# Outdoor Wood Fired Boiler



## Wojo (Apr 12, 2011)

First time poster. I hope y'all don't mind if I start with a request/question. 

Our house currently has an LP fired boiler, with heat provided by zoned baseboard throughout. The boiler is old and showing its age, and we have decided to replace it now...before we begin finishing the basement. 

I've been looking at options, and a wood fired boiler seems like our best choice for several reasons. We have access to 35 acres, 10 are ours and 25 more belong to close family friends, with all mostly wooded. I have an available fuel supply that'd be FAR less expensive than LP or electric. The wood boiler and installation would cost far less than a replacement LP boiler or forced air solution, and with the ready supply of fuel I should be looking at a return on investment of roughly 3 years. 

My second choice was to go with a geo thermal heat pump, but the cost would be twice that of the wood boiler and the return on investment pretty much matched the life expectancy, at 15 years.

What may serve as the clincher is that we have a wood boiler dealer less than 30 minutes from the house, and after stopping by on Saturday and talking with the owner we would definitely feel good about doing business with them.

As you can see, my mind is fairly made up. The model we're looking at does have LP backup for when we need to be away from the house for extended periods and can't stoke the fire. For power outages, like anything else when the power goes out we would lose heat via the boiler as the circulation pumps will not run. We have a wood stove, and will be keeping it for that very reason.

I would sincerely like to hear from folks who have, had, or have experience with a wood fired boiler. I would appreciate any advice, insight, or opinions.

Thanks in advance.

Dave


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## Ross (May 9, 2002)

We have two. An Empyre 250 and a 450. The smaller heats an old farm house the other three buildings. The biggest issue is sizing and set up. You're using baseboards already zoned so you should be OK but I suspect your LP boiler only ran the main circ pump when there was a call for heat. With the outdoor boiler you'll need a continuous running pump from the house to boiler then to your manifold's different circuits when calling for heat. Not sure what brand you're looking at but sizing the boiler to the job is important. Too big and you'll burn more wood than needed. Some will tell you a once a day loading is all you need. If that's true they're probably oversized. Now on warmer days we could only fill once and stir the coals a couple of times but it seems to work best (holding the temp we want) if you fill less and let it burn hot.

It would be well worth your time to try a site wwide search for the topic, as its been very popular. Welcome to HT!


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## Wojo (Apr 12, 2011)

Thanks much for the response and information. Good advice on the search. As predicted, it brought up quite a few posts.


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## Ross (May 9, 2002)

Of course new replies are alway welcome, and if you have any specific questions please feel free to ask.


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## Sunman (Apr 16, 2011)

Hello Wojo,
You certainly have a lovely setting for your Shangri La. I see a lot of Pine and Fir in your pix, so watch for the creosote buildup. We live in 150 yr old Log Cabin heating mostly with a Wood Stove. 

Donât have a wood boiler myself, however, I am familiar with a couple of units owned by friends and relatives. They seem to work quite well, but do have some issues that I have heard of:

Sometimes overheat and boil off, which they are designed to handle

Have to use a heavy duty cast iron circulator as the water becomes more oxygenated as it is an open pipe system for the boil off.

Tough to not produce too much heat on a warm Spring or Fall day. 

If you get one, here is what I would suggest:

1. Build yourself a well insulated 500 gallon water tank {4â x 5â x 3 Â½ â net}
2. Put 3 Heat Exchangers in the Tank. 
3. First Exchanger circulates water from Boiler heating the 500 gallon tank.
4. Second Exchanger transfers hot water from tank to your boiler where zones take over
5. Third Exchanger can be used for Domestic Hot Water.
6. Close off the boil off pipe with a 30 lb Pressure Relief Valve
7. Make sure you have an auto feed for water to your wood boiler.

What this does:

A. 500 gallons of water heated to 175 F releases 320,000 BTUs of heat to your house by the time the tank temperature drops to 100 F. 
B. Thatâs equivalent 4 or 5 gallons of LP for your Legacy LP Heating system.
C. You can turn off your Electric Hot Water Heater when wood boiler on.

To me, it just makes having a wood boiler a lot easier and convenient. BUT, I may have something wrong as I never did one like this, so I would appreciate feedback from Ross or others that have them.

This is how I handle Solar Storage. 

Good Luck, 
Sunman


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## Ross (May 9, 2002)

Most owb are high mass boilers already, using 200 gallons of water (average) . Not sure you really need the extra storage as they also have a very good recovery rate. Havn't measured it but if there's wood to burn the temp won't fall much more than 10 degrees. That said I can't think of a downside except from a management point of veiw you may get lazy adding wood risking a line freeze up from the boiler! It would likley make the domestic water heating better. Again no kicking a good cast circ pump but all I use are the little wet rotor circ pumps. Wilo Star three speeds lately.

Do not close off the boiler blow off pipe. OWB's are open types and not built to handle pressure. Yes to the auto fill water, I still haven't done it but I should. They don't lose so much to over heating but misc leakages (cheap chinese globe valves) will add up. For an open type boiler you would need a float tank in a heated area, level with the top of the boiler outside. Easily measured with a clear tube. It can act as a de-aerator too.


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## Wojo (Apr 12, 2011)

Hi all. I was going through my thread subscriptions and came across this one. I realized I never circled back after we made our decision. We went with a wood fired boiler from Central Boiler. If you'd like to see the details of our install, I detailed it HERE. 

Thanks again to you all for your recommendations. It all went into the mix for making our decision, and I sincerely appreciate it.


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## Wojo (Apr 12, 2011)

We didn't go with LP back up on the boiler. We instead had the old LP boiler inspected and repaired, and tied the two systems together via a heat exchanger. Should the wood boiler fail we have the LP boiler as a back up, and we have a wood stove as a third layer of redundancy. It's 16Â° for a high today, and dropping into single digits tonight. We take our heat seriously.  We're also using our wood stove exclusively in the early fall and in the spring, when we just need to take the chill off in the morning.


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## Studhauler (Jul 30, 2011)

All the people I know with an OWB use antifreeze instead of strait water.


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## haypoint (Oct 4, 2006)

Why not have a wood boiler in the basement and avoid the negatives of an outside heat source? Going outside to adjust the fire. Going outside to add wood to it. The short stack that allows the smoke into your house and the neighbor's. The greater amount of wood needed due to the heat loss with an outside furnace. The greater amount of wood needed due to the heat loss in the transfer of hot water from it to your baseboards.
The outside boiler allows for longer burns due to the large firebox. But long pieces of wood are harder to split. Unsplit wood doesn't dry nearly as well. Therefore, you'll get less heat from your longer, unsplit, firewood, requiring more wood and creating that "smudge" that has caused many communities to ban outsid wood furnaces. 
To control the heat in this boiler, air intake is limited. When more heat is needed, the air intake opens and the fire burns hot. When less heat is needed, the air intake closes. If you have slightly damp wood, it will smolder and the smoke stinks. Since they have smoke stacks about 12 feet in the air, the smoke drifts at that level. I think it is thermal inversion, I can't recall. But the smoke sort of stays around and drifts horizonally. I've driven through it going down the highway. 
So you wouldn't want an outside boiler in a place that the smoke could blow towards your house or the neighbor's.

A boiler in the basement allows you to capture all the otherwise lost heat from the outside of the boiler, warming your basement. The chimney will also add some warmth to your homestead. You can store wood in the basement and feed the boiler during a blizzard in comfort.


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## Jim-mi (May 15, 2002)

Would you not have freeze up problems with the outdoor boiler, when / if there is an extended grid outage.......?
A off grid friend / customer found out the hard way when he put in a out door boiler that those 6 pumps for his zoned system took far more electric than he realized and he really had to run his gas generator for long periods . . .$$$$$

Haypoint's idea of boiler in basement is a very good idea . . . . . . No grid electric . . .No freezing . . .because of your "wood stove"


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## Wojo (Apr 12, 2011)

Studhauler said:


> All the people I know with an OWB use antifreeze instead of strait water.


We did. Ours is a 50/50 mix of anti-freeze and water.


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## Wojo (Apr 12, 2011)

haypoint said:


> Why not have a wood boiler in the basement and avoid the negatives of an outside heat source? Going outside to adjust the fire. Going outside to add wood to it. The short stack that allows the smoke into your house and the neighbor's. The greater amount of wood needed due to the heat loss with an outside furnace. The greater amount of wood needed due to the heat loss in the transfer of hot water from it to your baseboards.
> The outside boiler allows for longer burns due to the large firebox. But long pieces of wood are harder to split. Unsplit wood doesn't dry nearly as well. Therefore, you'll get less heat from your longer, unsplit, firewood, requiring more wood and creating that "smudge" that has caused many communities to ban outsid wood furnaces.
> To control the heat in this boiler, air intake is limited. When more heat is needed, the air intake opens and the fire burns hot. When less heat is needed, the air intake closes. If you have slightly damp wood, it will smolder and the smoke stinks. Since they have smoke stacks about 12 feet in the air, the smoke drifts at that level. I think it is thermal inversion, I can't recall. But the smoke sort of stays around and drifts horizonally. I've driven through it going down the highway.
> So you wouldn't want an outside boiler in a place that the smoke could blow towards your house or the neighbor's.
> ...


There are a few reasons we went with outdoor vs. and indoor. First, our home is small. We're in the middle of finishing our basement, but even when that's done space will be a premium. Second, I would rather go outside twice a day to stoke the boiler than bring the mess and possibly insects into the house. Heck, I have to let the dog out anyway. Third, all of the research I did led me to believe something different about outdoor boilers than what you describe. Fortunately, my actual experience is not what you describe.


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## Wojo (Apr 12, 2011)

Jim-mi said:


> Would you not have freeze up problems with the outdoor boiler, when / if there is an extended grid outage.......?
> A off grid friend / customer found out the hard way when he put in a out door boiler that those 6 pumps for his zoned system took far more electric than he realized and he really had to run his gas generator for long periods . . .$$$$$
> 
> Haypoint's idea of boiler in basement is a very good idea . . . . . . No grid electric . . .No freezing . . .because of your "wood stove"


I have two pumps...the continuous circulation unit on the outdoor boiler, and a demand unit in the house that supplies our four zones. We have a small home. During an outage I have the option of running both of the pumps off of generator, leaving the wood boiler off and running only the demand pump on the LP furnace, or leaving all of it off and using our wood stove. The outdoor boiler tank and lines are filled with a 50/50 mix of anti-freeze/water, so freezing isn't an issue.


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## Wojo (Apr 12, 2011)

Heck, I sure am glad I came back to follow up. LOL.


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