Burn times: Gasifiers vs. natural draft water jacket boiler

Andrew L. · Oct 26, 2011

I read with envy all these posts from you guys that have gasification boilers. They sure seem to be efficient and use less wood than my system. The question I have before looking vary hard at replacement of my 5 year old unit is the burn time of most gasifiers (EKO, Tarm, Econoburn, etc. ) I've read through many posts and the most common answer is 4-6 hours of active burn time.

Here is my situation: I have a ThermoControl 2500 boiler in my garage. It's plumbed into 1000 gallons of pressurized storage and my old oil boiler serves as the backup (automatically - when it works). The Thermocontrol is a beast not unlike your typical OWB, but it does have secondary air tubes that place air in the back of the chamber for passive secondary air. No major complaints with the boiler at five years old. However, it is somewhat inefficient (tested at 76%) compared to gassers, uses about 12 full cords of dry hardwood per year to heat 4000sf, my garage, and hot water, and it does not completely combust the wood, leaving lots of black charcoal on the firebrick. (I think this is largely due to a lack of any grates to allow the ash to filter out. If I stir things up enough, the charcoal does get consumed). Very clean burning with not much smoke unless starting the fire. All the parts are simple and commercially available (no proprietary, expensive stuff).

The thing I love about this boiler is that I can fill it in the morning and walk away for at least 12 hours. I get home and there is always a bed of coals enough to re-ignite the new charge of wood without messing around. I basically fill the thing 2x per day and that's it. The fire gets lit in October, and stays lit until April. I don't even have kindling wood.

Is this sort of operation feasible with a gasser? I don't relish the idea of making a fire, lighting it, and waiting 10 minutes to flip the handle over to gasification mode once it's hot enough. Would there be a bed of coals hot enough to re-ignite new wood after 12 hours even if I got a large (300K btu) econoburn or something like that?

Thanks to you all for this site. It is a huge help !!!

Drew

ISeeDeadBTUs · Oct 26, 2011

I cant speak for Euro-style down-drafts, but I'm thinking that a 4 hour burn has reference to a FLAT_OUT burn. Which implies storage. If you get the same BTUs from a 4 hr FLATOUT burn as 12 hour smoulder, then you should be golden, as long as you have storage.

I agree that starting fires regularly would be tedious, so I don't. To over-simplify it, my GW is somewhere between your water stove and a Euro-style downdraft.

But I don't think you want to make a decision on hydronic unit based on burn times. My GW is a 100, so I bet I could make a 300 go at least 24 hours. But why would I want to? I also don't think you want to be making a decision this close to November in Upstate NY. Feed the beast ya got for this year and next year, when people are throwing gold into the streets, pick yourself up a nice new fancy boiler.

Andrew L. · Oct 26, 2011

Thanks for the quick response. I'm familiar with the Greenwood 100. A good friend has one and likes it. I'm definitly not making a change this late in the year, and am already "burning the beast". I'd need to win the lottery to afford a new gasifier at this point anyway.

Can your GW go 12 hours without refill and start back up without lighting a new fire?

stee6043 · Oct 26, 2011

The only folks around these parts that brag about long burn times are the old school OWB guys. Longer times between loading for X amount of heating means more waste, more wood burned.

I can squeeze 4 hours out of a full load of good wood. I also collect roughly half a million btu's in that time.

barkeatr · Oct 27, 2011

i HAVE a profab 200 gasser, outdoor unit. I dont have water storage but have a extreme mass house. My gasser will go into idle mode and the wood just sits there all black and charred. ITs not even smoking...but then when the fan goes on the fire starts again. THe profab is designed to run this way, storage is not a part of the design according to the manufacturer. I know, i will hear comments on this but Im just sayin. So to answer the question i can get 8-10 hour burn times pretty easy. I had a central boiler and find the this gasser much much easier to run.

with tihs profab there are two slots in the floor that lead to the gasification burn chamber, but on either sides of those slots, coals build up so you can get another fire started pretty easy. you must have dry wood with a gasser as im sure you know, so you can use this year to get ahead wood wise.

musclecar joe · Oct 27, 2011

I have an Econoburn 150 with no storage. I am heating a 3000 sq ft home and a 1200 sq ft garage. both well insulated. I am lucky to get 7 hours of heat (burn time) during January or Feb. I am always looking to find a way to cut my loading and restarting of fires less than 3 times a day. When I get home from work I have to restart and every morning. It sucks. Storage may help slightly but I have Rads so I have to keep my temp up to 180 so I would be storing btus that will not last long enough to make it worth it. I burn around 12 cord a year for my specific application. I wish I would have bought a Thermocontrol unit. would have burned the same amount of wood and only loaded 2 times a day. My fault for being taken by a salesman. Oh well too late now.

if you have in floor radiant and storage, the gaser is definatly the way to go. You will burn much less wood but yes, you more than likely will be liting fires more often. I certainly wouldnt mind that if I were only burning 4-5 cord a year. good luck with your research. the guys here are most helpful

Musclecar joe

flyingcow · Oct 27, 2011

I wonder how much less you would burn with a gasser? Maybe down to 9 cord? And that might be a stretch. You're already burning dry wood.

If that burns pretty clean, I think you might have a keeper. Seems to fit your schedule. Also, once i shut the door on my gasser, i walk away, no handle to turn.

willworkforwood · Oct 27, 2011

flyingcow said:
I wonder how much less you would burn with a gasser? Maybe down to 9 cord? And that might be a stretch. You're already burning dry wood.
If that burns pretty clean, I think you might have a keeper. Seems to fit your schedule. Also, once i shut the door on my gasser, i walk away, no handle to turn.

+1
If it ain't broke, don't fix it.

musclecar joe said:
I have an Econoburn 150 with no storage. I am heating a 3000 sq ft home and a 1200 sq ft garage. both well insulated. ... I burn around 12 cord a year for my specific application. ....
Musclecar joe

Sounds like it might be a bit undersized, but how about the heat loss calc - does it match up well with the 150? How warm do you keep the garage? Have you tried turning the garage zone off, just as an experiment to see what the difference is? Did you check/clean the heat tubes after last Winter?

rwh442 · Oct 28, 2011

I have a Thermo-Control 2000 model without storage and load 3 times per day. It's in my detached garage, and ironically we decided to call ours the "Beast" also. Over the last several years it has consistently used around 8 cords per heating season. It heats the house via water to air HX in a furnace plenum, detached garage via radiant heat from itself and attempts to heat probably 1/2 of my DHW via a very slow sidearm.

I like yourself have thought many times about what it would have been like to get a gasser but I can't get over the simplicity of the Thermo-Control unit. Like you said, once it gets going - clean and no smoke. Rake the coals, chuck in some wood and go to work in the morning.

After reading this forum for years I have decided to stick with mine because I seriously doubt if I would save an extreme amount of wood to make it worth my while to switch to a gasser. I see the situation of cutting less wood but splitting more of it smaller coming out about equal time wise.

Duetech · Oct 28, 2011

Andrew L. said:
I read with envy all these posts from you guys that have gasification boilers. They sure seem to be efficient and use less wood than my system. The question I have before looking vary hard at replacement of my 5 year old unit is the burn time of most gasifiers (EKO, Tarm, Econoburn, etc. ) I've read through many posts and the most common answer is 4-6 hours of active burn time.

Here is my situation: I have a ThermoControl 2500 boiler in my garage. It's plumbed into 1000 gallons of pressurized storage and my old oil boiler serves as the backup (automatically - when it works). The Thermocontrol is a beast not unlike your typical OWB, but it does have secondary air tubes that place air in the back of the chamber for passive secondary air. No major complaints with the boiler at five years old. However, it is somewhat inefficient (tested at 76%) compared to gassers, uses about 12 full cords of dry hardwood per year to heat 4000sf, my garage, and hot water, and it does not completely combust the wood, leaving lots of black charcoal on the firebrick. (I think this is largely due to a lack of any grates to allow the ash to filter out. If I stir things up enough, the charcoal does get consumed). Very clean burning with not much smoke unless starting the fire. All the parts are simple and commercially available (no proprietary, expensive stuff).

The thing I love about this boiler is that I can fill it in the morning and walk away for at least 12 hours. I get home and there is always a bed of coals enough to re-ignite the new charge of wood without messing around. I basically fill the thing 2x per day and that's it. The fire gets lit in October, and stays lit until April. I don't even have kindling wood.

Is this sort of operation feasible with a gasser? I don't relish the idea of making a fire, lighting it, and waiting 10 minutes to flip the handle over to gasification mode once it's hot enough. Would there be a bed of coals hot enough to re-ignite new wood after 12 hours even if I got a large (300K btu) econoburn or something like that?

Thanks to you all for this site. It is a huge help

Drew

I have a gasser and an OWB. My gasser operated about 10 hours at the longest during the heart of winter with good dry hard woods. But it idled a lot and is currently waiting to go in to a building with storage or at least modifications to allow it to burn out doors. So I currently use a "ceraminc" OWB that is a smoke dragon. I prefer the gasser. At least 1/2 less wood in a gasser. In the OWB however I have found that a fill will yeild 14 -16 hours of dry premium hard wood but a half load will yield around 12 +/- hours depending on the severity of the weather. All my wood is stored outside and so it is cold when it gets tossed into the boiler and my belief is a large load of wood burns btu's up just getting the wood hot enough to produce enough btu's to heat the water. I now load the front half of the chamber top to bottom after raking the coals in to a pile in front of the blower opening so I get a hot fire going which heats the wood and keeps the water warm enough to serve it's intended purpose. by the time the coals are burned the wood is throwing some serious heat into the chamber and not in to heating another large amount of wood. By principle OWB's burn and idle, burn and idle. The way I load when there is no more wood to heat (or actually the wood that was loaded is hot enough to burn outright) then the fire of the half load heats the water. Might raise some eyebrows but that is what I have going on in my unique boiler. It has no water jacket as it is primarily concrete with copper tubing but it kept us warm with -17 and 40mph winds last winter on 2 1/2 loads of good wood. Try different load configurations while the weather is still temperate and not dogmatic. you might burn less wood. We were aimed at 15 cord last year before I changed my approach and ended burning just 12 for the winter. The gasser only used 5 cords per winter for 4 heating seasons.

Andrew L. · Oct 28, 2011

Thanks to everyone for the replies. As always, it's been very beneficial. I agree with Rob H that it's hard to beat the simplicity of the TC unit and after going through all these replies, I think I'll just leave it alone. My wood doesn't cost much (lots of sweat and a little gas), and I enjoy cutting it.

Thanks again guys.

Drew

barkeatr · Oct 28, 2011

ya, it would be hard to make the payback numbers work replacing an already low cost heating system..maybe load the unit with less wood, but put use maple or use maple as the last to burn, so you end up with a good coal bed that will last hours..making the "restart" easier. good luck!

Andrew L. · Oct 28, 2011

With the TC unit, I burn almost 100% ash and it always goes at least 12 hours and still has a solid bed of coals. The unit almost never goes into idle (closing the damper), as the 1200 gal heat storage absorbs all the BTU's unless I happen to overfill it on a mild day. Even with the damper always open, the coals are there for the restart. Someone said in an earlier post - if it ain't broke, don't fix it. Sounds like sound advice.

rkusek · Oct 28, 2011

Andrew L. said:
With the TC unit, I burn almost 100% ash and it always goes at least 12 hours and still has a solid bed of coals. The unit almost never goes into idle (closing the damper), as the 1200 gal heat storage absorbs all the BTU's unless I happen to overfill it on a mild day. Even with the damper always open, the coals are there for the restart. Someone said in an earlier post - if it ain't broke, don't fix it. Sounds like sound advice.

If all the OWB users could easily incorporate 1000 gal of pressurized storage to their systems they wouldn't be smoke dragons anymore and probably burn less wood too. I like my gasser and have found a good startup routine that works for me. This year I'm excited to have storage that should keep my heat pump off while I'm working those 12 hr shifts. My EKO never came close to 12 hrs burning and rarely would their be any coals left after 9 hrs during the cold months (ie. getting home after an 8 hr shift). I am heating quite a bit of though. My main floor is 2200 sq. ft. and we keep it at 70 degrees. The basement is roughly the same size and only partially finished so it is a few degrees colder which is fine for working out or kids playing with scooters, etc. My pole barn is 30x60 and I keep it around 60 but it is insulated as well as the house. I'm envious that you have 12 cords of wood ready to burn. I only have about 3 cords that is in the 15-18% range. Going to split some today that I cut last winter but didn't get out of the trees before spring. As someone mentioned above I doubt you could justify buying a new boiler since you have storage which is giving you cleaner burns plus you don't have to split as small as I do. If you have the wood on your property I would change anything until your wear it out.

stee6043 · Oct 28, 2011

huskers said:
Andrew L. said:

With the TC unit, I burn almost 100% ash and it always goes at least 12 hours and still has a solid bed of coals. The unit almost never goes into idle (closing the damper), as the 1200 gal heat storage absorbs all the BTU's unless I happen to overfill it on a mild day. Even with the damper always open, the coals are there for the restart. Someone said in an earlier post - if it ain't broke, don't fix it. Sounds like sound advice.

Click to expand...

If all the OWB users could easily incorporate 1000 gal of pressurized storage to their systems they wouldn't be smoke dragons anymore and probably burn less wood too.

Unfortunately, the storage "dillema" is quite different for outdoor units vs indoor units. Depending on the specific situation you could have the danger of freezing water in an OWB should the fire go out every day (like most gassers do when run with storage). And if you don't have the freezing problem you're still going to have a waterjacket full of rather cold water every day when you do relight the fire. You'll put a fair amount of BTU's into just getting the water back up to normal temps every day. In an indoor boiler these btu's technically are not wasted. Whereas outside they are.

I personally don't think OWB's are particularly well suited for storage when you look at loss, convenience and the restarting situation. But that's just my two cents.

musclecar joe · Oct 29, 2011

willworkforwood said:
flyingcow said:

I wonder how much less you would burn with a gasser? Maybe down to 9 cord? And that might be a stretch. You're already burning dry wood.
If that burns pretty clean, I think you might have a keeper. Seems to fit your schedule. Also, once i shut the door on my gasser, i walk away, no handle to turn.

Click to expand...

+1
If it ain't broke, don't fix it.

musclecar joe said:

I have an Econoburn 150 with no storage. I am heating a 3000 sq ft home and a 1200 sq ft garage. both well insulated. ... I burn around 12 cord a year for my specific application. ....
Musclecar joe

Click to expand...

Sounds like it might be a bit undersized, but how about the heat loss calc - does it match up well with the 150? How warm do you keep the garage? Have you tried turning the garage zone off, just as an experiment to see what the difference is? Did you check/clean the heat tubes after last Winter?

Clean the and check the heat tubes every year and garage zone is off unless i am in there. Yes i think you are correct and I may be undersized. when I bought it the salesman sized it and said i would only load 2 times a day and burn 5 cord a year. I do not think a larger unit would save me wood though. thanks for your input.

mikjmartino · Nov 16, 2014

This is my first year with my Thermocontrol 2500. It is very well built and parts are simple like someone previously mentioned. Also, its made in Upstate NY. I called the manufacturer and actually talked to some really nice people. For me, there is value in that.

Now to the question on burn time. 4 to 12 hours for me. It depends on demand, wood quality and how much you put in it. It is a 17 cubic foot fire box so you can put a lot in. When it reaches temp, it shuts down and blackens the wood. When it gets air it lights back up. Just a few coals will light even the biggest DRY wood. This morning i didnt think there were enough to get it going but it fired right up.

I like the simplicity of the unit. I didnt get a Tarm because once the dealer said i might want a service contract, I was out. I don't want to even consider a wood stove with a led panel on it. As long as my Thermo Control has wood in it, I can get heat out of it. Yes I plug it in but that is only for the damper. I am smart enough to trick it into burning pretty efficient even with the power out. Also, the heat in the water jacket keeps my basement at 78 and heats my first floor pretty well. My zones run less that way too. Anybody that wants to "upgrade" and get rid of a Thermo Control cheap, let me know. I have friends that want them.

Fred61 · Nov 16, 2014

I'm sure most regular contributors here envy your ability to evaluate the awesome abilities of the Thermo Control before winter has even started.

goosegunner · Nov 16, 2014

I guess I am a little confused here, If you have 1000 gallons of storage how could it possibly burn 24 7 without ever stopping? Can't the boiler output enough heat to charge the tank? I would think if you put filled a 17 cu ft fire box at some point it would be idling continuously. If not it should be burning flat out for 12 hours, seems odd to me.

gg

mikjmartino · Dec 6, 2014

Fred61 said:
I'm sure most regular contributors here envy your ability to evaluate the awesome abilities of the Thermo Control before winter has even started.

I have 13 years experience with other indoor wood boilers at my house so I think I am pretty qualified to judge it in all temps. I hope they do appreciate it.

Its been 10 degrees here and I still stand by my results. 4-12 hours based on demand. Not to mention being a mason, I have seen hundreds of set ups, installed many different stoves and setups, been called about all kinds of issues and talked to hundreds of people about many types of wood heating.

I really do hope I can be helpful to everyone.

stee6043 · Dec 6, 2014

I hereby nominate this thread for "best revival from the dead award" for Q4 2014. Just a shade over 3 years in gap between the posts. Solid effort, everyone. Solid effort.

maple1 · Dec 6, 2014

4 to 12 hours with how much wood loaded into it?

With a 17 cu.ft. firebox, that could be a full cord of wood every 4 days. 7 cords a month. 40 cords a winter. Yikes.

mikjmartino · Dec 6, 2014

maple1 said:
4 to 12 hours with how much wood loaded into it?

With a 17 cu.ft. firebox, that could be a full cord of wood every 4 days. 7 cords a month. 40 cords a winter. Yikes.

I cut the wood to about 18 inches give or take a few and effectively stack it 2x1.5' so about 4.5 cubic feet for a 12 hour burn. Lets say 5 for easy numbers. I rake a mound of coals to the front so the turn to dust and spread the rest even across the firebox making sure i don't get close to the rear baffling.

Its 12 or 13 days a cord but to me that's not bad since I'm heating a 4100 sq foot house to 70-72 (sometimes gets hotter than the thermostat is set), my 2200 sq ft basement to 76-78 and keeping my 900 sq ft attached 3 car garage to a minimum of 50 degrees and heat my domestic hot water. The house is tight so I stay warm but I'm probably going to die from fumes from upholstery.

So if 10 cord gets me 4 months I'm thinking that is good. With my non gasser with 20 gallons of water, I loaded the little fire box every hour except night and the furnace still came on all the time. I got up at 5am to light it to help the house recover. I still spent 3k on fuel oil.

So far, 0 fuel oil burned.

maple1 · Dec 7, 2014

Have you considered insulating it some? Should help even out the heat in the house.

mikjmartino · Dec 7, 2014

maple1 said:
Have you considered insulating it some? Should help even out the heat in the house.

I did consider it but what we found is it keeps the floors on the first floor nice and cozy which my wife likes. 76-78 is not bad for the basement. Its a little warm but manageable.

Burn times: Gasifiers vs. natural draft water jacket boiler

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