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Post in 'The Boiler Room - Wood Boilers and Furnaces' started by GS7, Sep 28, 2013.
what? your wives dont feel that way about your boiler?
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Good one Maple. Voom. Right over my head! LOFL
52 replies and I don't feel the information is sufficient to make a well informed choice.
The biggest question is can the Woodgun work well without storage. AHS touts their on/off technology as a feature, but the website does not say if storage is required or the WG is factory rated to work without storage.
For you guys who are already burning, you know what I'm talking about. For the Woodgunners running without storage, do you feel confident you can open the unit at any time and throw dry splits on a coal bed without any repercussions. I don't doubt that it can shut down. The problem would seem to be the restart. As combustion air is reintroduced suddenly onto freshly gasified fuel, reignition is reported to happen explosively. The users experiencing this learn by necessity to time the fuel adds, to wait until the fuel is well burned down and load is there. If the unwary, casual operator can risk wood gas explosion just by following the factory literature, adding wood on a coal bed and running in auto, it would be a substantial design flaw.
For the Woodgunners running with storage, I have no doubt that all of the gasifiers can fall within 5% of each other on efficiency. The thing to keep in mind is the OP would be dropping in excess of $10,000. on a delivered installed boiler. It is not an action that can easily be undone if the choice proves unsuitable, and scary, for the application intended. Comparing the cost of the install averaged over the expected product service lifetime, there is very little monetary difference between the least and most expensive products offered.
I would absolutely like the Americans to compete with the best products in this market. When I was looking, I was told by my brother he knew a contractor friend with a Woodgun who loved it. It was recommended. I knew for my application I wanted a boiler that could turn down while staying on. The on/off operation was not a feature, it was something that would not work for me.
Don't think for a second I would bash Woodguns. It is in my nature to give a fair score for the work perfomed. Does the Woodgun survive this scrutiny. Would you send your kids or an unfamiliar operator in to add splts onto a hot coal bed at any time or would an explosion hazard be present.
Perhaps you guys involved in system design or those who install and service heating units could answer one question for me.
Can the efficiency calculation on the Woodgun be skewed by the high volume of air flowing through the unit and out the stack giving you a false (low) reading of the stack temperature? My unit would actually blow glowing embers out of the stack on to my roof whereas my Eko fan is adjusted down to the speed of a gerbal wheel giving it enough air to completely consume the oxygen but pretty likely have none left to flow up the stack.
In other words, Does the high volume cool the exhaust?
For wood boilers the ideal exhaust temperature is the condensing temperature plus one degree, correct?
Wouldn't too high of an input air volume equate to too high of a velocity through the heat exchanger (fire tubes in the water jacket) giving a higher exhaust temperature than desired?
mmm, no clue. I'm not a thermodynamics person, I could have this backwards.
You would have to assume a fixed combustion rate as flow varied, but that will not happen. Generally, higher combustion flow through rate and more turbulence will give you greater combustion output, skewing the number you are looking for.
If you could assume fixed combustion rate as flow through varied, the heat exchanger is removing heat as the exhaust gas passes through, a flow slower rate will yield a lower exhaust temp as same quantity of heat is removed from a smaller air volume (quantity). Faster flow through rate at the same combustion output rate, the heat exchanger removes the same quantity of heat from a larger volume (quantity) of air, yielding a higher exhaust temp.
I could have that backwards, I really should take a thermo class.
Actually, looking at Fred's post again, changing the quantity of input air as combustion rate is assumed to be fixed adds another independent variable.
Efficiency calculations are calorimetry. If you look at calorimetry methods, the requirements for accurate results can be very complex.
If I add more turbs to my boiler, I get reduced air flow through & lower stack temps.
If I take some out, I get more air flow through & higher stack temps.
Does that help?
I don't have a ton of experience operating my Wood Gun. I have 1 heating season. Nov 17 through April 1 in North NJ. I have NO storage.
With that said, there was a learning curve, but it wasn't much longer than figuring out how my Jotul Oslo works with its air damper.
I add wood on MY schedule. I put wood in my boiler in the morning before work, again after work, and once more when I go to bed. This is convenient for me.
If convenient for me, I wait for my boiler to be "running" on its own before adding the wood rather than using the purge timer.
If I won't be home in the evening, I just add more wood in the morning.
It's really not that tough.
It hasn't blown you across your basement yet? Or blown itself up through your roof? What is taking you so long?
For the E500 the problem is on the restart following a shutdown. While the wood load is burning, there is no problem with opening the firebox door and adding more wood. But, if the WG has shut down, then for the E500 the purge procedure must be followed and a puff to a near explosion is a possibility inside the firebox.
I installed a K-type sensor in the exhaust flue close to the WG that feeds a digital panel meter. By experience when that temp falls to the high 300F's, and if more heat is needed, then simply open the firebox door while the fan is running and the fire is burning and add wood, shut the door and walk away. Where the E500 is used, it is common to keep it burning at a relatively high to full burn for many hours by adding wood during the burn as indicated. Because the WG has storage, however, it no longer shuts down, as the storage takes the extra btu's so that the WG does not shut down for a later auto restart.
I have found the "explosion" only happens if you "catch" the boiler shortly after it closes the air damper and shuts the fan.
Generally speaking I add wood to the boiler when it is running on its own. This is pretty simple for me to time. In the morning, the very act of showering will use DHW and cause the boiler to run so I throw my day load in then. In the evening, I am usually not pressed for time so I will open the basement door periodically and throw wood in when I hear it running (I can't hear it running with the door closed, I could hear my oil burner in the past). For bed time the boiler is usually running since it is night and it is cold.
It's really not tough. With a bit of experience it is easy. Certainly not worse than the woodstove I used to feed. At least with the WG I load and leave. The stove required I hang around for half an hour to play with the air damper.
The thing to keep in mind is, there is a big difference between the enthusiast market who buy, build, and maintain their own equipment, and JQP, who needs an automated coffemaker to make his coffee for him.
There is a market in the millions of units, oil burners with no gas available and HW baseboard loads. The bulk of the market will not have the footprint or budget for big storage. That is representative of who will come to the board for their inquiry.
If you were going to buy, build, or install in this market in the millions of units, would it be a WG design, because of the no storage and accept the on/off cycling and puffing as a compromise. Not for you, for your customer, would you sell and install it, in a market that is in the millions. The first time you burned the customer's eyebrows off, you would be out of business and on the street. The customer and his lawyer would be living in your house, eating out of your fridge.
It is a market waiting for the right product imo. The pellet boilers are getting there but need imo, turndown, condensing rated, and direct vent, no chimney.
If the right product is not there for the average JQP, waiting and demanding the right product is a viable option for the majority of the market. It's getting cold and wrapping in blankets is not JQP's idea of a solution. So they will come to the board and ask what does work.
Gasifier said: ↑
Stop being on a crusade and failing to acknowledge that some of your problems were probably from lack of knowledge that you now have. There are guys out there who have been running Wood Guns for 20 years plus.
Simply reporting facts in a level headed and competent manner does not constitute a 'crusade'. It sounds to me like the boiler in question was installed and operated in a manner consistent with the manufacturer's claims and guidance, and it failed miserably. Fred has simply taken the time repeatedly to report that there is such a thing as a Wood Gun that fails.
Anyone is welcome to conclude that the failure could have been avoided, but it is certainly not Fred's job to figure that possibility out for them, let alone "acknowledge ... [his] problems".
Got to agree.......don't cut my head off because I run a Tarm...
Maple1, where are the girls? i missed that one....
The JQP who 'need automated coffeemakers' will have little time, patience, space & fortitude for dealing with firewood in the first place.
Storage doesn't need to be expensive, or take up big footprint.
I think there is also big potential in add on pellet heads myself. Remove your oil burner, bolt on a pellet head, feed it with a small bin/hopper, & away you go. Then you can pick up a few bags of fuel & toss them in the trunk when you're out buying your coffee beans.
I guess that has not much to do with the thread topic...
Good point dan. And I see and understand what you are saying. But, pertaining to what you say about the millions of units. Home heating is a big market.
Similar to the automobile or fast food market. GM, Ford, Chrysler, McDonald's, Burger King, etc. etc. etc. have all been sued by JQP. Some for burning their customers with coffee that is "too" hot. Some for selling automobiles that were not safe enough. Those people that sued are not living in the family home of the family who own McDonalds. Or of GM, Ford, etc. And these businesses are not out on the street.
The Wood Gun is a wood burner, not an oil or gas unit. You can not compare them and expect the same safety rules to apply. To a certain extent, the manufacturer has some responsibility of course. And I believe AHS, just like the rest of the manufacturers of these Gassification boilers understand that. In today's world, not having a business plan that includes the proper safety features in your product will not bring you success.
That being said, I would not allow my young child to operate my Wood Gun, just like I would not allow them to run my tractor/loader/backhoe. Not until I had spent sufficient amount of time teaching them how to run it and they were then old enough to respect and understand the dangers of said product. There won't be a child buying a Wood Gun or a Tractor/Loader/Backhoe. As an adult buying a Wood Gun, you have a certain amount of responsibility to read, talk to people, and become familiar with the product before you run it. Reading the operator's manual is always a good plan.
I wish more of the people in the world were prepared to accept their own responsibility as an adult instead of a lawsuit and blaming everyone else for their mistake and lack of responsibility.
The Wood Gun is not a complicated machine. It takes some getting use to, similar to oh let's say your riding lawn mower. Probably not the best comparison, but comparing it to a coffee maker really isn't a fair comparison either. It is a little more complicated than the lawn mower. But, they sell wood stoves and everyone of them can be dangerous or safe. They sell snowmobiles and everyone of them can be dangerous or safe. They sell boats and ......... you get my drift.
So that difference you were talking about in your first statement, "there is a big difference between the enthusiast market who buy, build, and maintain their own equipment, and JQP, who needs an automated coffemaker to make his coffee for him." is really kind of, well, really big!
Most people in our society today do not buy Wood Stoves. Most do not buy Wood Boilers. Most of the ones that do venture into the wood burning for heat have had this passed down through generations of their family. Some do take it up for the first time in their family. Yes. But all have a responsibility of their own to learn how to do it safely.
Those Attack guys got it goin' on, I tell ya....
Ok I need to jump back in here.
The "explosions" that DAN keeps talking about will NOT burn any ones eyebrows. You NEVER open the front loading door when the unit is OFF.
Call it an explosion or a puff back or whatever you want but it only happens IN the firebox when the front Load door is CLOSED, the unit is OFF (or in idle mode as everyone here likes to say) and the unit needs to turn back ON within a few minutes of shutting down (short cycle). So the Rear air intake opens (which is inside a closed steel box and ducted to 4" off the floor) and air is introduced into the fire box chamber that has a lot of gasification gases floating around. So yes there will be an "explosion" much like a back draft on a house that is on fire and a window or door is broken allowing air into the room.
HOWEVER, this short cycling can be avoided by having the differential setting on the high limit setting set to 30* or bigger. I have my hi limit at 200* with a 30* differential and have SOLVED the problem ( was it really a problem or just user ignorance) . So it has enough time from when it shuts off at the high limit and slowly drop to the differential setting to have the gases dissipate. WHALA no more explosions.
I agree flying cow. Not cutting anyone's head off because they run a different boiler. I suggest to all who are considering buying to look at several boilers. And to do storage and return protection. I strongly considered an HS Tarm and a Garn. Just think a mental note should be made by all that their is only one guy here who has had an indoor gasification boiler fail after only a few years in operation. Yes, it happened to be a Wood Gun. I believe it was an Eshland Wood Gun. I think. Not an AHS Wood Gun, an Eshland Wood Gun. And it could have been many things that made that boiler fail. Might have been some of the system set-up, might have been bad water quality, might have been that it was over sized and idled so much, might have been a bad piece of steel in that particular boiler, etc. etc. etc. ................
The only way to "burn eyebrows off" would be to operate the machine incorrectly, blatantly ignoring the owners manual AND the warning written RIGHT ON THE FRONT OF THE MACHINE!
It's a wood burning implement. It requires hands on attention. By following the directions it is just as "dangerous" to operate as a wood stove: burns.
By being stupid, I burned my arms loading the WG a few times grazing the door frame while putting wood in. The same has happened with my Jotul wood stove. I was too lazy to put on elbow length stove gloves. No more laziness, no more burns.
JQP is NOT the market a wood burner is built for. JQP needs to stick with their liquid fuel boilers...this is why most insurance REQUIRES them. They know JQP is too dumb to keep his own house warm safely.
I'll reply because my Jetstream is of the same general design in that it has no secondary air and always has excess air to ensure the burn stays clean. The excess air is only a few % at peak burn enough that it lowers stack temps through dilution.
The Jetstream's are not able to idle though and there are warnings in the manual about explosion risk puffing etc if attempting to reload mid cycle.
The efficiency loss in the combustion chamber carrying the excess air was calculated by Dr. Richard Hill and wasn't a huge amount as I recall and was a only a few % but you will get unrealistic numbers if you just use stack temp.
Has anybody put a combustion analyser to a wood gun at any phase of the burn cycle, i have not seen any posted results on this? In a gasifier secondary air is needed to convert carbon monoxide into carbon dioxide, a high burn temp on primary air alone is subject to high co and nox concentrations. A o2 sensor will show excess air in the fluestream but will not readily recognise the co change fast enough due to the resolution of the scales, o2 , 0-20.9% and co in the ppm range. The easiest way to mitigate high co without the ability to monitor is medium sized dry wood and not to overload the firebox. just wonder how clean any boiler can run without some secondary air
Infinitymike measures his rather often. He gauges it by how bloodshot the eyes of his little gremlins are. You know. The ones that relight his fires.
And also by watching if my neighbor is still walking around in his yard and hasn't passed out from the noxious fumes and or the flying chunks of coal that shoot out of the flue like a hand grenade launcher.
You put directional deflectors on yours. Didn't you! God damn cheater.