coated brick of a combustor stable at 600 or 700 dF.

The down side to the cat stoves is the added complexity, extra parts, blah blah.

I burn about 8 cords annually. I replace my combustor about every two years, about 8-10k active hours. There are folks here getting 12 and even 16k active hours out of a combustor; I work mine like a rented mule. Honestly, compared to an EPA cert non cat I am burning enough less wood to drop $200 on a replacement cat every single year and still come out ahead just on wood usage, with the wider dynamic range of the cat stove just gravy.

The hardest part of running a cat stove, for me, was leaving the darn loading door closed. I spent hours and hours and hours with my grandpa in his shop, opening the loading door every 20-30 minutes and poking at the coal bed to get it just so. I cherish those memories, but the skill is detrimental to cat stove operation. The hardest thing for me to do was to put down the poker and walk away for 12 hours at a time.

If a non cat can meet your needs they are simpler stoves, fewer parts, and less stuff to break. My cat stove isn't quite as dependable as an anvil, but it is plenty more dependable than my Toyota.

Poindexter - Thanks for your clear description of some of the differences between EPA non-cat and cat stoves. You know how this all goes, you start to think you've got it down and then someone else presents information in a different way and you get it more - you get just a bit smarter about it all!

One of the things this stove search has done is made me think about how my current setup works (really well!) and what I want to "gain" with a new stove. The cracked fireback on my Defiant is what kicked this all off. So, I hope to gain: a view of the fire (which I don't have now unless I open the doors and put on the firescreen) and more efficiency: less pollution and using less wood. Those are really the two things I'm really after.

What I don't want to loose is: the look of the stove - we love how the Defiant looks in our home, the ease of operation - our wood storage and starting supplies are set up for a side-loader, the simplicity of my current stove - I actually like messing with the stove, and the comfort that our large thermal mass gives us - right now we use that big old hunk of cast iron to charge that up with heat each day and that gets us through the night, even though the fire goes out. With a cat stove, that thermal mass is probably not as important - but it's what I have, and it's what I'm used to.

As I blab on and on here ... if I could get a left-side load EPA Defiant with a cat and the stove was high quality - I would probably be done!

Lastly, I enjoyed your comment about time with your grandpa and stirring the fire. My first exposure to wood heat was in my early 20's when I helped the farmer across the road from me with various things. When we were done, we'd always end up around his little Round Oak stove with a beer in his garage. After that first experience, I was hooked on heating with wood. I put a wood burner in the house I was renting that very next year. Very fond memories of that time.

 

[jetsam]

You get over missing thermal mass pretty fast when you have a stove that actually burns for 20+ hours.

Of your bolded points- I don't get cosmetics and can't help you there. Fireview you will get from pretty much any modern stove you pick. Efficiency will be better on pretty much anything, but still varies widely, so your stove choice matters here. Conversely, you're going to lose a little simplicity, and how much depends on the stove you pick. It's a good trade.

Ease of operation and comfort depend on your stove choice, wood quality, and how you run the stove.

I'd suggest picking 6 stoves that you like based on the specs, and then reading owners' threads on all of them here on hearth. There's a lot of information that is not in the sales brochure.

 

[black smoke signals]

Finding a good source for wood is just as important! Not all wood is created equal where I live.

 

[XmasTreefarmer]

once you go cat, you'll never go back. At least that's my way of thinking. After 40 years and I cant remember how many stoves. I got my first cat stove. Remarkable

That's sure what I'm getting from the forum and from replies to my post. I do think that this is a case of me not knowing what I might be missing, having never had a cat stove. I am considering cat stoves - I had originally not included them as a possibility, wanted to keep things simple, but I do need to be a little more open minded - getting harder to do the older I get!

 

[XmasTreefarmer]

You get over missing thermal mass pretty fast when you have a stove that actually burns for 20+ hours.

Of your bolded points- I don't get cosmetics and can't help you there. Fireview you will get from pretty much any modern stove you pick. Efficiency will be better on pretty much anything, but still varies widely, so your stove choice matters here. Conversely, you're going to lose a little simplicity, and how much depends on the stove you pick. It's a good trade.

Ease of operation and comfort depend on your stove choice, wood quality, and how you run the stove.

I'd suggest picking 6 stoves that you like based on the specs, and then reading owners' threads on all of them here on hearth. There's a lot of information that is not in the sales brochure.

Thanks for your comment on that fact that my thermal mass would still help, but not be such a big factor if I was burning a cat stove. All of these little tips are so helpful. Makes me realize how ingrained my thinking is because of my 30 years of burning the same stove in the same house.

And your suggestion about a list of possible stoves and then looking at owner threads - excellent! I'm already doing it and am almost embarrassed to say I've probably logged over a 100 hours since November doing just that. It's been a blast and I've learned so much. Certainly about the different stoves, but one of the most important things is that I know just where to start with burning an EPA stove - that is huge

 

[XmasTreefarmer]

Finding a good source for wood is just as important! Not all wood is created equal where I live.

Hey - Love the car you used for your avatar!

Wood is the one thing that I'm totally set on. I am actually a tree farmer and I have about 55 acres of hardwoods in addition to my Christmas tree acreage, Enough trees go down in storms or die for one reason or another to keep me will stocked in firewood.

I have learned a lot about wood seasoning on the forum. I've always used the simplistic 1 year CSS for all woods except White Oak and Hickory and 2 years CSS for that. Never owned a moisture meter until a few months ago. What an eye opener! I brought in a split of Red Oak just yesterday that just felt a bit heavy. What a great opportunity to learn something! I left it in the house to warm up for a few hours and then split it again and tested it. 17% on the outside and just over 20% on the fresh split, so it was close, but no cigar! That was from a stack that was CSS for a year in the sun with good air circulation and then about 7 months in a covered shed with sides. Going forward I'll be using 2 years CSS in the sun and wind and then 7 months to a year in the shed. That should do it!

Now that piece burned just fine in my trusty old "smoke dragon" non-EPA VC Defiant, but that's not going to cut it in an EPA stove.

 

[jetsam]

"Thermal mass" can actually be a bad thing.

Common materials with high thermal capacity pretty much all have lower thermal conductivity than steel- specifically, cast iron, firebrick, soapstone. These are good crutches for a stove with very short burn times since they can absorb heat and release it slowly- but they're bad for a heater that you want to release heat quickly.

A long-burning modern stove doesn't want or need the crutch. If you want long lasting heat, turn it down. If you want lots of heat right now, turn it up.

That said, I do remember old cast iron smoke dragons putting off tremendous heat- but we went through a LOT of wood, and burned them hotter than was probably safe or good for the stoves. My grandmother used to aim for "just barely glowing" as her measure of a good fire.

 

[jetsam]

Hey - Love the car you used for your avatar!

Wood is the one thing that I'm totally set on. I am actually a tree farmer and I have about 55 acres of hardwoods in addition to my Christmas tree acreage, Enough trees go down in storms or die for one reason or another to keep me will stocked in firewood.

I have learned a lot about wood seasoning on the forum. I've always used the simplistic 1 year CSS for all woods except White Oak and Hickory and 2 years CSS for that. Never owned a moisture meter until a few months ago. What an eye opener! I brought in a split of Red Oak just yesterday that just felt a bit heavy. What a great opportunity to learn something! I left it in the house to warm up for a few hours and then split it again and tested it. 17% on the outside and just over 20% on the fresh split, so it was close, but no cigar! That was from a stack that was CSS for a year in the sun with good air circulation and then about 7 months in a covered shed with sides. Going forward I'll be using 2 years CSS in the sun and wind and then 7 months to a year in the shed. That should do it!

Now that piece burned just fine in my trusty old "smoke dragon" non-EPA VC Defiant, but that's not going to cut it in an EPA stove.

I have no issues with 20% wood, personally. Drier is better, but 20% falls into my acceptable range.

Any surplus cut xmas trees are a good source of wood, too. They burn hot and will dry in one year. It's a lot of processing for a small amount of wood given the tree size, though.

Maybe you could give me a tip in that department if you don't mind the threadjack: How do you reliably seed a field of firs/pines? I planted maybe 50 seedlings that I got out of the woods this summer, and I don't know that any of them are going to make it.