needing information on pressurized wood boilers

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
  • Hope everyone has a wonderful and warm Thanksgiving!
  • Super Cedar firestarters 30% discount Use code Hearth2024 Click here
Status
Not open for further replies.

ditchdigger

New Member
Mar 10, 2014
26
iowa
Hello everyone, I'm new to the forum and looking for information after doing a lot of reading already. I'm currently using an unpressurized wood boiler, have had it for seven years and am wanting to upgrade to a much more efficient pressurized wood boiler. I'm currently heating a shop and house, and would like to add another house, a shop addition and two garages, along with a boiler and wood storage building in the future.

I'm not sure I want a stand alone outdoor type boiler, like I've got now, what I'm thinking is putting up a building to install an indoor unit inside it, we already have underground lines to one house and the shop now, the house has forced air and we use a heat exchanger and also a side arm for the hot water heater. My shop has infloor heat in the main shop and office, but this winter, is the first winter we had the shop up and running and have had issues with my current boiler keeping up to my heat demands now, without adding any more to the system.

I'm wanting information on the efficiency of some of the pressurized boilers on the market, what I have right now it burns wood and I'm thinking an after thought is to put out some heat in the process, but is far from efficient as I can get, this winter has been an eye opener as to needing something much more efficient.

I'm not sure how long of a post you folks want to read, I can add any information you want to know about, square footage, insulation types and thickness's, line length's and sizes and anything else.
 
I've grown up with Tarm. My solo innova is awesome. It's all I know though.
 
  • Like
Reactions: flyingcow
Lots of folks here with lots of boilers - but you should take a look at the Garn and Garn Jr.....just as a start! They are super-efficient and include the storage you need and fit well into the outbuilding scenarios.

http://www.garn.com

Isn't the Garn an unpressurized boiler? I've been told since I bought my current owb that if I go pressurized I would eliminate a lot of issues with the boiler rusting from the inside out through the water jacket, which seems to be a major problem I've been having with my unpressurized boiler now, is this true or just a sales hype I've been given?

I've been around a couple fuel oil boilers in the past, one we lived with in a house for almost 20 years it worked and preformed great, two lp gas boilers and neither of them gave me any trouble as far as leaks and rusting and also a couple in house forced air wood furnaces and those didn't cause me any grief either. So from past experience I've had great luck with pressurized boilers, not saying it would eliminate all my issues, but I was hoping it would solve a lot of them.

I've looked at the information on the web about the Wood Gun boilers, know nothing about them, never seen one in person and know nobody that has one, haven't as of yet got a hold of anyone at the company, its either busy or they don't call back when I leave a message.

The next question I have or at least wanting to know if what I've been told is true or not, that there is no such thing as an accurate means to get an efficiency rating on a wood boiler, with the variables in the kind of wood burned, moisture content, atmosphere pressure and a host of other variables involved, then how do some of the companies rate theirs, with an efficiency rating on them? Sorry if its a stupid question, but I've been given so much information from way too many people I'm now more confused than I was when I started. I've looked at some survey's of efficiency's of outdoor wood boilers, and those won't list the manufacturer or model number in their statistics, not sure what good they do anyone, but is there a comparison somewhere of the different makes and models of wood boilers that do list the efficiency of them?
 
"Isn't the Garn an unpressurized boiler?" Yes it is, I don't believe that they have issues with rusting out though. They test your water for free twice a year, and you have to put good dry wood in them, Some Garns 20+ years no rust problems. The only "issue" I see with an unpressurized boiler is you need a 400.00 + heat exchanger. You don't need expansion chambers though, or have to worry about blow-off valves, over firing, etc. The 1000 gals of water in my Garn Jr gives a lot of room for error about over firing. I did mine once, on purpose, steam comes out a pipe until it cools to below 212.
 
I've grown up with Tarm. My solo innova is awesome. It's all I know though.
By the looks of their website, they don't make a unit big enough for what I'll need, nice looking unit though, thanks for the reply of what unit you have.

Has anyone had an outdoor wood boiler and gone to a gasification unit and can tell me how much less wood they burned with the gasification boiler?
 
I'm not sure how long of a post you folks want to read, I can add any information you want to know about, square footage, insulation types and thickness's, line length's and sizes and anything else.
Bingo! What brand is your current boiler? What method of UG piping did you use? How much wood did you burn with your current set up?
 
The efficiency rating process in the US hasn't been hashed out yet, so you'll see all sorts of numbers. at least the europeans have a proper system sorted out.

the big thing you want to avoid is cycling a boiler.

Garn avoids this by putting all the heat into water at full speed (over 4-5 hours) and then using that heat for 12-24 hours.
they are unpressurized for lots of good reasons. they deal with the corrosion with anode rods and a serious commercial water treatment program. I have seen garns 20+ years old with no corrosion. I think you'll find that even a 2000 might be too small for what you want. the size and insulation levels of the houses and shops will determine the best course of action.

Wood gun works similarly, but IMHO you'll want to add storage. even if they say you don't need it. there are several people here that have them and can talk about storage vs no storage.

information from you will help. size and age/insulation level of houses and shops, distance between buildings, etc.....
 
  • Like
Reactions: Vizsla
Hi and welcome to the forum.

This question will bring a lot of opinions and personal preferences so keep that in mind.


I'm glad you brought up the Wood Gun.
Although I'm not heating anything of the size you are, I'm very happy with the Wood Gun.
I'm very surprised that you haven't been ble to get in tough with them.
When ever I call, they either pick up the phone or call back the same day.

I believe Jebetty has installed 2 Wood Guns in a school or some institution and they work well for him.
Wood Gun definitely makes some monster size units which should handle your heat loads.

As far as I know, Efficiency is based on a moisture content of 20%.
 
Oh boy! potential for 6 structures if I read your post correctly.
I would think a heat loss of your current structures and a design heat loss of your potential structures would be helpful for sizing your boiler.
since you are proposing an addition and several garages and another home you are in a good shape for designing a central heating source. I would incorporate your central system into the design of these new structures.
I would suggest posting a simple sketch to start with approximate S.F. and distances to existing and proposed structures. The Brand of boiler to me at this point is not as relevant for early planning.
An open mind to the system itself prior to boiler selection is a key element to entire efficiency.
There are many experienced minds here and most brands are represented here.
If you do not have a stock pile of wood drying currently I would get that going first CSS.
Low temp heat emitters are also important for the thermal storage component.

Here is a post that turned out very successful from this site. much smaller scale than yours but good results.

https://www.hearth.com/talk/threads/e-classic-1450-or-pm-optimizer-250.113337/
 
Last edited:
Although outdoor wood boilers are notoriously inefficient they will usually heat a large area as long as you put a full forest through the firebox. What OWB do you have? Are you sure you are not loosing heat to the ground on your UG runs? Is the slab heat built properly with good insulation and vapor barriers?

Usually when someone has a heat load such as what you are proposing, the guys here recommend a Garn but you may have a problem getting the full output of the unit because of your need for higher temperatures for your water to air heat exchanger in the house. The same will go for any gasser with storage since you will not be able to use all of the stored energy because the temperature will be below useful levels for your heat exchanger.
 
  • Like
Reactions: Vizsla
With 500,000BTU/h Tarms and 1,000,000 BTU/h Econoburns available, before we even get into multi units there is no heat load too big with these or other indoor models. Still curious as to what boiler he has and what it's claimed output is? Many a time we have seen much smaller indoor units replace much larger outdoor versions. Not knocking garn at all but just look at the Windhager thread were both Windhagers are smaller than just one of the 2 garns they replaced.

There is no job too big that a well designed system can't handle.
 
OK people, first and foremost, thanks for the replies and input, at this point anything is helpful and wanted, don't feel shy to tell it like it is, or how you see it, your not going to offend or hurt my feelings at all, I like to hear it like it is, and don't leave anything out, or leave it to me to imply anything, most times I get it wrong anyhow.

As for what I have now, I bought it on a whim and an urgent need with little background checking or asking questions, to say the least, if one can do anything wrong, I've done it more than once. I currently own wood doctor, not pressurized, and I'll admit, for the first few years, it worked good, but burned far more wood than I ever knew anything every could, the comment about burning the forest down to keep warm, is a mild understatement. We've had leaking issues with it, and quite frankly not wanting to offend anyone, I personally think its a waste of good metal in its design and efficiency, I won't even discuss warranty issues or lack there of, or my dealer support, nice guy, but.....

Its the second to the largest model they made, I'm told they're now a pressurized boiler, not wanting another round and looking for something better in terms of efficiency, its supposed to be around that half a million btu's mark, or so the claims go.

We've had issues this winter with not being able to maintain boiler temps, I'm also thinking there's not a big enough fan on the unit to feed the fire and keep it burning hot enough, but with the leaks we've had, which its currently leaking now........again, I'm hoping it makes it till its spring and we can shut it off for good and replace it.

As for the wood issue's, since this winter has set records on extended cold spells, we figured we had enough wood to last into next fall, cut, split and died, and it ate it all and we were out the middle of january, so we went down and took dead and down tree's out of the woods, and have literally shoveled those through the furnace, not sure it even slowed up long enough to breath myself, and we again ran out of wood in mid february, so back again to the woods for more, nothing ideal, just anything we could toss into the inhaling beast that might bring about some heat. As they say, when things go wrong, they really go wrong and compound issues. In over 40 years of heating and being around wood, I've never ran out, or even close, also never about froze to death in my own house either till this winter due to the lack of heat being produced.

As for specs, on the current system, we have an older two story house, about 100 years old a couple thousand square feet, has been remodeled several times and isn't bad to heat, believe me, I've lived in some old drafty, two story hotels of houses before that were impossible to heat due to no insulation, this is far from it, with the old lp gas furnace, which my dad put in back in the late 80's it would take anywhere from 1000-1500 gallons of lp a winter to keep it really nice inside, some mild winters even less. We have forced air heat in the house, and also a side arm hooked to the water heater for hot water. With the family getting old enough to go out on their own, we will no longer heat the water in the summer with a wood boiler, before with girls especially at home, [anyone with girls knows what I mean] and the boys still at home, we seemed to go through a lot of hot water, once the girls left, I wondered if the water heater was even used on some months, but that's another story.

My shop is a remodel in an old barn, we installed a hydraulic dooron one end, that fully opens up the whole end, 32x20 high and we bring equipment in and out all the time, we also installed in floor heat tubes in the shop, this is the first winter we had heat in it, which brings up a major issue, we want to have forced air fans on the wood boiler to bring my shop temps back up quicker, especially if we bring in cold equipment to work on, as they say a 25 ton piece of equipment coming out of -25 below zero temps a large block of ice to warm up, I want to speed that process up considerably, not something most do or even think about doing, but its what we do all winter long, work on equipment and get ready to go break it again next year in good weather working it. My current office is about 17x17 and has in floor heat, cement block walls and the pour in insulation in the blocks. the rest of the shop has anywhere from pour in insulation in the walls to over a foot of fiberglass blow in the walls to over a foot of fiberglass batts in the ceiling, the door is the poorest insulated in the building being only 4 inches of insulation in that.

My house is about 150 feet from the current boiler, the shop is about 40 feet, we have one inch pex insulated lines in the ground to each of them. I'd like to put an addition on the shop that would be 32x20 with about 15 foot ceilings, in floor tubes and a full width door on one end too, and forced air heat off the boiler for that in addition to the tubes in the floor.

I'd like to then build a building to house my heating source in, along with any water storage and some wood in as well, I'm tired of standing in a snow bank and the wind to shovel in semi loads of wood into the furnace, literally. What that size would be is in question.

I'd also like if possible to heat a second house, already on site, done, a newly remodeled house with a garage, and in the near future put an attached garage on my house, how or even if this is all possible, is yet to be seen, or even if it's feasible.

The next question that comes along is going to be what's my budget............... and as stupid as it sounds, I'm not sure, I'd like to weigh options and costs first, then decide which will give me the least grief, biggest bang for my buck over the longest period of time.............

As non politically correct as it sounds, so don't shoot me, I've even considered waste oil boilers for my shop or forced air heaters to supplement heating those needs, an add on gas boiler and everything else imaginable too, and yet I'm looking at wood the hardest. Any other questions, just ask.
 
Do you know what brand of pipe it is?
I'd have to go look to see if there is a brand on them, right off the top of my head, I don't recall, but its one inch green pex lines, foamed into four inch drain tile, there are no connections under ground, a continuous run for the shop, and another for the house, both come up by the owb now and two pumps at the furnace once for each line, both gruntfoss pumps.
 
I would suspect that your temp difference from beginning of run to end of run is too high. If you could measure that(delta T) You maybe surprised. You may not reuse that pipe on your next design if the delta T is to large.
 
That would be a good start.
pictures also are welcome here. "a picture is worth a thousand words"
 
Tell us how your slab heat is constructed.

Edit: and how dry your original hoard of wood was.
 
I seriously wonder if you'd be better off with a woodchip (not pellet) unit based on the scale alone, rather than a stickwood. Sounds like you either have or would be comfortable with the sort of equipment that might feed one, and it cuts down on wood-handling a lot.

As has already been mentioned, any heat load can be met by combining units (and I don't know that anyone has mentioned, but it also gives you redundancy in case of a breakdown - much better to have 2/3, half or even 1/3 of your normal capacity than to be out completely.)
 
I would suspect that your temp difference from beginning of run to end of run is too high. If you could measure that(delta T) You maybe surprised. You may not reuse that pipe on your next design if the delta T is to large.

I did the temps, not sure how accurate they are, I'm thinking I need a new laser temp gun, first off we had different fittings in the mix, some brass, some galvanized and the pex coming into the furnace was too close to the furnace to get an accurate reading and the brass was on the furnace, so that wasn't accurate at all to compare to. But the best I can deduce at the moment, is on the short run to the shop, maybe a degree or so difference from the outgoing of the furnace to the incoming into the shop, but that's the short line, and in the house run maybe a few degree's difference, but I'll admit I need to do it again with another temp gun. In the past we had the line exposed to the snow laying on top of the ground when I had the furnace at a rental house I used to rent, all winter long and the snow never melted off it ever and when we did the comparisons back then there was no temp drop on that same short line, we just moved it to our current location.
 
  • Like
Reactions: flyingcow
Tell us how your slab heat is constructed.

Edit: and how dry your original hoard of wood was.

The slab heat is constructed as follows, we used the insulation board under the concrete, the two inch stuff the concrete supply place sells to all the cement guys in the area, there is the black board all the way around the perimeter of the cement inside the building, a couple inches deeper than the insulation board under the cement. We did a couple things different on this deal, since the concrete is pretty thick to hold up my heavy equipment, 8-12 inches, some of the thinner concrete we stapled it to the insulation board, most we tied the heat line to the rebar in the center of the concrete slab, or half way down into the concrete. We have a service pit in the shop as well, we put in floor heat in that too, and used insulation board all the way around the perimeter of the pit walls, so they contacted the insulation board under the floor slab.

Since it was a remodel job of the old barn, there is a foot cement wide slab between the heated floor slab and the concrete wall and footing, basically under my insulation in the wall of the shop, then another black insulation board between that narrow slab and the wall, when we shot floor temps this past fall, that narrow slab was the same temp as the concrete wall behind it, and the floor was up to 30 degrees warmer so I'm not thinking we're losing much heat through the walls, the snow has never melted at all on the outside of the building anywhere.
 
  • Like
Reactions: henfruit
I seriously wonder if you'd be better off with a woodchip (not pellet) unit based on the scale alone.

I've actually given this considerable thought, we investigated this years ago, even before we bought the current owb, but back then, there weren't many small enough for me, most were for industrial applications.

The other problem we found was it was almost impossible to size the heat load to our needs, especially when it comes to warmer temps in the fall and spring, compared to bitter cold of mid winter. I even went as far as to contact one manufacturer and they were going to build a unit for me, I was to do the testing of it for them and make changes as it needed doing, turns out they never did build one, I backed out due to the possibility of biblical problems and issues and me having no back up system at all in case of a disaster and no heat.

Yes we are geared to handling the chips, would even think about buying a chipper to do my own, and yes we even had a model pickup out I liked, but at the time the total cost was so far out of my reach it was just a dream. Now there is far more companies making chip furnaces than even five years ago, if anyone can balance the load for me, so when its frigid out, I'm not working or sleeping in the cold, or blowing off hot water in the milder temps in order to keep the boiler fired.

I also haven't investigated this avenue in years now, not saying its out of the realm of reality, it sure would be nice to just take a skid steer and load bulk chips ever few days to meet my heating needs all winter long.
 
Status
Not open for further replies.