Garn vs. Wood Gun

[emesine]

I'm building new construction. I am looking into either a Garn or a Wood Gun. We are doing in floor radiant heating. Which is better, the Garn or the Wood gun?

I realize there may be a few strong opinions on this subject, what I am looking for specifically are details (dirt) on the two units-

What sort of maintenance is required on a weekly basis? (cleaning, ash removal, etc.)
What sort of maintenance is needed on a yearly basis? (spare parts, deep cleaning, etc.)
Reliability??
Ease of use for the wife? Need to light a fire every day- is that a problem?
Which is more efficient?
Lifespan?

We expect we will need something like 80 million BTU per season here in Indiana (3600 sq foot house built into the ground.)

Thanks!

Andrew

 

[Como]

I have no information on the Wood Gun, never seen one.

SWMBO said she could operate a Garn, could being the word.

But a Garn sounds overkill for new build.

 

[Jim K in PA]

I can't speak to the Woodgun, as I have never owned or operated one. The GARN is as simple as it gets. Lighting is quick and easy with the big draft induction fan. No smoke in your face since it is negative pressure at the fire box. Lifespan of the GARN should be at least 20 years, unless abused or neglected. Maintenance is nil - ash cleaning as per your usage and wood quality. I usually go a week or two between ash removal.

I will disagree with Durango's comment on the GARN being "overkill" for a new build. Your heat load is perfect for a GARN and it's integral storage. A properly designed system and well insulated house may allow you to do several days between burns with the WHS2000. You could probably get along fine with a 1500.

Search the posts here for LOTS of info on both machines. Feel free to check out my web site on my GARN install (link in sig).

Best of luck with whatever you decide.

 

[emesine]

Jim K-

Thanks for the info.

So, every 1-2 weeks you have to take a shovel and dig out the ash in the fire box. Doesn't sound all that bad. Many of the Garns I have seen online have a garbage can under the exhaust flue- does some of the ash end up out there? Is there any other cleaning routine?

Any idea on the efficiency of the Garn? The wood gun is quoted at 87%.

We are building 3600 sq feet to start, but we may have to add on in the future. We have 4 children, and are planning on at least 6. I may have 5-6000 sq feet by the time we are done. Plus heating for a pole barn, plus several teenage daughters showering..... the garn may not be big enough!

Thanks!

Andrew

 

[Jim K in PA]

Jim K-

Thanks for the info.

So, every 1-2 weeks you have to take a shovel and dig out the ash in the fire box. Doesn't sound all that bad. Many of the Garns I have seen online have a garbage can under the exhaust flue- does some of the ash end up out there? Is there any other cleaning routine?

Little to no ash is discharge from the flue, but you will have some small incandescent embers blown out during the burn. The 55 gallon drum (not a garbage can) will catch anything substantial. Some fill them with a little water, but I do not.

Any idea on the efficiency of the Garn? The wood gun is quoted at 87%.

The GARN, like any of the more traditional downdraft gassifiers, will have efficiencies in the 85-90% range during the peak part of the burn. I would not worry too much about a few percent either way, regardless of the type of gassification furnace you choose. Much more important for peak efficiency is dry fuel - 15-20% MC is best.

We are building 3600 sq feet to start, but we may have to add on in the future. We have 4 children, and are planning on at least 6. I may have 5-6000 sq feet by the time we are done. Plus heating for a pole barn, plus several teenage daughters showering..... the garn may not be big enough!

You may want two units!

 

[Singed Eyebrows]

Woodgun maintenance; On a weekly basis place ash receiver under front & rear inspection doors, pull ash from center tube, inspect refractory tunnels & remove ash if necessary, inspect refractory plug for seal. Use putty knife to clean ash from bottom of door openings. Scrape condensation & creosote from inside air intake manifold using ash rake. Open draft valve cover & inspect gasket for evidence of leakage. Inspect fuel chamber & remove ash residue. Center refractory pieces should be changed every 10 to 15 cords of wood. These just lift right out & are about $100.00 as told to me by a WG owner. The large refractory should be replaced every 10 to 15 years. The center refractory bricks contain the nozzles & in a real life situation expect about 1 1/2 to 2 years out of these. If I owned a WG I would just buy brick from Firebrick Engineers & drill them with a diamond holesaw. Clean the ash cyclone about 1 to 2 times a week depending on quantity of wood used. As for life span, a stainless boiler is capable of lasting up to 3 times longer than a carbon steel one as I found on a Google search awhile back. If this is accurate, I can't say. I will be posting a fuel chamber picture of a new E140 stainless WG as there are those that feel that the high expansion rates can cause stainless plate weld failures. You gotta see the number of stays in these boilers. Randy

 

[Como]

5,000 sq ft new build at 10 btu per sq ft = 50,000 btu simplistically.

Still sounds excessive.

 

[emesine]

50K btu per hour X 24 hours = 1.2 million BTU, which is exactly the storage for the Garn from 200F to 150F. So, on the coldest days of the year I will have to burn once per day just to heat my house. Add to that, of course, domestic hot water and an outbuilding later on.....

I'm just fine with not having to burn everyday. If I only have to fire up the boiler a 2-3 times per week during mild weather that is fine with me. Is there a problem with having too much storage, other than cost?

Andrew

 

[Jim K in PA]

Durango - in what way do you think the GARN is excessive? I don't want to put words in your mouth (or keyboard ;-) ). The GARN is not comparable to any other downdraft gassifier based on hourly Btu demand or output due to its integral storage. The GARN can easily put out 400K Btuh, which is more than just about anybody needs in terms of hourly demand except for perhaps a warehouse, but that is not the point of the GARN. The GARN can run at maximum efficiency, which is maximum output, for it's entire burn, regardless of demand. Excess heat is stored in the water, and drawn off during and after the burn as needed.

Andrew - the only downside to excess storage is standby loss. The GARN, as any other storage tank, needs to be well insulated to reduce standby losses to a minumum. This is not difficult, but should be considered in your analysis and comparison of systems.

 

[WoodNotOil]

If it were me, I would put the Garn in for your application. Jim is exactly right that sizing with Garns is not based on demand, as you store the heat and use it as you need. Insulate everything very well (house, boiler, barn, etc.) and you will not be disappointed. IMO

 

[emesine]

Assuming I put in a Garn....

It will be located on the ground floor level, above all in floor heating. I assume I can take water straight from the tank (without a heat exchanger) and run it through the pex tubing, as long as I use a mixing valve.

I guess if I want to transport water to a pole barn (~8 feet above the garn) I will need to put in a heat exchanger to a separate loop system. Also, if I want to heat anywhere at risk of freezing, I will have to use a separate loop containing antifreeze. I can't afford 2000 gallons of antifreeze!

Andrew

 

[flyingcow]

I'm enjoying my Tarm, its a really nice setup. But to do it over I would look at the Garn a lot closer. By the time I found it, I had already gone with what I got now. The dollars are close enough between my system and the Garn. Cool looking units!

I'm assuming you're putting this on a slab? These things are 15,000 to 19,000lb units when full of water.

 

[emesine]

Yes, I'm putting it on a slab. We are building a one story house with a walkout basement. The garage (and boiler room) will be on a slab at the level of the first floor.

Andrew

 

[WoodNotOil]

Assuming I put in a Garn....

It will be located on the ground floor level, above all in floor heating. I assume I can take water straight from the tank (without a heat exchanger) and run it through the pex tubing, as long as I use a mixing valve.

I guess if I want to transport water to a pole barn (~8 feet above the garn) I will need to put in a heat exchanger to a separate loop system. Also, if I want to heat anywhere at risk of freezing, I will have to use a separate loop containing antifreeze. I can't afford 2000 gallons of antifreeze!

Andrew

You will probably need a heat exchanger between the radiant floor and the Garn so that you can have a backup system in place for heating it as well. An on demand unit or small fossil boiler could be used as backup. The Garn is unpressurized which is why the heat exchangers are needed. Yes for other structures you will want them on their own loop and antifreeze in the lines as a precaution.

 

[emesine]

Our only utility available on the property is electric. We have no plans for propane or oil. I had considered adding an electric heating coil in the garn as a back-up. Should the power fail while we are away, we have friends who will keep an eye on the house. If my back-up is an electric coil in the Garn, do I need a heat exchanger?

Speaking of which, is there a thread out there on how to design a hydronic control unit- which pumps, thermostats, switches, etc. to use?

Andrew

 

[Der Fuirmeister]

For several months I looked at over all the units out there and narrowed the choices down to a Garn or the WG. I decided to buy both. A Garn for the shop and a WG for the home. Both very good units. From everything I've heard, a Garn and the SS WG are expected to have 20 year useful life. I have different needs at the shop and home. My home is similar to yours. Ranch with exposed basement / lower level. Still, getting a Garn into the house was a problem. The WG is smaller and allows storage away from the unit. The WG may not require storage, but I have yet to read about any gasifier system that isn't improved by storage. Both in more efficient burning and flexibility of use with extended times between burns. It also allows more flexibility when considering hot water heat or use for multiple buildings. I plan to use storage with the WG at home. I will be heating water and an outbuilding from the storage. The shop has in floor pex. We generate a lot of scrap wood in our business. The Garn should handle the scrap and pallet wood with fewer problems (nails) than the WG.

I'm applying for grants and tax incentive money with both units. Pat at WG told me they are waiting on testing results. Garn provided test results which have already been accepted by the state of WI for grants and tax deductions.

Information for these incentives for your state can be found through this link.....http://www.dsireusa.org/

Cost.....As you're probably already aware, when you compare size per size and add storage to the WG (for comparative benefits) they are very close in cost.

Finally, I wanted to have 6 or 8 kids, but I wasn't doing "the having" part. So we settled for 3. My wood stacking crew.......

 

[Gooserider]

Our only utility available on the property is electric. We have no plans for propane or oil. I had considered adding an electric heating coil in the garn as a back-up. Should the power fail while we are away, we have friends who will keep an eye on the house. If my back-up is an electric coil in the Garn, do I need a heat exchanger?

Speaking of which, is there a thread out there on how to design a hydronic control unit- which pumps, thermostats, switches, etc. to use?

Andrew

Don't think you'd want to put a backup coil IN the Garn, as that would mean needing to heat up the entire storage tank... I would go with the heat exchanger and have the backup be a separate electric coil that only heated the actual heating loop... Not sure if it would work, but one option that occurs to me is that if you are using the Garn to heat a DHW tank as one part of the loop, to have an electric element as a backup in the DHW tank (maybe used in the summer when it doesn't make sense to fire the Garn just for hot water?) - and rig the plumbing so that you could use that as a supplemental house-heat source if the Garn didn't work - probably wouldn't be enough to keep you cozy, (electric water heaters are slow...) but probably would be enough to keep the pipes from freezing... (Again, avoid sending the hot water to the Garn, you DON'T want to electrically heat that big tank...)

Gooserider

 

[WoodNotOil]

The company Radiantec has information on how hot water heaters can be used to heat radiant floors. I think Gooserider is right on with this suggestion as a backup with a heat exchanger from the Garn.

 

[emesine]

OK, if I put an electric coil in the garn....

1 KWH = 3400 BTU

16,000 BTU per degree of temperature rise in the Garn 2000

Assuming I have a thermostat that turns on at 115 and turns off at 120....

Each cycle, (5 degrees) will expend 80,000 BTU or around 25 KWH.

At 0.05 per KWH, that would mean $1.25 per cycle. Assuming I have 4 4500 watt coils (200 amps), it would take 5 hours to rise 5 degrees.

The heat loss from the Garn would probably be around 5-10 degrees per day (is that about right....) At that rate I would be losing $2.50 per day in heat.

For an emergency back-up system, that isn't all that bad- 200 amps is a LOT of power- not sure we will have that much available. I might have to use 2 4500 coils instead. It would take DAYS and $$$ to heat the unit up from a cold start. I am beginning to see the problem here.


Jim K in PA-

Where is a good starting point for understanding the TACO controllers? To save some $$ I would like to build my own control system. Can you point me to a good starting document (there are hundreds of documents on the TACO website.) Your website is great.

Thanks everyone for your input- this is VERY helpful information.

Andrew

 

[Gooserider]

I have mixed feelings about Radiantec - especially the way they seem to want to use the water heater both as the source for both DHW and heating, and run potable water through the heating system lines - They say it's a valid approach, and gives slight cooling benefits in the summer, but there seems to be a good bit of controversy about it at best... Of course, I don't get much choice about the matter since their method is illegal in Mass.

Even with the claimed cooling effect, I'm a bit dubious, and think it is probably best / safest to keep the DHW and heating in seperate loops. It just seemed like this might be a possible way to get at least SOME backup heat in order to keep pipes from freezing, etc.

Gooserider

 

[heaterman]

I can only speak for the Garn as I have no experience with the Wood Gun. The Garn, in lab tests conducted by an independent organization ran a couple points above 75% and surpassed the 2010 emissions standards. This is truly remarkable because the basic design has not been changed since it was introduced in the early 80's.

Cleaning is a non-event. Push the coals to the back, shovel out a couple scoops of ash and pull the coals back to reload if needed. I met an owner who purchased his Garn 1350 in the early 80's that told me he has only had the covers off the flue tubes twice in over 20 years of operation. On the other hand I have a customer who has to clean his flue tubes once or twice a winter. What's the difference? Wood moisture content basically. That and the fact that the guy doing the double cleaning is burning 150 face cords through 2-2000's per winter. Plus he has about a dozen different people running the units some of which are not too bright. For 95% of folks I can assure you there will be no issues with cleaning a Garn. The burn completely and never smolder the fire which results in almost complete combustion.

After having seen with my own eyes a Garn that has been in service since 1983 with no chemical treatment, I can only speculate what the life of a well cared for unit would be. 25 years + should easily be attainable with any nominal care.

Oversizing is not a concern. You simply fire it less often. You can only oversize storage to the point where heat loss from it becomes prohibitive.

 

[Gooserider]

If I was looking to do a controller, I'd probably skip Taco and friends, and look at NoFossil's setup - seems to me like his box probably costs less than most of the alternatives and is FAR more flexible and versatile...

Gooserider

 

[Jim K in PA]

I also concur that using the electrical element array as a backup heat SOURCE is not an ideal solution. It is intended to be used as an input supplement if you have off-peak electrical rates. I think a tankless propane fired water heater would make an excellent alternative backup system for the house, but it would not supply enough for an outbuilding or to substantially heat the GARN tank.

For your TACO research, look at the Zone Valve Controllers and Switching Relay Controllers. They are nothing more than switches set up to take input from t-stats and turn on/off other components. Look into Nofossil's setup if you want to save a little $$ and develop your own strategy. His will also give you data access and logging, I believe. For my situation, the TACO boxes were an off the shelf solution that meets my needs. They cost under $200 for the 6 zone units and use readily available "ice cube" relays.

 

[Gooserider]

I also concur that using the electrical element array as a backup heat SOURCE is not an ideal solution. It is intended to be used as an input supplement if you have off-peak electrical rates. I think a tankless propane fired water heater would make an excellent alternative backup system for the house, but it would not supply enough for an outbuilding or to substantially heat the GARN tank.

I agree, the electric water heater element would be far from an ideal backup, but earlier in the thread, we were told that electric was the only available utility, and that there was no plan to install propane or oil... Given that the only option listed was electric, I was trying to come up with a solution that used it in as sensible a way as possible...

(If it was my setup I'd consider either adding a small propane setup, or at least a gasoline generator so that I could run the Garn, with or without power (Plus some solar heaters for summer DHW), but I was working within the specified parameters)

Gooserider

 

[Jim K in PA]

I agree, the electric water heater element would be far from an ideal backup, but earlier in the thread, we were told that electric was the only available utility, and that there was no plan to install propane or oil... Given that the only option listed was electric, I was trying to come up with a solution that used it in as sensible a way as possible...

(If it was my setup I'd consider either adding a small propane setup, or at least a gasoline generator so that I could run the Garn, with or without power (Plus some solar heaters for summer DHW), but I was working within the specified parameters)

Gooserider

Did not intend to have my response be a criticism of your solution Goose. Sorry if I did so. Although not in the plan, Andrew may want to consider the propane option, as it is cost effective and the propane has an indefinate shelf life with no additives or maintenance necessary like an oil backup would. Since this was a discussion of backup options, the propane solution could still work with a loss of electric utility through a small backup generator to run the pumps and sensors.

Geez - we sure do get carried away spending everyone else's money, don't we? :lol: