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OWB vs. Indoor wood boiler

Started by nctacoma, February 11, 2012, 09:20:04 PM

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nctacoma

Hello,

Can somebody educate me on the benefits and differences between an outdoor wood boiler and indoor wood boiler? I am starting to think about one or the other and I really don't know too much about either of them.  I have heated with woodstoves for many years, but never boilers.  This would be tied into a system with hydronic baseboard heat and a indirect hot water heater
Why does it seem like outdoor wood boilers are so much more popular than indoor wood boilers? 

doctorb

Both work fine.  OWB's usually have a larger volume of water in their jacket, which stores a lot of energy.  Many indoor wood boilers use an auxiliary tank to do the same thing.  Some talk about fire risk - indoor vs. outdoor - as a fire in either would be devastating, but your home would not be damaged with an OWB. 

Both of these units burn a fair amount of wood.  Hauling it indoors is extra effort, especially if there's a good distance to your woodpile.

Indoor wood boilers negate any heat loss from an OWB to your basement.

Local regs. may permit one or the other.

I am sure there are many other comparisons and similarities.  I like having the wood outside.  No mess, no bugs, and prep it right next to the OWB so there's less hauling.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

thecfarm

I had a indoor boiler at my other house. It was a nice unit. Kept me nice and warm. It was a pressurized unit. The only thing about it,I could not shut it down enough to control the fire if I filled it up with some small dead wood. I have a Heatmor now,not pressurized and I can burn cedar that has been leaning against another tree that is dry and the Heatmor will smother the fire out between cycles for keeping the water up to temp. Mine works on a forced draft by fans. If the fans did not come on the fire would just about go out.The mess of the wood is all outside too.I like the OWB much better than my inside one.I have alot of dead standing pine that I am burning now. I'm trying to get through the winter without depending on good hard wood. I have burned some hardwood,just because the trees were in the way of half dead.Some will say you have to go out in the cold to fill them,I had to go out in the cold to bring wood in to fill my other boiler. It's a whole differant way to burn wood too. I can fill my up and it only burns what it needs to keep the water at a certain temp.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

beenthere

nctacoma
I've had an indoor wood boiler closed system under some pressure for 30+ years. I don't think I'd want anything different as it is a perfect fit for me.
I've been told I can't get a replacement because of some requirement that all indoor wood boilers must be steam certified. ?? ??  To me, it isn't any different from an indoor hotwater heater in the need to be steam certified.

I can tend to it as I work in and around the house, and can get 8-10 hours out of it if necessary. However, I put in one or two pieces of firewood as needed which in 0 deg F is about 2-3 hours, more or less. Burn about a cord of 2-3 yr old split dry wood in 3-4 weeks. Longer if oak, a bit shorter with the ash I'm burning.

Company has been out of business for 30+ years.

I have propane gas boiler for backup, and a 30 gal pre-heat tank to temper the water going into the domestic hot water heater. The wood boiler has a 9 gallon water jacket.
Heats my 2800 sq ft (that is two floors) through the toughest winters we've had in WI since I installed it in 1976.


 
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

John Mc

Pretty sure there are some pressurized indoor wood boiler systems out there. I know they are popular in Europe.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

doctorb

Beenthere-

You have the cleanest basement I have ever seen!
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

albirk

I was thinking the same thing doc

bandmiller2

Doc.,pretty much covered it.Sometimes its a matter of not having a propper chiminey or one you'd trust with wood.Mess outside is a biggie.Usally indoor will use less wood. Frank C.
A man armed with common sense is packing a big piece

True North

I have had both, and I like the OWB hands down.

sparky1

I can see insurance being a difference. I told my insurance guy I was purchasing an OWB. He told me i didn t have to do anything different, as long as the flame is outside. I know its like that for alot of people in my area, maybe other parts of the country are different??
Shaun J

Mooseherder

Does the insurance man reduce the premium on the house because it is safer with the Furnace outside or is it a one-way street?

thecfarm

Mine did not go down. I suppose if I tear down the chimmey and take out the wood stoves and my FHA oil furnace than it MIGHT.  ::)
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

sparky1

insurance go down, hahaha.... their as crocked as the oil companies!!   nope just a one way street, but i have heard of companies not covering houses if they had an wood furnace in the house. My company kinda threw a fit about me having a wood burning fire place.  I told the guy if he didnt like it ill call someone else.  so they "let it slide"
Shaun J

bull

I have an IWB My little brother has an OWB. OWB will cost more than IWB.... IWB no need to get dressed and go out into the cold to get warm !! IWB uses 60 % less wood than an OWB..  IWB requires less maintainence and has fewer breakdowns !!

thecfarm

There's a guy down the road with a mobile home,bought it brand new,around '95. Wants to put in a wood stove into it. Insurance company would cancel him if he did it. He even tried to let him have a licensed wood installer do it for him to get around the insurance thing. Still no. But the kicker is,if he would of bought it all set up to burn wood he would of been all set. Can't add on and put a stove in either.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

chevytaHOE5674

My insurance company got to the point that I would have needed an extra policy to continue covering the house with my basement woodstove. So I went with an OWB and my insurance man said that my premium would go down a tad. Wasn't much decrease but it sure beat the price of the extra rider policy they wanted me to get.

I like not having to put wood in my basement, gives me a lot more room in the basement for storage and other stuff. Keeps the mess outside, no worry about cleaning the chimney when its below zero outside, no worry about a chimney fire, and it is easy to have the neighbor kid load the OWB if I have to go out of town without worrying about somebody coming in my house while I'm gone.

thecfarm

I have the older style Heatmor,The only difference with my IWB I had are 2 blowers. That's why I bought a Heatmor. A very simple design. The back looks just like IWB,same controllers and circulators. I should of bought this unit when we built the house. I need a way to get rid of my dead wood. I still had to go out in the cold to get the wood and bring it inside to burn with my IWB. This OWB is one of the few things that I have brought and been very happy with it.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

sparky1

as a kid we had a wood furnace, I know not the same as in IWB. loved how warm the house felt. another advantage of in inside furnace is if the power goes out you still have heat. I still think the advantages for myself having the owb outweighed the inside furnace. It might not be the same for everyone, but the right choice for me.  No mess in the basement. I have a log house and i was worried about bugs (that was my biggest reason), the fire issue is also a big one, carbon monoxide as well.  there are some disadvantages as well..
Shaun J

Holmes

I installed a lot of Tarm indoor wood boilers and they are good. I like the idea of the inside boiler and keeping most of the btu's inside the house, but having had to go to houses in the middle of the night to fix overheated boilers that the owner left the door ajar and gone to bed has cured me from wanting the boiler inside the house. Those people were very lucky they did not burn their houses down.
Think like a farmer.

gspren

I have had both and by far the biggest reason I now have an outdoor stove is my wife, she doesn't like the smell in the house and there is no posibility of burning inside without an occasional puff of smoke when loading or cleaning the stove. I also like the mess outside, when handling wood there are always pieces of bark, dirt etc.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

LorenB


I have lived with our H.S. Tarm indoor boiler since 1999 and I really like it.  You can see one here:

http://www.woodboilers.com/product-detail.aspx?id=47

Our boiler is the dual-fuel model, with the backup being LP gas.  You can also order the boiler with an oil-fueled backup.  The boiler can be set to switch automatically to the backup burner if the wood fire goes out.  If desired, you can select wood only operation.  You can also select backup fuel only. 

This has been the mildest winter in our 18 years in southern Indiana.  I have burned about one cord of dry firewood so far this season (12 February).  This is unusual.  It would be more normal for us to burn three to four cords of wood during the winter season.  This includes wood to heat all the hot water. 

The H.S. Tarm boiler uses a secondary combustion chamber where additional air is injected into the hot gasses.  The combustion is excellent.  There is NO creosote downstream of the secondary combustion chamber.  There is lots of creosote in the firebox itself. 


Quote from: Holmes on February 12, 2012, 10:27:04 AM
I installed a lot of Tarm indoor wood boilers and they are good. I like the idea of the inside boiler and keeping most of the btu's inside the house, but having had to go to houses in the middle of the night to fix overheated boilers that the owner left the door ajar and gone to bed has cured me from wanting the boiler inside the house. Those people were very lucky they did not burn their houses down.

I have had this happen to me twice, but neither time did it get out of hand.  Those two times did give me a good scare, though.  I didn't have to call someone to come cool my boiler down; it's a simple matter to turn the heat on inside the house and run some hot water (from the heat exchanger water heater) down the drain. 

This problem occurs ONLY if the owner leaves the door open (even a crack) and has inserted enough wood to heat the boiler full of water to a dangerous point.  I used to leave the firebox door open a crack to get a fire started.  I have stopped doing that unless I am standing next to the boiler. 

I don't think that this situation would ever cause a house fire, but it certainly could cause the boiler to open a safety valve and vent steam.  I guess if there were even more wood in the boiler after it had drained itself, you could get a fire, but even then it's enclosed in the boiler's firebox.  My guess is that the worst you could do is ruin the boiler.  That result is no small matter; the boiler is thousands of dollars. 


Quote from: gspren on February 12, 2012, 03:14:31 PM
I have had both and by far the biggest reason I now have an outdoor stove is my wife, she doesn't like the smell in the house and there is no posibility of burning inside without an occasional puff of smoke when loading or cleaning the stove. I also like the mess outside, when handling wood there are always pieces of bark, dirt etc.

We do get smoke inside the house occasionally, although very rarely now.  The trick is to start a small fire first, then add more wood after the fire gets burning well.  If you load the firebox up with a cold boiler, the fan will not supply enough air for the size fire you are trying to start, and it will smoulder for quite a while.  Smoke will escape from the auxiliary burner hole and/or the flue vacuum regulator.  (I don't know the proper terminology for that item.  There is a Tee fitting in the stovepipe that leaves the boiler.  It has a flapper in it that will open to allow ambient air to enter the chimney if the chimney is drawing too much vacuum.  I'm sure this is to prevent the chimney from sucking air through the fire when the boiler's fan is off.)

As far as the mess is concerned, it certainly could be an issue.  Our boiler is installed in the basement, in its own room with the water heater and water softener.  That room has an outside door through which I bring firewood.  The mess is contained entirely in that room, which I sweep up occasionally.  You must keep the area directly in front of the boiler clean, because hot coals and embers sometimes fall from the loading or clean out doors. 

One of the keys to using a wood-fired boiler, including mine, is to load an appropriate amount of wood.  If your heat load is low, don't fill the firebox full.  This will prevent the hazard of an overheated boiler if you don't get the door closed properly.  It will also cut down on the smoke issue.  Last, and perhaps most important, it will prevent long periods where the boiler has a smouldering fire in the firebox.  This situation creates gasses that encourage corrosion and should be avoided if possible. 

The water temperature in the H.S. Tarm boiler is controlled by starting and stopping the combustion air fan.  This fan has a damper that closes automatically when the fan shuts off.  When the fan shuts off, virtually all air is blocked from the firebox.  If you shut the fan off manually (by switching the boiler off) the fire will extinguish.  It will not ALMOST extinguish; it will go completely out.  During normal operation, if heat is being removed from the boiler, the fan will cycle enough to keep the coals hot enough to ignite when air is again provided.  The system works very well. 

Our installation includes an additional safety system.  I think it is required by the H.S. Tarm instructions, and maybe also by the building code, but I don't know.  My boiler and radiant floor system was installed by a professional.  Tarm Biomass (the U.S. distributor) told me that they would not warranty the boiler unless it was professionally installed.  Now that I see it, I realize that I would never have done it right. 

The additional safety system is a large baseboard heater that is used to dissipate boiler heat in the event of a power failure.  If the boiler loses power, valves automatically open to allow the boiler water to thermosiphon to the baseboard heaters. 

All in all, I really like our indoor boiler.  One of the main reasons for choosing it over an outdoor unit is that I was unable to find any outdoor boiler with a secondary combustion chamber. 

I used to travel for my work, and for my wife (who refuses to deal with the boiler) I would leave the boiler set up to switch to LP gas after my last load of wood burned up.  Since I retired in 2007 we have bought only one tankful of LP gas (which we also use for cooking).  This season, our 500 gallon LP tank is still over 50% full. 

-- Loren
Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

doctorb

One thing I have learned from the FF is that people who are active in their lives like what they have and don't really want an alternative.  For the years I have been here, the gasifier versus non-gasifier OWB discussion has been prevalent.  This current topic seems to be turning out in a similar fashion.  Those with OWB's are happy and put up with the rigors of that life, and those with indoor wood furnaces are just as happy, accepting a different set of issues with their choice.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

DeerMeadowFarm

My wife is a neat freak....we don't call her "O.C. Debbie" for nothing.  ;)

We burned wood in the basement of our first home, a small ranch, for 14 years. Cut wood, load it on the truck, stack it in the wood shed, every week throw/haul a week's worth of wood down to the base ment through the bulkhead, stack it up next to the stove, burn it.

When we built our "dream" home we said, no more wood! Oil was under $1/gallon. Well....prices went up.

We bought an OWB and we love it. We never minded the work of wood all that much (we grew up burning wood since the 70's gas crisis) and it's a good lesson for my daughter to learn to be more self-sufficient. We were splitting wood this weekend and I split a piece that had obviously seen bugs as there were the tell tale tunnels. My wife inspected the peice (like we used to) and said "Looks OK, I can't see any bugs" to which I replied, "Doesn't really matter with the OWB". Big smiles!  ;)

Chuck White

Benefit of Outside as opposed to Inside:

1. Safety!  The fire is not in your house.

2. No mess in the house.

3. Drop in insurance premiums.  When I removed my wood fired furnace from the basement, (switched to oil) my policy dropped 7%.


Benefit of Inside as opposed to Outside:

1. Don't have to go outside to fire it!

2. No heat loss.

3. Easier to monitor.
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

Gary_C

There is another problem with indoor burners of any kind that offsets any heat savings from having the stove indoors.

The chimney sends the products of combustion outside along with a lot of air from inside the house. That air has to come from somewhere and the cold outside air infiltrates thru every crack, door, and window in the house. Yes you can put in a air make up heater to control the air make up but they are costly too. Plus the exhaust in the winter takes moisture out of the house and requires some type of humidification.

So having the heater in the house creates more problems than you gain from having the insulation losses from the stove stay in the house. 
Never take life seriously. Nobody gets out alive anyway.

JSNH

I have had both.

Heating with wood In New Hampshire.

I have been heating with wood for 31 years. The first 10 with an air tight wood stove in the house. I burned good dry hard wood. The house was either too hot or too cold. You had to bring the wood into the house and the house was drafty due to pulling in combustion air. You had to clean the chimney.

I then got a wood gasification furnace it also stored the heat in a 2,000 gal water tank. I burned good dry hard wood. I heated that way for 17 years. It would be similar to the tarm with a storage tank. It worked well every room was exactly the temp you wanted. Base boards for heat. I don't think I burned 300 gal of oil in those 17 years. It burned so hot no chimney cleaning was required except to pull a bit of dust out of the clean out every other year and weekly heat exchanger clean outs. You had to bring the wood into the house and the house was drafty due to pulling in combustion air plus when it was running the fan and circulator were loud. In the dead of winter I would have a fire for 6 to 8 hours a day. Every day was bring wood in start fire 15 or so minutes. Each hour fill with wood 5 minutes each time. So that was 40 minutes a day in the winter. The stove's fire brick burned out and it needed a major rebuild. The fire brick shapes in it were custom and no longer available plus the tank developed a leak. I replaced it with an outdoor boiler.

I went with a standard Central Boiler 5036 outdoor boiler. It is great. I am into my 4th winter. I did not want a gasification one. I am glad I did not get of those. In my opinion they are too complicated and problematic. I may burn a bit more wood but I burn everything, pine, hemlock poplar and hardwood. I swear it runs better with pine. No chimney cleaning. No wood in the house. No drafts. No sound. I spend way less time filling, poking, cleaning and can spend more time with the family. 5 minutes in the morning and 5 minutes at night. I am saving a half an hour a day thats over 3 days saved in 6 months. The house it totally comfortable. We have more room in the house without the wood stove and without the furnace. No mess no bugs no smoke in the house.

mrwood

I have never had an indoor wood model. The cb OWB was my first experience to a wood burning stove. The only way I sold it to my wife was that it was outdoor. She really hates smoke and the mess of wood. After haveing this outdoor, I could not amagine without one. I swear by it. I enjoy the work. It does chew up more wood than say and indoor IMO. but for me the other benefits make up for it.

Grunex

About five years ago our old indoor furnace was getting tired, had a few cracks in it as it had been installed in the early 70's,  seemed every day I would come into the house and find the wife and baby tired, sleepy and within a few minutes I'd feel the same way.  One day I went to town and bought a carbon monoxide detector and installed the batteries. Before I made it half way down the steps the alarm went off!!!!   I had suspected the source for a little while, but didn't know it was that bad!!!  I went back to town and bought a number of space heaters in order to keep the house warm for a few more weeks (late Feb when this happened) and promptly ordered steel to build my own OWB.  It's not fancy, but at least the carbon monoxide is not in the house any longer.  I just could not justify that kind of health risk!  My insurance went down, and I designed the system, built it, and installed it for a grand total of around 6500.00 dollars.
As I said it was nothing fancy, the system consisted of a yard shed type structure for the boiler, a well insulated boiler, pex, two side arm heat exchangers, a forced air heat exchanger, and a heat exchanger to cycle water into the house.  (for radiator type heating) and lastly circulator pumps to get the hot water where it needs to be.  we've had absolutely zero problems with it since it was built.  I burn a lot more wood right now that I used to but my electricity cost have gone down, fuel oil is zero, and propane is zero.....
www.grunexlandclearing.com
Maintaining America's Heartland one acre at a time.

Farmertan

I had an indoor unit installed in November, and love it. It's a WoodGun with oil backup. In our town, they are pretty ignorant about wood boilers and the permitting process is difficult. Once I showed them the info and emission specs, they were ok with it. I do not think they would permit a non-gasifier. As for indoor vs outdoor, I can totally understand the pros and cons I've read. I don't worry about burning down the house because my boiler won't burn well with the door open, and not at all with the blower shut down, which happens automatically at 185 degrees. I also have a smoke hood vented to the outseide that captures the puffs that some out when I open the door. Having never had an OWB, I can still see pros and cons:

OWB Pro: no noise, dust, smoke in the house if the chimney is properly sited.
Con: having to go outside in the wind/cold/rain/snow (imagine doing that if you've got the flu)

IWB Pro: no heat loss, load the boiler without changing out of my pajamas, nice, warm basement and workshop
Cons: bringing in wood (not an issue for me because I have a walkout basement with garage door), noise

DGK

I have a Greenwood Hydronic Wood Boiler installed in my attached garage. The reason I went with the indoor one was because the insurance company would only insure the outdoor boiler if I cleared a very large  area 50'+ radius around it of all trees, buildings, combustibles, etc. Since my property is nicely treed and I wanted it to stay that way, indoors it went. Having it in the attached garage gives the benefit of being able to load and monitor it without going outside, the only drawback is that you do get some smoke in the garage when loading on occasion. I have recently installed a smoke hood with fan to exhaust any escaping smoke. This is an older pic without the smoke hood.


 
Doug
Yukon, Canada

LT40G38 modified to dual pumped hydraulic plus, HR120 Resaw, EG200 Edger, Bobcat S185,Bobcat S590, Logosol PH260M3, Sthil MS660's, MS460,MS362's MS260, Trailtech dump trailer, F350, F700 Tilt-Deck log/Lumber Hauler, JD440B Skidder, Naarva S23C Processor

Piston

Thank you to all who have contributed to this thread, it was very educational for me. 
-Matt
"What the Lion is to the Cat the Mastiff is to the Dog, the noblest of the family; he stands alone, and all others sink before him. His courage does not exceed his temper and generosity, and in attachment he equals the kindest of his race."

TCBNH

I've been researching the same subject.  I have a friend that move from an indoor to an outdoor simply because he had access to a lot of pine that he could get for free and he was afraid of burning that in his indoor boiler.  I've heard that outdoor boilers are less efficient just because of location.  I work with a guy that used to install TARM indoor boilers....he says they are fantastic and very efficient, but they are also very expensive.
JD 510 backhoe, Kubota M5400, Oliver 1250, Farmi winch, Timberwolf TW3 splitter, Dodge 1 ton dump

711ac

Quote from: Gary_C on February 14, 2012, 12:20:53 PM
There is another problem with indoor burners of any kind that offsets any heat savings from having the stove indoors.

The chimney sends the products of combustion outside along with a lot of air from inside the house. That air has to come from somewhere and the cold outside air infiltrates thru every crack, door, and window in the house. Yes you can put in a air make up heater to control the air make up but they are costly too. Plus the exhaust in the winter takes moisture out of the house and requires some type of humidification.

So having the heater in the house creates more problems than you gain from having the insulation losses from the stove stay in the house.
My indoor wood boiler uses outside air for combustion! Just as all high efficiency heating appliances do. ;)

beenthere

Quote from: Gary_C on February 14, 2012, 12:20:53 PM
There is another problem with indoor burners of any kind that offsets any heat savings from having the stove indoors.

The chimney sends the products of combustion outside along with a lot of air from inside the house. That air has to come from somewhere and the cold outside air infiltrates thru every crack, door, and window in the house. Yes you can put in a air make up heater to control the air make up but they are costly too. Plus the exhaust in the winter takes moisture out of the house and requires some type of humidification.

So having the heater in the house creates more problems than you gain from having the insulation losses from the stove stay in the house.

I have an indoor wood boiler (35 yrs now), and I don't think this summary is even close to right. Sorry Gary.   :)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

nctacoma

as an update to this thread, We were able to get a wood boiler at our house.  We went with an indoor wood gasification boiler made by Froling.  IT is made in Austria.  It will heat all of our hot water baseboards and supply us with all of our domestic hot water.  We have been using it for about three weeks now.  One fire a day or sometimes every other day.  The installer estimated that we will use less than 6 cords a wood a year.  For summer hot water they said one fire a week will be sufficient.  The boiler is connected to two 300 gallon thermal storage tanks which act like a battery for the heat and hot water systems.  So you don't need the boiler to be firing to have heat available. 

I normally fire it in the morning before I leave for work and just check the temperature at night of the tanks to see if I need to top it off with another small fire.  So far I haven't had to, but it isn't winter yet...

WmFritz

Have you been heating with wood... if so, how many cords have you been using?

From everything I have read, Froling builds quality boilers. Does your unit have Lamba controls?
~Bill

2012 Homebuilt Bandmill
1959 Detroit built Ferguson TO35

nctacoma

We have been heating with wood before the boiler. We were using about 4 cords and using the propane boiler as backup. The problem was we could only have two warmish rooms in the house. The room the woodstove was in as well as the room above it. Rest of the house was frigid.
Yes the boiler has the lambda controls.

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