Frustrated with exaggerated efficiencies and BTU output?

[John Ackerly]

We just wrote up a blog post on manufacturers who post reliable efficiency numbers on their websites and some that don't. Its really frustrating seeing all these exaggerated claims year after year. I thought the NSPS would bring some faster changes, but lots of companies are just ignoring some of its provisions - like posting a summary lab report of stove certified since May 15, 2015. (The NSPS is ambiguous on this and may apply to all stoves in production, but no one can dispute that stoves certified since May 2015 need to disclose their summary lab reports.)

http://forgreenheat.blogspot.com/2016/02/wood-and-pellet-stove-companies-that.html

The only companies we could find that post reliable efficiency numbers on their websites were Blaze King, Kuma, Seraph, Travis and Woodstock Soapstone. By "reliable" we mean the same numbers that an EPA accredited lab provided to the company. BTU output is the other big area and is important to help consumers right size their appliance. The EPA has been passing along very exaggerated numbers for way too long. We think the EPA should just drop all BTU output numbers on their list of certified stoves unless they are actual outputs produced by a lab using an approved calculation.

 

[DougA]

MY GAWD You want truth in advertising?

 

[begreen]

I note that the EPA is listing CSA B415.1 tested efficiencies for the new Regency hybrids. Jotul lists for all their stoves. PE like Travis only lists for some.

 

[branchburner]

We think the EPA should just drop all BTU output numbers on their list of certified stoves unless they are actual outputs produced by a lab using an approved calculation.

Even lab outputs aren't going to be that helpful to consumers that don't address poor draft, poor wood, or poor operation.

What would be more helpful is to list a variety of roughly estimated real-world outputs when using dry wood vs, green wood, or using a 28' sq inch flue vs. a 144 sq inch one. Then people would spend less time worrying about fantasy-world numbers and more time worrying about running their stove for peak performance and minimal emissions. They could just size their stove based on actual (useable) firebox capacity and burn technology, which is what many stove shops and forum members suggest, anyway. (I don't think I've ever heard anyone say "pay close attention to those BTU numbers", but plenty of people say "ignore 'em.")

It's pretty simple: cat stoves and cat/hybrids, when run properly, are going to have highest efficiencies and lowest emissions, and bigger fireboxes have bigger potential heat output. The EPA should post a statement to that effect and call it a day.

 

[3650]

Seems to me there are way too many variables to come up with a solid number that fits every application. Just thinking out loud.

 

[jetsam]

It's always nice to hear that you bought your stove from a good company! Thanks, BK!

 

[DougA]

IMHO just making a list of stoves that can accurately compare apples to apples is an enormous struggle.
Let's set sights on realistic goals first.
Comparing green wood vs seasoned wood vs dry wood is an exercise in futility given all the species and all the variables of dryness. I moved my chimney 20 ft from an existing one with the identical length and went from poor draft to overdraft. It's no different than people who get different results on mpg on the same car due to their driving habits. Realistic comparisons from accurate lab and real world experience would be an amazing goal.

 

[jetsam]

I would tend to think that for this reason, if you throw out the numbers that you got from the controlled conditions at the third paty lab and go with whatever the marketing department thinks, you are purposely obfuscating the issue.

You can say "well the real world is more complicated", but that doesn't change the fact that the test results from the lab using the same methodology should be fairly consistent.

If you read a couple lab test reports, they actually detail their methodology. (broken link removed to http://blazeking.com/TestReports/PrincessInsert_OMNI_web.pdf)

 

[John Ackerly]

Even lab outputs aren't going to be that helpful to consumers that don't address poor draft, poor wood, or poor operation.

It's pretty simple: cat stoves and cat/hybrids, when run properly, are going to have highest efficiencies and lowest emissions, and bigger fireboxes have bigger potential heat output. The EPA should post a statement to that effect and call it a day.

Yes, the case for pellet stoves is much stronger, since they operate in homes much closer than they do in labs, compared to wood stoves. If the EPA posted a statement, it would certainly help, but for pellet stoves, having actual BTU output would be really useful.

 

[AmbDrvr253]

I have to agree there are WAY toooooo many variables here. Though I do believe it is a good starting point to know that, under ideal conditions, the BTU output is helpful.

 

[branchburner]

for pellet stoves, having actual BTU output would be really useful.

Yes, a pellet stove (even though there must be some variation in pellet quality, too) is really akin to an oil burner or other mechanical heating technology, where the type of installation and variables in user input have far less ability to impact BTU output. But in addition to the variables of fuel quality, draft and operating technique, wood stoves are the only heating devices that deal with the burn cycle.

So, rather than a constant BTU output, you have a spike in heat output that then tapers off. Even if the maximum output and average output numbers from the lab end up being close to real world, it's hard for someone who hasn't already heated with wood to judge how those BTU numbers translate into how their living space will feel to them.

The nice thing about cats and hybrids is you have a greater ability to oversize your stove without overheating your space, getting more control over the heat spike in the burn cycle, with lower emissions as a bonus.

 

[Highbeam]

We can't even get accurate firebox volumes from most of the manufacturers and that should be mathematically certain.

 

[branchburner]

We can't even get accurate firebox volumes from most of the manufacturers and that should be mathematically certain.

Heck, Jotul won't put ANY firebox volumes in their brochures, accurate or not. But even with a precise volume, it can be hard to know the ease with which you can actually load the stove full, what with burn tubes and baffles and glass needing clearance. And whether it's top, side or front-loading can be a factor in the practicality of your split size.

I tend to cut my wood around 18", give or take. Two stoves I used had a firebox roughly 12x15x20, and one 12x15x24. But that extra half-foot of volume potential was largely unrealized unless I cut 4" longer!

I think knowing a ballpark range is pretty useful. To me, below 2 cu ft is small, 2-3 medium, and over 3 is large. For my house and climate, I would never need a large, and never want a small.

 

[begreen]

Many stove mfgs. provide firebox measurements of the entire area, including above the baffle. This is not helpful information. It does not reflect the burning capacity. What the consumer wants to know is how much wood can be loaded into the stove?

 

[nrc]

The problem with the EPA's BTU numbers, at least according to what I've read, is that they're just providing information on the BTUs that were produced during a test that is intended to measure efficiency and emissions. There is no effort there to burn for maximum heat output.

 

[Highbeam]

What the consumer wants to know is how much wood can be loaded into the stove?

That is one reason but mainly it's about heat output. Even if you can't utilize 100% of the firebox, a 3 CF stove at 600 degrees makes a certain amount of heat that is relatively constant across all material types and shapes. Rather than utilize EPA BTU numbers, the trend on this site (as it should be) is to compare firebox sizes. We know that a 1.5cf stove makes way less heat than that 3cf stove that is also a non-cat, plate steel, apples to apples.

 

[iamlucky13]

Even lab outputs aren't going to be that helpful to consumers that don't address poor draft, poor wood, or poor operation.

It seems to me we can boil the topic down to three alternatives:

1.) Trying to address in testing almost every possible test point. I'd contend the resulting set of numbers is almost useless because they span such a wide range of conditions that few, if any customers can correlate their own expectations to.

2.) Having a single (or very limited set of), standardized test point. It will be known not to be realistic for users under anything except ideal conditions, but if at least consistently performed between models and brands (at least to the degree that adherence to the testing standard is enforced), would be useful for comparison.

3.) Having no testing at all on the basis of the impracticality of applying limited tests to everyone's experience.

#2 is sort of the goal now, but is not consistently done.

I know there's also been talk about replacing or complementing the crib wood test with a cord wood test for better applicability to real world use, but as I understand it, not much progress has happened on this front because it is harder to control consistency.

It's pretty simple: cat stoves and cat/hybrids, when run properly, are going to have highest efficiencies and lowest emissions, and bigger fireboxes have bigger potential heat output. The EPA should post a statement to that effect and call it a day.

I more or less agree with you here. The EPA definitely should be clear about the general principals most likely to affect performance, and that test results do not guarantee real world performance. At least on one of most important matters - seasoned wood - they do offer a consistent message.

 

[stoveguy2esw]

one of the problems on the pellet stove side is that they for the most part were rated as "Exempt" for so long, so actual testing for emissions was not done, hey, it costs a fair amount of money to have it tested and quite a bit more in development. back in the day a manufacturer could just throw air at it until it burned "clean" (to the eye mostly) with regulations drastically reducing the areas where exempt stoves could be sold the industry is being dragged kicking and screaming into the "certified" age. problem this causes is that the vastly inflated BTU numbers advertised back then have literally been accepted as "gospel' by the consuming public, so when companies post the actual numbers they get KILLED in the marketplace (trust me I'm on the receiving end of this conversation constantly.)

the truth is most customers simply do not need the BTU outputs listed with the stove to heat their hoes to start with. I heat m little 1250 sq ft ranch here in Va. with an average output of less than 12K BTU/HR many folks are able to do it with even less. but when they shop and see the 27K max BTU output on the flyer and the stove they are replacing was "listed" by the manufacturer as a 60K BTU unit, they think "im not buying that thing it cant heat my house" even though their "60K BTU " unit was turned down to low most of the time and was probably only outputting a fraction of its (less than 60K BTU) capability. ive literally had to sit here and explain the math to folks more times than I can count.

as for woodstoves, a "real world" listing is a PIPE DREAM, there are far and away too many variables to even think even a moderately accurate representation could be achieved. even when burning wood of the same species literally the age of the tree the section of the tree , moisture content, chimney size and height, all will factor in and some will be larger factors than others.

think wood species, its weight per cubic unit of measure. for example, take a 1 lb block of balsa wood, it contains roughly 8500 BTU per lb of potential,now, a 1 lb block of locust contains roughly the same 8500 BTU of potential as well, however it is much smaller in size because the wood itself is vastly more dense. so, in a typical firebox one could load much more wood (by weight which is what matters) into it than they could with our balsa wood, so the output of the stove as well as its burn time will be vastly different.
I know this is an extreme example but it illustrates my point.

moisture, water don't burn, but it has to leave the wood before the wood will burn (remember the old adage about putting green wood in the fire for an overnight burn? it was done so the green wood would spend half the cycle cooking out the moisture before it actually burned.) moisture reduces output because the wood contains only so much energy and removing the water by flashing it to steam uses part of that energy budget evaporation is a cooling function, the steam sequesters energy and transports it out with the smoke so less is available to be conducted into the mass of the firebox, thus , it don't get in the home. now, with the loss of that fraction the firebox itself does not heat up as readily which means the wood is not heated as effectively and thus it does not outgas as readily (the outgassed wood is what's actually burning , not the physical log) so the energy release is retarded in this way as well. in secondary burn stoves this hurts even more because the heat loss as well as the moisture in the smoke prevents secondary combustion in a stove for a much longer period, so by the time the secondary's are firing the wood load is damned near spent.

I could go on and on, ive literally written chapters about these effects alone, im not going to bore you with the actual math, but the effects are astounding. (as anyone who has tried to fire a non-cat with green wood and got almost ZERO heat can attest)

 

[ddown]

I can't see where the EPA does much good in anything between power plants, diesel technology, Wood stoves, have they really made anyones life better?

 

[bholler]

I can't see where the EPA does much good in anything between power plants, diesel technology, Wood stoves, have they really made anyones life better?

Well our stoves are way better now than they were before the regs. Our cars are more efficient and run cleaner. Power plants run cleaner so yes they have improved life for just about everyone. Do i think they over step in some situations? Absolutely. Have they totally screwed up at times? Absolutely. But deal with those situations and don't over look the good that has come out of their work

 

[JA600L]

I can't see where the EPA does much good in anything between power plants, diesel technology, Wood stoves, have they really made anyones life better?

Absolutely. I work in a diesel equipment shop. There is a tremendous difference in air quality when somebody runs an older engine vs one made in the last 5 years. One gives you a headache, watery eyes, and nasty cough. The other could run a half hour before you begin to smell it. We turn the exhaust fans on either way. Be thankful that somebody out there cares about your health.

 

[iamlucky13]

There is a tremendous difference in air quality when somebody runs an older engine vs one made in the last 5 years.

I think it's more there's a tremendous difference in air quality when somebody runs a 5-15 year old engine vs. one made either in the last 5 years or more than 15 years ago

The latest regulations put a higher priority on nitrogen oxide suppression than on complete combustion. It alarmed me at first how many new-looking trucks I saw blowing visible smoke (but not enough that I think they were deliberately modded to "roll coal") until I looked into what the latest regulations were and what it takes to achieve them. In some instances, EPA regulations can represent significant progress. In some instances, they can make 2 steps forward and 3 steps back.

 

[3650]

EPA doesn't make sense to me when it comes to vehicles. In Europe cars get 60-80 mpgs and polute a little more. Here due ro all the emission controls vehicles get 12-30 mpgs. They burn cleaner but we use 3 times the fuel to go the same distance. Seems to me it evens out so the only one benefitting is the oil companies since we use 3 times as much.

 

[begreen]

How many cars in Europe get 60-80mpg? Yes there are some, but not many and remember they test for mpg differently than we do. That said, one factor that helps them achieve higher mileage is that they are content to drive smaller, lighter cars with smaller engines. That raises their overall average higher. The other difference is that they have many more diesel powered cars than here and many have manual transmissions.

 

[bholler]

Also your 12-30 for our cars here is pretty low I mean my 3/4 ton 4x4 work pickup gets 13 to 14. So what new vehicles get 12 mpg? Not many and there are many over 30 mpg here