# Boiler efficiency and wood use



## Downeast Farmer (Jan 20, 2013)

I'm newly here and seeking hard numbers on boiler efficiency as measured by wood use.  Has anyone here switched from a conventional wood boiler (Memco, New Yorker, etc.) to a gasification boiler (Garn, Frohling, etc.) and tracked the difference in wood consumption for similar heating loads?  Boiler manufacturers make claims about 50% or higher wood savings; does anyone have actual records showing such savings?


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## maple1 (Jan 20, 2013)

I'm only half way through my first winter with a gassifier & storage, so it's too early to tell yet. But I still have a lot of wood left. It was around 7.5 cord per year with the old one - I don't expect to halve that, but it's looking like I might be down at least to 5, maybe even close to 4.


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## flyingcow (Jan 20, 2013)

The claim of 50% in savings might be a little high. But you need seasoned wood to run in a gasser. A memco or new yorker will burn whatever you put in it. You could see 25%? gain in wood usage when you compare seasoned wood to green? in a memco/NY boiler.


I have no experience other than my gasser, but you should look at a solid 30% less wood consumption, more with 2 yr seasoned wood might even push closer to 40%. Plus the coolness factor when you show your buddies your burning wood, and no smoke out of the chimney. For me it's the way to go.


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## Paver56 (Jan 20, 2013)

I went from a new yorker wc-130 to a Froling.  I never burned only wood in the new yorker, I used coal and wood.  I heat around 4,000sf, all radiant.  We built our house 4 yrs ago.  It is insulated well.  I have had the Froling along with 1500 gallons of unpressurized storage running for about a year now.  It had beed a little mild here but this year, heating my water all summer, I used around 5 cord.
There is no comparison at all between the two.  The new yorker, in my opinion was very inneficient. I was basically a slave to it when it was cold out.  Being able to burn once every 24-36 hours is great.  In the summer I go 7-10 days between fires.
To answer your origional question, I do not know if it would be a 50% savings in wood consumption, but I think it would be close.


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## BoilerMan (Jan 20, 2013)

Paver56, I like your sig!

Downeast, I switched from a NYwc130 to a gasser, had storage before and have been tracking wood consumption.  I burned the same well-seasoned wood in the NY as I do in the Attack, and had storage before with the NY.  All things being = and I have not been through a whole winter with the Attack yet, but I think it's safe to say 1/3 less wood is a very conservitive number.  50% would be if one really burned their Memco/NY dirty and cold, ie. worst case.  If one runs a wood boiler like that, then they may not be a good canidate for a gasser, unless they really want to change their ways.  Bottom line: smoke = lost potential heat that would have made it into the water to be used for something useful  like keeping you warm. 

TS


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## hobbyheater (Jan 21, 2013)

Downeast Farmer said:


> I'm newly here and seeking hard numbers on boiler efficiency as measured by wood use. Has anyone here switched from a conventional wood boiler (Memco, New Yorker, etc.) to a gasification boiler (Garn, Frohling, etc.) and tracked the difference in wood consumption for similar heating loads? Boiler manufacturers make claims about 50% or higher wood savings; does anyone have actual records showing such savings?


 




My interest with wood boilers started in the late 70s. Our first boiler was like the one pictured above. In one year it burned 22 cords of dry old growth Douglas fir wood that had lots of bark attached. It was also a write-off at the end of that first year as the metal that was not surrounded by water was burnt out and fractured.
Our second boiler was made in Denmark.  A small cast iron sectional down drafter with a triple pass heat exchanger.  Its wood consumption was sixteen cords a year. This boiler used the dutch oven concept of a fire box totally surrounded by water.  We had to put a tray on the floor underneath it to catch the liquid creosote that would drip out the bottom of the clean out door.  I added storage (1046 imperial gallons) to this boiler in hopes of eliminating the creosote on the floor.  The creosote now moved from the floor to the chimney. The surprise or prize was that storage dropped its wood consumption to ten cords a year.




With the creosote problems we were having the second boiler and when we learned of the concept of wood gasification,  a Jetstream was soon heating our storage system.  Our wood consumption now averages  4 - 4 1/2 cords a year.




This picture was taken with the Jetstream firing at full capacity.  From burning 22 cords a year to 4 cords per year on average. Thirty years of operating this system has shown some very small issues can alter efficiency and if several of these issues are compounded, efficiency numbers can be greatly effected.


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## Downeast Farmer (Jan 21, 2013)

This is my first foray into online posting and I'd have to say it's really great; thanks everyone.
   For most of the last 25 years we heated an old farmhouse on a windy ridge with a Memco boiler and it seemed that our 200-acre woodlot was barely large enough to feed it.  Then a couple of years ago we moved into a larger house in town.  We now have a Newmac wood furnace with an oil furnace backup and I buy my wood tree length from a local logging outfit ($90 per cord, or thereabouts).  I burn from 150 to 300 pounds of wood per day in this Newmac and someone must feed the beast every couple of hours.  On those rare days I get the place to 65F I'm treated like visiting royalty.  During this fairly average year I will burn about 15 cords of dry maple.  Something more efficient seems in order.
   I'm imagining the most efficient system to heat our house for the next 30 years and it seems from what I've read here and elsewhere that such a system would feature a wood boiler with storage and radiant heat.  I'm now trying to cost out that system and amortize those costs over 30 years to see if it's worth it; thus the interest in wood savings.  I gather 30% savings over a conventional wood boiler (or 40% over my wood furnace) is reasonable.
   The next issue I'll be looking at is the durability of the boiler.  Do you guys with your state-of-the-art gassiers feel that you have 30-year boilers?  They seem so complicated and component-rich that I wonder if your average farmer could maintain such a boiler for an extended period without a second mortgage.  On the other hand, maybe expecting such a long service life from a fairly new technology (the Garn and hobbyheater's Jetstream's boiler excepted) is unreasonable.  So, a Garn maybe?
   Is it sensible to design a 30-year wood heating system?  What components would your system have?  The constraints for me are: 1) no or nearly no fossil fuel use, 2) the minimum use of sustainable fuel, and 3) a system I can maintain (there being no one in my neck of the woods to do it for me).
  (I realize that a major part of this is reducing the heat loss of the house (which is now about 70 BTU/sf and for a number of reasons is unlikely to get much below 30), but that's an issue for another day.


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## Downeast Farmer (Jan 21, 2013)

And by the way, hobbyheater, anyone who goes from 22 cords a year to 4.5 is my personal hero.  Move to Maine and set up shop as a consultant.


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## Nofossil (Jan 21, 2013)

My brother is a fanatic, and has by far the best data I've seen. He weighs his firewood every load and keeps a diary. Here's the bottom line:

He originally had a traditional indoor boiler, operated at maximum achievable efficiency. He did short daily flat-out burns of well seasoned wood, and added a second heat exchanger to extract heat from the flue gas. He had some heat storage to maintain house temperature between fires. It burned very clean - virtually no creosote or visible smoke. In the pursuit of efficiency, he kept his water jacket way too cool and the boiler eventually rusted out.

When it died. he built a gasifier out of stainless steel. His wood consumption dropped by 40%.


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## flyingcow (Jan 21, 2013)

Downeast welcome. The gasser's are not complicated. I drive truck. It's easy. To  burn with a gasser


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## flyingcow (Jan 21, 2013)

Oh yeah, I like your red tractor, but I'll raise you a blue one.


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## Downeast Farmer (Jan 21, 2013)

Yes, Flyingcow, blue's nice, too, as are green, orange and gray, all for being so simple, and all of which I've used one time or another.  One of my sons did the signature and as he does most of the tractor work I'm grateful for it.

So, you're not worried about maintaining that Tarm, I take it.


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## hobbyheater (Jan 21, 2013)

Downeast Farmer said:


> During this fairly average year I will burn about 15 cords of dry maple. Something more efficient seems in order.


 


http://lamppakuuma.com/ This furnace has been getting good reviews on Hearth.


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## hobbyheater (Jan 22, 2013)

Downeast Farmer said:


> The next issue I'll be looking at is the durability of the boiler.


 




What has given the Jetstream its longevity is the fact that it is easy to repair. It is a very simple boiler; one aquastat to control the blower and circulator.




Refractory repair in progress.




The refractory repair completed. The refractory nozzle below the air injection pipe is easy to make and can be installed in 15 mins. through the clean-out door at the back.
	

		
			
		

		
	




The heat exchanger being moved back into position.
You have mentioned the name Garn. The Garn boiler is worth consideration. It has a simple system of fire brick in the fire box. The refractory nozzle is simple in construction and looks easy to replace and the company still stocks parts for the boilers that are thirty years old. The boiler comes with ample storage and again is simplistic in design.
I have never done the math but if you were to add 2000 gallons to some of the other boilers, there would likely not be much difference in price.


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## 91LMS (Jan 22, 2013)

flyingcow said:


> Oh yeah, I like your red tractor, but I'll raise you a blue one.


 
dont want to derail thread but i will put in a vote for a good ole red.  she's either on the hay rake or the blower!


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## kopeck (Jan 22, 2013)

There's a lot of variables in wood use.  Is it seasoned properly, what kind of wood is it? 

I started using my boiler sometime in mid November and I'm around 2 cords in, maybe a bit shy of that. 

I'm burning a bunch of red maple and poplar, not exactly BTU rich but it's what I have.  I figure I'll get through the main heating season on about 4 cord, if I had better wood probably that number would be closer to 3.

My parent have a house about the same size as mine and a ThermoPride wood furnace and they usually go through about 6 cord.  A bit of apples and oranges but that might give you an idea of usage.

K


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## kopeck (Jan 22, 2013)

flyingcow said:


> Oh yeah, I like your red tractor, but I'll raise you a blue one.


 
When's the last it snowed up there?  We were suppose to get 3-6" today last night but they swung and missed big time.  Other then the snow after Christmas we haven't had anything to speak of down here.  I hoping February picks up...

K


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## augercreek (Jan 22, 2013)

We are going on our third winter with a Garn 1500 and love it.Most days we fire it just once a day(three loadings)about a wheel barrow of wood.Days like today-20* with wind we will use two loads this evening.Each time you start a burn you must start a fire as there are no coals to restart. It is fired different than a OWB.We heat a 2400sf house,1000sf shop,300sf green house,and domestic water.We burn from September to the end of May.The first year I estimated we used 6 cord less wood than the OWB we had before.Most of our wood is Aspen Black Ash,Alder bushes and what ever else gets in the way of the chain saw.Wood burning is such a variable due to outside temps and type of wood you have.If you have wood like ours you'll twice as much as if you had Oak,volume wise.One thing I would do different would be to get a 2000 Garn as it has more water.If you operate it like the manual says I think it will last a very long time.A friend of mine has had one since 96 and has only changed out the fire bricks once and some of the gaskets and the anode rods.You have your water tested once a year and you're good to go.It is truly smokeless and never any creosote.
                    Your brother in Christ  Jerry


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## flyingcow (Jan 22, 2013)

Downeast Farmer said:


> Yes, Flyingcow, blue's nice, too, as are green, orange and gray, all for being so simple, and all of which I've used one time or another. One of my sons did the signature and as he does most of the tractor work I'm grateful for it.
> 
> _So, you're not worried about maintaining that Tarm, I take it._




No problems. Scrub the tubes when needed. Right now about every 10 to 14 days. In the summer once every month or so. Depends on how dry and how much wood you burn.


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## flyingcow (Jan 22, 2013)

kopeck said:


> When's the last it snowed up there? We were suppose to get 3-6" today last night but they swung and missed big time. Other then the snow after Christmas we haven't had anything to speak of down here. I hoping February picks up...
> 
> K


 
Sundas morning we got 6 to 8 inches. Today it was too cold to snow. I delivered into Portland this am. They were supposed to get 4 to 8 but never saw a flake.


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## kopeck (Jan 22, 2013)

flyingcow said:


> Sundas morning we got 6 to 8 inches. Today it was too cold to snow. I delivered into Portland this am. They were supposed to get 4 to 8 but never saw a flake.


 

NOAA's snow depth map has most of the county between 8-12", which surprised me I thought you folks had more then that on the ground?

I rolled out of bed thinking I was going to have to shovel this morning.  Like you said, not even a flake on the ground.  We did get some flurries later on this morning but it's not even a coating.

K


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## 91LMS (Jan 22, 2013)

kopeck said:


> NOAA's snow depth map has most of the county between 8-12", which surprised me I thought you folks had more then that on the ground?
> 
> I rolled out of bed thinking I was going to have to shovel this morning. Like you said, not even a flake on the ground. We did get some flurries later on this morning but it's not even a coating.
> 
> K


 
got a buddy doing some tower work in portage this week, wasnt a sled or trailer in dean's parking lot....  sad for the economy this late in the season already.


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## kopeck (Jan 22, 2013)

91LMS said:


> got a buddy doing some tower work in portage this week, wasnt a sled or trailer in dean's parking lot.... sad for the economy this late in the season already.


 
Yikes.  I stopped in at Norther Outdoors yesterday and they only had 2 or 3 trailers there.  They do have some snow though and I saw a fair amount of trailers heading south on 201.  The county really counts on that revenue, this is their tourist season.

K


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## 91LMS (Jan 22, 2013)

kopeck said:


> Yikes. I stopped in at Norther Outdoors yesterday and they only had 2 or 3 trailers there. They do have some snow though and I saw a fair amount of trailers heading south on 201. The county really counts on that revenue, this is their tourist season.
> 
> K


 its been quite a while since they had a good year.  i remember plenty of seasons we had snow enough to do over 3k w/o trying.  they had snow but open water, now its pretty frozen but snow settled a lot.  plenty of snow to ride but wondering if folks have backyarditis???  no snow in the backyard so they dont bother to do their winter vacations?


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## jebatty (Jan 22, 2013)

> ... seeking hard numbers on boiler efficiency as measured by wood use.


 
So far the only practical way I have found to do this is based on a key assumption: wood moisture content (MC). Plus stack temperature needs to be known and the wood has to be weighed. And if the efficiency of one boiler is to be measured against another, then they both have to be heating the same space under substantially identical conditions.

For efficiency of one boiler, my Tarm, I have calculated efficiency in terms of btu's to storage as compared to btu's in weighed wood burned, and also efficiency in terms of btuH heat loss as compared to btu's in weighed wood burns. For the first, I have measured efficiency of about 82-84%, and for the second about 88%. My assumptions are that MC = 20% and my measured stack temperature is assumed a constant 400F (although it varies over a burn, from a high of about 450F and then all the way down to fire out and boiler shutdown). Based on this, wood has 6050 btu/lb.

So, if I burn 100 lbs of wood, my boiler input btu's are 605,000. At 83% efficiency in converting these btu's to stored btu's in my 1000 gal storage tank, the tank temperature would have to rise by about 60F. Since my boiler is in my shop, boiler skin heat and flue to the ceiling, as well as heat loss from plumbing, is also heating the shop. This extra heat increases my measured overall efficiency to about 88% by way of shop heat loss. At this time I cannot account precisely for the remaining 12% of efficiency loss, although I have some ideas.


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## flyingcow (Jan 22, 2013)

91LMS said:


> its been quite a while since they had a good year. i remember plenty of seasons we had snow enough to do over 3k w/o trying. they had snow but open water, now its pretty frozen but snow settled a lot. plenty of snow to ride but wondering if folks have backyarditis??? no snow in the backyard so they dont bother to do their winter vacations?


 

getting off topic, but as a rule you won't see many sleds up here until February, actually closer to school vaca time. Too early, too cold. I've spent quite a few yrs grooming sled trails. Save your time and hours for feb/march, was the general plan.


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## kopeck (Jan 22, 2013)

flyingcow said:


> getting off topic, but as a rule you won't see many sleds up here until February, actually closer to school vaca time. Too early, too cold. I've spent quite a few yrs grooming sled trails. Save your time and hours for feb/march, was the general plan.


 
Did your Solo Innova warm you up when you got in from grooming?  See, we're back on topic!

I usually head up in February and you are right, a bit warmer and usually more snow.  Back when I had more time and more funds I would try to get up a couple of times a season, it could be quite cold riding in January.  Still, I think such a poor winter last year and a slow start to this year might be keeping some folks at home.  I hope it pickup up for you folks up there.

K


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## heaterman (Jan 22, 2013)

Here's a little real world data.

4 years ago we did a system overhaul for a customer who had been heating his 3800 sq ft house and DHW with a typical outdoor wood burner.  He was having a 4800 sq ft pole barn built (16 foot ceiling) for machinery repair on his farm and wanted a radiant slab to heat it. I had installed the OWB for him in 1995 and it was not going to do the job for both the house and the new construction so I suggested a Garn 2000.
He typically used between 20-24 face cords of wood per year with the OWB serving the house. (Drafty old farm house) They keep the shop at 60* all winter plus heat the house and DHW with the Garn. His wood consumption actually runs about 18-20 per year now with the Garn even though the load is substantially increased. I would say that if he was just heating the house alone as he did before his wood consumption would be nearly half of what it was with the OWB.


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## Downeast Farmer (Jan 23, 2013)

So, heaterman, that's 18-20 face cords, or 9 to 10 standard cords for all that load after the Garn, yes?


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## maple1 (Jan 23, 2013)

18 face cords = 6 real cords.

Most places, anyway.


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## kopeck (Jan 23, 2013)

A cord (as you probably know) is 4'x4'x8'.

A face cord is just the face side, so if the pieces are 16" it 16" wide by 4' high by 8 foot long.

So like maple1 said, just 1/3 of a full cord, in most places. 

K


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## James Reimer (Jan 23, 2013)

I switched from a conventional OWB smoke dragon to a Portage and Main Optimizer 250 this winter.  I would say a 50% wood savings would be a gross exaggeration.  I would say I have seen approximately 25% wood savings over previous years so far.  I used to burn 15-18 full cords a year so we'll see what the end result is at the end of this burning season.


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## kopeck (Jan 23, 2013)

James Reimer said:


> I switched from a conventional OWB smoke dragon to a Portage and Main Optimizer 250 this winter. I would say a 50% wood savings would be a gross exaggeration. I would say I have seen approximately 25% wood savings over previous years so far. I used to burn 15-18 full cords a year so we'll see what the end result is at the end of this burning season.


 
 I don't think you can expect quite a big a gain when your still talking an OWB that gasses, everything I've read about them they use the gassification process more for smoke control then efficiency.

That being said 25% is still a nice gain, one I wouldn't scoff at!

K


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## jebatty (Jan 23, 2013)

This does not result from actual measurements of efficiency. My old shop was heated by an OWB, and then I replaced it with the Tarm. My estimate was that the Tarm used about 1/3-1/2 the wood of the OWB based on "look and feel" of the operation. I didn't pay much attention to dry wood with the OWB, although it was not first year green wood. I remember well loading wheel barrows full of wood into the OWB, twice a day, and then struggling to keep the shop semi-comfortable, plus huge amounts of smoke, so much so that on one occasion someone stopped by thinking the place was on fire. Much, much easier with the Tarm and initially open storage with 3 old 175 gallon oil tanks for storage.


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## NHFarmer (Jan 23, 2013)

I haven't posted in a while but I couldn't resist. I too live in an old drafty farmhouse and I used a ton of oil and still froze. Tonight it is 8* outside and a comfy 70* as I type this. I do not have much in the way of data but I can tell you I burn about 10 cords per year to heat the house plus hot water all summer. I have a Tarm and has been very easy to run and maintain. My wife starts most of the fires and runs it during the day with no trouble. They really are no more complex than any other wood boiler. The other thing with a gasser is no creosote or smoke from the chimney. That gives me good peace of mind. I wouldn't hesitate to go with a gasser.


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## heaterman (Jan 23, 2013)

Downeast Farmer said:


> So, heaterman, that's 18-20 face cords, or 9 to 10 standard cords for all that load after the Garn, yes?


 

That would be correct. He and his boys cut their wood about 24" in length so two "ricks" from a full 4x4x8.


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