Why Is 50-93 Over 40% More Effient Than 30-90 at Low Burn ?

According to Hitzer's website the 30-95 is rated at a minimum output of 11K BTU at lowest setting burning 1 pound of coal per hour (30# goes 30 hrs)
Its big brother 50-93 is rated at a minimum output 16K BTU burning one pound per hour of coal (50# goes 50 hours)

This tells me that the 50-93 is a superior stove because it can generate 16K BTU per # of coal vs. 11KBTU per # of coal.
I can't see a design difference between the two that would explain why the 50-93 is over 40% more efficient ?

If these numbers are accurate - the 50-93 is one heck of a performer

For starters, 50-93 has a bigger hopper. 50-93 has more surface area directly under the finned heat exchanger. I would say it is a combination of two things; Bigger heat exchanger for disipating more heat quicker. And a much wider hopper for gasses to rubb against, while going around, and out the smoke pipe.

If those figures were correct the 50-93 would indeed be a super stove. But given the fact that coal on the high end has around 14kBTU per lb. I wouldn't go trading in your stove unless the 30-95 isn't keeping up with your heating demands. Being that coal stoves of even a simple design are 90% efficient, I don't think you will find a significant difference in efficiency from one coal stove to the next. Stoves are best picked first on minimum and maximum heating needs,then cost, and other design features as desired.

Pete69 wrote:If those figures were correct the 50-93 would indeed be a super stove. But given the fact that coal on the high end has around 14kBTU per lb. I wouldn't go trading in your stove unless the 30-95 isn't keeping up with your heating demands. Being that coal stoves of even a simple design are 90% efficient, I don't think you will find a significant difference in efficiency from one coal stove to the next. Stoves are best picked first on minimum and maximum heating needs,then cost, and other design features as desired.

Speaking of efficiency - how do you like that Chubby ? Ive heard that it has a very long burn time on a bucket of coal.

I haven't hooked the Chubby up yet. It is rated at max 50-60kBTU, is reputed to burn over 18 hr. and up to 70 hr. depending on draft and heat output settings, holds 35-40 lb. of coal and is 85-90% efficient, without using any baffle or heat exchanger on my model. They do make a model with a heat exchanger. Of course I would expect to have to tend it every 12 hr when running it full out. Definitely a simple design, but well made and a nice looking stove. Looking forward to running it. It will soon be piped into a currently unused flue in my basement.

Pete69 wrote:If those figures were correct the 50-93 would indeed be a super stove. But given the fact that coal on the high end has around 14kBTU per lb. I wouldn't go trading in your stove unless the 30-95 isn't keeping up with your heating demands. Being that coal stoves of even a simple design are 90% efficient, I don't think you will find a significant difference in efficiency from one coal stove to the next. Stoves are best picked first on minimum and maximum heating needs,then cost, and other design features as desired.

I keep my 30-95 on low idle most of the time when I'm not in the shop. When I am in the shop, I run the stove like as if I were heating a house. I can say this; When running the 30-95, & 50-93 like they are supposed to be run(not at low idle), they use just about the same amount of coal every 12 hours. Yet, the 50-93 puts out way more heat. Haven't technically measured the output, but feels like 50-93 puts out double the BTU's of the 30-95. You are right Pete, the 50-93 is a "Super Stove". This is why I say the 50-93 is more efficient that the 30-95. Having both these stoves, and running them both at the same time, I see the differences first hand. I do agree with pete69 when he says not to step up, unless 30-95 will not keep up. There is a fine line when it comes to choosing one of these two stoves for average home heating. If you need lots of serious heat, you had better choose the 50-93. Like has been mentioned before; (Stove in basement = 50-93) (Stove in living quarters = 30-95) (Stove in living quarters without fan = 50-93)

Do you have a pic of the Chubby? Interested in one of those for our back upstairs hallway. Also I know that the new 50-93's you can take the hopper out. Does that allow you to load more coal but it all burns at once like the 354? I am being torn between the 50-93 and the Alaska Kodiak.

Thanks,
Glenn

No pick. of the Chubby yet, but check out this video http://vimeo.com/3060371

smokeyCityTeacher wrote:This tells me that the 50-93 is a superior stove because it can generate 16K BTU per # of coal ... If these numbers are accurate ...

As Pete hinted, the numbers are not accurate. The average pound of coal only contains 13K BTU, so the stove can't possibly extract 16K BTU from it.

oliver power wrote: I can say this; When running the 30-95, & 50-93 like they are supposed to be run(not at low idle), they use just about the same amount of coal every 12 hours. Yet, the 50-93 puts out way more heat.

That doesn't sound right. I could be wrong, but I bet if you check the draft through both flues, you may be pulling harder on the 30-95 flue, and could reduce coal consumption by adding a Baro. Not trying to knock the 50-93. Not my style, but nobody who owns one has ever had anything but praise for them.

Pete69 wrote:

oliver power wrote: I can say this; When running the 30-95, & 50-93 like they are supposed to be run(not at low idle), they use just about the same amount of coal every 12 hours. Yet, the 50-93 puts out way more heat.

That doesn't sound right. I could be wrong, but I bet if you check the draft through both flues, you may be pulling harder on the 30-95 flue, and could reduce coal consumption by adding a Baro. Not trying to knock the 50-93. Not my style, but nobody who owns one has ever had anything but praise for them.

Yes Pete, you're wrong here. The chimney's aren't far apart, and are identical. The 30-95 is a super great stove, and will really crank out the heat if it needs to. I like mine a lot. The heat from the 50-93 will take your breath away. Both my chimneys have a good strong draw; even in the summer time with no stove burning.

There are no stoves that can extract 16,000 btu/#/hr from any anthracite

coal which has only 12,500 BTU available per #.A good design will get about

9,000--10,000 btu/#.

BigBarney

BigBarney wrote:There are no stoves that can extract 16,000 btu/#/hr from any anthracite
coal which has only 12,500 BTU available per #.A good design will get about 9,000--10,000 btu/#.
BigBarney

Seems every stove maker likes to exaggerate a bit. Now the coal producers are exaggerating too.
I see many testing reports on this form where labs will report that such and such a coal is producing > 13K BTU/hr/#

So - going by your numbers 10K / 12.5K = 80% efficiency
and so most coal stoves will not do much better than 80%

Ive heard of devices that pulverize the coal into powder and precisely control the air mix into a controlled turbulence and get over 95% efficiency.
Wonder what the theoretical limit is on heat extraction for coal.... hmmm

we'll leave that one for coal berner, he has an Axe/And and that's about as high tech as you can get in your basement :=)

In modern power plants they achieve very high efficiency of

combustion,but lower extraction of heat from the gases

because the transfer of heat to the water is limited by

the thermal conduction of the boiler.

With a coal powder you get a near complete burn of

bituminous coal with its superior burn characteristics and

high heat value.Pure carbon combustion in a 100% burn

gets ~14,500 btus there are few bituminous seams get over

the 15,000 BTU mark,because of the high heat values of

the long chain volatiles in the coal and the low ash.

BigBarney