Outdoor Wood Boiler heating Questions

[BodyMovin]

Hello all,

I wanted to thank you all in advance for any responses I will receive. This is a heating question for my shop and home.

My situation is that I have a forced air electric heated home and electric space heaters in my shop. My house has two electric furnaces heating about 3,300 sqft. We have a wood fireplace that supplements the heating in the winter time but its really not the best way to try and heat that much space. Due to the fact that our electric bill in the winter is pushing 650 bucks a month even with burning wood in our fireplace we are looking at different more cost effective options. The heaters in the shop are only used maybe once a week for a couple hours so the cost there is low.

We have considered adding another indoor fireplace or wood burner, or a wood add on furnace. Gas was considered as well but we are looking to be as economical as possible. We would like to stick to wood as I have a lifetime supply of firewood available, we like the heat firewood brings, and I enjoy cutting and splitting it. We are however tired of the mess that comes with bringing the wood in the house and with the placement of the electric furnaces (in the attic) will make an add-on wood burner difficult. Along with the increased insurance costs of an indoor wood burner.

This brings me to the outdoor wood burner. This seems to be a good choice to heat not only my home but also my detached 30x48 shop as well as provide hot water to my water heater. From the research I have done so far I understand I will need to run at least two water lines. One from the boiler to the house and one from the boiler to the shop.

My immediate question is, could one water line run from the furnace to the house service two electric furnaces? The furnaces are at opposite ends of the house. Ideally, I would like to run one line in, provide hot water to the water heater as well as to the one furnace located right above the water heater in the attic and then on to the second furnace through the attic. I do not know if the heat loos would be too high to do this or if i would need to set up an entire new loop for the second furnace.

I have not talked to a dealer yet as that is the plan this summer but I am starting to do the research now on what I think I might need as to not go blindly into the dealer.

Thank you again for any input.

 

[ericm]

Like you I also have a lot of wood.

Fireplaces are terrible for heating. The cheap builder quality zero clearance fireplace I had would make the house colder when it had a fire in it. I replaced it with a stove that's effective for heating. This is the first winter using it and it's been very nice. Now I'm keeping warm with the wood I cut rather than giving it away.

If your fireplace is large enough you can get a stove insert that fits inside it. They can be very effective. You may need to install a liner in the chimney.

I address the mess from wood by hauling it inside in plastic boxes. Most of the mess stays in the box. I keep a small brush and dustpan by the stove to sweep up whatever drops on the hearth. My wife hasn't even noticed.

I realize this is not the option you're asking about but it may provide some useful information should you reconsider. It probably costs a lot less.

 

[BodyMovin]

Like you I also have a lot of wood.

Fireplaces are terrible for heating. The cheap builder quality zero clearance fireplace I had would make the house colder when it had a fire in it. I replaced it with a stove that's effective for heating. This is the first winter using it and it's been very nice. Now I'm keeping warm with the wood I cut rather than giving it away.

If your fireplace is large enough you can get a stove insert that fits inside it. They can be very effective. You may need to install a liner in the chimney.

I address the mess from wood by hauling it inside in plastic boxes. Most of the mess stays in the box. I keep a small brush and dustpan by the stove to sweep up whatever drops on the hearth. My wife hasn't even noticed.

I realize this is not the option you're asking about but it may provide some useful information should you reconsider. It probably costs a lot less.

Thank you for the comment. This is the path I want to take but I am not the only voting member in the house. In fact I think my vote counts for less than my wife

Our fireplace is custom and was a pretty penny. Plus it looks pretty when there is a soothing fire going. I do not think replacing it will be a valid option I can get past my voting committee. One thing I am intrigued about is being able to provide constant, cheap heat to my shop and well as my water heater. A few of my neighbors have them and swear by them but I think they are biased. It is a huge initial investment but I think in my case with my high electric bill it will pay for itself in a couple years.

 

[ericm]

The insert goes inside the fireplace. We replaced our fireplace because it was too small for an insert. We also removed the ugly fake rock surround that stuck out and ate up space. My wife hated it so it was not hard to convince her. She likes being able to warm up next to the stove. Sometimes she had to fight the cats for a spot.

Example insert: https://www.woodlanddirect.com/Fire...on-EPI3-Oakdale-Wood-Burning-Fireplace-Insert

Most stoves and inserts have windows so you can see the fire.

 

[larry4406]

I suggest you join and surf Hearth.com It is specific to these types of questions.

Endless hours of details on wood burning and hydronics.

I think the highest efficiencies come from wood gasification units. These typically run full tilt at max efficiency dumping heat into water storage tanks (500-1500 gallons) which then are used in pumped hydronics. I recall reading that the users typically have one 6-10 hour burn per day.

I went down the rabbit hole of reading but never implemented..

(I have a wood stove in my family room. I bring wood in using 5 gal mud buckets).

 

[finn]

I wouldn’t try to heat a house with a fireplace. The efficiency isn’t there. We have a wood stove in our house, but we just use it on extremely cold days when the radiant can’t keep up (16’ ceilings, and a wall that is mostly glass) or during the fall and spring shoulder season when the radiant can’t respond fast enough to the temperature swings.

We have a fireplace insert with an electric blower in another house. It works ok.

Problem with either of these systems is the mess. Both from bringing the dirty wood inside, storing the dirty wood, and bringing the dirty ashes out and disposing of them..

Outside wood boilers were popular around us, but I think the popularity is waning. They are still a lot of work, and seem to have short lives and high maintenance, mostly leaks, but the pumps aren’t in an ideal environment and are prone to failure.

With propane and natural gas relatively cheap, the popularity of outdoor wood boilers seems to be, as I said, waning.

There are also permitting issues, as some locales have banned them because too many owners are using green wood that makes the neighbors more than a little upset.

 

[Bondo]

I have done so far I understand I will need to run at least two water lines. One from the boiler to the house and one from the boiler to the shop.

My immediate question is, could one water line run from the furnace to the house service two electric furnaces? The furnaces are at opposite ends of the house. Ideally, I would like to run one line in, provide hot water to the water heater as well as to the one furnace located right above the water heater in the attic and then on to the second furnace through the attic. I do not know if the heat loos would be too high to do this or if i would need to set up an entire new loop for the second furnace.

Ayuh,...... At my last house, I built my own outdoor wood boiler,........
That house was heated by hydronic baseboards, so I plumbed my outdoor boiler, directly into the oil boiler in the cellar,.....
Easy peasy cheap/ free heat,.....

Anyways,.......
For yer application, Ya might be able to use a larger water line to the house, to move enough Btus to do exactly what you wanta do,......
At worst, ya run 2 lines to the house,.....

For the water lines from the boiler to the buildings, go for the Best,.....
I didn't,........ If I had, my wood consumption probably woulda dropped by 1/4, maybe more,....

'n while I despise craig, the owner of the hearth website, I agree with Larry,.....
The info, resources, 'n help from the members there, can't be beat,.....

 

[fitter30]

First should look at windows, doors and insulation. See if your utility companies offer a energy audit which includes a blower door test tells how airtight the house is and what rebates are available. Wood is not cheap how much is your body worth and time.

 

[ericm]

An energy audit is a good idea. We had one done and it showed us some inexpensive things we could do to make the house more efficient and comfortable. It paid for itself. If you can get one done for free that's even better.

I have so much wood from fallen or dead trees or trees that needed removal that I've been giving it away. The only added effort to make my own firewood is splitting and stacking. I don't have enough data yet to tell how much we're saving on propane but twice now I've seen the propane delivery guy show up, look at the tank gauge, shake his head and put only a little in. And with the stove making the house nice and warm does not seem wasteful like it does with propane.

 

[ericm]

An energy audit is a good idea. We had one done and it showed us some inexpensive things we could do to make the house more efficient and comfortable. It paid for itself. If you can get one done for free that's even better.

I have so much wood from fallen or dead trees or trees that needed removal that I've been giving it away. The only added effort to make my own firewood is splitting and stacking. I don't have enough data yet to tell how much we're saving on propane but twice now I've seen the propane delivery guy show up, look at the tank gauge, shake his head and put only a little in. And with the stove making the house nice and warm does not seem wasteful like it does with propane.

 

[BodyMovin]

Thank you everyone for the comments. Lots to think about. My house is only a year old and performs pretty well really for as much open space and windows as we have. The energy audit we had performed as required by the county seemed to show good results. My home is two story lofted with concrete finished floors and it just takes a lot of heat to warm to floors in the dead of winter. Its great in the summer as the house stays cool without even running the a/c but we pay for it in the winter. It is very pretty but I would not do it again.

I'll join the hearth forum to get more information from that group. Again thank you for your comments.

 

[J king]

I can say that I have and have used a outdoor wood burner and it’s been great. I heat my 2400 sf garage and 1800 sf house plus water. No mess and heat at a flick of a thermostat in the garage. I use probably 8-10 cord of wood a year and the garage is 70 deg. When out there or 50 all the time.
Costly to install but I get free wood so it pays for itself fast.

 

[juddspaintballs]

This is my second house with an outdoor wood boiler. My dad is on his third house with one. I'm fairly well versed in heating with outdoor wood boilers. Hearth.com is OK for information. outdoorwoodfurnaceinfo.com is a great site for information as well, specifically on all of the brands.


I highly recommend NOT GOING CHEAP on the underground lines. Wrap insulation around the pex lines shoved inside of drain pipe is not a good solution. Ground water will get in and ruin it and you'll spend your whole time heating the ground instead of your house. Logstor, Thermopex (Central Boiler dealers sell this), and a couple other pipes are what you want. Something with a thicker/harder casing and closed cell spray foam for insulation. Going cheap here is the number one mistake most people make. The underground piping is very important to get right.


As for the rest of it, it is pretty easy. Once you have hot water in the house, you can do anything with it. For the furnaces, you'll want to install a hot water to air heat exchanger (coil). www.freeheat4U.com is a great place to find quality coils. Put one in each air handler sized to fit your ductwork. You'll then wire in a second thermostat or a mult-function single thermostat to control just the air handler without kicking on your electric heat. As for how many BTU's you're pulling from the hot water and such, you'll have to do some calculations based on your water temperature, desired delta, and flow rate to see if you can do it as one big loop or two different loops. All information you can find on those websites above.

 

[nadogail]

Have you considered solar? Both for heating water and Photovoltaic?

 

[BodyMovin]

Great information. I am pretty much sold on the outdoor wood boiler concept for my heating solution. I would just like to get as much information as I can so I can be as informed as possible.

 

[Sureshot]

I used a boiler in my shop to heat both the house and shop so I can comment that I liked the heat it gave in the house. I retrofitted a forced air oil burner with a heat exchanger so it could run with either heat source. Two thermostats so if something went wrong or for vacation etc the oil furnace would keep the house from freezing up.

One of the unexpected benefits was a better use of the thermal mass.The air temp from the heating ducts wasn't as hot as with oil so the furnace fan ran longer which gave the mass time to warm, the fan in turn ran longer but it also stayed off longer so I think an equal amount of total time of fan. While on oil you felt the "chill" in the house when the fan was about to kick in, with the boiler the temp seemed much steadier, maybe due to the slower changes.

My setup had the water lines come into the garage across the ceiling and into the crawlspace to the furnace room. On the return line I installed a manifold to divert the return water through a heat exchanger to heat the garage. I never ran the heater unit as just the exposed warm lines through the garage kept it at a great temperature.

The shop was heated with a heat exchanger for the first year with no thermostat, just plug the fan in and let it run, unplug when too warm(40x60x16). I ran infloor heat the next summer and loved it.

My first thoughts with your setup would be to run the house furnaces in series with the prefered or heavier loaded one being the priority. The domestic hot water could likely use the residual heat to preheat your incoming water and possibly add a heat exchanger on the primary heat line to keep the water hot. I belive you would just use your existing hot water system then add the additional heating/reheating system.

This system was in Saskatchewan.

 

[juddspaintballs]

If you're heating domestic water, you heat that before the air in the air handler. You want the hottest water heating your domestic water (160-180 degrees to raise your ~65 degree water). If the water going through your air handler(s) is only 130 degrees, it's still making plenty of hot air to blow around but that same 130 degrees wouldn't heat your domestic water up nearly as quickly and you'd still be relying on your water heater to do the task.

 

[Joemctag]

And get the stove or insert with the flue that brings in the combustion air from outside. Otherwise cold air is drawn in through all your house’s small openings when the stove is burning and using your house’s air.

 

[Muttly]

This is my second house with an outdoor wood boiler. My dad is on his third house with one. I'm fairly well versed in heating with outdoor wood boilers. Hearth.com is OK for information. outdoorwoodfurnaceinfo.com is a great site for information as well, specifically on all of the brands.


I highly recommend NOT GOING CHEAP on the underground lines. Wrap insulation around the pex lines shoved inside of drain pipe is not a good solution. Ground water will get in and ruin it and you'll spend your whole time heating the ground instead of your house. Logstor, Thermopex (Central Boiler dealers sell this), and a couple other pipes are what you want. Something with a thicker/harder casing and closed cell spray foam for insulation. Going cheap here is the number one mistake most people make. The underground piping is very important to get right.


As for the rest of it, it is pretty easy. Once you have hot water in the house, you can do anything with it. For the furnaces, you'll want to install a hot water to air heat exchanger (coil). www.freeheat4U.com is a great place to find quality coils. Put one in each air handler sized to fit your ductwork. You'll then wire in a second thermostat or a mult-function single thermostat to control just the air handler without kicking on your electric heat. As for how many BTU's you're pulling from the hot water and such, you'll have to do some calculations based on your water temperature, desired delta, and flow rate to see if you can do it as one big loop or two different loops. All information you can find on those websites above.

All great info here, I self installed OWB in house and barn 10 years ago.
If you have wood available go for it. Good underground pipe is a must, for your demand you might need 1-1/4" pipe for the house run.

Too bad you didn't get some tube in all that concrete, it is a great heat sink.

The Central Boiler website has some of the best install diagrams for different systems.

 

[BodyMovin]

I am kicking myself now that I did not run hot water pipes in the floor when I had the chance. We talked about it but the price I was quoted we a tough pill to swallow at the time. Now I realize it would have be totally worth it.

After some of these comments and more thinking I am considering an indoor wood boiler. Install it in my attached garage as there is plenty of space since it is an over-sized three car. Plus it should help keep the garage warmer. I also think I will have a better shot at getting my better to actually put wood in it from time to time. The cost to install seems like it would be less as well.

Thinking about this model.

https://www.econoburn.com/index.php/ebw200-170h

 

[larry4406]

I am kicking myself now that I did not run hot water pipes in the floor when I had the chance. We talked about it but the price I was quoted we a tough pill to swallow at the time. Now I realize it would have be totally worth it.

After some of these comments and more thinking I am considering an indoor wood boiler. Install it in my attached garage as there is plenty of space since it is an over-sized three car. Plus it should help keep the garage warmer. I also think I will have a better shot at getting my better to actually put wood in it from time to time. The cost to install seems like it would be less as well.

Thinking about this model.

https://www.econoburn.com/index.php/ebw200-170h

I think some insurance companies get their ******* in a wad if you install a wood burner in your attached garage. At least so says many a thread on the net.... YMMV.

 

[greenskeeper]

What is the size and layout of the house....you might be surprised how much heat you can get out of a fireplace insert woodstove for minimal cost if you can find a quality used unit that is the largest you could fit in your fireplace.

 

[juddspaintballs]

Most insurance companies don't like wood burners in unoccupied structures (garages). A know a few will flat out refuse to insure an unoccupied structure with a wood burning device in it.

 

[Firebrick43]

Do you have natural gas available?

Look at something like a Jotul insert to replace the fire place and line the chimney(most important part) they have glass doors that stay clean to watch the fire and have a beautiful design.

As for the wood boiler all my buddies that have them are slaves to cutting the wood. They are all cutting 18-24 cords a year and always behind. Equipment is 10-14k installed and fairly high maintenance. Pumps, fans, controllers, motorized dampeners, a coils, and domestic heat exchangers and maintaining the water to prevent corrosion. Seen a lot of them rusted out in 15 years, because the system is open and therefore oxygen filled. A cord of wood measures 4x4x8. Even if you buy logs while a logging truck hold 6-8 cords in a load of logs depending on the logs size and how well stacked. Then they all start buying skid steers, tractors, bigger trucks, bigger or skid steer mounted splitters, and trailers just to deal with the mountains of wood. And therefore little/no savings. Many abandon them going back to propane after the boiler holes itself and are happy for their time back.

And unless you cut, split, and dry your wood a year in advance, which none to because of the shear volume, your neighbors will dislike you or maybe even hate you do to the smoke belching out constantly in milder weather.

 

[TractorJeff]

Do you have natural gas available?

Look at something like a Jotul insert to replace the fire place and line the chimney(most important part) they have glass doors that stay clean to watch the fire and have a beautiful design.

As for the wood boiler all my buddies that have them are slaves to cutting the wood. They are all cutting 18-24 cords a year and always behind. Equipment is 10-14k installed and fairly high maintenance. Pumps, fans, controllers, motorized dampeners, a coils, and domestic heat exchangers and maintaining the water to prevent corrosion. Seen a lot of them rusted out in 15 years, because the system is open and therefore oxygen filled. A cord of wood measures 4x4x8. Even if you buy logs while a logging truck hold 6-8 cords in a load of logs depending on the logs size and how well stacked. Then they all start buying skid steers, tractors, bigger trucks, bigger or skid steer mounted splitters, and trailers just to deal with the mountains of wood. And therefore little/no savings. Many abandon them going back to propane after the boiler holes itself and are happy for their time back.

And unless you cut, split, and dry your wood a year in advance, which none to because of the shear volume, your neighbors will dislike you or maybe even hate you do to the smoke belching out constantly in milder weather.

Funny? I've heard the same as this fellow! Downside is when you get older (retire) you are STILL cutting wood!

 

[GeorgeP8420]

I'm not quite sure what you are trying to do but I can tell you that about nine years ago I purchased an outdoor furnace that was made from two bottled gas tanks. One was a 500 gal and the inside one was a 300 gal. It was made by someone down south and I purchased it from a sign on the roadside. It is filled with water between the tanks. It required me to buy insulated lines for circulating the hot water to my home and water heater and returning the cool water back to the furnace. All together I spent about $6500 on this project. It has been an excellent heat source for us. I have an unlimited source for firewood so it has repaid me for my investment. I do think an outdoor furnace would be very helpful for you. Here where I live outdoor furnaces are very common. We also have a back-up furnace in the event it ever fails.