REAL WORLD GPH TEST

I think the link is dead. Never mind it worked finally

---edit by craig---

do this and you can see all the pubs:
http://www.omni-test.com/publications/

You can find exactly the stuff I was talking about mentioned in that study - for instance:

1. Another key finding of this study is that there is no correlation between actual emission rates of older stoves and their original certification value, that is, emission rates reported in the certification process do not represent emission levels of stoves in homes after extended use.

2. particulate emissions of the certified stoves evaluated in this study appear to have become higher with use

3. A key finding of this study is that total particulate emissions (GPH) cannot be used as a surrogate measurement for woodstove POM emissions (the bad guys- Polyaromatic Hydrocarbon Emissions).

4. No direct statistical correlation between emissions and wood moisture, burn rate or stove condition could be made due to the number of variables associated with real-world in-home use of woodstoves.
(in other words, all bets are off)

So there is some of the science. I hope this can help to educate those who think shopping by the numbers means anything.

Ah, and for a few words of science about my "cheating" guess:

"Although the effects of these factors have not been quantified, the overall concern is that EPA
NSPS testing can be manipulated and a practiced technician can prepare custom results."

And, for maybe the last time, the summary which I have always used as my guide to consumers:

"in summary, burning cordwood in-home under real-world conditions is unlike that conducted
following Method 28. The certification process should be viewed as a licensing process and it
needs to be emphasized that emission rates obtained from it are not closely correlated to
emissions from actual in-home use. "

So, please, buy any stove which is EPA certified and has a good reputation for standing up over years of use.

And to beat the dead horse even further, the enclosed chart shows what the stove put out - in comparison to their rated GPM by the manufacturer.

The Defiant Encore, which was rated 1.6 GPH by the manufacture, put out 24 GPH

The Pacific Energy Models (3 on the list) were rated at approx 4 GPH by the manufacturer....

one put out 5.23
one put out 4.40
and one put out 14.33

My goodness, learning something new every day.

My reaction is that it is a fascinating read, but they seemed to be getting a great deal of soup from very few oysters... 16 stoves is a TINY number, and I would wonder about problems with sample sizes to begin with. It seems that the data they said showed no correlation on things like wood moisture I think reflected the fact that the samples were so small that there simply weren't enough data points... All but one of the cat stoves were in the Portland group for instance, which had both higher emissions and higher moisture.

I would say the study is interesting but woefully inadequate to draw any meaningful conclusions from...

1. Need a MUCH bigger sample size, probably several orders of magnitude larger - more like 1600 stoves than 16

2. Need evidence that stoves chosen were representative of the population in brands, level of maintainance, useage patterns, wood moisture levels, etc...

3. Need more of a geographic spread to cover more climates.

4. It would have been interesting to bring the "impaired" stoves back into spec, and perhaps do the "missing" routine maintainance on the others and see how / if that helped the results, etc.

Gooserider

Webmaster said:

And to beat the dead horse even further, the enclosed chart shows what the stove put out - in comparison to their rated GPM by the manufacturer.

The Defiant Encore, which was rated 1.6 GPH by the manufacture, put out 24 GPH

The Pacific Energy Models (3 on the list) were rated at approx 4 GPH by the manufacturer....

one put out 5.23
one put out 4.40
and one put out 14.33

My goodness, learning something new every day.

Click to expand...

Web,,,,,WAY TOO SMALL a sample size AND I think that the Defiant getting the black eye at 15 times its certified output tells you something was wrong......plugged cat ot not being used properly or something else.....no other explanation for it being so out of wack......same can happen with cars...test one where the owner never changed or cleaned the PCV, air cleaner, plugs, etc and you get a polluting automobile......same with stoves....don't maintain the cat or use wet wood, etc, and you get bad results........and I don't buy that line about wood moisture not affecting GPH.........

It does make sense that the non-cat stoves would show the least degradation over time though, especially when not maintained well as they're the most simple and require the least user intervention. What doesn't make sense is the wide range of values seen. I have to wonder if the same fuel was used in all the tests.

No one would claim that 16 houses is a large enough sample.

However, the conclusions stand pretty well - that being that test result per current EPA testing do not correlate with stoves in the field using cord word. I agree that the Encore test stinks...and would think that if they tested 10 encores they would do much better.

But let's not quibble about what the original question and debate is/was!

The question was whether someone who bought a PE made the wrong choice and was going to pollute the world because they failed to choose the stove with the lowest numbers. We could argue what the definition of "is" is, but all the data shows and says the same thing, that being that published EPA testing numbers should not be used as a shopping comparison....end of that story (hopefully).

On a related subject, it is likely that VC stoves are designed with hard woods in mind since that represented BY FAR their largest market for the first 20 years (and probably still), whereas a lot of non-cats were "western" stoves designed for softwoods. Maybe Corie will educate us as to whether a typical manufacturer uses a lot of various wood species in the R&D process.

In any case, I think we can put this one to bed and get onto helping folks with their decisions and safety, etc.

The cat stoves sure seemed to pump some junk. If nothing else, the sample size shows a large difference between certified and actual numbers.

I agree, shopping "by the numbers" isn't real useful, which is why you might have noticed I do NOT consider EPA numbers in anything I've ever suggested, and don't plan to. At best they might be a far secondary consideration if choosing between two otherwise equally good stoves, which is seldom the case.

However looking at the study, I saw lots of stuff on the Encore in particular that made me suspicious.

1. They had less to say about that stove's condition than they did about many of the others, particularly the KF stoves. It felt like they didn't do as thorough a job evaluating it as the others. Among other things they mentioned rain leaking into one corner of the stove, but no discussion of what that might have done to it's condition.

2. It was one of the oldest stoves in the study, installed in '89, where most of the others were installed a couple of years later.

3. While they said nothing about the cat's condition beyond that it was cosmetically OK, it sounded like it was still the OEM cat, which may have been approaching EOL just from age.

4. The use descriptions weren't consistent with the amount of wood claimed to be consumed.

5. While drier than some of the other Portland stoves, they were still burning 25% moisture wood, which is worse than we reccomend here

6. They didn't give stove temps, but the stack temps they listed were pretty low, suggesting the stove was being run in "smoulder mode" most of the time, or at least at a much lower temperature than Elk claims to run his stove at.

7. While the chimney height was good, it was going into a masonry flue of unspecified size - might they have been pushing the cross sectional area?

8. They only had two weeks worth of data on that stove, most of the others had three.

Seems to me like any of these conditions could have been enough to cause the stove to do worse than a more typical Encore might have otherwise have done

Webmaster said:

And to beat the dead horse even further, the enclosed chart shows what the stove put out - in comparison to their rated GPM by the manufacturer.

The Defiant Encore, which was rated 1.6 GPH by the manufacture, put out 24 GPH

The Pacific Energy Models (3 on the list) were rated at approx 4 GPH by the manufacturer....

one put out 5.23
one put out 4.40
and one put out 14.33

My goodness, learning something new every day.

Click to expand...

for the record, the manufacturer doesnt make up the GPH rating on the cert card they put the GPH total specified by the testing agency on the cert card. this card must be attached to the unit when shipped to the dealer/ retailer. usually it is attached to the door to the unit. this tag with the proper GPH numbers and efficiency rating are required to be posted in this way by EPA. so , in reality the GPH rating is not by the manufacturer, but by the testing agency.

Does the testing agency also determine the EPA required efficiency on the label? My hearthstone had a low efficiency rating on its tage like 62% and no real description of the number. We see these types of labels and equate them with the "energide" ratings on water heaters, furnaces, and other appliances to actually mean something and have a bearing on energy consumption. If EPA knows that the figures are not to be used for purchasing decisions then they shouldn't force the manufacturers to label the stoves like that.

The labels even have the little bar chart that shows efficiency of 50-100% and an arrow pointing at the unit's performance.

You have to read the label really carefully when it comes to efficiency and also check to see if the manufacturer claims any. According to my limited knowledge, the EPA does NOT specify that a manufacturer test for efficiency, just for particulates. For many years, the hang tags used averages or else had arrows with blunt (flat) bottoms that gave a range.

Also, keep in mind all the former info about these stoves not being tested with cord wood in any real world situation. So even if the manufacturer did an efficiency test, it does not equate in any way to a "plug-in" appliance type of test.

Then there are the hundreds of other variables. We talked about how hot the rear and flue collars of the everburn VC got. In a situation like this, an installation with a lot of exposed single wall pipe could add 10% or more to the efficiency, while the same stove stuck back into a masonry fireplace with an exterior wall might suffer (this might be 60%, the one with pipe might be 70%+).

So, once again, your mileage WILL vary....and do not compare with appliance testing or automobile testing. As the real experts say, the test is basically a licensing one - meaning you either get your OK or not (pass-fail).

There is a lot of interesting reading in the Tiegs reports about the fact that stove manufacturers have NOT been improving their stoves due to a declining market and no real impetus to do so. I can show you a picture of an Avalon or a VC encore both from 1986 and you cannot tell the difference from today.

Notice tag pic - it says "Not tested for efficiency, the value given is for similar heaters....."

BB you crack me up, LOL.

Gooserider said:

I agree, shopping "by the numbers" isn't real useful, which is why you might have noticed I do NOT consider EPA numbers in anything I've ever suggested, and don't plan to. At best they might be a far secondary consideration if choosing between two otherwise equally good stoves, which is seldom the case.

However looking at the study, I saw lots of stuff on the Encore in particular that made me suspicious.

Click to expand...

This is starting to sound like a Clinton vs. Bush debate!

"I was suspicious when I found out that President Bush's brother was in charge of security at the WTC".......
"Was that Encore red? I heard they put out less heat".
"What was the IQ of the person firing that Encore?"
"Who has more ties to Al-Queda and the war machine - PE or VC?"
"Since they are both Canadian, did the fact that they have mandated health care affect the results?"

:coolgrin:

Bottom line - look at that tag, look at those studies - look at what the EPA and the scientists say. 100% of known data points to the fact that GPH should not be considered in a buying decision. If a customer wants to do so, that is their choice.....but IHMO it is foolish to go against all the studies and recommendations.

It appears that most EPA stoves operate at somewhere between 4 and 15 GPH in the field, depending on everything from the user to the weather to the age of the product. We could start a separate thread about how this might be improved. It is my guess that the wide variances are due to BOTH design and the other factors (operator, wood, climate, etc.).

But, as I have said many times, the best stoves would be more forgiving of these things. A dealer will often qualify a customer for some of them --- like "How are you going to use this stove?" or "Your chimney sounds sluggish, a hot burning non-cat might work best"....etc, etc, etc.

We've had people on this forum who removed their catalytic converters! So why should we assume people will replace them as they age? Typical consumer behavior says they will not (as a whole), especially if such replacement involves a high cost or a professional.

My guess is that 90% plus of current stoves are non-cat for this and other reasons. As other threads have covered, cats are great for certain things - long and low burns being foremost among them. But the excess costs and complexity (yes, even having to close a bypass is just one more step for the consumer) are making most casual wood burners steer toward non-cats. OTOH, stoves like the Woodstock and Blaze King and Encore are the favorites of those who do their research and need those qualities (long burn, etc.)

Webmaster said:

You have to read the label really carefully when it comes to efficiency and also check to see if the manufacturer claims any. According to my limited knowledge, the EPA does NOT specify that a manufacturer test for efficiency, just for particulates. For many years, the hang tags used averages or else had arrows with blunt (flat) bottoms that gave a range.

Also, keep in mind all the former info about these stoves not being tested with cord wood in any real world situation. So even if the manufacturer did an efficiency test, it does not equate in any way to a "plug-in" appliance type of test.

Then there are the hundreds of other variables. We talked about how hot the rear and flue collars of the everburn VC got. In a situation like this, an installation with a lot of exposed single wall pipe could add 10% or more to the efficiency, while the same stove stuck back into a masonry fireplace with an exterior wall might suffer (this might be 60%, the one with pipe might be 70%+).

So, once again, your mileage WILL vary....and do not compare with appliance testing or automobile testing. As the real experts say, the test is basically a licensing one - meaning you either get your OK or not (pass-fail).

There is a lot of interesting reading in the Tiegs reports about the fact that stove manufacturers have NOT been improving their stoves due to a declining market and no real impetus to do so. I can show you a picture of an Avalon or a VC encore both from 1986 and you cannot tell the difference from today.

Notice tag pic - it says "Not tested for efficiency, the value given is for similar heaters....."

Click to expand...

actually, EPA does ensure that a minimum efficiency is met. the manufacturer can test for a "certified efficiency rating" however this test is quite expensive and requires frequent re-testing so few manufacturers will go there. the listed efficiency rating reflected on the hang tag is actually considered "default" meaning that the unit met the minimum required for the type of unit it falls under.(different types of units have different minimums required) in other words the unit did at least meet the percentage listed, likely exceeded it but the manufacturer accepted the default rating rather than go through the certified actual efficiency ratings testing.

EDIT: as for the car analogy, how many cars are on the road today that have far higher emmissions simply because they have 2 year old oil in the crankcase and the same air filter that the manufacturer installed at the factory? i bet the actual answer to that question would amaze anyone. (personally im very anal about oil changes ive stopped at jiffy lube on road trips in the past ,now i just get oil and filters changed before any appreciable road trip even if its ahead of schedule)

Car info, yes cars increase pollutants over time but states like us in NY have to pass emissions tests EVERY year (if you fail your car cant go on the road untiul repaired, our stoves do not.

Because its a source of income.