Why is Axeman Andersen considered the Best?

Bob wrote:

mikeandgerry wrote: I keep a thinner fire because I don't have the load you do

What do you mean by a "thinner fire"? How do you control the thinness of the fire in the AA boiler?

It is not really something you can observe with the AAA. In general I am only referring to controlling the average size of the fire for variable heat output.

In the 130-m you have an 11" diameter fire pot over a reciprocating grate. Above the fire pot is the coal feed tube. It is one column of fresh coal, on top of a burning fire, on top of a bed of ash. All of that is like the AHS. Bear in mind I haven't seen an AHS but Yanche has written extensively about his so I know that the grate drive mechanism is different. Anyway, the feed tube of the AAA has a large cam (offset lobe on the tube) that reciprocates a rod that drives a ratchet that reciprocates the grate. The rod can be driven different distances by adjusting the "shake adjuster" which is a slide stop that regulates how far the cam drives the rod turning the ratchet. The result is that you can adjust the number of teeth taken on the grate ratchet from one to three. This determines the rate at which the grate reciprocates (known as "shake" to AA) and thus how fast the coal feeds through the system. One tooth is minimum (the grate must reciprocate), three is maximum throughput. One tooth is a thinner fire, three is a thicker fire (bigger fire).

The other aspect of fire size control is the anthrastat. The AHS has an ash sensor which Yanche has indicated is superior to the radiant sensing thermostat (anthrastat) that the AAA has. I don't know the difference but the result is the same; Setting the anthrastat to a higher temperature keeps the fire pot thicker with fire, i.e. a bigger average fire. The grate will shake longer until fire gets closer to the grate satisfying the higher anthrastat setting and shutting off the movement of the grate. The result is a thicker fire in the pot.

Also, try the AA Anthratube information library that Yanche was so kind to post on the web.

Hope it helped.

mikeandgerry wrote:

Bob wrote:

mikeandgerry wrote: I keep a thinner fire because I don't have the load you do

What do you mean by a "thinner fire"? How do you control the thinness of the fire in the AA boiler?

It is not really something you can observe with the AAA. In general I am only referring to controlling the average size of the fire for variable heat output.

Thanks for the explanation. I think I understand your use of terms and how you conceptualize the operation of the unit.

After reading your explanation I realize that I conceptualize the process differently--I think of the adjustment of the grate shake and the anthrastat setting as controlling the rate at which ash (or potentially coal if the settings are way off) is removed from the fire box. To my way of visualizing the process the physical size of the fire (the volume of the coal that is burning) is relatively constant over a fairly large range of adjustment of the grate shake and anthrastat setting.

I think of the heat output of the boiler as being determined PRIMARILY by the minutes per hour that the combustion blower operates--not what you describe as the thinness of the fire. However I do understand that a very small grate shake combined with a very low temperature setting on the anthrastat will significantly limit the removal of ash and, at some point, reduce the volume of burning coal.

Now that I understand your thinking and have laid out mine I really don't know which is the better way to conceptualize the operation of the boiler.

Just an aside on the differences in operation of the AA and AHS unit. As I understand your description of the AA unit the grate shaker is operational when the combustion blower is operational and the range of motion is the variable that is controlled. On my AHS unit with the thermocouple heat sensor the grate has a constant stroke (range of motion) but operates intermittently--only when the thermocouple senses low ash temperature. Further, it is my understanding that on the AHS unit that uses the proportional timer the grate stroke is fixed but the shake is an adjustable percentage of the time that the combustion blower operates.

Bob wrote:

mikeandgerry wrote:

Bob wrote:It is not really something you can observe with the AAA. In general I am only referring to controlling the average size of the fire for variable heat output.

Thanks for the explanation. I think I understand your use of terms and how you conceptualize the operation of the unit.

After reading your explanation I realize that I conceptualize the process differently--I think of the adjustment of the grate shake and the anthrastat setting as controlling the rate at which ash (or potentially coal if the settings are way off) is removed from the fire box. To my way of visualizing the process the physical size of the fire (the volume of the coal that is burning) is relatively constant over a fairly large range of adjustment of the grate shake and anthrastat setting.

I think of the heat output of the boiler as being determined PRIMARILY by the minutes per hour that the combustion blower operates--not what you describe as the thinness of the fire. However I do understand that a very small grate shake combined with a very low temperature setting on the anthrastat will significantly limit the removal of ash and, at some point, reduce the volume of burning coal.

Now that I understand your thinking and have laid out mine I really don't know which is the better way to conceptualize the operation of the boiler.

Just an aside on the differences in operation of the AA and AHS unit. As I understand your description of the AA unit the grate shaker is operational when the combustion blower is operational and the range of motion is the variable that is controlled. On my AHS unit with the thermocouple heat sensor the grate has a constant stroke (range of motion) but operates intermittently--only when the thermocouple senses low ash temperature. Further, it is my understanding that on the AHS unit that uses the proportional timer the grate stroke is fixed but the shake is an adjustable percentage of the time that the combustion blower operates.

I have the AHS 130 boiler with the proportion timer control of the grate shaker. The grate is moved by a gear head motor turning a crankshaft. The crank length is 1 inch, resulting in a total movement of the grate of 2 inches. The grate motor is only powered when the combustion blower is powered. The run time is further reduced by a ten minute percentage timer. For me 3.25 minutes out of ten is a typical setting. This means ash is only being removed a small percentage of the typical demand for heat. The boiler design is really a stack of coal in various states. On the grate is burnt coal in the form of ash, atop it is burning coal, next is fresh coal from the coal hopper. It's all fed by gravity. The boiler produces little heat if the combustion blower is not running. Heat is produced when the combustion blower draws air up through the bottom grate sides and causes the coal to burn vigorously. The hot gases are drawn away from the glowing red coals through the boiler tubes.

I would not describe the physical size of the fire in "thinner or thicker" terms. It's more a total volume, that grows as demand increases. After the high point limit on the aquastat is reached the combustion blower stops. Some combustion gases continue to burn for a short period of time. But soon the only heat added to the boiler water is that via the conduction from the burning red coal to the boiler vessel.

The grate timer is an electric clock motor type timer so it remembers the last point in it's operation. It just picks up there when the combustion blower is next turned on by the aquastat. Increasing the timer setting will increase the removal of ash. This will lower the location of the glowing coals. Increase it to much and you will not see any fire at all and hot burning coal will be in the ash bucket.

In my opinion the AHS thermocouple ash grate sensor is a far more reliable sensor that the A-A radiant heat mechanical sensor. Internally it's likely a spiral wound bi-metalic snap action contact. The thermocouple electronics will be much more accurate, repeatable and hold it's set point with age. Obviously all three grate control methods work. The component cost (not selling price) of all three are similar.

Thanks for the explanation. I think I understand your use of terms and how you conceptualize the operation of the unit.

After reading your explanation I realize that I conceptualize the process differently--I think of the adjustment of the grate shake and the anthrastat setting as controlling the rate at which ash (or potentially coal if the settings are way off) is removed from the fire box. To my way of visualizing the process the physical size of the fire (the volume of the coal that is burning) is relatively constant over a fairly large range of adjustment of the grate shake and anthrastat setting.

I think of the heat output of the boiler as being determined PRIMARILY by the minutes per hour that the combustion blower operates--not what you describe as the thinness of the fire. However I do understand that a very small grate shake combined with a very low temperature setting on the anthrastat will significantly limit the removal of ash and, at some point, reduce the volume of burning coal.

Now that I understand your thinking and have laid out mine I really don't know which is the better way to conceptualize the operation of the boiler.

Just an aside on the differences in operation of the AA and AHS unit. As I understand your description of the AA unit the grate shaker is operational when the combustion blower is operational and the range of motion is the variable that is controlled. On my AHS unit with the thermocouple heat sensor the grate has a constant stroke (range of motion) but operates intermittently--only when the thermocouple senses low ash temperature. Further, it is my understanding that on the AHS unit that uses the proportional timer the grate stroke is fixed but the shake is an adjustable percentage of the time that the combustion blower operates.

Yanche tells me that the AHS does work a bit differently. I have not studied it. The stroke of the AA grate is a fixed two inches. The stroke that is variable is in the linkage that drives that grate. You are correct that the grate can only operate when the blower is running. The unit is designed to idle down between calls for heat. When there is a call for heat, the feed tube, blower and grate switch will operate, though the grate switch is also controlled by the anthrastat. The grate cannot operate if there are no calls for heat (like when you are on vacation) . Accordingly, a timer, set to operate the unit for one minute every hour, will idle the fire indefinitely (and eject ash) if there is no call for heat.

According to the AA operation manual, the shake adjuster will physically change the thickness of the fire in the firepot. There is a wide range of acceptability depending on the load of the unit. If the fire is too thick for the size of the load, the unit will experience a high limit shut down. If the fire is too small for the size of the load, pick up will be too slow.

In the summertime, if you are running your unit for domestic hot water (no other loads), obviously the number of calls for heat is limited. Moving the shake adjuster to one tooth and the anthrastat to 120d allows the fire to idle at a smaller size, what AA calls "thin". In the middle of January, with daytime temps below zero and 1000 sq feet of radiation to service, the shake adjuster needs to be at two or three teeth and the anthrastat at 140d.

The boiler is capable of high output at the low settings (thinner fire) but it takes considerable time to pick up the fire to achieve that rate because it has to kick out all that ash and stoke a lot of new coal into a bigger fire. If you were away and it got very cold, the unit will maintain the t-stat temps by running more often and longer. But, at the higher anthrastat and shake settings that would occur much more quickly for the convenience of the owner.

These adjustments are just "fine tuning" for efficiency. Your AHS controls do the same thing in a different way.

Center



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Video 1 burn around 15 mins

http://www.engtechs.com/temp/coal/102_4352.mov

Video 2 fan plate temp then stack temp

http://www.engtechs.com/temp/coal/102_4353.mov

My compliments to U235a4 for the fine photos and video.

Low stack temp and high fire tube temp is the sure sign of efficiency.

BTW, such photos are not possible with the 130m. Chamber small too see around to the fire tube leading to the fan.

Also visible is the anthratube's cam turning in the stack temp vid.

Thanks

I was curious about the efficiency debate and I was able to contact two veterans of our govt. testing lab.

The AA has a constant rate of feed, of a known value of coal BTUH, and probably that's why they can come up with an efficiency rating.

From what I retained in my pea coal brain, the govt. testing in the lab utilizes figures from many sources. A known BTUH content of an exact amount of coal, a CO2 amount, a stack temp, an incoming air tem, an incoming water temp, and extraction value, and increase value, a constant feed rate of coal, the outside temperature or environment temperature and some other things I've forgotten.

Since the efm has a variable rate of coal feed and since the quality of coal differs depending upon its source, we can't give an efficiency rating.

With such variables in coal quality, I think an efficiency test would change percentages often.

And with that, I'll walk backwards out of this zone of my non-expertise.

stoker-man wrote:I was curious about the efficiency debate and I was able to contact two veterans of our govt. testing lab.

The AA has a constant rate of feed, of a known value of coal BTUH, and probably that's why they can come up with an efficiency rating.

From what I retained in my pea coal brain, the govt. testing in the lab utilizes figures from many sources. A known BTUH content of an exact amount of coal, a CO2 amount, a stack temp, an incoming air tem, an incoming water temp, and extraction value, and increase value, a constant feed rate of coal, the outside temperature or environment temperature and some other things I've forgotten.

Since the efm has a variable rate of coal feed and since the quality of coal differs depending upon its source, we can't give an efficiency rating.

With such variables in coal quality, I think an efficiency test would change percentages often.

And with that, I'll walk backwards out of this zone of my non-expertise.

It is true that there is always fuel for the AA to burn but it won't burn it if the blower isn't on. In that sense, I would think that all stokers are variable fuel feed.

It was simply my understanding that less coal provided the same heat as a hand fired boiler. I would surmise that any of today's modern stokers are, more or less, similarly efficient at the AA but the AA was the pioneer way back when.

As for the methods of calculation....I too will walk backwards out of the room.

U235a4 wrote:Center



Left



Right



Video 1 burn around 15 mins

http://www.engtechs.com/temp/coal/102_4352.mov

Video 2 fan plate temp then stack temp

http://www.engtechs.com/temp/coal/102_4353.mov

Wow that thing is noisy

stoker-man wrote:I was curious about the efficiency debate and I was able to contact two veterans of our govt. testing lab.

The AA has a constant rate of feed, of a known value of coal BTUH, and probably that's why they can come up with an efficiency rating.

From what I retained in my pea coal brain, the govt. testing in the lab utilizes figures from many sources. A known BTUH content of an exact amount of coal, a CO2 amount, a stack temp, an incoming air tem, an incoming water temp, and extraction value, and increase value, a constant feed rate of coal, the outside temperature or environment temperature and some other things I've forgotten.

Since the efm has a variable rate of coal feed and since the quality of coal differs depending upon its source, we can't give an efficiency rating.

With such variables in coal quality, I think an efficiency test would change percentages often.

And with that, I'll walk backwards out of this zone of my non-expertise.

I didn't realize there was a debate about efficiency. The higher the better! The 84% efficiency number quoted in the A-A Bureau of Mines Report is combustion efficiency. The amount of potential heat in a fuel converted to actual heat. It is only one part of total efficiency. Other efficiencies are equipment efficiency, how well the heat created by the combustion process gets transfered to the boiler water or furnace air, and seasonal efficiency, how well the equipment operates in all seasons. For example if you heat domestic hot water with your boiler all year round, the last thing you want is a boiler with lots of water in it and poor insulation in the summer months. You are just wasting heat by radiation and you will have low summertime seasonal efficiency.

Combustion efficiency in the Bureau of Mines report was measured with a laboratory grade Orsat. This measures the CO and O2 content of the combustion gas. Combined with the flue gas temperature measurement allows you to calculate combustion efficiency. Today a somewhat obsolete instrument the, Bachrach Fyrite would be used. It uses the same chemical absorption principles as an Orsat. The latest combustion instruments use digital readouts with solid state sensors. In my opinion they are not as accurate as a Fyrite.

To say that combustion efficiency of any coal appliance cannot be measured is just wrong. It's a simple measurement. What's more difficult is equipment efficiency measurements.

cArNaGe wrote:Wow that thing is noisy

Actually, they are not that noisy. His video seemed much noisier than reality. Before I bought my AA 130m I was quite worried because I had no point of reference. After owning one for a couple of months it really sounds like a furnace blower from the 70's and 80's with the added "tinkle" of the coal tube. Mine is under my bedroom and it has never been a problem. Actually, the muffled roaring sound is quite reassuring. My wife loves it!

Also, you have to remember that the unit is for central heating, i.e. it's not in your living room.

My AA130 is right below my sitting room and all I hear is a whirring and a clunk occasionally (grate solenoid). Red Oak floors and no carpet. Very quiet.