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Posted By forestdh,
Jan 30, 2013 at 8:35 PM
You hit the nail on the head with the green wood comment Hobby.
the issue is the testing differences between the US and the EU... specifically the difference between HHV and LHV.
quick synopsis in here:
the Lambda controls make a big difference in the amount of CO going up the stack. Brian stated the truth a kind of roundabout way: The effecta test literature I'm looking at lists the CO emissions of a 75 % reduction with the Lambda controls engaged. 2715 PPM vs 490 PPM. that CO is a product of not enough air supply to burn the fuel, as anyone who made it thru high school chemistry should remember. that is fuel that didn't get used. so the proper metering of secondary air should be able to get you a few more percentage points. anyone who wants to balance that equation out and come up with the actual amounts is welcome to.
so 92% is reasonable. you just need to ask: "92% of what?"
gaseous fuels and solid fuels aren't the same animal, and perhaps shouldn't be tested and treated the same way.
certainly you wouldn't want to approach 100% in a wood burner, because of the nasty results. maybe 92-93% is the best place you can get to with a solid burner, because if you burn a wetter than usual batch you end up with condensation, and a mess. maybe it's 95%, I donno.
I do agree the difference in the numbers can be confusing to plenty of people.
but you'll be hard pressed to argue that the Lambda controls aren't doing anything, but I certainly expect someone to try.
Full disclosure: I'm the Effecta distributor for the upper midwest.
There are several co housing projects in VT and NH, bascially everyone has a small private space and then the community has large public spaces. The community is generally surrounded by a large common forest and gardes. Most of them use Garns and require that everyone has a shift at running the boiler. I havent personally used a Garn but it sure looks like that would be the best fit.
Too much air can also generate lot's of CO though it will have the opposite effect on flue gas temp as too little air.
And speaking of physics/chemistry.......Actual efficiency of anything much above 86-87% with solid fuel having a maximum moisture content of 20% will cause condensation. To get any real world numbers above that you have to have extremely dry fuel like pellets and a very regulated combustion program.
I realize what you are saying though about the HHV vs LHV used in the efficiency equation. The Euro's use the higher number as can be seen in some of the specs floating around for their ultra efficiency gas fired equipment. Some of these are actually rated at up to 110% efficiency which when you think about it would be akin to a perpetual motion machine that makes more energy than it uses.
For all practical purposes the lower heating value must be used when talking about cordwood because flue gas condensation should be avoided at all costs.
A quote from the Wiki article:
The LHV assumes that the latent heat of vaporization of water in the fuel and the reaction products is not recovered. It is useful in comparing fuels where condensation of the combustion products is impractical, or heat at a temperature below 150°C cannot be put to use.
Boy o boy have we made this poor guys thread wander all over the place.......
Bottom line, this "Hearth Board" seems to conclude that a Garn is the best fit, as they also did with the older Father John's thread.
thank you for all the sound advice. I understand the concerns about burning green wood and we do not intend to burn greenwood. We intend to store seasoned and drying wood in the same area and if by chance the person feeding the boiler dipped into the wrong pile greenwood could make its way into the mix. since we will have a medley of residents and visitors helping with both splitting and tending to the boiler its only fair to assume that at some point the seasoned and green wood will get mixed up. that being said a boiler that will not malfunction or see excessive buildup from this type of error is an advantage.
with the garn is it reasonable to assume we could heat domestic water in the summer by burning a load once or twice a week?
what is the best way to get into contact with the garn manufacturer about pricing?
this system will be above my design abilities can anyone recommend a company for the design aspect of the system ?
is it posable to use the garn as a storage tank for a solar water heater?
With that many acres of wood available why would you ever need to consider burning green or wet wood? It seems like you have enough man power and already dead wood to provide an ongoing supply of top quality dry wood. Start the project with a covered, ventilated wood shed.
Where in these VA mountains are you located?
If you can, I recommend contacting Father John at http://www.syonabbey.org/contact.html to set up a visit. I did this when I was considering a Garn to heat multiple buildings....Great experience seeing things in person and talking with Father John.
It really depends. Hot water for 10 people- I'd guess you are looking at a few fires a week but there are a lot of variables here.
I would contact Garn to find out who rep's your area. They should be able to design whatever you need. A Garn whs2000 is likely $15k+, for a rough idea.
Father John had plans to do just this. Not sure if he did or not. Often with solar hot water, smaller tanks at higher temps can provide more usable hot water than larger tanks at lower temps but again, it all depends.
Good luck with the project,
Contact Jamie Parsons at 434-531-2784. He's the Garn factory rep in Virginia. firstname.lastname@example.org
I have run across a number of older Garns here in Michigan that were installed in the 80's with solar panels connected to them. One particular installation sticks in my mind because the owner only had two panels connected to his old 1350 Garn. He told me just those two panels would keep the Garn at 110* all summer long. He figured the solar input supplied about 70% of the hot water load on his farm. The system was designed so that domestic water circulated from the well to a storage tank and then into the standard water heater. Water from the storage was constantly circulated through a heat exchanger which was connected to the Garn. In effect he was simply preheating his domestic hot water supply to whatever temperature was available and then using a standard water heater to "finish" heating the water to his desired temperature.