Does anyone NOT like their Garn? How do you feel about your Garn?

[Floydian]

Howdy folks-
This site has been invaluable to me. I found it looking for info on wood stoves and now I'm committed to wanting to go the gassifier route.
I've spent many, many hours on here and really appreciate the knowledge-Thanks to All.
My situation is I'm looking for heat/DHW to two houses approx. 385' apart. So I'm comparing two downdraft units+storage(one in each basement) VS.
a Garn+underground lines (sprayfoam in trench vs. prefab) +building.
I visited a Garn 1500 yesterday and was certainly impressed. I'm visiting someone with a Tarm at the end of this month and I'm hoping to see an
EKO in operation as well. These are some tough decisions but I'm enjoying the research.
This has been a great thread and really shows how some things work for some people and don't for others.
I don't know what works for me. YET.

Just wanted to say hello and thanks.
Noah

 

[ThisWarmHouse]

Just wanted to throw some info out there for the people asking about Garn efficiency.

When calculating total system efficiency there are two numbers you are dealing with. Combustion efficiency and transfer efficiency. To get system efficiency you multiply combustion efficiency % by transfer efficiency %.

Combustion efficiency is a number that has been used and abused by those in OWB marketing especially. Some companies that really wanted to over rate their combustion efficiencies would weigh the wood they were burning and then burn the ash that was left over and figure out what % of the wood didn't burn. This is ridiculous as your wood is going to burn down to the same amount of ash in most situations. So these companies would burn wood with low ash content and say "We have 99% combustion efficiency". This method doesn't look at factors like how many BTUs are stored in the wood and how many of those BTUs are actually combusted so it totally ignores the potential for gasification ignoring the fact that 50 - 60% of your btu's are actually going up your chimney in the form of unburned gasses and smoke. So for combustion efficiency if a boiler is not gasifying it can not even have 50% combustion efficiency in reality.


Transfer efficiency is the percentage of heat that is combusted that actually makes it into your home/storage. If you are creating 100,000 btu's of heat in the firebox and gasification chamber but 20,000 btu's are going up the chimney than you have an 80% transfer efficiency. One misconception I had when I first got into this industry was thinking "why not just make a better heat exchange system and get the transfer efficiencies even higher. The problem with this is if you get your stack temperature too low (below 300) you can get condensation and corrosion problems. So there is a wall regarding how high transfer efficiency can be. This is why since most gasifiers have very similar combustion efficiencies and you can only get transfer efficiencies up only to a certain level it seems that most all of the popular gasifiers are in a very similar efficiency range.


Looking at a traditional OWB that has a real world combustion efficiency of 50% and a transfer efficiency of around 50% (hot stack temps) you multiply the 2 numbers together and you find out that many typical OWB's actually have a total system efficiency of around 25%!


The Garn has been tested by an outside laboratory and it has a total system efficiency of up to 84% (factors include wood type, moisture content and other burn practices). I'll have to get the individual combustion and transfer efficiencies for you. But the total system efficiency is the number that really matters anyways

 

[Zick]

The way I figure it the smallest Garn would cost 6-8 grand more than my GW100 installed. That is 40 cords of wood in todays market. More than 4 years of fuel for me plus the wood needs splitting. How much less if any would I burn with a Garn over that 4 years?
Jeez, 20 grand could get you a GW100 and a 5 acre woodlot plus you could let the wood grow for 4 years adding 30% wood mass.

This is/was my delema just recently since I have both a Greenwood and Garn dealer close to me.
I was originally going to go with a GW100 due to it's price and simplicity but found there are some disconcerning problems/complaints with the gw100's.
Then I found the Garn WHS1500 and it looked perfect, simple to run/maintain, almost no complaints about and it's an all in one package but the price shocked the hell out of me.
But then I started pricing out what a gw100 with a storage tank (not home made) together would cost and found that the Garn was really not much more. Now granted you could make your own storage or not use one at all but you would be probably using more wood in the long run.

 

[ThisWarmHouse]

The way I figure it the smallest Garn would cost 6-8 grand more than my GW100 installed. That is 40 cords of wood in todays market. More than 4 years of fuel for me plus the wood needs splitting. How much less if any would I burn with a Garn over that 4 years?
Jeez, 20 grand could get you a GW100 and a 5 acre woodlot plus you could let the wood grow for 4 years adding 30% wood mass.

This is/was my delema just recently since I have both a Greenwood and Garn dealer close to me.
I was originally going to go with a GW100 due to it's price and simplicity but found there are some disconcerning problems/complaints with the gw100's.
Then I found the Garn WHS1500 and it looked perfect, simple to run/maintain, almost no complaints about and it's an all in one package but the price shocked the hell out of me.
But then I started pricing out what a gw100 with a storage tank (not home made) together would cost and found that the Garn was really not much more. Now granted you could make your own storage or not use one at all but you would be probably using more wood in the long run.

I'm a Greenwood and Garn dealer so take this with a grain of salt. When looking for the best value don't just look at your upfront costs. You also have to look at the other end of the bookend. Longevity. If your Greenwood only lasts you 60% as long as a Garn is it still going to save you money in the end when you have to replace your system? I'm not saying that's going to be the case. It's just that Garn has the long track record with 25+ year old systems still running in the field and Greenwoods have only been on the market for 4 years. So we just don't know.

 

[tigermaple]

Let me say I love the Garn concept and studied the " which boiler" problem intensely for several years before getting a gw100. If there was a smaller Garn type I would have been all over it. I felt just heating something so massive to warm 3000sf was a waste to begin with. There are surely measurable heat losses in doing so.
As far as storage, I don't have any so I don't know what I'm missing. How much less wood would I burn with storage?

 

[ThisWarmHouse]

Let me say I love the Garn concept and studied the " which boiler" problem intensely for several years before getting a gw100. If there was a smaller Garn type I would have been all over it. I felt just heating something so massive to warm 3000sf was a waste to begin with. There are surely measurable heat losses in doing so.
As far as storage, I don't have any so I don't know what I'm missing. How much less wood would I burn with storage?

There are definately some situations where a Greenwood just fits better, that's the whole reason we sell both systems. Don't think that I'm saying the Garn is always the better choice.

Regarding storage I think most Greenwood owners don't have extra storage. The benefit of the storage isn't just for efficiency and how much wood you would burn. It also effects time between burns, how much smoke you produce and also gives you an extra buffer to protect you against thermal spiking.

 

[heaterman]

Let me say I love the Garn concept and studied the " which boiler" problem intensely for several years before getting a gw100. If there was a smaller Garn type I would have been all over it. I felt just heating something so massive to warm 3000sf was a waste to begin with. There are surely measurable heat losses in doing so.
As far as storage, I don't have any so I don't know what I'm missing. How much less wood would I burn with storage?

Standby losses are definitely a factor when you are storing btu's in 1500-2000 gallons of water. The fact is though that these are easily dealt with by using your head during installation of underground piping and insulating the Garn itself. With a little planning, use of the appropriate materials and due diligence during the process, the standby losses can be brought to a point of being negligible.

 

[Zick]

The way I figure it the smallest Garn would cost 6-8 grand more than my GW100 installed. That is 40 cords of wood in todays market. More than 4 years of fuel for me plus the wood needs splitting. How much less if any would I burn with a Garn over that 4 years?
Jeez, 20 grand could get you a GW100 and a 5 acre woodlot plus you could let the wood grow for 4 years adding 30% wood mass.

This is/was my delema just recently since I have both a Greenwood and Garn dealer close to me.
I was originally going to go with a GW100 due to it's price and simplicity but found there are some disconcerning problems/complaints with the gw100's.
Then I found the Garn WHS1500 and it looked perfect, simple to run/maintain, almost no complaints about and it's an all in one package but the price shocked the hell out of me.
But then I started pricing out what a gw100 with a storage tank (not home made) together would cost and found that the Garn was really not much more. Now granted you could make your own storage or not use one at all but you would be probably using more wood in the long run.

I'm a Greenwood and Garn dealer so take this with a grain of salt. When looking for the best value don't just look at your upfront costs. You also have to look at the other end of the bookend. Longevity. If your Greenwood only lasts you 60% as long as a Garn is it still going to save you money in the end when you have to replace your system? I'm not saying that's going to be the case. It's just that Garn has the long track record with 25+ year old systems still running in the field and Greenwoods have only been on the market for 4 years. So we just don't know.

Yet another reason I'm leaning more toward a Garn. Sounds like they do last a long time with proper maintenance. I saw the one thread on here where the entire side of the GW was rusted through. Now that may have been operating error or manufacturer defect but it just didn't sit well with me. Also, I haven't been able to find out what happens if the refactory casting cracks enough where it falls apart. Does GW cover this under warrenty? I've heard that they will send you a mortor type patch but what if the casting is beyond patching and needs replacing?
We are building a new home this year and hope to be in it for at least 20 years.

 

[Floydian]

"Standby losses are definitely a factor when you are storing btu's in 1500-2000 gallons of water. The fact is though that these are easily dealt with by using your head during installation of underground piping and insulating the Garn itself. With a little planning, use of the appropriate materials and due diligence during the process, the standby losses can be brought to a point of being negligible."

Heaterman,what would you consider negligible heat loss for underground piping? This is a big concern as my conversations with several retailers of
the highest quality prefab options say I could see a loss of 1 or so degrees over 200' @10 gpm. My calculations show that could be between around 120k btu's/day or more. Times that by 2 for 2 houses and thats a lot of loss IMO. I've seen better claims with sprayfoam in the trench but even at half of that is still adds up over a year.
Am I close with this math?

Any estimation of heat loss for a Garn building thats the minimum size for the unit and space around the door to load it comfortably, assuming its very well insulated?
These numbers could be huge in a situation like mine.

Thanks,
Noah

 

[ThisWarmHouse]

The way I figure it the smallest Garn would cost 6-8 grand more than my GW100 installed. That is 40 cords of wood in todays market. More than 4 years of fuel for me plus the wood needs splitting. How much less if any would I burn with a Garn over that 4 years?
Jeez, 20 grand could get you a GW100 and a 5 acre woodlot plus you could let the wood grow for 4 years adding 30% wood mass.

This is/was my delema just recently since I have both a Greenwood and Garn dealer close to me.
I was originally going to go with a GW100 due to it's price and simplicity but found there are some disconcerning problems/complaints with the gw100's.
Then I found the Garn WHS1500 and it looked perfect, simple to run/maintain, almost no complaints about and it's an all in one package but the price shocked the hell out of me.
But then I started pricing out what a gw100 with a storage tank (not home made) together would cost and found that the Garn was really not much more. Now granted you could make your own storage or not use one at all but you would be probably using more wood in the long run.

I'm a Greenwood and Garn dealer so take this with a grain of salt. When looking for the best value don't just look at your upfront costs. You also have to look at the other end of the bookend. Longevity. If your Greenwood only lasts you 60% as long as a Garn is it still going to save you money in the end when you have to replace your system? I'm not saying that's going to be the case. It's just that Garn has the long track record with 25+ year old systems still running in the field and Greenwoods have only been on the market for 4 years. So we just don't know.

Yet another reason I'm leaning more toward a Garn. Sounds like they do last a long time with proper maintenance. I saw the one thread on here where the entire side of the GW was rusted through. Now that may have been operating error or manufacturer defect but it just didn't sit well with me. Also, I haven't been able to find out what happens if the refactory casting cracks enough where it falls apart. Does GW cover this under warrenty? I've heard that they will send you a mortor type patch but what if the casting is beyond patching and needs replacing?
We are building a new home this year and hope to be in it for at least 20 years.

Greenwood covers the refractory for the 10 year warranty. They don't cover surface cracks which are just cosmetic and don't affect the function of the unit, but if a piece cracks all the way through they will replace it. The newer multi-piece refractories they are making are much better than the old single piece ones they had. I've had bad experience trying to move used units with the old single piece refractory, they tend to collapse during transport. The new multi piece design doesn't seem to have those type of problems.

 

[Zick]

Greenwood covers the refractory for the 10 year warranty. They don't cover surface cracks which are just cosmetic and don't affect the function of the unit, but if a piece cracks all the way through they will replace it. The newer multi-piece refractories they are making are much better than the old single piece ones they had. I've had bad experience trying to move used units with the old single piece refractory, they tend to collapse during transport. The new multi piece design doesn't seem to have those type of problems.

Thanks ThisWarmHouse, I didn't realize they are now using multi piece design vs one single piece.

 

[BrownianHeatingTech]

You and I may be using different terminology but talking the same point. I understand combustion efficiency to be different from boiler efficiency. The first relates purely to combustion, and I think all of the gasification boilers are within 1% or so on this, ranging between 97-99%. The second relates to efficiency in transferring the combustion heat to the water (my use of the term "boiler efficiency"). I think this is what your efficiency numbers relate to.

As I'm using it, "combustion efficiency" means the entire process, from wood in, to exhaust gasses and hot water leaving the boiler.

This is in contrast to "system efficiency," which includes standby losses, piping losses, etc. etc.

Combustion efficiency is the efficiency of the heat plant, itself, under full-burn operation. System efficiency is energy (fuel) in, versus energy (heat) delivered to the living space.

We run across that difference quite often in fossil fuel systems. An oil boiler with an internal coil ("tankless" or "warm start") may have the same 85% AFUE (combustion) efficiency as a similar boiler with an indirect water heater (ie, a "cold start" system) next to it. However, the system efficiency of the first will be about 55%, while the system efficiency of the second will be about 65%. The difference results from not keeping the boiler hot all summer just to produce domestic hot water. The reason the system efficiency is still lower than the combustion efficiency is because of additional losses, like burning heated indoor air, using a significant amount of oil just to heat the iron block, before delivering heat to the house, etc.

System efficiency will always be lower than combustion efficiency. How much lower can depend upon the design of the system pretty dramatically, even with identical boilers.

There are other factors, as well. A Garn (or any boiler with storage) being used all summer for domestic hot water will have a lower system efficiency as a result of keeping that tank hot all summer. However, by not using fossil fuels to produce domestic hot water, and using inexpensive wood instead, the lower efficiency really isn't that important. Slightly lower efficiency utilization of an inexpensive, renewable fuel is going to beat higher-efficiency utilization of an expensive, non-renewable fuel, both economically and environmentally.

Joe

 

[jebatty]

Regarding standby losses, I made this pretty much go away by installing the Tarm and the 1000 gal storage in a space to be heated anyway. All "standby losses" simply provide heat that otherwise would be drawn from the system.

I realize this is not possible for many, but do what you can, and if you are planning new home or building construction, allow for it. It represents a substantial gain in effective system efficiency.

 

[BrownianHeatingTech]

Regarding standby losses, I made this pretty much go away by installing the Tarm and the 1000 gal storage in a space to be heated anyway. All "standby losses" simply provide heat that otherwise would be drawn from the system.

I realize this is not possible for many, but do what you can, and if you are planning new home or building construction, allow for it. It represents a substantial gain in effective system efficiency.

That applies during the heating season, but constitutes a loss when you don't need the heat there (ie, portions of spring, summer, portions of fall).

Joe

 

[jebatty]

Agreed. I don't use my system for dhw, just space heating. My storage has removable insulation. I take some off during colder periods and put some back on when not much heat is needed. During Spring/Fall, I may fire the Tarm only once every 4-6 days; during this current cold spell (lows down to -20F and some highs not clearing 0), I fire 4-7 hrs/day.

 

[heaterman]

"Standby losses are definitely a factor when you are storing btu's in 1500-2000 gallons of water. The fact is though that these are easily dealt with by using your head during installation of underground piping and insulating the Garn itself. With a little planning, use of the appropriate materials and due diligence during the process, the standby losses can be brought to a point of being negligible."

Heaterman,what would you consider negligible heat loss for underground piping? This is a big concern as my conversations with several retailers of
the highest quality prefab options say I could see a loss of 1 or so degrees over 200' @10 gpm. My calculations show that could be between around 120k btu's/day or more. Times that by 2 for 2 houses and thats a lot of loss IMO. I've seen better claims with sprayfoam in the trench but even at half of that is still adds up over a year.
Am I close with this math?

Any estimation of heat loss for a Garn building thats the minimum size for the unit and space around the door to load it comfortably, assuming its very well insulated?
These numbers could be huge in a situation like mine.

Thanks,
Noah

Let me visit a couple job sites have been in in operation for a year or two and get I'll get back to you on that with some examples.

 

[Floydian]

"Standby losses are definitely a factor when you are storing btu's in 1500-2000 gallons of water. The fact is though that these are easily dealt with by using your head during installation of underground piping and insulating the Garn itself. With a little planning, use of the appropriate materials and due diligence during the process, the standby losses can be brought to a point of being negligible."

Heaterman,what would you consider negligible heat loss for underground piping? This is a big concern as my conversations with several retailers of
the highest quality prefab options say I could see a loss of 1 or so degrees over 200' @10 gpm. My calculations show that could be between around 120k btu's/day or more. Times that by 2 for 2 houses and thats a lot of loss IMO. I've seen better claims with sprayfoam in the trench but even at half of that is still adds up over a year.
Am I close with this math?

Any estimation of heat loss for a Garn building thats the minimum size for the unit and space around the door to load it comfortably, assuming its very well insulated?
These numbers could be huge in a situation like mine.

Thanks,
Noah

Let me visit a couple job sites have been in in operation for a year or two and get I'll get back to you on that with some examples.

Thanks Heaterman, I'd appreciate that.
Noah

 

[drpolc]

On GARN's longevity vs. other open-system boilers... I called GARN and they confirmed and enhanced my understanding.

1) All seams are welded inside and out. To do this you need access to all seams once unit is assembled. GARN has a manway... go see a GARN somewhere... likely they will let you crawl inside and see for yourself. This prevents crevice corrosion.

2) All steel is grit blasted (a more expensive process to get all the slag and microscopic crud - that can hid and encourage corrosion - off the steel).

3) GARN uses 3/16 and 1/4 inch steel.

4) GARN's water tank is rounded, not rectangular. This prevents sedimentation from sitting on welded seams which can facilitate corrosion over the long haul.

5) The bottom of every GARN is coated with epoxy. This prevents sedimentation from laying against the metal on the bottom of the tank.

6) Self sacrificing anode rods. Every GARN has these rods to detect any stray electrical currents that could accelerate metal corrosion.

7) Best of all... GARN has an effective and ongoing chemical treatment and analysis plan. Buy a GARN and with the chemical treatment you get 5 years of bi-annual testing. The treatment company will send you a kit to take a water sample every 6 months. You send it in to the company and they provide GARN and your local distributor with a complete water analysis with recommend remediation plan if needed.

Hope this helps

 

[slowzuki]

Regarding some comments earlier related to space, I'm finding the clearances required for most boilers makes them take up a lot more space than you would think. I'm assuming the garn can have items touching the water jacket and only needs clearance on the front where sparks may jump out while loading.

 

[Jim K in PA]

Regarding some comments earlier related to space, I'm finding the clearances required for most boilers makes them take up a lot more space than you would think. I'm assuming the garn can have items touching the water jacket and only needs clearance on the front where sparks may jump out while loading.

GARN recommends about 2" clearance on the sides, about 18" at the rear (which you want anyway for access to the rear piping) and about 5' clearance at the front for safe loading. I have less than that on the sides of mine. I agree that the only places of real concern are the rear flue exit and the loading door. The rest of the GARN is water jacket, so will not exceed the temperature of the water, and is actually less. My WHS2000 is in a 6'x6'x12' space with a 10' shed at the door end for wood storage and loading. I ran all my piping through the side wall into the garage where I have my primary loop. See my setup in my link below.

 

[Eric Johnson]

Regarding some comments earlier related to space, I'm finding the clearances required for most boilers makes them take up a lot more space than you would think. I'm assuming the garn can have items touching the water jacket and only needs clearance on the front where sparks may jump out while loading.

Like mine, Ken?

 

[slowzuki]

Eric yours is nice and tight due to the masonry, I'm thinking in terms of plunking one down in a wood framed building. Mine needs 24" on one side, 12" on the other, like 24" at the rear and a bunch at the front. Then with the flue requirements added, I get a pretty big footprint. With my storage tank being 5 ft in diameter and 10 ft long with no clearance, I really start to see the advantage of the Garn when you are going with storage.

 

[Eric Johnson]

I started out with a wood-framed boiler room (with my old, conventional wood-fired boiler), but found it difficult to sleep at night. Concrete and steel was certainly worth the extra expense and effort. Luckily, the EKO 60 just fit, because I built the room for the old boiler. And I learned that I'm not much of a mason when it came time to fit the doors, but that's why they made caulk, right?