# 10,000 gals of 180 degree water would keep the house warm for a long time



## SolarAndWood (Jun 11, 2009)

http://syracuse.craigslist.org/zip/1216259312.html

Its a little overkill for my needs but the price is right if it works for yours.


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## stee6043 (Jun 12, 2009)

I can't imagine this being used for residential hydronics!  Man...the heat loss from this tank alone would be enough to heat my house!  Not to mention the fact that I'd have to burn my EKO 40 for five days straight just to get it up to temp....ha.  

If it were mine I'd cut it in half and make two wood sheds out of it....


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## SolarAndWood (Jun 12, 2009)

I considered cutting an end of it and using it on end.  Decided that a little patience in my tank search was better than another project of that magnitude.

I like your wood shed idea.  I think I would stand it on end and put a silo roof on it.  My wood shed is going to be 10 feet below where my first year drying pile is anyway, wouldn't even need to lift the wood and wouldn't ever need to stack it.  Wonder what the wife would think.


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## muleman51 (Jun 12, 2009)

My neighbor has a Recycling business (junk yard), he has several tanks that he has cut open for wood storage. They work very well for that! He actually can pick them up with his large payloader and put them close to his OWB when he needs them, real handy.


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## Nofossil (Jun 12, 2009)

If I were designing a new house, I'd consider designing in storage on this scale. That would give you many days between burns - weeks, even. You could build a fire on the weekend and not worry about it until the next weekend.


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## stee6043 (Jun 12, 2009)

This would be quite a setup - figure your usable temps for storage are 140-180 degrees.  That's roughly 3,600,000 usable btu's per fully loaded tank (in a perfect world of course).  I believe an EKO 80 has 275,000 btu/hr output.  Assuming you were only charging the tank with the EKO (no other heat loads) it would take a 13 hour burn at peak efficiency to bring the tank back up to temp.

That's actually not as bad as I would have guessed.  You could burn your boiler all day Saturday and potentially heat off of it for the better part of a week.  Assuming a constant demand of 30,000btu/hr you could get five (5) full days of heat from this tank (assuming no heat loss from the tank).

Sadly...for my humble EKO 40 it would take pratically three days of burning twelve hours a day to get this tank back up to temp.  Probably more like five days since I'd have to heat the house at the same time.  Obviously with a big enough boiler this thing could be useful - but I think I'd still make a woodshed out of it!


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## SolarAndWood (Jun 12, 2009)

nofossil said:
			
		

> If I were designing a new house, I'd consider designing in storage on this scale. That would give you many days between burns - weeks, even. You could build a fire on the weekend and not worry about it until the next weekend.



Kind of what I was thinking.  At the end of the heating season, you would have enough DHW through the 4th of July.  I could still integrate something this size into my renovation/rebuild.  I could probably build a building adjacent to my boiler room for close to the same price as a big commercial tank.

Also adjacent to my boiler room is a 12 x 12 block room with a 8 foot masonry ceiling.  What do you think about blocking in the small doorway,  insulating the inside of the walls and putting a liner in it?  I always thought it was too big but maybe its worth considering.


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## SolarAndWood (Jun 12, 2009)

stee6043 said:
			
		

> Obviously with a big enough boiler this thing could be useful - but I think I'd still make a woodshed out of it!



With ya, but the zoning guys have gone easy on my rehab to this point and that might push them over the edge.  I'm not sure you need that big of a boiler for it to be useful.  I burn 24/7 now and have no intention of changing that with the boiler as I prefer to put the heat directly into the house anyway.  So, when peak load isnt required, the heat store gets built up and we can disappear for a few days without running on backup.  BTW, your humble EKO 40 is my dream machine.


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## Hansson (Jun 12, 2009)

http://translate.google.se/translat...detalj.asp?id=51&sl=sv&tl=en&history;_state0=

50 000 liters


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## SolarAndWood (Jun 12, 2009)

Hansson said:
			
		

> http://translate.google.se/translate?prev=hp&hl=sv&js=n&u=http://www.baxi.se/visa_kunder_detalj.asp?id=51&sl=sv&tl=en&history;_state0=
> 
> 50 000 liters



That is a beautiful display.  If I had such a system up and running, I would probably have a smile on my face though.


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## Hansson (Jun 12, 2009)

yeah but he had to burn a long time to get the hole tank warm. The boiler is a 50KW baxi innova


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## SolarAndWood (Jun 12, 2009)

Hansson said:
			
		

> yeah but he had to burn a long time to get the hole tank warm. The boiler is a 50KW baxi innova



I'm OK with that as long as the boiler keeps my house warm before it heats the tank.  I usually have a 7-8 month burn anyway.


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## karl (Jun 13, 2009)

If you insulated it, you could lower the heat loss alot.  Plus is doesn't have to be full of water.  I would build a wood shead around it.  So all that heat I had left over would dry the wood for next year.

Here's an idea.  Get 10 or 12 of these and insulate them.  Then use solar to heat them up all summer and get two to three months of free heat.


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## jebatty (Jun 13, 2009)

Just for fun, occasionally I do a "pressure tank" search on e-bay, and multi-thousand gallon tanks frequently are listed. Typical prices (plus shipping) are around the $1/gal level. If I built a new home or even a new shop building, I definitely would consider a large pressure tank(s). The 1000 gal (3784 liter) I have is very good; the Tarm Solo 40 heats that very easily into the 180F+ range; and a larger tank with a gasifier definitely has its advantages.


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## SolarAndWood (Jun 13, 2009)

karl said:
			
		

> Then use solar to heat them up all summer and get two to three months of free heat.



Any idea what kind of collector area it would take to accomplish this during the summer?  My new roof has a 1000 sq ft solar south face pitched for year round production which for me is obviously biased towards summer.  It is 7/12.  It is planned to be covered with PV but they could be mounted on poles.  Does 1000 sq ft even get me in the game?  If I do solar water, I want a super simple system that just compliments the boiler.  I don't see the payback in an evacuated tube system especially when the boilers do an amazing job generating heat and wood seems to be a better way to store the BTUs.


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## SolarAndWood (Jun 13, 2009)

jebatty said:
			
		

> Just for fun, occasionally I do a "pressure tank" search on e-bay, and multi-thousand gallon tanks frequently are listed. Typical prices (plus shipping) are around the $1/gal level. If I built a new home or even a new shop building, I definitely would consider a large pressure tank(s). The 1000 gal (3784 liter) I have is very good; the Tarm Solo 40 heats that very easily into the 180F+ range; and a larger tank with a gasifier definitely has its advantages.



I have been shopping for one in the 1500-3000 gallon range.  I have a lot of flexibilty at this stage of construction but that window is probably going to close by Fall.


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## DaveBP (Jun 13, 2009)

If I had it to do over, knowing what I know now, I would frame my house and pour basement support for a big propane tank standing on end. Drop it in with a crane. 2000 gallons would be something like 4' dia. X 22' long.
Make a central chase right up to the attic and have room at the top for a Hansson-style open expansion tank at the top. I saw a diagram for something like this on a German eco-energy site. A couple years ago I would have thought, "Those crazy Germans!". Now I'm jealous.


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## SolarAndWood (Jun 13, 2009)

Like that.  I could probably still do that.  While I have the trusses up over the section where I would locate the tank, I could slide it in horizontally on the second floor and rotate it down to the basement.  The house originally had a flat roof with 14" I-Beams supporting it.  So, slide it in, set up the block and tackle and lower it down.

I don't know a whole lot about tank science other than more water holds more btus.  What is the benefit of having it vertical as opposed to horizontal?

Is that a common tank?  Or is it a horizontal tank I build a base for?


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## DaveBP (Jun 13, 2009)

> What is the benefit of having it vertical as opposed to horizontal?



Beside taking up less floor space the only advantage of vertical tanks for pressurized storage that comes to mind is that they are easier to keep well stratified. Since seeing the result of some of Jebatty's tests I'm not sure that is a deal breaker. As long as you introduce the water into the top of the tank without a lot of turbulence (larger pipe is better) it seems to stay separated well enough. 

In my case, the basement is my workshop and I wouldn't want to give up the room for a horizontal installation there but giving up a closet upstairs would be acceptable to me. I'm using two 500 gallon propane tanks horizontally but stacking them on top of one another to fit up under the stairs and take the least usable floor area. A number of others on this forum have done something similar.

There are a few standard propane tank sizes for reference here:

http://propanetanks.us/


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## SolarAndWood (Jun 14, 2009)

Does it make a difference for unpressurized?


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## Gooserider (Jun 14, 2009)

SolarAndWood said:
			
		

> Does it make a difference for unpressurized?



Within limits, theory says you can get better stratification out of a tall skinny tank than you can out of a short fat one, regardless of whether it is pressurised or not, thus in theory the vertical tank would be better either way.  However one problem that does come up with a non-pressured tank is that the taller it is, the higher the water pressure exerted on the tank walls near the bottom, due to the combination of increased water pressure and the fact that the weight of the water is distributed over a smaller area - this can rapidly develop into a strength problem for materials commonly used by home builders...  It is also an issue for pressurised tanks, but they are typically built strong enough that it isn't a problem.

One issue that also needs to be kept in mind if designing a house around a big tank is that sooner or later you WILL need to replace the tank, just like the boiler, etc...  It is important to design the structure in such a way as to allow for replacement without needing to do major demolition / reconstruction...  I.e. if doing a vertical skinny tank, design a removable roof section so that it can be removed and replaced w/o needing to replace the entire roof.  Alternatively make the outside wall non-structural / removeable...  (Note that the ability to replace things is also a code reqirement, though not all inspectors will catch that one...)

Gooserider


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## pybyr (Jun 14, 2009)

As much as I am intrigued with wood gasification boilers/ storage (and happy with my Econoburn) if I were designing and building a home from scratch, I'd strongly consider doing something similar to what some friends of mine just did-- open floorplan house, with lots of south facing windows, and a well-designed (but not super-fancy) masonry heater going up through the center of the dwelling, with extremely good insulation and air sealing in the outside walls.  The beauty being-- no pipes or pumps (and associated power requirements/ maintenance).  Their house is astonishingly warm whenever I've visited, and it takes them astonishingly little wood or effort to get and keep it that way.  They have in-floor radiant in the first floor floor, but it apparently rarely needs to run.


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## jebatty (Jun 14, 2009)

> I’d strongly consider doing something similar to what some friends of mine just did-- open floorplan house, with lots of south facing windows, and a well-designed (but not super-fancy) masonry heater going up through the center of the dwelling, with extremely good insulation and air sealing in the outside walls.



Could not agree more, exception being I would not fully endorse the masonry heater, mostly because it does not generate the high temps of gasification boilers and therefore is less efficient from a combustion perspective, and because of the extreme efficiency related to low temp radiant systems. 

Although the shop is heated with the Tarm, our house meets most of the criteria listed, and is heated (1500 sq ft main floor) only with a small wood stove we installed in 1990. SW facing windows, open floor plan, as well insulated and sealed as our house can be, given its vintage. New construction, and even remodels to extent possible, needs to focus first on energy conservation through these techniques. Then, the heating system to supply only what Mother Nature does not offer for free.


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## kuribo (Jun 14, 2009)

> Could not agree more, exception being I would not fully endorse the masonry heater, mostly because it does not generate the high temps of gasification boilers and therefore is less efficient from a combustion perspective, and because of the extreme efficiency related to low temp radiant systems.



Why do you think that? A properly designed and built masonry heater combusts wood using gasification as well and generates the same high temps....Additionally, masonry heaters have efficiency levels at least as high as gasification boilers, some even higher. In a systems context, they have even better efficiencies as there are no pump losses, frictional losses, idling inefficiencies, storage losses, etc....


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## jebatty (Jun 14, 2009)

> A properly designed and built masonry heater combusts wood using gasification as well and generates the same high temps....Additionally, masonry heaters have efficiency levels at least as high as gasification boilers, some even higher.



I can be convinced. Point me to the info or data that shows this and you will have me converted.


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## kuribo (Jun 14, 2009)

see the data on the masonry heater association site. Here is a place to start:

http://heatkit.com/html/lop-arc.htm


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## Hakusan (Jun 14, 2009)

Masonry heaters are the original wood gasification heater. They burn hot and fast (1300F or higher) transferring the heat to the masonry mass which slowly releases it. You can even build with a bake oven and hot-water coil to pull more advantage out of it. Other names for this type of stove are Kachelofen (with an umlaut over the o), tile stove as well as Russian, Siberian, Finnish, or Swedish stove/fireplace.

http://mha-net.org/


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## kuribo (Jun 14, 2009)

Efficiencies can be over 80%:

http://www.stovemaster.com/html_en/designsysadvstesting.html


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## kuribo (Jun 14, 2009)

Hakusan said:
			
		

> Masonry heaters are the original wood gasification heater. They burn hot and fast (1300F or higher) transferring the heat to the masonry mass which slowly releases it. You can even build with a bake oven and hot-water coil to pull more advantage out of it. Other names for this type of stove are Kachelofen (with an umlaut over the o), tile stove as well as Russian, Siberian, Finnish, or Swedish stove/fireplace.
> 
> http://mha-net.org/




I have seen figures of 1500-2000F for firebox temps with 200-300F stack temps in some tests.... Without the pumps, plumbing, and storage losses, overall system efficiencies they have clear efficiency advantages over the current crop of boilers.

They aren't for everyone but for someone in the design stages of a new home whereby one can be integrated into the home, they have many advantages over any of the boilers including aesthetics, simplicity, longevity, and efficiency....


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## Hakusan (Jun 14, 2009)

kuribo said:
			
		

> Hakusan said:
> 
> 
> 
> ...



I think most masonry heaters work around 1800F, but the design and size varies that. But I agree with everything you say. If it were not for the cost, I would get one like a shot.


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## Gooserider (Jun 15, 2009)

According to the MH advocates, most homes aren't good candidates for retrofitting an MH, but if doing new construction the cost of putting in an MH instead of a conventional masonry fireplace is not that bad, I think they said 10-15% extra over what a standard FP would cost, IOW, probably a good bit less than what it would cost to do a boiler + storage, etc. setup...

Gooserider


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## kuribo (Jun 15, 2009)

Built one in my new home. It is about 1.5X bigger than the average masonry heater. I will do the facing myself. The unit cost me around $8000 for everything. Should last at least 2-3 times as long as a boiler and it has a bake oven. Try making pizza in a boiler....


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## jebatty (Jun 15, 2009)

> I can be convinced. Point me to the info or data that shows this and you will have me converted.



I only spent about an hour looking at the references listed above for masonry heaters, so I didn't catch everything. It appears to me that masonry heaters are worthy of consideration, particularly in new construction, where a central radiant heating mass will meet the need for space heating. Like a wood stove, but probably even more so, their best use likely is in larger, open space designs that can take advantage of the radiant heat. 

Masonry heater function is comparable to a wood stove by providing a thermal mass to transfer radiant heat to a space. While wood stoves do this by a slowed, and therefore, long burn times to achieve a long period of radiant heating, masonry heaters do this by a fast burn with heat transfer to the masonry which then provides the long period of heating. 

I didn't happen to spot info that showed operating temps in the 1800F+ gasification range, although logically this seems possible due to the fast burn rate against a masonry surface. I'm somewhat skeptical though, but only because gasification boilers use a high temperature ceramic gasification tunnel that can withstand these high temps for extended periods, and I didn't notice that masonry heaters use a similar material that can handle these very high temps.

Average net heat transfer is in the 60-65% range. Average particulate emissions were somewhat higher than EPA Phase II wood stoves. Average btuh output is in the 8K-10k range. Test were done with wood at about a consistent 20% MC. Wood burn is at a high rate with rich air supply and various long-path designs to capture the exhaust heat in the masonry before entering the flue. Exhaust flue temps were in the 300F-700F range. Heat captured in the masonry mass continues to radiate after the fire burns out.

I's sure that I didn't catch everything, and particular designs claimed characteristics different from what I have stated, although I think I have been fair in capturing the "average" masonry heater characteristics.

Conclusion: being "converted" is not the appropriate term, because there is no one "best" wood heating appliance. Masonry heaters clearly are a reasonable choice with distinct advantages and clearly can perform very well in certain space heating circumstances.


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## kuribo (Jun 15, 2009)

jebatty said:
			
		

> I can be convinced. Point me to the info or data that shows this and you will have me converted.
> 
> I didn't happen to spot info that showed operating temps in the 1800F+ gasification range, although logically this seems possible due to the fast burn rate against a masonry surface. I'm somewhat skeptical though, but only because gasification boilers use a high temperature ceramic gasification tunnel that can withstand these high temps for extended periods, and I didn't notice that masonry heaters use a similar material that can handle these very high temps.



Masonry heaters have a firebrick core (some of the kit versions available use castable refractory pieces that make up the core) which is made to handle the extreme temperatures of gasification. There is no iron or steel sheeting to warp, crack, or burn through like you see in the E-Classic boiler or others. The entire firebox and flue channels are made of refractory which is what is used, though sparingly, in wood boilers.




> Average net heat transfer is in the 60-65% range. Average particulate emissions were somewhat higher than EPA Phase II wood stoves. Average btuh output is in the 8K-10k range. Test were done with wood at about a consistent 20% MC. Wood burn is at a high rate with rich air supply and various long-path designs to capture the exhaust heat in the masonry before entering the flue. Exhaust flue temps were in the 300F-700F range. Heat captured in the masonry mass continues to radiate after the fire burns out.



Performance various depending on the type of heater design, how it is constructed, and the moisture of the wood. 20% is rather high moisture content. Heat transfer rates are typically around 20,000- to as much as 35,000 btu/hr with flue gas temps in the range of 300-400F. Efficiencies are, as you mentioned, 60-65% though there are designs with measured performance in the 75-80% range.

Again, without the plumbing, storage, etc, and a direct conversion to radiant heat, masonry heaters are as efficient as wood boilers. They last a lot longer and have many other advantages already listed here. They work best in new construction where they can be made an integral part of the home design. They can be  retrofitted successfully in many, but not cases. They do not come up second best when compared to a wood boiler and should be considered on an equal footing........


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## jebatty (Jun 15, 2009)

Many of us, especially me, need to be careful about broad generalizations. All wood boilers are not the same, as indeed are not all masonry heaters.



> There is no iron or steel sheeting to warp, crack, or burn through like you see in the E-Classic boiler or others. The entire firebox and flue channels are made of refractory which is what is used, though sparingly, in wood boilers.



The comment regarding warp, crack or burn through is hardly a fair characterization of wood boilers designs of Tarm, Eko, Garn, Wood Gun and others of their general types, many of which have been in service for more than 20 years. There are also are other types, what I call the traditional water jacket outdoor wood boiler, which have different characteristics. But it is unfair to lump all wood boilers into the same category, just as it would be unfair to lump all masonry heaters into the same category.



> 20% is rather high moisture content. Heat transfer rates are typically around 20,000- to as much as 35,000 btu/hr with flue gas temps in the range of 300-400F.



20% is not a high moisture content for cord wood, seasoned and stored outside. It is in fact the MC used in most of the various tests cited, and I suspect that is so because it is a typical cord wood MC experienced by homeowners. In addition, 18-20% MC would be the norm in my area based on ambient humidity and climate, and I suspect in some climate areas outdoor stored wood would normalize at higher MC, and in other climate areas would normalize at a lower MC.

The Masonry Heater White Paper cited at http://heatkit.com/html/lop-arc.htm shows average BTUH output of 7248 for five commercially available masonry heaters for in home use, so my comment of 8K-10K BUH actually was high for average performance. I don't doubt that some designs do better than others, but the average is much less. If the calculated heat demand falls within the range of a masonry heater, it clearly would be an option for a homeowner, but a prospective purchaser would have to be cautious if BTUH requirements are in excess of the 7248 average so as to be sure to acquire a masonry heater that could meet the expected performance demand. 

Thank you for your input, as I have seen little on masonry heaters in this Forum. The information is helpful and shows one other good option where it fits.


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## SolarAndWood (Jun 16, 2009)

Thanks for all the great discussion.   We have heated with a stove exclusively in the middle of the house four seasons now.  While I appreciate the simplicity and my wife's frequent soups, chili etc that are cooked on it, the shape of the house doesn't lend itself to a central space heater.  It has worked great while we have basically lived in one 1000 square foot open space, but I hope to have the other wing of the house and the walkout lower level finished this year.  These spaces will be nearly impossible to heat effectively with the stove.

I assume that it is cost/logistics that keeps everyone from going big with storage?  The cost of the backup boiler/fuel is a lot cheaper than big storage, especially given that the backup will be purchased either way?

What is the biggest homemade storage out there?  Is my 12 x 12 block room too big to insulate and line?  Or are the advantages of pressurized so great that I should blow one of the walls out and put a few propane tanks in there?  This is very feasible as I have 4 foot wide windows on the lower level.

Thanks again for all the great feedback.


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## pybyr (Jun 17, 2009)

SolarAndWood said:
			
		

> What is the biggest homemade storage out there?  Is my 12 x 12 block room too big to insulate and line?  Or are the advantages of pressurized so great that I should blow one of the walls out and put a few propane tanks in there?  This is very feasible as I have 4 foot wide windows on the lower level.
> 
> Thanks again for all the great feedback.



The beauty of pressurized storage is that you don't need a heat exchanger between the boiler's water circuit (which generally needs to be sealed so that it does not take on oxygen and corrode the boiler) and the storage.  This not only saves the cost of the heat exchanger (copper coils in the tank or a flat plate heat exchanger) it also removes the need for a couple of extra pumps, and also improves the efficiency of the heat transfer between boiler and tank and tank and house.  That said, the pressurized system will require a larger ( and more expensive ) expansion tank than a non-pressurized system.

Bigger is better, within reason, but not simply for the sake of size.  Ideally, what you should do is figure out your heat needs for the space you are going to heat, and then give thought to boiler size, and then also to your lifestyle patterns (when you are home and when/ how often you are OK with building fires).  You probably do want a mass of water big enough to be a "flywheel" to meet your heat load so that you (or someone else) need to tend the fire all the time to keep the space warm, but you don't want storage so big that it takes huge effort tending a fire in your boiler to get/ keep the storage at temperature.

Somewhere here in the boiler room there are good explanations of how to calculate the heat storage potential of a given volume of water, but I don't recall the specific discussion threads-- I'll try to sketch out some of the variables in hopes that it makes sense for you.

Specific heat of water =  British thermal unit per pound per degree Fahrenheit (1 Btu/lb-°F)

weight of water per gallon (roughly) 8.34 pounds per gallon

then you need to figure out the maximum feasible and minimum useful temperatures of your storage.

if it is unpressurized storage with a liner, then the max. temp. your liner can handle will limit the max temp of the storage

if it is pressurized storage, then the max. temp. will be as high as you can comfortably run without risk of steam in the system

the minimum temperature of your storage for your calculations will be based on the minimum temperature that your household heating system can extract useful heat out of.  radiant floors get an advantage here; baseboards supposedly fade out between 140 and 120

Take total gallons of water, and then the max achievable and minimum useful water temps, and then the btus per degree per gallon, and you'll see how much heat a given volume of water can store.

these folks sketch out the practical application of some of this relatively well here:

http://www.slatevalleyboilers.com/index_files/heatstoragetanks.htm


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## SolarAndWood (Jun 17, 2009)

pybyr said:
			
		

> if it is unpressurized storage with a liner, then the max. temp. your liner can handle will limit the max temp of the storage
> 
> if it is pressurized storage, then the max. temp. will be as high as you can comfortably run without risk of steam in the system



We are used to burning 24/7 and I am sizing the boiler to continue to do that as I prefer to put the heat directly into the house whenever possible.  The two strategies I have come down to is:

1.  put in minimal size storage for a 85K btu boiler to smooth out the bumps and use backup when gone for more than 24 hours, maybe as little as 500 gallons
2.  go big with storage and largely eliminate the need for backup or solar collectors for DHW in the summer

The unpressurized is pretty compelling given the 12 x 12 block room that is of pretty little value otherwise and the relatively small heat exchanger required for the smaller boiler.  If I go 5 feet, it would be in the neighborhood of 4000 gallons.  Has anyone tried to build a tank this big?

Given the small heat exchanger, it seems that pressurized is a lot more money for that kind of volume?  Given that I am using radiant floors, the lower temps are less of an impact.  Didn't I also read somewhere that higher temps take more energy to achieve?


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## Gooserider (Jun 17, 2009)

Storage is mostly a balancing act - it is really preferable to keep your BTU's stored as fuel, rather than as hot water because hot water doesn't "keep" very well compared to fuel...  If it were possible to turn a wood fire on and off as quickly and easily as it is to control a fossil burner, then we wouldn't use storage at all.  But since wood is consumed more efficiently when it burns in one continuous, high temperature burn, you need someplace to put the "extra" BTUs that are produced but you don't need right at the moment...

Pybr pretty well described most of the factors that one should consider when sizing storage, what I would add is that a good sizing metric is to figure out approximately how many BTU's your boiler can put out during a single burn cycle, and base the size of the storage on how much it takes to store ALL the output of one burn, if you start at your minimum working temperature and the fire burns out as you hit the design max for the storage.  This will give you your most efficient use in the summer when only making DHW.  In the heating season, you might not get the storage to maximum without building two or more fires, but it will still have the desired "flywheel" function to make the boiler work efficiently...

As a practical note, it seems most of us end up with 500-1500 gallons of storage, other than the Garndroids, who are a different class of beast all together...  I think there is a practical reason for this in that it is a good balance point for most of us.

In terms of using your block wall room for storage, I would want to look very carefully at how the walls are constructed - storage sized volumes of water are very heavy and will exert major forces on the walls of the container, which MUST be designed to handle them.  A standard construction block wall will NOT have been adequately built for this task...  Foundation walls that have lots of dirt behind them for support will probably be OK, but a freestanding single layer wall probably would not be up to it, and the longer the unsupported wall length the weaker it will be...  Blocks CAN be used to build a tank wall, but they require lots of rebar and filling all block spaces with concrete to reinforce them in order to do so.

Gooserider


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## SolarAndWood (Jun 17, 2009)

Gooserider said:
			
		

> it is really preferable to keep your BTU's stored as fuel, rather than as hot water because hot water doesn't "keep" very well compared to fuel...



That certainly has been the benefit of heating with a stove in the middle of the living space.  The cart of wood next to the stove makes for instant gratification.



			
				Gooserider said:
			
		

> how many BTU's your boiler can put out during a single burn cycle, and base the size of the storage on how much it takes to store ALL the output of one burn, if you start at your minimum working temperature and the fire burns out as you hit the design max for the storage.  This will give you your most efficient use in the summer when only making DHW.  In the heating season, you might not get the storage to maximum without building two or more fires, but it will still have the desired "flywheel" function to make the boiler work efficiently...



If the pressurized systems can efficiently achieve the higher temperatures, it would seem that one 500 gallon propane tank achieves this and is pretty cost effective.  It is also the most compact solution.  I assume integration of a propane tank is largely a do job?  No invention/fabrication required?



			
				Gooserider said:
			
		

> In terms of using your block wall room for storage, I would want to look very carefully at how the walls are constructed - storage sized volumes of water are very heavy and will exert major forces on the walls of the container, which MUST be designed to handle them.  A standard construction block wall will NOT have been adequately built for this task...  Foundation walls that have lots of dirt behind them for support will probably be OK, but a freestanding single layer wall probably would not be up to it, and the longer the unsupported wall length the weaker it will be...  Blocks CAN be used to build a tank wall, but they require lots of rebar and filling all block spaces with concrete to reinforce them in order to do so.
> 
> Gooserider



That has been my reluctance of using the existing room.  However, it is earth on three sides and a large storage solution would largely eliminate the need for using backup.

The single propane tank solution is compelling.


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## Gooserider (Jun 17, 2009)

I would be hesitant to greatly decrease the size of my storage just because of going from non-pressure to pressure - It seems to me that the efficiency advantage is relatively minor, as I'm not seeing people report huge differences between the temperatures they run the two sorts of storage at.

One of the things that I do see is that while some folks plumb their pressure tanks in pretty much the way they are, others are doing more to add extra fittings and so forth to the tanks - you can read lots of pressure storage setup descriptions in the threads.

IMHO some form of at least minimal backup heat is a requirement.  My understanding is that many insurance / mortgage companies require it, and it may also be a code requirement in some places...  If nothing else, I would want to ensure that I could go away on an extended winter vacation and not have to worry about things freezing if I'm gone longer than the storage tank allows for...  Note that this does NOT necesarily mean a full blown second heating system, all it means is something with enough capacity to keep the house above freezing.

Gooserider


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## Wet1 (Jun 18, 2009)

I was just casually reading this thread, but one other thing you might want to keep in mind with unpressurized tanks (especially with a tank/room of that size) is evaporation and moisture issues with unpressurized systems.  It's one thing to effectively seal off a 500 gal. unpressurized tank, it might be a different matter trying to seal off the top of a 12' x 12' x 5' room/tank.


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## SolarAndWood (Jun 18, 2009)

The room is all masonry including the ceiling, but certainly mold is always a concern.  I think that a patient tank search will eventually dictate the solution.  The windows that I put in the house were meant for a old brick building remodel.  The architect missed by a 1/4" on the width and there was no reworking the building.  So, 45 matching windows with screens still in their shrink wrap end up at my house for 25 cents on the dollar.  It just took almost 2 years to find them.


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## Chris Hoskin (Jun 18, 2009)

not to re-hijack the thread, but one significant difference between a masonry heater and a boiler with storage is that the tank allows you to release the heat as needed and where needed whereas the heater just radiates heat uncontrolled.  I grew up with a masonry heater in the kitchen and I am a big fan.  Not only an efficient comfortable way to heat with wood, but normally a beautiful focal point of your home.  I say put in one of each! 

Regarding tanks, one of the benefits of un-pressurized storage is that you can have the tank serve a solar hot water collector(s) too.  Just add another heat exchange coil for the collector and the tank does double duty.  Not a solar expert, but my sense is that if you plan to do this over-sizing should be avoided.

Chris


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## Justburnit (Jun 19, 2009)

Hi Guys,
I haven't been on in awhile but this thread caught my eye. I have used a 5,000 gallon unpressurized storage two seasons now. As far as sealing the tank-room I used rubber membrane.

The lower part is one piece folded in the corners. The upper section is bonded all around. Best I can tell it works fine. This picture was taken early and the 2X4s are a temporary structure to support the membrane during construction.


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## SolarAndWood (Jun 19, 2009)

Good morning Charlie.  I went through your posts and didn't see construction details or your thoughts on system performance.  Did I miss them?


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## Nofossil (Jun 19, 2009)

Justburnit said:
			
		

> Hi Guys,
> I haven't been on in awhile but this thread caught my eye. I have used a 5,000 gallon unpressurized storage two seasons now. As far as sealing the tank-room I used rubber membrane.
> 
> The lower part is one piece folded in the corners. The upper section is bonded all around. Best I can tell it works fine. This picture was taken early and the 2X4s are a temporary structure to support the membrane during construction.



Holy Guacamole, that's a lot of storage! Could you share construction details about the outside walls? Perhaps some performance data or quality of life stories? Inquiring minds want to know.


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## Justburnit (Jun 19, 2009)

> Holy Guacamole, that’s a lot of storage! Could you share construction details about the outside walls? Perhaps some performance data or quality of life stories? Inquiring minds want to know.
> Signature



Yes I can, but I should start a separate thread about my system.


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## SolarAndWood (Jun 20, 2009)

Justburnit said:
			
		

> > Holy Guacamole, that’s a lot of storage! Could you share construction details about the outside walls? Perhaps some performance data or quality of life stories? Inquiring minds want to know.
> > Signature
> 
> 
> ...



https://www.hearth.com/econtent/index.php/forums/viewthread/39073/

Thanks for posting that Charlie;  it is exceptional.

I took a light down to get a good look at my masonry room this morning.  I hadn't noticed before but it has a parge coat over the block and the 4th wall is only 6' with a finished top while the rest are 8.  It makes me think it may have been a cistern at one point with the one side shorter and the way the parge coat wore up to 6' compared with the top 2 feet.  I think it may have been the last owner that broke a 2' section of block out to put a sump in to solve the problem they caused when they poorly sited an inground pool just downhill of the house and destroyed the drainage system.  With the aid of my father in laws 12 ton hoe, I took care of the drainage problem and my pool maintenance burden over the winter and no longer need the sump.

The inner dimensions are 10' D x 8' W x 8' H with the exception of that 4th wall.  The ceiling was made by laying down some kind of corrugated fiberglass panels and pouring what looks like 3 or 4 inches of concrete over it.  If I put 2' of foam on top and 1' on the sides and floor, I end up with 8' D x 6' W x 5' H or something like 1800 gallons.  I would have to replace the small section of block they removed and create a top hatch, but that seems pretty doable and I have a big headstart toward a decent size tank.

Any rough estimates on material cost for the liner and insulation?  My guess is that it is on the order of 2 full weeks work to replace the small section of block, build the hatch, insulate and install the liner.  The alternative is to walk a $3000 1500 gallon commercial tank like the STSS into that same room, set it up in a morning and be done.  Or go smaller with the 2 500 gallon propane tank solution.  Thoughts?


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## Justburnit (Jun 21, 2009)

> If I put 2’ of foam on top and 1’ on the sides and floor, I end up with 8’ D x 6’ W x 5’ H or something like 1800 gallons.  I would have to replace the small section of block they removed and create a top hatch, but that seems pretty doable and I have a big headstart toward a decent size tank.



I got my block foam from, Roger the foam guy in Northville NY. He is on Rt 30 just west of Sacandaga lake. I will PM his phone. I am not sure of current pricing. He advertises in the Want Add Digest.
The membrane I used was from a pool supply, found online. I bought the 0.040 thick 20' X 25' and was about $150 shipped. The top piece was found used from a roofing company for #25 each.

Be careful with unsupported block walls. Backed by earth they are fine, A bit limited in shear loads though. I could not get honest data but I would want some metal in the wall. If you can add some rods and pour in some of the cells it would be of value to ensure the lower section can not shear out from water loads.
I used 6" of foam on the bottom and if you had 9" sides and a foot on top would be more than enough. With copper coils or a plate type exchanger I would add a 1" sheet of Hi R to the sides and top so you can run the tank temps all the way up.

If you have economical access to a company with spray foam I would consider the pressurized system. This eliminates the transfer losses giving a larger dynamic range for the system to operate in. To me 1000 gallons of pressurized seems for effective than the transfer losses to and from a 1500 gallon. In my opinion the swimming pool tanks greatly lack in insulation. If you can get coils from them that maybe of value but for that money I would go pressurized.

I originally had a 1000 gallon in ground oil tank, it had to go so I could insure the place. My original thoughts were to insulate it but this was back before I was working on the Masonry stove and long before committing to a wood boiler. Would might have worked well. I will never know.


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