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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.

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