Opinions Needed one my idea for a wood heat system.

[deerefanatic]

Hi all, I am getting ready to build a homemade wood gasification boiler for our farm to heat the house, shop, and milk house domestic water. This system uses a 1200 gallon stainless bulk tank for thermal storage (pressurized is my goal) and a homemade gasifier for supply. I plan to run the system even in summer to heat DHW for the house and milk-house (a big hot-water consumer)....

Eventually I'll had some solar collectors to the mix as well..

I have drawn up some plumbing schematics in Adobe Illustrator (pardon my sad drawing skills! ) for you folks to look over and critique for me..

Thanks in advance for any comments/criticism..

-Matt

Newbie Boiler Man!

 

[deerefanatic]

I might add that the plumbing for the shop with the small air handler and radiant floor heat is all finished.. The rest has not been done yet....

 

[brad068]

deerefanatic, I take it you like the "green iron". Myself, I am partial to the blue ones. Although, I do like them Kubotas. Am curious as to what style of gasifying boiler you are going to build. I like fabrication! :coolsmile:

 

[Bob Rohr]

In the first drawing, what causes flow into or out of the buffer tank? I don't see a circ pump in that circuit.

Do you plan on running the same water temperature to the air handlers and radiant? You might consider a mixing valve to the radiant. typically 100- 110F is plenty for a concrete slab. Anything over 140 is frowned upon by the concrete folks, ACI etc.

Also you will need some return water temperature protection for the boiler. A cold radiant slab (large thermal mass) can suck up BTUs as fast or faster than that boiler could produce them. Boilers are dumb, something needs to keep an eye on return temperature and react accordingly.

Make sure you have plenty of safety relief capacity, on any homemade boiler especially. 30 psi, and enough BTU rating 790,000 is a common off the shelf size. You'll need mega expansion capacity, based on your drawings.

Homemade pressure vessels scare me, find a boilermaker to guide you. A little pressure, a lot of heat, goes a long ways.

hr

 

[deerefanatic]

Yep, I like that "green iron" though the blue stuff is all we have on the farm right now!


Thanks for the tips on the piping.... So a mixing valve is in order for the concrete slab eh? Should help temper it's desire for wood too! Plus, being I'll run this system year-round for DHW, I can leave the thermostat set year round and I won't have to "heat up" that slab at the beginning of winter.....

Yes, the overall system diagram doesn't show circ pumps..... I'm planning on a chain-reaction type of setup, where the boiler heats the tank, and the tank heats everything else so to speak.......

The gasifier is going to be the unit that this guy: http://mysite.verizon.net/vzew10av/id1.html sells. Nice set of plans all around and a really knowledgeable guy... I don't want to share too many of the details of the unit because I'm not sure how he'd feel about it and he's given me lots of advice already......

The more I think about it, the more I'm beginning to think a primary/secondary system is the way to go........ More efficient I think......

Also, I'm toying with making the stove a glycol-treated loop with a heat exchanger hooked to the tank.... That way if I go with solar or equivalent and don't run the stove very often, I don't have to worry about freeze-ups........

As for the pressure, I'm only going to run 10 psi max on the system..... Just enough to be "closed" and do away with the corrosion problems of an open system. And to store a little more heat in my water. Definately will have relief valves.. I plan to hydrotest my tank when I get it all welded up by filling with water, then pressurizing the water with air, that way it can't explode, just crack, but not explode........

 

[brad068]

deerefanatic, before you get started on that glorified greenwood check out my build pics -uploaded pics for garnification. I followed the Garn principle and built my unit out of a 1500 gal dairycool bulk tank. My money is and will probably always be on the garn setup. I have seen two of these units still in operation after 20+ years. Pressurized storage is not at all what its cracked up to be. Check out Garns website, you'll see how they operate and there made in Minnesota.

 

[Bob Rohr]

Yep, I like that "green iron" though the blue stuff is all we have on the farm right now!


Thanks for the tips on the piping.... So a mixing valve is in order for the concrete slab eh? Should help temper it's desire for wood too! Plus, being I'll run this system year-round for DHW, I can leave the thermostat set year round and I won't have to "heat up" that slab at the beginning of winter.....

Yes, the overall system diagram doesn't show circ pumps..... I'm planning on a chain-reaction type of setup, where the boiler heats the tank, and the tank heats everything else so to speak.......

The gasifier is going to be the unit that this guy: http://mysite.verizon.net/vzew10av/id1.html sells. Nice set of plans all around and a really knowledgeable guy... I don't want to share too many of the details of the unit because I'm not sure how he'd feel about it and he's given me lots of advice already......

The more I think about it, the more I'm beginning to think a primary/secondary system is the way to go........ More efficient I think......

Also, I'm toying with making the stove a glycol-treated loop with a heat exchanger hooked to the tank.... That way if I go with solar or equivalent and don't run the stove very often, I don't have to worry about freeze-ups........

As for the pressure, I'm only going to run 10 psi max on the system..... Just enough to be "closed" and do away with the corrosion problems of an open system. And to store a little more heat in my water. Definately will have relief valves.. I plan to hydrotest my tank when I get it all welded up by filling with water, then pressurizing the water with air, that way it can't explode, just crack, but not explode........

You don't want to have to heat the tank before you can send heat to the loads. that, to me, is one of the big advantages to primary secondary. The fire goes right to the loads as soon as the boiler reaches adequate temperature. It can charge the tank when it satifies all the loads, no hurray really.

Use glycol sparingly. it's expensive, messy, leak prone, lower heat transfer ability, and it needs to be maintained. glycol the solar loop, or use a drainback.

hr

 

[deerefanatic]

Ok then... I've been looking at Primary/Secondary more and more and am beginning to think that's the ticket... Not too complicated either.. Plus, zone valves aren't as expensive as I initially thought......

I didn't really want to go with glycol anyhow... Probably if I insulate the lines from the stove to the control hut, I won't need to worry....

Garnification: I've seen your pics already.... But I liked this system due to the fact that it's mostly masonry.. With steel prices the way they are, I thougt it'd be cheaper to build.... But, the heat exchangers on this unit are going to be expensive to get unless I'm really lucky....

The unit I've got plans for is an all-block outer structure, with a solid firebrick firebox...... the primary and secondary air enter the firebox and combust, go out the first flue and then either to atmosphere (fire start mode) or back into the block structure to heat the heat-exchangers before going back out the second chimney.

So, please explain to me how a steel product like your garn can outlast a masonry product like what I'm thinking? It just doesn't seem like it should be able to..........

Not arguing, just trying to understand......

 

[Bob Rohr]

Once you understand the concept of primary secondary and all the features and benefits it brings to the table you will be convinced.

I have had other contractors come behind me and cut apart my systems and add ball valves between the tees. I sent Primary Secondary books to their company trying to explain the concept. They refuse to believe flow can move in more that one direction and at different flow rates in that piping. That concept has been around since the 60's. A B&G;engineer, Gil Carlson brought it to the industry back then.

Some old dogs refuse to learn new tricks

In the April 1999 issue of PMmag.com John Sigenthaler P.E. wrote an article "Mixing Wood with Water" It has some great info and formulas for piping and buffering wood boilers. I've done a few systems as shown in that article, including two of my own with excellent results. Siggy's own home has a 18" wide custom steel tank two stories tall about 20 feet long as a buffer tank/ radiant wall. Clever way and place to store that energy in the heated envelop.

I'd like to convince him to do a follow up control article. That seems harder than the piping to get right without some control wiring background.

I believe that article is still in the Archives at the PM site. It may not have all the pictures and diagrams however.

I've not seen a wiring specific article or book addressing wood boilers. NoFo is certainly capable of such an article It would be a huge help to the industry and wood boiler owners. I suspect there are a lot of swings and misses. I've had plenty myself when it comes to complex control logic and wiring.

Here are a couple reader friendly books on the primary secondary topic. Find them at www.heatinghelp.com bookstore.

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[MarcM]

No other advice to add except that to make sure you know where and how the bulk tank is insulated. I looked at using some old square bulk tanks but they had virtually no insulation on the top (since they were made to keep heat out, rather than in). I suppose the newer oval and round tanks are uniformly insulated all around?

 

[deerefanatic]

Yep, the old square ones had lift open tops to clean them... Mine is a round unit... Insulated all around... I'll probably wrap it with some more layers once I'm satisfied that it doesn't leak.......

Thanks for the info on Primary/Secondary and the book references........

 

[brad068]

Ok then... I've been looking at Primary/Secondary more and more and am beginning to think that's the ticket... Not too complicated either.. Plus, zone valves aren't as expensive as I initially thought......

I didn't really want to go with glycol anyhow... Probably if I insulate the lines from the stove to the control hut, I won't need to worry....

Garnification: I've seen your pics already.... But I liked this system due to the fact that it's mostly masonry.. With steel prices the way they are, I thougt it'd be cheaper to build.... But, the heat exchangers on this unit are going to be expensive to get unless I'm really lucky....

The unit I've got plans for is an all-block outer structure, with a solid firebrick firebox...... the primary and secondary air enter the firebox and combust, go out the first flue and then either to atmosphere (fire start mode) or back into the block structure to heat the heat-exchangers before going back out the second chimney.

So, please explain to me how a steel product like your garn can outlast a masonry product like what I'm thinking? It just doesn't seem like it should be able to..........

Not arguing, just trying to understand......

I am a fan of refractory but there is a limit to everything. How many gallons is the heat exchanger/storage chamber for the boiler you are looking at building? After reading some of the problems associated with the mass refractory units like the Greenwoods when you have a power fail on these the hx can get to hot and boil-not an issue with a Garn. Garns don't smolder, they don't idle, and from that they don't creseote up. The pics that I posted show a factory Garn with the bottom cut open. I aquired this from a guy that said it was leaking and it was, the bottom of the water tank rusted through. Some say from electrolsis, I say from sediment and not properly maintaining pH. I replaced the bottom and the unit works fine. To my amazement the flue pipes had some pitting but where more than half there yet and this was built in 1985. Ther were no leaks/cracks in any flues or firebox and the secondary burn chamber ceramic was half there. These things a bulletproof!

With a Garn you set the timer, throw in kindling and wood, light kindling, shut door, and walk away 99% of the time. When I hear about a second chimney, start up mode, additional pumps and hx, etc..etc.. I get dizzy. In the words of High E "Simple is Better!"

 

[deerefanatic]

I'm not sure how many gallons of water in the hx's of this unit, but it's not much.... maybe 10 total......

yah, I know what you mean on power outage failure, I'm going to have it set up so that a power failure totally seals the unit up and smothers out the fire.....

I like the fill and let it idle if necessary...... That's where I disagree with you.... Complicated can be VERY nice if set up correctly!

 

[EForest]

I'm not sure how many gallons of water in the hx's of this unit, but it's not much.... maybe 10 total......

yah, I know what you mean on power outage failure, I'm going to have it set up so that a power failure totally seals the unit up and smothers out the fire.....

I like the fill and let it idle if necessary...... That's where I disagree with you.... Complicated can be VERY nice if set up correctly!

The problem with a large refractory is that there is no "off" switch. When it's hot it stays hot! You need to plan on backup power to dump the excess heat until the fire dies and the refractory cools or the power resumes.

 

[brad068]

I'm not sure how many gallons of water in the hx's of this unit, but it's not much.... maybe 10 total......

yah, I know what you mean on power outage failure, I'm going to have it set up so that a power failure totally seals the unit up and smothers out the fire.....

I like the fill and let it idle if necessary...... That's where I disagree with you.... Complicated can be VERY nice if set up correctly!

The problem with a large refractory is that there is no "off" switch. When it's hot it stays hot! You need to plan on backup power to dump the excess heat until the fire dies and the refractory cools or the power resumes.

Exactly. There are so many btus stored in the refractory that a boiler over is inevitable. You need to circulate to rid the heat, snuffing the fire ain't going to solve the problem. Fill and idle is the worst way to burn chunk wood. You either burn full bore or don't light it.

 

[deerefanatic]

Right, I understand that..... Either way, It does come down to one thing: Cost....... I can build this refractory unit for WAYYY less than a Garn style system and use my stainless tank for thermal storage..... If I garnify it, I'll be cutting my thermal storage way down and spending a fortune on steel...... With this unit, all the metal I need is rebar for the grate, some plate for the door, and some angle for hinges, lid frames, etc.....

In case you haven't noticed, steel scrap is up to $300/ton right now.. It's not cheap....

All in all, I've just never been crazy over the Garn way of doing things..... I know that refractory stays hot a long time.... That's one thing I like about it. While you have to light your fire every day so that you can walk off, I just throw some wood in mine and the refractory lights her off.....

As for idling, I don't mean the "half-smother it out, then fan it like crazy to get it going again" type of idling that OWB's are known for.... The primary air control on this thing HAS to be throttled or it will melt the 1" rebar firegrate!! (the guy who designed it has done this) We're talking some serious heat here.... Exhaust gasses leaving the firebox can exceed 2000F in wide-open burns.... By throttling back, you can get the gasses down to around 1200F, which is still very hot and will burn very efficiently, while conserving wood and producing a longer burn.... That's the kind of idling I'm talking about.

And as a side note, we've been told that the area we live in rarely sees power outages, and if we do get one, that's what a generator is for. Heck, without power, our house and barns will freeze, so a boiled over boiler is the least of my concerns... I'll be keeping power to it for that reason alone...... Or, push-comes-to-shove, a simple zone valve attached to the mains with a spring return to open could also serve a protection service... Power out, water is drained from the heat-exchangers automatically.. No fuss, no muss....... But like I said above, I gotta keep the power goin' to keep the places heated... 1200 gallons of hot water don't do me a bit of good if I cant pump it where it's needed......

 

[brad068]

Have you seen a mass refractory and a garn in operation? My guess is that you haven't. Videos don't do justice, for the garns anyway. You want some serious heat, my unit will put out @500,000 btus and High E's puts out @800,000. I seen a Garn melt down a 8" cast iron compressor pulley that he was experimenting with in the front of the secondary chamber.
Good luck with your build and hopefully you can post pics and in the future.

 

[Bob Rohr]

Never substitute cheap for safe! If you feel the cost of materials or the project is causing you to use less than adequate materials, design, and manufacturing process... wait until you can save up the cash to buy, or build it correctly and safely.

Mixing fire, high temperature water, steam potential, pressure, electricity and dangerous emissions all in one box needs to be done properly and carefully. We don't want to read about you in the paper.. unless it's good news

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[deerefanatic]

Don't worry, I've never been a risk taker....

Nope, never seen either in operation.......

Hmm...... you're really trying hard to win me over aren't you?

 

[Eric Johnson]

The Garn is more than a piece of equipment--it's a cult.

 

[deerefanatic]

I see that! LOL!!

 

[daleeper]

deerefanatic,

I am watching this with much interest, thanks for the link to the source of your plans, I have not seen this set of plans before. The price seems to be right, are they complete? Without spilling proprietary information, is the design similar to the seton, or does it approach combustion totally different? Seton does sell a set of plans, but I haven't seen that anyone here has built one, and they are priced in such a way that you need to be real serious about building one to spend the money on the plans.

I have enjoyed viewing the garn video, and like the concept, but have not seen anyone with plans for that type of unit, and would agree with you that a refractory type construction looks more doable on paper. I would love to see a set of plans for the garn type of system. I would like to see any of these gasification units, all we see around here are the OWB's and the smoke that goes with them. Good luck and keep us posted as you proceed.

 

[deerefanatic]

I'm not sure.... Never looked over the principal for the Seton boilers... Was turned off by their ridiculously high price for plans.....

I have a few doubts on the drafting setup of the design in the plans I bought from A&C;contracting actually... I'm gonna email him and ask some more questions on that.....

Basically this thing works on the principal of massive amounts of refractory to achieve gasification......

 

[hkobus]

This system uses a 1200 gallon stainless bulk tank for thermal storage (pressurized is my goal)

-Matt

Newbie Boiler Man!

I missed this initially, but I seen the expansion tank in the drawing. I do not know any bulk cooler tanks to be pressure tested, other than the refrigerant coils in between the inner skin and the insulation. The tank it self is nowhere near pressure resistant. To prove the fact, there are many tanks that were "sucked" in by simply pumping the milk out and blocked venting. :red:

 

[deerefanatic]

Hmm... I wondered about that...... They are pretty thin material........

so just cap her off to negate steam loss and call it good eh? How about an open-topped elevated expansion tank? just the weight of the water pushing down? It should be able to handle that I would think.........

It's still "closed" as long as you keep roughly the same water in the system all the time......