Efficiency Riddle

[kwa]

Below are two steel convection type stoves. One was rated with the current method and the other with the New B415 method. Both have the same size firebox.

Based on just these number which would you pick? Stove A or B? "none" is not an option.

Do you think one will perform better than the other or about the same?

After enough replies I will post the name of each stove and the rest of their ratings. Maybe the answers will surprise you, maybe they won't, but it would be interesting to see nonetheless.

 

[Todd]

I know what stove A is but wouldn't pick either til I found out which has a longer burn time.

 

[jeff_t]

Yeah, trying to figure out what B is.

 

[Highbeam]

The "current" method could be any one of several possible methods used in the recent years. As such, it is totally bogus.

 

[kwa]

The "current" method could be any one of several possible methods used in the recent years. As such, it is totally bogus.

I guess you are right. I don't know enough about all the various methods to say if it is bogus or not. All I can say is I wish somebody would pick a standard that makes sense to the average Joe and stick to it. Sure does make it hard to pick a stove.

I guess the real question is will a stove rated using the B415 method perform closer to the actual published specs or the ones using the other methods?

 

[BrowningBAR]

To me, I do not care about efficiency or emissions, and we all know burn time numbers are vague. All I go buy is actual firebox specs and the burn technology behind it.

 

[Highbeam]

All are quite efficient. They have to be in order to meet the emissions requirements. Of the two you list, the catalytic will always be more efficient in the low burn but similar at moderate to high burns.

Look at the burn times. 9 hours vs. 20 hours for the same amount of wood. That's at low burn rates of course but it is obvious to me that the more desirable stove is the one that has the ability to burn for a longer time.

 

[woodchip]

To me, I do not care about efficiency or emissions, and we all know burn time numbers are vague. All I go buy is actual firebox specs and the burn technology behind it.

My thoughts exactly, type of wood and time seasoned is far more important to me than a percent here or there or a gram of emissions here or there.........

 

[kwa]

I agree. I am not concerned with emissions so much as advertised burn time. One stove says 20 hours on low and the other 9 hours on med.low.

Just curious were reality is. If the 20 hour stove was tested at med.low using the same standard as the other stove would they then be more comparable in the real world as far as burn time? Maybe you would only get 9 hours out of the 20 hour stove using the same method. I don't know.

As someone has noted in another thread, when the temp goes down you will turn the stove up. So is it realistic to think that you will burn on low all the time? And if not, then why use that number if it is not what the average person will actually do?

Maybe they should all use the same method and post scores for high, medium, and low and let the buyer decide which best fits their environment.

Not looking for answers to the questions above, just thinking out loud. I don't think they can be answered accurately because the data either does not exist or it does exist and has not been published. Either way, it leaves a lot of questions unanswered for those buyers that don't just take things at face value and run with it.

 

[fox9988]

In theory, the two stoves have the same size firebox, therefor hold the same amount of btu's (wood). Producing the same amount of btu's, the two stoves will have the same burn times, if equally efficient. Low burn rates allow you to control heat output on a warmer day to preventing short fires/relights, and prevent overheating a small space, with a big stove. Long burn times reflect how long the stove can stretch out those btu's. Some advertised burn times are exaggerated, BK's are not.

 

[Backwoods Savage]

Efficiency ratings are just something to throw around and are meaningless to most folks.

In the end, the bottom line is: Will this stove heat your home?

 

[laynes69]

B415 is Canadian clean air standards, just like the EPA certified for the U.S. If I recall, the new B415 test uses seasoned cordwood. What I've heard is the B415 method is closer to a real world results due to the use of cordwood.

 

[Waulie]

Efficiency ratings are just something to throw around and are meaningless to most folks.

In the end, the bottom line is: Will this stove heat your home?

This. Efficiency does matter, but not nearly as much as the function of the stove. For example, if you're in Virginia or the Pacific Northwest, the ability to burn for 20 hours on a very small load (i.e. a very low heat rate) means more than it does to someone in northern Michigan or Alaska. A set amount of wood can produce a set amount of heat. The more efficient the stove, the more heat you will get out of that wood. But, the higher the heat rate you need from that amount of wood, the less burn time you're going to have. It's really not that complicated. If I had a Sirocco, I would only be able to use 20 hour burn times for maybe a month each season as it just isn't going to be enough heat for me the vast majority of the time. The rest of the winter, I would be refilling that stove pretty darn often as 1.8 cft just isn't very much wood.

 

[fox9988]

Agreed Waulie. I'm on the other end of the spectrum. I have a large pre-epa that has worked well for the past 30 years. I moved it to a new, well insulated, tight house and, It will do ~30hour burns (probably, I've never burned it this way) but smokes and makes Large amounts of creosote. In the old house it wasn't a problem because it was burned much hotter. In my mild climate, with my house, I need long clean burns that don't make creosote or overheat my house. I don't think I can get this without a cat stove.

 

[kwa]

That makes sense. If two stoves have the same size firebox and used the exact same type and amount of wood then they would start out as equals.

After the fire is lit, it comes down to how efficiently the stove allows the wood to burn and how many btu it can put into your home over time vs. going up the chimney.

That is where the various technologies and stove materials come into play. Looking at it that way I think it will be easier to evaluate various stoves and determine which is a better fit for a given scenario.

 

[fox9988]

That make sense. If two stoves have the same size firebox and used the exact same type and amount of wood then they would start out as equals.

After the fire is lit, it comes down to how efficiently the stove allows the wood to burn and how many btu it can put into your home over time vs. going up the chimney.

That is were the various technologies and stove materials come into play. Looking at it that way I think it will be easier to evaluate various stoves and determine which is a better fit for a given scenario.

IMHO-exactly!

 

[Ashful]

I go with the one that's not an ugly steel box.

Could not care less about a minute difference in emissions between two EPA-qualified stoves. Burn times, range of control, and something that doesn't make me cringe every time I walk past it are all that matter.

 

[Todd]

Both stoves will heat a similar size but IMO the BK will do better in a warmer climate or shoulder season temps because it has the advantage of a lower BTU output and long burns. Controlling the output of the Rainier in more moderate temps would be by the amount of fuel you load in the stove. In cold weather both will be about equal in burn times and output.

Something else to consider, if you want to burn low and slow all season long it would be easier to step up in stove size with the BK because of the t-stat control which allows you not to over heat the place and maintain the long burns. So maybe you might want to compare the differences between the Rainier and the new Sirocco 30, Ashford 30 or Princess?

 

[Huntindog1]

Some thoughts, some stoves are better at getting their heat out into the room. Is there a rating for that?

Some stoves store their heat and release it over a longer period of time like soapstone.

I would say in most cases stoves have excess heating capability as people tend to buy more stove than they need, so efficiency isnt an issue.Your not trying to squeeze every little bit of heat out of the stove.

Efficiency may come into play if you want to cut less wood.

Lastly remember where we came from old stoves were only 30% efficient.

 

[Highbeam]

That makes sense. If two stoves have the same size firebox and used the exact same type and amount of wood then they would start out as equals.

After the fire is lit, it comes down to how efficiently the stove allows the wood to burn and how many btu it can put into your home over time vs. going up the chimney.

That is were the various technologies and stove materials come into play. Looking at it that way I think it will be easier to evaluate various stoves and determine which is a better fit for a given scenario.

You are about to find yet another trick in the stove industry. BTU claims. They are even more meaningless than efficiency ratings. BTU output of any stove is the same for a given size stove at a given temperature. A big hot box is a big hot box. So the btu ratings are nothing but a factor times firebox size.

Eventually you will discover that the only real variables are firebox size and technology (cat vs. non cat). Really, that's it.

 

[Huntindog1]

I went and looked up some things and it looks like the BTU rating is supposed to be for how much heats gets into the house.

I guess maybe I thought temperature readings were taken in the firebox and maybe on the stove surface and somehow calculated the BTU's.

I can see now how there could be lots of different ways to do it.

I wonder how all the insulated firebox stuff effects efficiency does that hold too much heat in the box and lets more heat travel out the stove pipe?

In another thread we were discussing putting the layer of insulation on top of the baffle board so as to get the firebox heated more quickly and maintain heat easier for the secondary burn.
Would that effect getting heat out into the room?

Check this out:
http://www.chimneysweeponline.com/btutest.htm

http://www.omni-test.com/publications/Efficiency_article.pdf

http://www.omni-test.com/publications/Efficiency_Eye.pdf

http://www.omni-test.com/publications/1 LHV HHV Variation rev10.pdf

http://www.omni-test.com/publications/ECAddendum (Revision September 2-2009).pdf

 

[Huntindog1]

Here is an interesting Sentence:

http://mb-soft.com/juca/print/311.html

For comparison sake, using LHV gives results about 8% higher that the same results using HHV. Thus, an 80% device (LHV) is 74% efficient using HHV. A 45% HHV reading is equivalent to about 49% LHV.

 

[kwa]

Those are good links. I've poked around chimneysweep.com before. Good info.

Now I'm looking at the Hearthstone Shelburne cast iron non-cat. One of the main driving factors for me between various stoves is clearance, even with shields I just can't make some of them fit my space.

So far I like the Hearthstone Shelburne because:

1. It looks like I can get it to fit.
2. It has a 2.0 cu. ft. firebox - about as big as I need for only 1000 sq. ft. space
3. All cast-iron and said to be "built like a battleship" by chimneysweep. (That's important to me)
4. I like the fact that cast iron can heat up quicker but also hold some heat after the burn. (The middle ground between steel and soapstone)
5. It's a non-cat which I think will be more forgiving if I have to use less than optimal wood at times.
6. Has a flat top I can use for warming/cooking if needed.
7. Long enough burn time to get through til morning.

So far it seems to meet all of my requirements for a rugged, attractive, low maintenance piece of equipment. It's still early though, something else could still catch my eye.

 

[Highbeam]

Those are good links. I've poked around chimneysweep.com before. Good info.

Now I'm looking at the Hearthstone Shelburne cast iron non-cat. One of the main driving factors for me between various stoves is clearance, even with shields I just can't make some of them fit my space.

So far I like the Hearthstone Shelburne because:

1. It looks like I can get it to fit.
2. It has a 2.0 cu. ft. firebox - about as big as I need for only 1000 sq. ft. space
3. All cast-iron and said to be "built like a battleship" by chimneysweep. (That's important to me)
4. I like the fact that cast iron can heat up quicker but also hold some heat after the burn. (The middle ground between steel and soapstone)
5. It's a non-cat which I think will be more forgiving if I have to use less than optimal wood at times.
6. Has a flat top I can use for warming/cooking if needed.
7. Long enough burn time to get through til morning.

So far it seems to meet all of my requirements for a rugged, attractive, low maintenance piece of equipment. It's still early though, something else could still catch my eye.

Yikes, maybe a new thread? My heritage is supposed to be 2.3 CF but actually measures under 1.5 CF. I can get overnight burns but just barely, I would not want a smaller stove if the intent was to make it overnight. The Hearthstone company has been good to me. The heritage is heavy but not a durable design in my experience.

 

[kwa]

Yikes, maybe a new thread? My heritage is supposed to be 2.3 CF but actually measures under 1.5 CF. I can get overnight burns but just barely, I would not want a smaller stove if the intent was to make it overnight. The Hearthstone company has been good to me. The heritage is heavy but not a durable design in my experience.

Wow! So not only do I have to question efficiency claims but firebox size as well? That's just great.......... lol