EPA vs. Pre-EPA: Fuel Consumption, a flawed, but meaningful experiment

[BrowningBAR]

Past few days I've been comparing the Heritage with the Vigilant in terms of how much fuel it goes through. My experiment is not perfect and neither is the accuracy. Reason for this is that I am awful at determining wood species, nor did I weigh the splits before inserting them into the stove. I've run this "experiment" three times. The vigilant was used as the time in which the reload was made. Reload time was determined by stove temp and ash bed. The experiment was not run consecutively as the Heritage would have gained an advantage as it had more coals and heating capacity upon reload.

Vigilant:
Fuel: 6 medium to large splits ranging from 20-23" in length
High temp of burn: 500 degrees all three times.
Temp in which the stove spent the majority of it's time: 450 degrees, 450 degrees, 475 degrees
Burn time: About 6 hours
Temperatures at reload: 300, 275, and just above 300 degrees

Heritage:
Fuel: 4 medium splits ranging in 17-19" in length
High temp of burn: 500, 500, 525 degrees
Temp in which the stove spent the majority of it's time: About 475 degrees all three times.
Burn time: About 6 hours
Temperatures at reload: 325, 325, 325 degrees (oddly consistent, but nice)

The Heritage is clearly using less fuel consistently. The second of the three times the Heritage had only 3 medium splits and what I would call a small split in addition due to the shape of the other splits. The high temps were intentionally limited to 500 degrees.

 

[johnstra]

Those are really good burn times from you Heritage. I could only get 4 hours or so out of a load of oak (15% moisture content) and that was with the primary all the way off. Looks like you're running about the same temperatures as me. How long do you let it run wide open before cutting back the air?

 

[BrotherBart]

I did a scientific experiment also. The last year with the old stove I burned six cords just like always. The second and every year after with the new stove I burned three. And the scientific measuring instrument I am married to says the place has never been this warm before.

 

[BrowningBAR]

Those are really good burn times from you Heritage. I could only get 4 hours or so out of a load of oak (15% moisture content) and that was with the primary all the way off. Looks like you're running about the same temperatures as me. How long do you let it run wide open before cutting back the air?

A few things:

1. I found that the Heritage can sit at 300-325 for quite some time. Far, far longer than the cast iron Vigilant.

2. I have it shut all the way down and I have the Key Damper closed also. Last night I had the stove loaded with the air shut off and the damper closed with the stove locked in at 550 degrees. I woke up 7-8 hours later with the stove at about 275 with plenty of coals. And my wood isn't perfect either. Each year it gets better, but I still have some "unacceptable" wood in my piles.

 

[BrowningBAR]

I did a scientific experiment also. The last year with the old stove I burned six cords just like always. The second and every year after with the new stove I burned three. And the scientific measuring instrument I am married to says the place has never been this warm before.

Also, the Heritage is less complicated with only one lever to mess with as oppose to the really complicated two levers of the intrepid cat stove!

 

[precaud]

And the scientific measuring instrument I am married to says the place has never been this warm before.

Now BB, you know it's not wise to marry your experiments, or any part thereof... ;-)

 

[joshlaugh]

That is a good experiment. I am in year 4 with my heritage and still improving on how I load it etc. I seem to get to about 450-475* with hickory but can't hit 500*. I can get it to cruise about 400* for a while. I usually add 3 medium splits, sometimes 4 and get a good burn for approx 4 hours. I usually reload at 300 degrees. I, too, notice that the stove can sit at 300* for quite a while. Good luck and I am glad that the stove is working out for you.

 

[Rob From Wisconsin]

Those are really good burn times from you Heritage. I could only get 4 hours or so out of a load of oak (15% moisture content) and that was with the primary all the way off. Looks like you're running about the same temperatures as me. How long do you let it run wide open before cutting back the air?

A few things:

1. I found that the Heritage can sit at 300-325 for quite some time. Far, far longer than the cast iron Vigilant.

2. I have it shut all the way down and I have the Key Damper closed also. Last night I had the stove loaded with the air shut off and the damper closed with the stove locked in at 550 degrees. I woke up 7-8 hours later with the stove at about 275 with plenty of coals. And my wood isn't perfect either. Each year it gets better, but I still have some "unacceptable" wood in my piles.

Interesting....
I've had several brands/types of stoves, and our current stove (Hearthstone also), is the only stove that I could get away
with "double dampering". As a matter of fact, I get some of my best/longest burns using this method. Is it characteristic
to soapstone stoves, or perhaps it is because I have a lined & "warm" flue??

 

[BrowningBAR]

Those are really good burn times from you Heritage. I could only get 4 hours or so out of a load of oak (15% moisture content) and that was with the primary all the way off. Looks like you're running about the same temperatures as me. How long do you let it run wide open before cutting back the air?

A few things:

1. I found that the Heritage can sit at 300-325 for quite some time. Far, far longer than the cast iron Vigilant.

2. I have it shut all the way down and I have the Key Damper closed also. Last night I had the stove loaded with the air shut off and the damper closed with the stove locked in at 550 degrees. I woke up 7-8 hours later with the stove at about 275 with plenty of coals. And my wood isn't perfect either. Each year it gets better, but I still have some "unacceptable" wood in my piles.

Interesting....
I've had several brands/types of stoves, and our current stove (Hearthstone also), is the only stove that I could get away
with "double dampering". As a matter of fact, I get some of my best/longest burns using this method. Is it characteristic
to soapstone stoves, or perhaps it is because I have a lined & "warm" flue??

I tend to have very strong drafts from all three chimneys, so I figured the damper was the right move. So far, so good.

 

[Renovation]

Thanks for a fascinating experiment.

If you're ever inclined to do it again, how about weighing the wood? It could be as simple as stepping on a bathroom scale with the wood in our arms before loading. Considering all the great data you took, that would give a better estimate of relative consumption, which would be fun to know.

 

[BrowningBAR]

I just got a 5 hour burn from 3 medium size splits. It maintained 500+ degrees for nearly 3 hours.


At this point I am using half the wood that the Vigilant is using

 

[Dune]

Thanks for a fascinating experiment.

If you're ever inclined to do it again, how about weighing the wood? It could be as simple as stepping on a bathroom scale with the wood in our arms before loading. Considering all the great data you took, that would give a better estimate of relative consumption, which would be fun to know.

Wouldn't really matter. The stove temp isn't telling the btu output.

 

[Renovation]

Thanks for a fascinating experiment.

If you're ever inclined to do it again, how about weighing the wood? It could be as simple as stepping on a bathroom scale with the wood in our arms before loading. Considering all the great data you took, that would give a better estimate of relative consumption, which would be fun to know.

Wouldn't really matter. The stove temp isn't telling the btu output.

Yessir, but at least it would be a bit more data. Agreed that it's really hard to do a controlled experiment with so many variables, including weather.

The best proxy for efficiency I can think of is flue temperature, imperfect as that is. I figure the heat has to go somewhere, and as long as the wood is burning completely and the heat's not going up the flue, it's heating the house.

Come to think of it, that's not even true. One if the claimed benefits of cats is that they burn gasses the EPA doesn't monitor, *yet*, like this chart:

http://www.chimneysweepnews.com/combustor-Envicat230.jpg

from this article: http://www.chimneysweepnews.com/Combustors.htm

So various combustion types and stove designs can extract more energy from a given amount of wood, even with the same flue temp.

Oh well, I guess we'll have to trust the EPA figures? And anecdotal evidence, like BrotherBart's and BrowningBAR's reports.

I now return you to your thread, already in progress.