Got my new stove!!!

franco b wrote:

lobsterman wrote:It is totally agreed that the DS machine is a more powerful heater than the Chubby. No comparison, no argument. My point is the higher heat output can only come from burning more coal per hour.

As the heat output goes up the DS Machine stove will do it more efficiently. Even at a rate of 40 pounds per day it will put out more heat than the Chubby because of its greater heat exchange surface and hopper feed. You are assuming equal efficiency which the smaller stove just can't do except at very low firing rates. To reach 60 or 70k BTU output the Chubby would have to burn well over 100 pounds per day. The sides would be glowing red and the stack temperatures would be out of sight.

Respectfully disagree, the Chubby will run at the 40lbs per day rate at 90% efficiency and NO stove will beat that. At higher burn rates, I agree with you and the reason has nothing to do with the hopper but rather the increased convective cooling due to the large size. The Chubby blower with its forced convection will do even better for higher burn rates.

nortcan wrote:Hi, could you please give the exact amount of anthracite you need (pounds) for 24Hrs period , at a certain outside T*? I don't know the quantity of the hood and of the grain shovel you talked about.
Thanks

Shovel is 58oz. I'm not sure of the hod but one 50 # bag of nut anthracite will last me 1.25 hods. If that makes sense.

But seriously, they are two very different stoves. I was bringing in two bags of nut every day with the Chubby and I was burning it. Now I feel like I am bringing in one bag of nut a day. I know I'm probably burning more coal with the DS. Its a given. But what does matter is that instead of burning 100# a day and still being cold was not fun for me. Burning 100# a day now and not worrying about being cold is priceless.

My math on how much I'm burning is probably off. I don't know how much coal my hod holds. Its not written on it anywhere. For all I know it could hold 10 pounds. What I do know is that I'm running the DS less than I was the Chubby and I'm getting more heat out of it.

lobsterman wrote:

franco b wrote:

lobsterman wrote:It is totally agreed that the DS machine is a more powerful heater than the Chubby. No comparison, no argument. My point is the higher heat output can only come from burning more coal per hour.

As the heat output goes up the DS Machine stove will do it more efficiently. Even at a rate of 40 pounds per day it will put out more heat than the Chubby because of its greater heat exchange surface and hopper feed. You are assuming equal efficiency which the smaller stove just can't do except at very low firing rates. To reach 60 or 70k BTU output the Chubby would have to burn well over 100 pounds per day. The sides would be glowing red and the stack temperatures would be out of sight.

Respectfully disagree, the Chubby will run at the 40lbs per day rate at 90% efficiency and NO stove will beat that. At higher burn rates, I agree with you and the reason has nothing to do with the hopper but rather the increased convective cooling due to the large size. The Chubby blower with its forced convection will do even better for higher burn rates.

That seems a little high do you have proof of that? If so why is it so high? I have a mpd and baro on my DS so If I fire it moderatly am I getting 90% efficency?

Coalfire wrote:That seems a little high do you have proof of that? If so why is it so high? I have a mpd and baro on my DS so If I fire it moderatly am I getting 90% efficency?

This is a great question and I do NOT have proof of the efficiency. There is an interesting older thread here on BTUs:
BTU output question
The efficiency is stated so by the manufacturer. I do know that the Chubby has a suspended fire pot inside the outer steel cylinder. This is a safety feature so if the pot or grate should crack, the fire is contained. No firebrick is used. I do know that I can operate it with the MPD fully closed and a good burning fire gives a low stack temperature. The ability of the Chubby to stay cool is dominated by convection. This is true of any stove. This is easy to understand because the radiative part of the heat energy goes as the FOURTH power of the temperature, but doubling the temperature does not give 16 times the heat output (!). The stove gets hot much quicker than this fourth-power law because the heat transfer is convection limited.

lobsterman wrote:

Coalfire wrote:That seems a little high do you have proof of that? If so why is it so high? I have a mpd and baro on my DS so If I fire it moderatly am I getting 90% efficency?

This is a great question and I do NOT have proof of the efficiency. There is an interesting older thread here on BTUs:
BTU output question
The efficiency is stated so by the manufacturer. I do know that the Chubby has a suspended fire pot inside the outer steel cylinder. This is a safety feature so if the pot or grate should crack, the fire is contained. No firebrick is used. I do know that I can operate it with the MPD fully closed and a good burning fire gives a low stack temperature. The ability of the Chubby to stay cool is dominated by convection. This is true of any stove. This is easy to understand because the radiative part of the heat energy goes as the FOURTH power of the temperature, but doubling the temperature does not give 16 times the heat output (!). The stove gets hot much quicker than this fourth-power law because the heat transfer is convection limited.

I can close my MPD the whole way too. Maybe the DS are that efficient that they actually create coal 110% efficient, I will read that thread on btu output after work.

Thanks, Eric

There are more than one type of 'efficiency'

You can have very good burning effieciency, that is burn the coal completely, leaving no unburnt, wasted BTUs in the ashes..

You can have good efficiency getting the available heat from the fire into the room, transfering heat into the room efficiency.

Both are exclusive,, you do not automaticly have both if you have one type..

So, lets look at the second effieciency,, the first , the burning efficiency in a hand fed stove is usually pretty good.

A small stove with less heated surface area, will not radiate or conduct to the air as much heat as a larger stove,, for the given coal burned or the given surface temperature of the stove 'skin'. A larger surface area will radiate more, and conduct more to the surrounding air [creating passive circulation].
If a stove has a jacket and an electric fan washing heat off the heated 'skin' then the heat transfer is even better.. in this case a smaller, but fan equiped stove may have better heat transfer into the room than a larger passive [no fan] stove..

But the measurement of the coal used, the skin temperature and the Flu pipe temperature are what are needed, along with the stove skin area.. Someone who loves math can figure it out..

But 40# per day burnt in a small stove will not transfer as much heat into a room as 40# of coal burnt in a stove with a larger heated skin surface area.. unless the stove is terribly inefficient, and a hopper fed stove, like the DS is not ineffiecient.. or we'd have lots of comments, threads on the 'excess coal used' etc.. and we don't have that for the DS units..

So I am not the least bit suprised that the DS is transfering more heat into IOF's house than the smaller Chubby.. The chubby was undersized for the heating needs and desires for IOF..

IOF" I'm glad this is working out for you, and the Chubby found a new home too.

Greg L.

BTW: first impressions of coal use can be off by quite a bit.. Try to figure out your use for a week at a time.. this will average out better..
Sort of like stating the fuel mileage your car/truck gets based on one tankfull... average 5-10 tankfulls for a 'real' number..

GL

..I'm burning approximately 70# in a 24 hour period with my DS Machine 96,000 btu stove..my house is 1700 sq. ft..outside temps have been in the 20s at night, in the 30s during the day..I need more insulation in the attic..

First night I had the DS fired up it went 18 hours. I shook down saw that it used maybe a half hopper and contemplated just letting it be for a few more hours. I am however, trying to keep the same 12 hour cycle that I did with the Chubby even though I know I can now go much longer between shakes and fill-ups with the DS.

Hi, yes I come back with the same things .... but what I dont understand is that; why with a very smaller fire chamber on my Vig.11 I can have the same and even higher temp. in the house? Same house, same anthracite. With the stove in the original mode, I ran it at 450* to 600* F on the griddle. Now with almost 1/2 from the original fire chamber size, I still run at 450* to 600*F and get the house with the same T* as before.
The stove is rated 50K BTU for 2000Sf. Sound correct, my house is 2200 Sf but where is the error? Smaller F.Chamber with much less anthracite burning, same confort even better...The stove (outside) form is the the same...
My idea: stove ratings, theories, maths or whatever...nothing is absolute.

LsFarm wrote:ut 40# per day burnt in a small stove will not transfer as much heat into a room as 40# of coal burnt in a stove with a larger heated skin surface area.. unless the stove is terribly inefficient, and a hopper fed stove, like the DS is not ineffiecient.. or we'd have lots of comments, threads on the 'excess coal used' etc.. and we don't have that for the DS units..

GL

Efficiency = heat in room divided by energy released in combustion.
40 lbs per day burned in the Chubby has ALMOST ALL THE ENERGY going into heat in the room. You cannot do better than that with the world's largest stove! At very high rates, yes, the big stove will win. Perhaps Fire is in this regime. I was just questioning the sanity of the Chubby /DS comparison on a per pound burned basis.

budster wrote:..I'm burning approximately 70# in a 24 hour period with my DS Machine 96,000 btu stove..my house is 1700 sq. ft..outside temps have been in the 20s at night, in the 30s during the day..I need more insulation in the attic..

Well, this sounds sensible. Let's estimate for arguments sake that the DS and Chubby both have a similar high efficiency when burned sensibly. 70 lbs per day is getting you about 35k BTU/hour and I only claim to be doing 20k BTU/hour in my Chubby.

BTW BTU/hour is an archaic unit which s equal to about 0.3 watts, so burning 70 lbs of coal per day efficiently is the energy equivalent of 10,000 watts, continuously, day and night (!). How would you like to pay for that electric heat? (LOL) We all all winners with coal, that perhaps we may agree on.

franco b wrote:

lobsterman wrote:This is a great question and I do NOT have proof of the efficiency. There is an interesting older thread here on BTUs:
BTU output question

That is an interesting post by Doug. It is not valid though in figuring a stoves ability to transfer heat into a room. Efficiency is also assumed at the various damper settings. In the examples given for the Chubby a firing rate of 8 pounds per hour is used. That's 192 pounds in 24 hours. Without some sort of forced draft I don't think you could get a Chubby to burn that much in 24 hrs, and if you could, I think you could throw away the stove because it would be damaged from over firing. The assumption is then made that by closing the damper, efficiency will increase by 30 percent while still firing at 8 pounds per hr. This assumes you could get enough draft to burn the coal at that rate.

What about getting that 50, or 60, or 70k BTU heat into the room. No mention is made, but by consulting the figures giving BTU emissivity per sq. ft. and calculating the the surface area of the Chubby above the fire pot you can get a figure of how hot you would have to run the stove. You better have a flame proof suit to tend it.

I don't believe a batch fed stove can reach 90 percent efficiency except at one point in the burn cycle when volatiles have been burned off and the firing rate is low enough to be commensurate with the heat exchange surface, avoiding excessive stack temperature. That sweet spot.

Stoves with an extended heat exchange like William's Glenwood or stoves with a blower can extend that sweet spot, especially if the blower has variable speed. A hopper can also help in the burning of volatiles by partially coking the fed coal and capturing the heat normally wasted by feeding cold coal in a batch.

Agreed. the Chubby is a great 20k BTU per hour steady burner. Perhaps it can do twice that with somewhat reduced efficiency without over firing, I don't plan to go there with mine (not interested in buying that much coal, LOL). I have a 140k BTU/hour gas furnace with 85% efficiency and if it runs 15% of the time my Chubby puts out the same heat. That is why is simple numbers, the Chubby heats my house adequately.

franco b wrote: A hopper can also help in the burning of volatiles by partially coking the fed coal and capturing the heat normally wasted by feeding cold coal in a batch.

Let me put a myth to rest here. The heating of coal in a hopper does not come for free-- it takes energy to do that, in fact the same amount of energy if the coal was heated to the same temperature in the firebox or in a hod on the floor. Anthracite has an extremely low percentage of volatiles so not much to be gained there either.