# Hot Water Storage



## Eric Johnson

I'm thinking about turning a poured concrete cistern in my basement into a hot water storage reservoir. Does anybody have any links to (or information about) building a non-pressurized hot water storage tank?


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## webbie

Funny, but this info was around 20 years ago and may have been buried on the back burner. Maybe some old time solar junkies have some of the info around - I remember a system that you can build out of plywood - the company sold large rubber liners for your plywood box! Worked like a champ for building storage - heat was transfered to and from using standard 100 foot copper tubing which comes coiled. Of course, you have to do all the calcs as far as storage, etc.

Here's a possible lead - see what the folks at Real Goods Trading Co. are up to - they used to have a lot of solar experts in house and maybe they can at least head you in the right direction.

http://www.gaiam.com/realgoods/

Here is a link to a similar tank type:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Tank.htm

Try some google on EPDM site built solar storage, etc.


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## keyman512us

Eric:


> I’m thinking about turning a poured concrete cistern in my basement into a hot water storage reservoir. Does anybody have any links to (or information about) building a non-pressurized hot water storage tank?



Eric,
I'll share some observations(from personal experience). I too have a wood fired boiler (not a true OWB but might as well be with all the 'grief I'm getting'). It has a gross output of 85,000/hr and can easily and very comfortable heat my homestead. When I fire it...I fire it "Full bore"(hot fire=no smoke)...which is tricky to do unless you don't mind 80+ temperatures..so storing/shedding heat is something I have dealt with. I use a 120 gallon water heater as an accumulator/buffer tank to balance the system. "Storing" hot water for heating is tricky...and not all it's cracked up to be. In theory great idea..real world? Unless you have a "super efficient" home (which I doubt either of us claim)...it leaves something to be desired. In milder weather it works best. I can store the heat and get a "couple of showers" worth of hot water out of it, with the "fires out" (both wood and oil). If you plan on running wood fire in "cycles" might not be so great..."continous" good idea. I would suggest you use your (what was it 4,500 gallon cistern?) more as a "radiant heater" than a storage tank. 4,500 gallons at 80-100 degrees is more attainable than 180-200 (to get it that hot I think you might 'go chernoblyl' with any boiler...lol) As an "old timer' told me once "If your basement is warm...your house is warm". I would therefore lean towards using it as "radiant heater" to keep the basement toasty warm.
You could always add a smaller "tank upstream" at a later date.
If I had a 4,500 gallon set-up in my basement...I would use it as a "Hot tub"...lol


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## keyman512us

Eric,
I just looked up the post you quoted "10x15x6":
10 x 15 = 150sq/ft x 6' Depth = 900 Cubic Feet x 7.48(#gals/cu ft) = 6,732 Gallons

Good sized tank!


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## Eric Johnson

I've been successfully heating various houses with various different boilers for about 15 years without the benefit of hot water storage, but they say it's a good idea with gasifiers, which is what I'm going to be putting in over the summer, so I think it's worth a shot. My approach has always been to fire the boiler up in the fall and not let it go out until the following spring.

Anyway, I think I'll block off a section of the cistern so that I have about 1,000 gallons of capacity. That would be roughly 4x8x5. With a rubber pond liner and some foamboard insulation it's not very expensive and since I'm dealing with concrete walls, integrity of the structure isn't a problem like it would be with a similar tank made out of studs and plywood. My supply and return lines from the wood boiler conveniently run right above the cistern, so I think a three-way valve on the supply line controlled by an aquastat on the gas boiler pressure vessel is about all I need to pipe it in. When the gas boiler (zone distribution) vessel hits the set point, the valve diverts the flow from the wood gasification boiler through the heat exchangers in the tank. When the gas boiler is below the set point, the valve goes the other way and I get direct flow between the two boilers. This way (the way I've got it figured) the tank serves as a place to store excess heat. Ideally, the whole system would sit at around 180 and the feed from the gasifier would always flow through the tank. The new boiler has a rated output of 205K btu.

You all are going to tell me I'm crazy, but for a heat exchanger I'm considering using a couple of cast iron radiators immersed in the tank. It would be a lot cheaper than copper coils, and I doubt there would be enough oxygen in the water to cause much of a corrosion problem, especially if I give them a few coats of decent paint.

Maybe this is an oversimplified design, but it's what I've come up with so far just doodling on the back of a cocktail napkin, so to speak.

I'd really prefer to deal with a pressurized tank, but no way am I going to get 1000 gallons for anywhere close to what modifying the cistern will cost, which I estimate to be about $500, not counting the piping and controls, but including the ci rads, which I already have.


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## webbie

To add to the discussion:
1. Obviously you have to calculate the min. temp that your house radiation works properly at - my guess is 140.
2. Then you have to take the highest temp you can get the water to - which is prob 190

So the 50 degree difference is your heat storage. Do the calcs as far as 1 BTU = 1 pound of water 1 degree and you will find your heat storage....then work backwards to determine what it can do for you and how long it will take to charge.

As far as heat exchangers, do the math and make certain the exchanger can transfer the total output of the boilers. Copper coils are relatively inexpensive. You can also use finned coils - like a typical DHW coil from a boiler.


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## Eric Johnson

Well, "relatively" is a relative term. One design I saw uses 540 feet of 3/4-inch soft copper for an 820-gallon tank (SSTS/Tarm). At today's prices, I'm guessing that soft copper goes for around $2 a foot, if the price for rigid copper is any indication. I thought about using finned 3/4-inch copper baseboard, too.

Thanks for the math guidance. Not my strong suit, but I'll work the numbers and see what it looks like. BTW, I'd say you're about right on with your estimates. 140 is about the minimum in my system for effective heating on most winter days.

Alright, just fooling around with these numbers:

1 gallon of water = 8.34 pounds
So it would take 8,340 btus to raise 1,000 gallons of water by 1 degree F.
And it would take 417,000 btus to raise that same 1,000 gallons of water by 50 degrees F.
So a tank full of 190-degree water represents 2 hours of output by the gasification boiler.
Assuming no other load on the boiler, would it then follow that it would take 2 hours to raise the tank temp to 190 from 140? (I'm guessing longer).

I'm lost. What does this tell me?


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## Nicholas

I am looking at the Tarm or greenwood GWB's too,
wondering if the whole "storage" is worth the effort, I have no idea, it makes sense, kinda like a "Liquid Masonry heater"
What adout the controls, do they add more complexity with storage ?

Greenwood does not sugest storage ?

Nick


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## webbie

Eric, that starts letting you know how much storage you want to do X job. Makes sure there are no surprises as to what you want to get out of it, etc.

BTU in and out are the same, so the time to charge....from 140 to 190, would be about two hours minus whatever losses in the piping system. With 100 then, you could count on 8 hours of heat at about 50,000 BTU per hour to draw down the tank.

Nick, not much complexity here. Some relatively simple controls can do the job - either solar type electronic controls or boiler aquastats.


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## Homefire

Eric,
Have you thought about automobile radiators?  
Seems they would be more efficient and easier to work with 
as far as the install.
As for the cistern, why not think of it as a swimming pool.
I have a wooden pool that is lined with foam to keep the splinter
and such off the liner. I have the heat exchanger from a glass sterilizer
that I want to install to extend the swimming pool use into Oct/Nov.

The concrete and earth will help with heat storage after they get up to temp.
Try your local use hospital / restaurant supply for the heat exchangers
from steam cabinets or sterilizers.

good luck


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## Eric Johnson

That's what I love about plumbing & heating: there's a bunch of different ways to do just about everything.

Thanks Craig--that helps.

Nick: From what I've been able to learn, gasification is quite a bit different from conventional wood burning in the way you tend and view the boiler. One guy describes it as just focusing on the tank temp rather than what the temp is outside or how warm you want the house. If you maintain the right tank temp, everything else should take care of itself. The tank gives you flexibility to fire the boiler less often and at your convenience. That compares to a conventional boiler setup (like I have now) where if you want to heat the house up, you have to crank up the boiler to get hotter water into the system. Another big difference between gasifiers and conventional boilers is that the gasifier doesn't have a big bed of coals sitting in the firebox when it's idle. When the blower shuts off on a gasifier, the process basically halts--a lot more like a oil- or gas-fired appliance. So instead of having your heat "storage" in hot coals in the firebox, you have it in stored hot water. 

My whole understanding of heating with a wood-fired boiler is centered on the conventional approach and equipment, so it's a bit of a challenge to figure out the gasification alternative, but I think the benefits of gasification (cleaner burning, greater efficiency) make up for the added expense and work involved in setting up a tank.

In short, I don't think you need a tank with a gasifier, but it works a lot better if you do. As to the Greenwood, I'm not sure about water storage. If it's like the Garn, (and I think it is), then the water storage is built into the unit. The Garn comes with something like 1,500 gallons of capacity in the boiler jacket, I believe. I'm not sure if it's pressurized.


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## Rhone

Just finished talking to a friend at my work about his old solar system that had the tank.  Here's the words straight out of the horses mouth.  



> I had a 2,000 gallon tank in my basement, vinyl coated cement covered with insulation.  The 2000 gallons wasn't pressurized, but I had a 30 gallon stainless bung tank with stainless tubes in the middle of it that was pressurized from the well.  That bung tank transferred the heat from the surrounding unpressurized water to the pressurized and gave me 30 gallons.  For 9 months of the year the solar panels would heat the 2000 gallons to 140F, the other 3 months it was more like 100F, still pretty good.  But, stainless is extremely difficult to weld and near the bung tank there was the smallest pinhole leak in one of the welds.  That leak over time overfilled the 2k tank and the water went into the vinyl, the cement, the insulation, it was a mess and was going on for probably a month or more before I noticed.  It was drained, rewelded, and happened again in another place.  So, I replaced the stainless bung tank with coils of copper which worked better, they didn't develop any leaks but there wasn't 30 gallons so it didn't work as well.  Then, I had problems with the solar panels and took the whole system out after 10-12 years.



His solar & tank system was installed by a fly-by-night operation of the 80's so take it for what it's worth.  Does make an interesting point about leaks developing inside the storage tank, and that the coil route seams to be the better route to go.  If you do stainless, better use threaded connections.


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## Eric Johnson

Webmaster said:
			
		

> Eric, that starts letting you know how much storage you want to do X job. Makes sure there are no surprises as to what you want to get out of it, etc.
> 
> BTU in and out are the same, so the time to charge....from 140 to 190, would be about two hours minus whatever losses in the piping system. With 100 then, you could count on 8 hours of heat at about 50,000 BTU per hour to draw down the tank.
> 
> Nick, not much complexity here. Some relatively simple controls can do the job - either solar type electronic controls or boiler aquastats.



I'll catch on eventually.

If the goal is to match the heat exchanger capacity in the storage tank with the boiler output, then there's not enough room in a 1,000 gallon tank for enough cast iron radiators to do the job. Maybe I'm looking at the wrong information, but cast iron rads are rated at between 5,000 and 10,000 btus each, which isn't much when you're trying to get to 200,000 btus per hour. (I must be missing something because the heat exchanger in my late '50s vintage gas-fired cast iron boiler is no bigger than a couple of average-sized ci rads). A comparable amount of 3/4-inch soft copper coil, according to the mfg website, would be about 900 feet. At $3/foot, I don't think so.

But if btus/hour is the goal, why not use a 200K btu/hour flat plate heat exchanger or a similarly-sized shell-and-tube arrangement? I don't know if the heat exchanger needs to be immersed in the tank, but it seems that you could circulate water from the tank through the heat exchanger and back in again, just like any other heat exchange situation. Or maybe you could even immerse the flat plate exchanger in the tank. I don't know. A 30-plate, 1-inch 200K btu flat plate heat exchanger is probably less than $500 these days.

So my question is, would a flat plate heat exchanger be a reasonable alternative to an immersed coil? I mean, that's how most OWBs get their heat transfer into people's houses, mainly because the OWBs aren't pressurized and are usually full of glycol.


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## Eric Johnson

OK, here's a diagram of what I'm talking about. Important details like pressure relief valves, low-water cut-off, expansion tanks, DHW are included but not shown.

This may or may not make sense. Any and all comments and (polite) suggestions are welcome.


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## webbie

I'll have to study the diagram later, but you are right in thinking that a flat plate may be the way to go! These have come a long way - I remember Tarm made some big advances in them over 12 years ago and have to assume that the entire industry followed along.

One warning - if any side of the heat exchanger ends up using water exposed to the air (open tank, etc.) make certain that water is protected against corrosion, etc. - it might be that some plates have one side that is designed for this....for instance, pool heating (usually cupro-nickel). 

Once again I am behind the times. We used tube-in-shell heat exchangers because copper was cheap back then and the plate ones had not really been perfected.

Oh, and when it comes to heat exchange area, consider that your oil boiler throws a 2000 flame against the cast, while your unit is going to be exchanging only 200 degree water - big difference!


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## Eric Johnson

I updated the diagram a little so that the most efficient transfer is now from the tank back into the system. This way, the tank charges up more slowly, but that may not be an issue. I assume there are some inefficiencies in this design (constant circulation), but I'm trying to keep it simple so that I can understand it, at least at the beginning. The bells and whistles can always be added later.

The flat plate heat exchangers available today all seem to be made of stainless steel brazed together. OWBs use them in a big way to get heat from the unpressurized vessels into pressurized systems. I'm using one right now to transfer heat from my wood boiler into the gas boiler vessel and it works very well. I use it because I have glycol on the wood side. The big ones--400K btu/hour and up, are going for $200 to $300, if Ebay buy-it-now offers are any indication. I think I paid around $350 for my 150K btu 3/4 inch unit about four years ago.

Anyway Craig, as always I appreciate your help and expertise.


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## Reggie Dunlap

I am about to buy a Tarm Solo for a new house I am building. After some research I don't think I'm going to install a storage tank. The concept is good but it seems like a lot of work and money to set it up. The tank takes up a lot of space also. If I change my mind I can add the tank later.

The Tarm tanks are ridicuously expensive, if I was going to do it I'd try to find a cheaper alternative. I think any stainless tank in good condition would work, and it could be insulated with Icynene-type spray foam.


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## webbie

The thing with tanks is pressure vs. non-pressure. Large pressure tanks can be expensive - even more so if they are built to the normal high standards required by ASME.


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## Eric Johnson

All other things being equal, I would go with a pressurized tank and forget about all the hassles involved with heat exchangers. Plus, there's no chance of anything growing in a pressurized tank. One good idea is an old propane tank, like the ones you see sitting in people's yards. My understanding is if you can find them, they go for about $1 a gallon, so a 500 gallon tank wouldn't break the bank. Getting it into your basement might be another matter entirely.


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## keyman512us

> Getting it into your basement might be another matter entirely.



If you go this route Eric, let me know...I'll give you a hand! (always interested in 'what the other guy is doing' when it comes to wood boilers')
Keep us informed on what you end up doing...


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## Eric Johnson

Thanks keyman. I'm going to see if I can find any scrap propane tanks before doing anything on the cistern. I've got a Bilco door into the basement, but a 32-inch door going through a concrete wall at the bottom of the stairs. So I don't know. A couple of 500-gallon tanks would be nice.

Is your system gravity feed or pumped, keyman? Presurized? Are you connected with another boiler with a heat exchanger or is it piped direct? DHW?


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## keyman512us

> Is your system gravity feed or pumped, keyman? Presurized? Are you connected with another boiler with a heat exchanger or is it piped direct?



Eric,
...My setup is piped direct (started the whole thing 'primitive' trying to keep it simple...and economical). The add on boiler is an actual 'fire tube' boiler with turbulators...not a 'water jacket', pressurized, ASTM, H rated, the whole nine yards...Very safe set-up...self extinguishing..."overfiring" is next to impossible...a T&P is installed such that if she gets too hot...the T&P relief dumps onto the fire to 'quench' it. Eff. I figure 50% or better (conservative estimate)

The 'whole set-up' is well balanced. I could heat three house with it...If I didn't mind filling it every hour(lol)  If I had the time, money and resources...I would probably build the same boiler five times bigger...and give the OWB manufacturers a run for the money.

I am at a "cross roads" at this point...and may actually move it indoors. "I have a wood (or coal)fired boiler...it is operated outdoors...Does that make it an OWB?...NOT!"

Probably the smallest fire-tube boiler ever built...but it works like a charm!


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## Eric Johnson

I've got a 1979-vintage Royall 150,000 btu/hour pressurized boiler set up in a cinderblock boiler room in my barn. My system is full of glycol. How you you protect against freezing?


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## Eric Johnson

Here's how I plan to do the tank. I got most of the rubble cleaned out of the old cistern last weekend. Fortunately, no unpleasant surprises (like a pile of asbestos). Just construction debris from the past half century of renovations. I found some old radiator steam vents, so I guess this place had a steamer before getting hot water. Interesting. Also the remnants of some big old rat traps. The list goes on.

Anyway, here's the tank schematic. About $500 altogether, not counting the piping, pumps, htexch, etc. I'm not exactly sure how to configure the input and output lines in the tank. If you think about it, the flat plate heat exchanger works both ways, so sometimes it's recovering heat from the tank, while at other times it's charging it up. And sometimes it's in a state of equilibrium. The way I have it envisioned now, it's most efficient at heat recovery, which I think makes the most sense.

Please share any thoughts or (polite) suggestions on this.


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## Eric Johnson

Here's what I'm working with for a tank. I have to build a cinderblock wall in the foreground to create the 4x5x7-foot space, but that's about it. I'll probably fill the blocks with vermiculite.


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## Eric Johnson

View from the outside.


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## keyman512us

Here's something you asked earlier that I missed Eric:





> Maybe I’m looking at the wrong information, but cast iron rads are rated at between 5,000 and 10,000 btus each, which isn’t much when you’re trying to get to 200,000 btus per hour. (I must be missing something



The part you are missing is this: At 5-10k btu's what is your transfer media? A: (air)...what you want to do is tranfer heat from water to water...big difference! (more heat transfer quicker). Your radiator idea for heat transfer is a good idea Eric...(it got me thinking). I'm no engineer on paper but... the firing rate of your boiler with the imersed radiator will work with the tank.

To answer your previous question...About freeze up protection? I have a second circulator tied into the "incoming loop"...using a check valve loop and a simple control circuit. I have an outside temperature sensor to "engage" the circulator. The way it's setup is this: If the boiler temperature drops below 140 the "main" circulator shuts off (to allow the system to "build back up)...if the outside air temp is below 27 degrees the second circualtor "cuts in" reversing the flow (instead of drawing hot out of the top....it draws cold from the bottom). The simple thing to do would be to fill the system with glycol...but I don't want to waste any or spill any if I make changes to the system. Not going to spend major dollars on something the "smoke zealots are "out gunning for". 

Good luck with your system...keep us posted!

P.S. ....If that huge cistern were in my basement, when "pouring the wall" I would make provisions to allow "for more water" (a couple pipes on the bottom and one at the top "capped" for future use)...leave yourself some "value added options".


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## Eric Johnson

I like the circulator idea, keyman. I'm going to insulate the living daylight out of the lines and if that doesn't do the trick, I'll rig up the main circulator like you suggest.

Craig straightened me out on the radiator idea. Unless you've got 2,000-degree fire hitting the cast iron, there's not enough heat transfer to make a difference. 190-degree water ain't gonna do the job. I've got a flat plate heat exchanger currently transferring heat from my glycol-based 150,000 btu wood boiler system into the water-based house system, and it does the job just fine, so I'm sure a flat plate will work with the tank. Plus, no water in the tank is displaced by the heat exchanger. When I install the new boiler, I'm going to forget the glycol and pipe it direct.

And I am keeping my options open with the tank. If the 1,000 gallons works like I hope it will, I can build a second, 1,500-gallon tank right next to it, using up the rest of the cistern. Having two tanks would probably be better than one big one.

Thanks for the input. You know I'll post the progress.


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## keyman512us

Eric:





> Craig straightened me out on the radiator idea. Unless you’ve got 2,000-degree fire hitting the cast iron, there’s not enough heat transfer to make a difference. 190-degree water ain’t gonna do the job. I’ve got a flat plate heat exchanger currently transferring heat from my glycol-based 150,000 btu wood boiler system into the water-based house system, and it does the job just fine, so I’m sure a flat plate will work with the tank. Plus, no water in the tank is displaced by the heat exchanger.



Eric:
Not to contradict 'Web', you or anyone else here that may a lot of "valuable thoughts"... But you are approaching the situation somewhat in the wrong manner. I'm speaking "from my education on this matter"...which is of the best type of education you can get: First hand,hands on actual operating experience. Here is a couple things (theory for comparison value based on my exp):
Using "my system" as reference: Living area- 1800 sq/ft, 1800sqft ("other") main boiler (oil)110k btus/hr (think of it as "on-demand-instaneous-'on call'...heat SOURCE" )... wood fired boiler 85K btu (think of it as constant fire-long duration...heat SOURCE)...so we have the heating load and (DMHW for two). Why go into detail you say?
The reason is you have to diferentiate between the heat SOURCE and the conveyance/transfer MEDIA (water or air...conductive or convective)...and your end PRODUCT. You start a fire to heat water to heat air...you need to break the whole thing into the simple basic three processes you are dealing with. The fire-Source, the water-Media, keeping your house warm/the hot water we need to enjoy life-the PRODUCT. As anyone with a "mechanical background" will tell you ('HVAC guys'..are a great wealth for the 'theory')..there is no such thing as "Hot or Cold"...only degrees of heat transfer. The hardest transfer if from the fire to the media- water is harder to heat than air (conductive versus convective)...Your boiler is going to do the job wheter you try to store the heat or not. Think of "using that heat" kinda like the way you use electricity, you have to view the heat storage as a "battery". The hardest work is already done by trapping the heat...into the water...and is simple to release because of the stored energy. Webs' analogy of the 2000 degree fire hitting the cast iron is already 'null and void' becuse the boiler already did it for you. You have already "done your homework" even the thought of the propane tank idea (which as a DIRECT method is a good one by the way...something my system uses). Direct vs INDIRECT (with an 'exchager') are both the same efficiency just indirect uses more TIME in the equation. With a boiler setup TIME...needs to be taken into consideration. Direct method with an 'accumulator' tank (120 gallons for mine) once the system is "balanced" I can bring that 120 gallons 'up to temp' from say 58 degrees to 140 in ten minutes. I use both method accumulator-direct, and "Non recoverable" indirect. 
The reason I bring this up is this: Try using both the exchanger and the "radiator" in your "storage system". Place the radiator at the bottom of the tank...have the exchanger draw from the top of the tank...and you should get the most "bang for the buck" 

"....I'm not even going to describe the concept of a 'runaway ramp' for a wood fired boiler.."


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## keyman512us

What happened to Reggie? lol

Reggie: If your are still following the thread check in with us please... Did you buy the TARM solo unit??? 

Web? (Or anyone else? ) ") Do you have any contacts at TARM? Long range I'm thinking of a gassification boiler for "inside the house"...lol 

Eric? What specific model is your new boiler? Any links?


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## keyman512us

Eric:
I like this diagram you came up with...here's my idea to "tweak it":

Change control #1 to a "triple acting aquastat" (so once the gas boiler is up to temp it diverts the hot water to the radiator #2 at the bottom of your tank). The valving/piping allows for "two additional modes"...(long and short duration heat storage...kinda valueble if you see a 'cold snap' in the forecast) ")

Nice design work...I'm not to handy with the computer...lol


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## Eric Johnson

Thanks for the tweak, keyman. I'll have to look this over and figure out what you're suggesting. It's like wiring: I have to look at this stuff long and hard and do some heat scratching before it sinks in. Actually, I have a more recent schematic here:

http://www.nefpexpo.net/thewholeshebang.pdf

On the boiler, I've pretty much decided on the EKO 60, which is a 205K btu/hr gasifier imported from Poland. Similar to the Tarm Solo 60 but cheaper and with some different features. One of my main motivators, aside from the price, is that the EKO will take 24-inch wood, of which I currently have about 20 cords stacked in the backyard and another 20 or so blocked up out in the woods. The Tarm maxes out at 20 inches, so that's a big factor for me. The people I've corresponded with who have EKOs say they operate as advertised: no smoke when they're running and not much tending.

Here's the link to the place I'm getting it from. He's one of the U.S. distributors. New Horizons in West Virginia is the importer.

http://www.cozyheat.net/eko.htm

Dave at cozyheat was extremely helpful in designing the piping scheme. There are things unique to gasifiers that affect the way they're piped and pumped, and I needed it to fit into my current scheme with a minimum of modification. And we were able to do that, so that most of my expense will be in the cost of the boiler, not the piping. Considering the price of copper these days, that's pretty important as well.

If you're thinking about any new boiler, you should check with the Mass. dept of Revenue and see if they offer a tax credit. In NYS, it's $400 if you buy a high efficiency boiler. At 85-90%, wood gasifiers definitely qualify.


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## slowzuki

I'm following your project with intereset Eric, as I'm going to be hooking my boiler up this summer in a similar fashion.   I'm using indirect storage, an insulated bulk milk tank with a copper loop or auto rad based heat exchanger.

The pressurized main loop is pressurized so my boiling point is a bit higher for a bit better heat xfer to the storage.   I may put some glycol into the tank too if my heat exchanger is a large enough area.  The main problem is you don't need much of a heat exchanger when the tank is cold but once it starts getting close in temp to the boiler you need more and more xfer area.


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## Eric Johnson

My experience with flat plate heat exchangers is limited to my current setup, which is glycol in the wood boiler and plain water in the house's system. Both are pressurized. My wood boiler temps get up to about 190, and the temp in the gas boiler vessel goes down to about 120 when there's a heavy call for heat. So there's a good heat differential across the exchanger, though the wood boiler temp won't stay nearly that high for long with a big heat demand from the house. But the bottom line is that 95% of the time, my 150,000 btu/hr flat plate heat exchanger is able to get enough heat out of the wood side to comfortably heat my big old house and DHW. Not during extended periods below zero, however. That's below zero in Fahrenheit.

I've never used heat storage, beyond the 50-gallon electric hot water heater and the 30 or so gallons around the gas-fired boiler vessel, but I suspect that a lower heat transfer rate across the heat exchanger at higher storage tank temps would not be a big issue, since (at least the way I have mine diagrammed), the tank charges up over time--basically taking up what the house doesn't. The critical function would seem to be recovering heat from the tank and again, if the water is hot enough, the transfer rate is not as important.

That's just me trying to think this through with no practical experience.

What kind of boiler do you have or thinking of getting, slowzuki?


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## Reggie Dunlap

Keyman,
I have not bought the Tarm yet, but I probably will this summer. I've looked pretty hard at the EKO's but I think I'll buy the Tarm Solo 40 for a couple of reasons. 

First, Nichols has been importing them for many years and they are only a couple of hours south of me. To me that means long term local support for parts if necessary and no shipping charge for the boiler.

Second, the price I was quoted for the Tarm 40 is not too far from what EKO's website advertises. I'm not sure if it's an apples to apples comparison, but it's close enough.

I think the EKO's are are probably just as good as the Tarm's, but I'm leery of them because they havn't been around very long and no one around here knows anything about them. Most plumbers and heating guys around here are familiar with Tarm. I do wish the Tarm would take 24" wood.  I've heated the house with a Hearthstone Mansfield for the last 8 years and never understood why they didn't make it big enough for 24" logs.

Reggie


----------



## Eric Johnson

Those model numbers are the KW ratings, I think. So an EKO 40 should be about the same size as the Solo 40. You can't go wrong with a Tarm. Better warranty, too.

One thing the EKO does that the Tarm apparently doesn't is allow you to set the fan to run for brief periods during idle, which is supposed to keep the fire going when there's no call for heat. The Tarms will go out if they idle for too long, which means restarting the fire. Other than that, the impression I get from talking to people with both brands is that they work about the same. I think the basic technology is identical.

One of the regular posters at heatinghelp.com, hot rod, is an alternative energy p/h contractor and he has an EKO 40, I believe.


----------



## slowzuki

The problem with tank storage is when your house is not pulling heat, and the tank is near full and you are trying to charge the tank the last bit.  It can cause the boiler to overheat.  A fellow I know has a 120k BTU unit with a 2000 gal tank and his plumber didn't use enough loops in the storage tank so he has to charge his floor at the same time at the tank during the last stage because his boiler over heats.  Once charged though he goes 3-7 days before recharging.  I'd like to get him setup with a better system, he currently cracks a bypass valve manually to do this.

I've got a Jetstream boiler, old fashioned rig but sort of similar to the newer ones.  The wiki I made, http://en.wikipedia.org/wiki/Jetstream_furnace explains a bit.



			
				Eric Johnson said:
			
		

> if the water is hot enough, the transfer rate is not as important.
> 
> That's just me trying to think this through with no practical experience.
> 
> What kind of boiler do you have or thinking of getting, slowzuki?


----------



## Eric Johnson

Interesting. Very interesting.

That sounds like quite a rig you've got there, slowzuki. I'm intrigued by your claim that it can burn partially dried wood without smoke. Sort of matches the claims by this manufacturer, whose local sales rep just contacted me, though a post I made at Mother Earth News:

http://www.adobeboiler.com/file.html

They say you can burn partially dried, unsplit wood and only have to clean the ash pan out every two or three months (!). The ash part sounds a little fishy to me. I'll be up in Bangor in a couple of weeks, so maybe I'll scoot over to Hamden and checkitout.

Thanks for the explanation on the problem with charging up the tank that one last little bit. I have a greenhouse to dump excess heat into, so I should be able to get around any problems there, but I can see where that might be a problem in the summer when trying to charge the tank up for DHW. The EKO is supposed to idle well, but the manual has a couple of pages devoted to strategies to avoid overheating, so it's obviously a concern.

I do have a couple of questions for you. First, do you think I can use a flat plate heat exchanger to get heat into the tank, vs. all that copper coil? I mean, we're talking more than 600 feet of the stuff for an 800-gallon tank. There's got to be a cheaper way.

And secondly, you seem to have some knowledge about gasifiers. Any opinion on the Orlan/EKO line?


----------



## slowzuki

1) the partly dried wood - burns it fine due to the very turbulent air stream, the catch is the refractory has to get up to temp first so you can't start a burn on wet wood.  You start dry on the first rank then the next stack (its loaded in layers) is wet.

2) Re flat plate, if sized big enough it will of course work.  I hope to use some old finned baseboards or get the set of coils a fellow has.  Still a few hundred bucks in copper.  The flat plate means another circulator and I'm really trying to use a few zone valves and only one circulator so if the power fails my ups can run it as long as possible.  My manual has 4 or 5 different piping schemes to reduce the number of components and simplify the controls.

The coil my 120k BTU unit calls for is 100 ft of 1" soft copper at 10 gpm or 4 coils of 1/2" finned copper coils, 16 turns in 32 inches, in parallel also at 10 gpm on a 1" header.  I will be trying to use some different components.  I have access to some truck condensors, it looks like 4 in parallel should be about right.  The fins are way larger than needed for immersion but it won't hurt.  If that falls through it will be some auto condensors or rads.

3)  I looked at the New Horizons and liked what I saw plus the consumables are cheap, could stock up for a few years worth of nozzles with breaking the bank.  I suspect there may be some more advanced models available but they have a pretty good controller and solid straight forward construction.   My insurance company won't let me put an unlisted appliance in my building unfortunately so that leaves them out of the picture.


----------



## Eric Johnson

Is your Jetstream UL listed, or are you looking at something new?

I think replacement nozzles for the EKO are about $50 each. Do you think they need replacement regularly?

Flat plates are getting cheaper all the time. You can get a pretty big one for under $500. I'm going to try my 150K unit with the 1000-gallon tank and see how it works. If the power goes out, I'm pretty much out of luck anyway, what with all the pumps and fans, etc. on my system. Fortunately, I live in town, so power outages are rare events that typically don't last long. Famous last words.

I used to live up in a small town in the Adirondacks where the power went out all the time. We had a Marathon wood boiler hooked up to an old gravity-feed heating system with a bunch of cast iron rads and big old iron pipe. No power needed on that system--it even had one of those bimetal draft door controls. Just load it with wood and go to bed. It was a sweet setup.

Keyman seems to think that a cast iron rad will work if immersed in a tank. I thought so, but then Craig talked me out of it. A lot of surface area there. I don't know how long the rad would last but if you hooked it up right and kept the oxygen levels down, it might last a good long time. I also thought about using 3/4 or 1" finned baseboard cores, but finally decided to go with what I've got on hand and I know works, which is the fp htx.


----------



## Burn-1

Eric,

While I was looking at the Seton boiler site for one of the other threads I saw that he has some
flat plates for sale. The price and BTU/hr seem right for your plans with the EKO.

Flat plate  (toward the middle of the page)


----------



## slowzuki

The jetstream is listed, I was looking at something new though too.  I started pricing and was able to find some jetstreams still out there.

I get a lot more energy out of 1000 gal than you will because I only need 80 F water for my floor so I can use the whole 200 f to 80 f heat storage.  You may find that you want to add more storage to fire less often in the spring or fall (or summer domestic).  The only thing I hope to keep going in a power failure is circulation from my storage to my floor.  I can keep my building from freezing for probably a week in the middle of winter if I have that pump running even without firing. 

I was a bit confusing in my statement about the coils, the baseboard coil would be for my domestic preheating also immersed in the tank.

The nozzles typically need replaced every 4-5 years of regular use in almost every other design.  I'm sure theirs is no different.  If you save a spare one you can make a mould to cast your own incase they stop importing them.  A local fellow casts Jetstream nozzles.




			
				Eric Johnson said:
			
		

> Is your Jetstream UL listed, or are you looking at something new?
> 
> I think replacement nozzles for the EKO are about $50 each. Do you think they need replacement regularly?
> 
> Flat plates are getting cheaper all the time.
> 
> Keyman seems to think that a cast iron rad will work if immersed in a tank. I thought so, but then Craig talked me out of it. A lot of surface area there. I don't know how long the rad would last but if you hooked it up right and kept the oxygen levels down, it might last a good long time. I also thought about using 3/4 or 1" finned baseboard cores, but finally decided to go with what I've got on hand and I know works, which is the fp htx.


----------



## Eric Johnson

Thanks Burn 1. That website is a little hard on the old eyeballs, but it's got a lot of good information. I'm going to start off by using the flat plate exchanger that I have. It's a 30-plate, 150K btu model which has worked pretty well for me. We'll see how well it performs on the new system.

That's good advice on the nozzles, slowzuki. I have space for another 1,350 gallons of storage and if the 1,000 gallon tank works out, then it won't be hard to add the additional tank. I think having two separate tanks will offer more flexibility than one big one.

That's an interesting point about your water temps and what it means for heat storage. Am I correct in assuming that by adding a four-way mixing valve to my biggest zone, that I could get by with lower temps in the system and get more out of my tank(s)? That's something I considered before deciding to go with the tank. I've got 11 cast iron rads on one zone.


----------



## slowzuki

Eric I haven't exactly followed your setup but basically traditional rads run intermittently with high temp heat so the last one in the loop will still have enough heat output.  Running them longer reduces the high-temp requirment and so does making smaller zones.  If you are talking using the 4 way so your circulator runs continuously and your boiler/storage tank just react to the demands from the mixing valve that is a type of approach.

Mixing valves in a technically way waste a bit of the total efficiency in a system, only in that the higher you go above the ultimate temp you need at the rad, more loss occurs in the system and you lose more up the stack.  Of course we can only drag out boilers temps down so low before condensing the flue gases, and running super hot water intermittently in rads is just as inefficient as the mixing valve.

If you say need 170 f to heat on your main loop right now continuously, splitting that loop (assuming the first rads in the loop are oversized or are covered to reduce output) and making another parallel loop dropping the heat requirement to say 130 f would really increase the capacity of your thermal battery.  You still output the same amount of heat but can get it from a lower temp source.  Wish I could explain this in person rather than typing.

A good system would have had the rads sized for their location in the loop.  Some old residential systems didn't have this, only covers over rads if the room got too hot while the later rooms froze.  If it was accuratly sized in the first place, makes it harder to break the loop, or at least without adding more thermostats and another zone valve or circulator.


----------



## Eric Johnson

I've got my hands full just getting the boiler installed and operating and the tank built over the summer, but a four-way valve is one thing I might do in the future. The loop I described is the heating system for the original house, which is an 1865 farmhouse, probably added some time in the early 1900s. Everything's been replumbed at least once since then, probably in the '80s during major renovations. So I don't really know. I do know that if we had continuous circ of 170-degree water through that zone, we'd cook. I'm thinking more like 140 on an average winter day to keep the place toasty. I have two other zones with 2 rads each and an attached greenhouse.


----------



## Reggie Dunlap

Here are the Tarm prices if anyone is interested. They have a sale going on until May 15.

Solo 40 140k BTU $6145 
Solo 60 198k BTU $6740

After May 15
$6895
$7495

Also there is no sales tax in NH


----------



## Eric Johnson

Thanks Reggie. That's useful.

Do you know if that includes shipping? Last time I checked, it did.

If you can get the Solo 60 to take 24-inch wood, I might go the extra $500.


----------



## Reggie Dunlap

Eric,

I think it does include shipping.

Reggie


----------



## Burn-1

I saw this on Craigslist earlier today, a free multi-fuel TARM

Free older Tarm multi-fuel

A good score if someone could use it


----------



## slowzuki

Eric how's your evaluation going?  I've vaccumed out the nest and trapped the 5 mice that where in my Jetstream.  I've got a photo of it on my blog, http://www.onthefarm.ca/

I've been collecting piping and valves for the plumbing, also busy moving my sawmill before the ground thaws too much.


----------



## Eric Johnson

It's going pretty well. I got the cistern cleaned out and poured a little mortar mix into a form on the top to level everything out, and sunk a few studs to hold the 2x6s down around the permieter of the tank. This weekend I'm going to lay up the block along the one wall to create the 1,000-gallon enclosure and put in the foamboard. Then I have to order the pond liner. Given the price of fuel, probably best to do that before shipping charges go even higher.

I have some concerns about priming the pump and keeping it from cavitating when it's hooked up in a non-pressurized environment. I have a nice Grundfos 20-42 3-speed pump that I was going to use on the tank side of the heat exchanger, but now I think I'll just go with a $50 Taco 007 from Ebay and see how it holds up in a semi-oxygenated, possibly-cavitating application. I thought it would be fun to fool around with the speeds, but I have other places on the system where it will be just as fun if I put the pump somewhere else.

My plan of attack on this project is to peck away at it over the summer, working on different elements of the piping as time and spare change allows. It should be ready to go by late July or early August, and that's when I'll have the boiler delivered.

I'll post pics of my progress on the tank over the weekend.


----------



## Reggie Dunlap

Eric,
Sounds like you are making good progress. When will your new boiler arrive?

I just gave Tarm a deposit on the Solo 40 boiler. I went down to their shop in Lyme NH and looked at how they set up the system that heats their building. It's pretty impressive. I was planning on not having a storage tank, now I'm not sure. I'm tempted to try a 500 gallon pre-cast concrete tank in my basement which I could buy for around $500. Any thoughts on this?

Reggie


----------



## Eric Johnson

I'd wait and see how mine works out, since it's basically the same thing. My pre-cast tank is just built into the foundation, is about the only difference. Actually, you might want to consider building a block enclosure in a corner of your basement. Two walls and you've got your tank, for a lot less than $500 and it's easier to move cinderblocks than a concrete tank. It doesn't even have to hold water, since you have a liner for that. Or instead of concrete, build the two walls out of plywood and studs.

A pressurized tank (like an old lp "submarine" tank) is probably the best way to go. I'm told they go for about $1 a gallon, so for the same price as the concrete tank, you could get a steel tank that doesn't require a heat exchanger. Much better in many ways than a non-pressurized tank.

But if you want to go unpressurized, I should have mine up and running by September, and then you can learn from my experience before making a commitment.

My understanding is that gasifiers will work without hot water storage, just not as efficiently. A tank gives you flexibility to run the thing under optimum conditions. Check out my other thread in this forum for more information about HW storage.


----------



## Reggie Dunlap

I was thinking about lp tanks also. I called my local gas supplier and they claim that a new 500 gallon tank would cost me $2500. I thought that was a little steep. You are right in that a steel tank would be nice-no heat exchanger needed. The precast tank is the lower half of a 1000 gallon septic tank, I was hoping it would be watertight and not need a liner. My plan was to spray expanding foam insulation around the outside of the tank. That way the 5" thick walls of the tank act as a thermal mass along with the 500 gals of water.

Reggie


----------



## Eric Johnson

That might work pretty well. The LP tanks people use for hot water storage are used--they get them right before they go for scrap. What's the difference between a new LP tank and a used one? I have no idea.


----------



## Eric Johnson

I worked on the tank over the weekend and managed to get about half the wall up. It's about as high as I can make it now, and comfortably work inside with the liner and the foam insulation. I guess it's time to bite the bullet and buy that stuff and get this thing done. If it ever warms up, I'll be able to get into the piping end of things. Anyway, here's a few shots of the progress. Obviously, I'm no mason.


----------



## Eric Johnson

Here's a couple of "before" pics.


----------



## slowzuki

That pic reminds me of wifes grandmas house.  After she died we were staying there and wh has a cistern.  Hadn't thought too much of it and I used the tap to brush my teeth and flush the toilet.  After a few days the pump was making noise in the basement and we went down to see.  The is was leaking pretty bad and I got to peeking around.  Flashed a light across the cistern and just about choked, 4 big bloated rats floating around on top!


----------



## Eric Johnson

Got the 45 mil Firestone pond liner today. It's basically just a rubber sheet, about the thickness and appearance of an inner tube. It's going to be a lot easier to work with than I thought. Think tarp.


----------



## wg_bent

Eric Johnson said:
			
		

> Got the 45 mil Firestone pond liner today. It's basically just a rubber sheet, about the thickness and appearance of an inner tube. It's going to be a lot easier to work with than I thought. Think tarp.



what are you using to seal the seams?  What's the top going to be?


----------



## Eric Johnson

Here's the diagram, Warren.

No seams except where the lid meets the walls, as shown. I'm using a 15' x 20' sheet for the tank and a 5 x 10 piece for the lid. I think any roofing cement designed for a EPDM rubber roof will do the trick, but I'm not going to seal it all up until I know it works.


----------



## wg_bent

So just curious... rather than use a heat exchanger, why not use a giant coil of copper?  From experience in cooling beer (which includes some knowledge of small commercial installations) copper coils work well.  Most large breweries do use heat exchangers but a lot of the reasons for that are ability to sterilize the equipment, but in some smaller installs I've seen, the hot liquid is run through a copper coil immersed in cold liquid.  4 bbls or beer (100 gallons or so) can be cooled from 212 to about 80 in 20 minutes.  That's a pretty fast transfer rate and dirt simple.

You'd need a second coil to pick up the domestic hot water and a third for the hydronic heat though.


----------



## Eric Johnson

Copper coil is the way it's traditionally done, but at $2-$3 a foot for 3/4-inch soft copper these days, you're talking real money for any decent heat exchanger. Guys I've talked to who have 60kw Tarms and 800-gallon tanks have about 600 feet of coiled copper. I'm going to try to do it with a $250 flat plate and a $50 pump.

I'm confused about your 3-coil suggestion. Are you saying use one coil to charge up the tank and another one to reclaim the heat? That sounds more efficient, but a lot more complicated on the pumping and piping end of things.

For DHW, I already have a shell and tube heat exchanger hooked up to my electric water heater that works just like another zone on the heating system, and it works great.


----------



## wg_bent

O.k. I missed the point on the DWH and the way you've got it hooked up.  so yes, 2 coils.  Wow, that would be like 2400 bucks worth of copper tubing.  I can see why your going with the heat exchanger.  It's been a while since I've bought copper tubing in any form.  I wonder if there isn't some sort of radiator system that could work.  Like 3 or 4 car radiators hooked together or something like that.  I'm just thinking out loud... sounds like the heat exchanger is the way to go.  I was wondering about the insulation also though.   think 1 layer of the foam is enough?  I have no idea, just thinking out loud again.  (I tend to over build EVERYTHING I do.  My basement has like R26 insulation in it!)


----------



## Eric Johnson

I thought about a couple of cast iron radiators and slowzuki is talking about using a car or truck radiator on his system. I also thought about finned copper baseboard, which I have a supply of. But in the end, I decided to go with something I'm familiar with, which is the flat plate. In fact, I'll be using the same one that's currently getting the heat from my wood boiler (glycol) into the house system (water). It works great hooked up to two pressurized systems. How it will work with an unpressurized tank, remains to be seen. Obviously, there's no optimum way to pipe the inlet and outlets, since the heat exchanger will be delivering heat part of the time and recovering at other times. But tweaking it will be part of the fun.

Every tank design I've seen, including the commercial units, use the 2-inch foam. You need to use the more expensive, foil-wrapped yellow stuff. Conventional blue and pink foam can't take the heat, apparently. So that's $30 for a 4x8 sheet. It makes a really nice surface for the rubber liner to rest against.


----------



## slowzuki

Eric I'm a bit concerned about the idea that it can't take the heat, I've got that stuff under my steel roof.  

I've found another milk tank and will be putting in an offer today. It is an 800 gal tank on a skid c/w compressor and condensor and fan.  The evaporator coils outside the tank are blown and the compressor seized when it lost the coolant.

I'm thinking 1$ a gallon for my offer.


----------



## Eric Johnson

That's what I've read, but I wouldn't be surprised if it's not true. Anyway, intermittent heat is probably different than more-or-less constant temps between 130 and 190, which is what I hope I can get. Worst case scenario, you might wind up with mildly corrugated foam boards.

That's a big tank. I'd say that $1 per gallon for ss sounds good.

How are you going to get the hx into the tank, slowzuki?


----------



## titan

Eric Johnson said:
			
		

> Copper coil is the way it's traditionally done, but at $2-$3 a foot for 3/4-inch soft copper these days, you're talking real money for any decent heat exchanger. Guys I've talked to who have 60kw Tarms and 800-gallon tanks have about 600 feet of coiled copper. I'm going to try to do it with a $250 flat plate and a $50 pump.
> Eric, is the plate exchanger similar to ones found in hot water- to-glycol heating systems?If so,it should be the most efficient, as they offer a lot of exchange-surface area in a reasonably small package.


----------



## Eric Johnson

Yes, the same piece of equipment. The one I have is rated at 150,000 btus per hour. I have no way of verifying that, but it has heated our big old house for the past four winters when mated to a 150 Kbtu wood boiler, so I know it's capable of charging (and discharging) the tank if I can get adequate flow through it. The new boiler is going to be about 200 Kbtu, but not all of its output is going to the heat exchanger and the tank. Some is going directly into the house.


----------



## titan

Eric,200,000 btu's-that's a mother of a boiler!If you were really bored you could run PEX tubing under the driveway and use it as a"dumpzone" from that system.Goodbye shovels-hello snowmelt. :coolhmm:


----------



## Eric Johnson

I've got a 12x24' single-pane greenhouse for a dump zone. I've got a 1" copper line going into the tank and will have a 3/4-inch pex loop into the greenhouse.


----------



## wg_bent

Eric Johnson said:
			
		

> That's what I've read, but I wouldn't be surprised if it's not true. Anyway, intermittent heat is probably different than more-or-less constant temps between 130 and 190, which is what I hope I can get. Worst case scenario, you might wind up with mildly corrugated foam boards.
> 
> That's a big tank. I'd say that $1 per gallon for ss sounds good.
> 
> How are you going to get the hx into the tank, slowzuki?



The foil lined stuff is more R value/ inch and cheaper anyway.    be sort of cool to install one of these things in my crawl space.  I have a crawl space that's the size of my dining room and kitchen combined but is only about 3' tall.  I'll be watching how this works closely.  Keep us posted Eric.


----------



## keyman512us

Eric Johnson said:
			
		

> Yes, the same piece of equipment. The one I have is rated at 150,000 btus per hour. I have no way of verifying that, but it has heated our big old house for the past four winters when mated to a 150 Kbtu wood boiler, so I know it's capable of charging (and discharging) the tank if I can get adequate flow through it. The new boiler is going to be about 200 Kbtu, but not all of its output is going to the heat exchanger and the tank. Some is going directly into the house.



Eric...
I still like your idea of the radiators...I'm no engineer, and I know "everyone has chimed in on the subject" but a cast iron radiator (submerged in water) is going to have a higher heat transfer rate than it would trying to exchange heat to "free/open air" 

If you already have the radiators....I would try it out...you "might be pleasantly surprised".


----------



## Eric Johnson

I'm going with the flat plate, keyman, but maybe if I do a second tank I'll give the rad idea a shot. I think you're right that they will transfer more heat in water than in air. That's a lot of surface area on those things.

Anyway, after doing some plumbing re-routing on Saturday, I bit the bullet and bought the insulation on Sunday and since it was raining, decided to put it into the tank. That went pretty well, so I gave the liner a shot. Here's a few pics.

The middle one shows some rough-cut 1x8s that I secured along the top of the tank to have a place to staple the edges of the liner.

The next couple of shots show the insulation, 2-inch poly-whatever, in place.


----------



## Eric Johnson

Here's a couple of shots of the rubber liner being installed. It's not easy to do, in part because the big sheet of rubber (15x20 feet) is rather bulky, and it has to be hung just right to fit. I'm working on it. Patience has been paying off so far. Glad I put in the wood on the top and glad I didn't try to build the whole wall first. I pretty much have to get the liner hung just right before I finish the cinderblock wall, then put the rest of the blocks in, measure the space for the lid, and put that together.


----------



## slowzuki

Looking good Eric,

I put in my offer on the 800 gal milk tank last week but haven't heard back.  I found out it is mounted on a skid with a compresser and some radiators.  Maybe some useful plumbing bits on there.


----------



## Eric Johnson

Good luck on that, slowzuki--I hope it works out.

After spending the better part of my weekend in "the tank," I can see the appeal in a steel version of same.

Are you going to use a heat exchanger or run at low pressure and pipe it direct? And if it's a heat exchanger, how are you going to get it into the tank?


----------



## slowzuki

I'm running a closed loop heat exchanger.  The tank has an openable insulated top for the ever important cleaning that all milk equipment gets.  I will have two coils, the main one and my domestic pre-heat.

The biggest problem is size, the tank isn't very tall but is 12 ft long.  I hope to build a workbench on top of it to disguise its stealing of my shop space.


----------



## slowzuki

Hey Eric how is the work going?

I haven't heard back on my tank bid yet so I've decided to start looking for some 3 ft high IBC's to make into my storage and workbench.


----------



## Burn-1

FWIW here's a link to a photo description of how a guy from one of the local renewable energy initiatives in central NH built his own concrete tanks for use with his Tarm. 

Tarm installation and water tank construction

There's a *lot* of copper in this system which also has a solar thermal component


----------



## wg_bent

Burn-1 said:
			
		

> FWIW here's a link to a photo description of how a guy from one of the local renewable energy initiatives in central NH built his own concrete tanks for use with his Tarm.
> 
> Tarm installation and water tank construction
> 
> There's a *lot* of copper in this system which also has a solar thermal component



That guy has a lot of time and money on his hands!


----------



## Eric Johnson

Interesting.

I'm waiting for either a very hot day or a rainy day to get back down into the basement to finish putting in the liner. It's about halfway hung. I've also been building a new sidearm heat exchanger for my DHW. The one I have now has 3/4-inch boiler water inlets and outlets (with a 3/4-inch core), and I want 1" outlets. It's easier to build a new one (using a 1.5-inch shell) than it would be to try to take the old one apart. If you've ever built one or tried to take one apart, you know what I mean. Most of the materials I had on hand. If you've priced copper fittings lately, especially the larger sizes, you know that's a good thing. A 1.5-inch copper tee, for example, goes for about $15 at Home Depot. You can buy fittings for much less on Ebay, but you have to buy them in (usually mixed) lots, and finding the right parts can be more trouble than it's worth.

I'm going to try to use the old sidearm heat exchanger for the greenhouse. I don't know if it has the capacity (1.25-inch shell with a 3/4-inch tube), but it won't cost me anything to find out.


----------



## slowzuki

Yikes, I got a heat exchanger tossed in with my free boiler, sounds like it was a good deal.


----------



## Moose

First post, love the site spent many hours browsing through the many ideas people have come up with.  Eric love the homemade holding tank  and was curious how it turned out.  I am really leaning tward doing a similar install and was hoping to gain some valuable information from your install.  I curious oh how big your flat plate heat exchanger was.  Ive been heating with wood since I was old enough to remember but I am brand new to the wood boilers.  I bought a house with a fuel oil boiler and I'm leaning twards a add on with a heat storage tank.  Thanks for all the great info.


----------



## GibsonGuy

This is my first post.  I just bought an EKO 60 and have it hooked to a chimney, but no plumbing yet.  I have to have that done professionally.  I bought mine from CozyHeat as I live real close to them.  I am struggling w/ the water storage concept (because of the cost), but was happy to read all of the alternative methods.  For the large storage units, is the water treated to keep it from freezing?  I really like the cistern idea and am wondering if one could build a cistern out of SIPS.  I called a manufacturer and I can get a 4 X 8 structural panel for around $90.  It would seem to me that one could use these panels for 2 sides and maybe a lid into a corner of a basement.  The floor wouldn't need anything but the foam and the liner.  I'm a little worried because Dave & Zenon both stated that that my house is a little large for a 40 and small for a 60.  I'm thinking water storage may be very important in my case.   Any input would be greatly appreciated.  John


----------



## Eric Johnson

I'm still working on it, Moose. I can let you know in a couple of weeks. Other than that, everything seems to be working great. I have some concern about the structural integrity of the wall I built, so that's something I have to work out. I'm going to rest a couple of floor joists on it, which should provide enough weight to keep everything in place. Let's hope, anyway.

I think hot water storage is important, John, but I understand your hesitation to make the investment. Without it, you're going to have to find a place to dump heat during warmer weather. Once you use your boiler for awhile you'll understand why a tank is desirable. Too bad they don't make an EKO 50. I think it's a really great boiler--I'm really happy with mine so far. There's a few EKO owners on this site--nofossil is the one with probably the most knowledge and experience--so I'm hoping we can collectively get the most out of our investment.


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## Eric Johnson

I'm going back and forth on the heat exchanger idea for the tank. I just priced 1" soft copper and it's $5.50 per foot, plus (9%) tax, so that's more than a grand for 200 feet of hx that I would probably need. That's more than I want to spend right now, but maybe after fooling around with the flat plate hx/mixed tank approach I'll change my mind.

Currently (and this changes day to day) I'm back to the flat plate approach, but instead of basic dip tubes, I'm going to drill a bunch of 1/8-inch holes in two sections of pipe that are plugged on the end, and force the water through them on the top and bottom of the tank. I'm trying to spread out the flow across the length of the tank, and create as little circulation as possible in the process. It won't cost very much and it just might work. Again, everyone I've talked to, including the guy selling the soft copper, seems to think it will work.

Let me run this one by the math guys: I calculated the area of a one-inch section of pipe opening. Then I ran the same calculation for a 1/8-inch hole. Then I divided the area of the one-inch pipe opening by the area of the 1/8-inch hole, and came up with a number. On a four-foot section of pipe, that's 64 holes, or 32 on a side, spaced at 1.5-inch intervals. Am I correct in assuming that this will distribute water over the 4-foot span at the same rate that would flow from the end of a one-inch pipe opening?


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## slowzuki

Nope, you need much more area for small holes than with an equal area large hole.  Think of piping, your one inch pipe flows more than 4 half inch pipes.  I'm not sure I would get too fancy with the laminar storage etc until you've tried it out.

I've attached the Kerr HX designs for the 120k BTU/hr Jetstream


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## Eric Johnson

That's pretty cool, Ken. I like the hard copper option on the bottom. However, at more than $3.50 per, the 40 or so 90s needed for 80 feet of the thing put the price right into the range of soft copper, and with 80 opportunities for leaks to spring. But I like that simple design. I'm guessing you could just stand that thing up in the tank and pump through it both ways, no?

On the holes, I used pi-r-squared to calculate the area, giving me 64 1/8-inch holes to equal an inch. Pretty fancy for a journalist. Are you saying I need more? If so, do you have an equation handy?

I'm going to use CPVC for the in-tank piping, so doing it this way isn't a lot of extra work or expense. However, as always, Ken, I will give your advice serious consideration.

The boiler's performing really great, even without the tank. We get a nice clean burn (i.e., no smoke) during normal operation. Some smoke on cold startup that lasts about 10 minutes and just a few wisps when it's idling. Hard to believe you can get that much heat out of such a small pile of wood. Where are you at with your project?


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## slowzuki

I'm a bit behind as I'm building a room to put the boiler in first.  Wedding's burned up all of last weekend, and this weekend will be dominated with installing windows in the building where the boiler goes.  I'm thinking the boiler will first fire in Dec.  The old woodstove is still doing duty for now.

You will need about 2-4 x the area of the single larger opening to get the same pressure drop.  You may wish to bandsaw or dremel a couple of slots down the length then solder a cap on the end to solidify the newly free "legs".  Or just drill more holes, or you could use the biggest increaser you can find and pop a screen on the end so the velocity is extremely slow coming out the end.
Ken


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## Eric Johnson

Thanks, Ken. That's what I needed to know.

Your wedding? If so, you can probably forget about getting the boiler fired up this season (yuk, yuk!). But congratulations if that's the case.

If you get a chance, please give us some background on your boiler (I think you said you have two or three of them). It looked pretty neat, the little I saw of it.


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## slowzuki

Haha, not my wedding, been married a couple of years now.  I have a bunch of info on the boiler on wikipedia and on my webpage www.onthefarm.ca but the basics are this:

-Water cooled wood chamber, water cooled fire tube boiler.
-Forced and induced draft resulting in slightly positive combustion chamber in use, negative while loading (fd turns off)
-Wood loaded vertical through the top, 40 lb softwood, 60 lb hardwood per loading
-Wood falls down into a refractory combustion chamber where primary combustion and release of gases occurs.
-The combustion zone is blasted by a 100 m/s air jet from a preheated tube, almost always runs with an excess oxygen condition
-The burning continues into a insulated refractory tunnel with adequate length to have mixing of the excess air with any left over particles.
-Upon leaving the tunnel the gasses enter the fire tube heat exchanger and leave.

So advantages over "conventional" gasifiers, burns wetter wood easier but still needs to have the combustion chamber prewarmed by a hot fire.  Easy to load, takes up to 40" wood, 36" is the practical limit though.  Dry wood can be loaded unsplit once chamber is hot.

Disadvantages? High jet speed ejects fair amount of ash out the stack.  Tunnel only lasts 5 years from extremely high temps despite SS fibre reinforcement although it only costs 50$ or so to replace.  Pressurized stack needs to be well sealed including taped joints to prevent ash ejection.  Water storage is a requirement because no idle controls are fitted.  It will auto relight up to a few hours after cutting power due to stored temps but will smoke like a conventional boiler if no power is provided.

There is lots more but thats the gist of it.


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## Eric Johnson

I'm confused. From the diagram, I gather that it's not pressurized. However, your search for an in-tank hx tells me that it must be. So what does "vented to the atmosphere" mean?


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## BrotherBart

In a refinery "vented to atmosphere" meant out into the open air and given the stuff we were cooking the Feds usually showed up real quick. Unlike water vapor that would come out that boiler jacket.

Watching you guys talk about this stuff is fascinating.


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## slowzuki

Well, initially the Jetstream was used in open loop systems with lots of chemicals.  They then progressed to pressurized and eventually even a low pressure steam approval through the ASME pressure vessel design.  I have one of the prototype open system one thats was pressurized and the sides are all bowed out.  The approved models have 3/4" rod through the exchanger array to tie the wide flat sides together.

The early models were all welded wereas the newer ones got rid of 4 corner welds using rolling and stamping to make one single weld location.



			
				Eric Johnson said:
			
		

> I'm confused. From the diagram, I gather that it's not pressurized. However, your search for an in-tank hx tells me that it must be. So what does "vented to the atmosphere" mean?


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## slowzuki

Also note this diagram doesn't show the nozzle and preheat tube, the PDF on my website shows more of the guts of the thing.


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## Eric Johnson

enord said:
			
		

> saw a guy do a tank with chipboard,2x10's, & vinyl pool liner. pumped a tarm gassifier into it. covered it with 3" foam. u  might want to insulate cistern walls.



I've got 2 inches of foam board between the liner an the tank walls. And the blocks are full of vermiculite. The lid is going to be a 2" piece of foam board with epdm on the inside. Any heat leakage I get is just going to heat the basement. And if I don't get the heat exchanger right, that may be the only benefit I get from the tank.


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## Eric Johnson

A gas water heater is kind of a big shell-and-tube heat exchanger, when you think about it. You'd have to weld some connectors of some sort on the ends. If the pressurized side was the gas vent, then I don't think you would have to worry about corrosion, since the inside walls of the tank are already protected. You might want to leave the baffle in there, too.


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## begreen

Eric Johnson said:
			
		

> Any heat leakage I get is just going to heat the basement. And if I don't get the heat exchanger right, that may be the only benefit I get from the tank.



That, and a real large hot tub


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## leaddog

[quote author="Eric Johnson" date="1192052278"]I'm still working on it, Moose. I can let you know in a couple of weeks. Other than that, everything seems to be working great. I have some concern about the structural integrity of the wall I built, so that's something I have to work out. I'm going to rest a couple of floor joists on it, which should provide enough weight to keep everything in place. Let's hope, anyway.

Your tank will be hold alot of weight and make sure it is shored up GOOD. You can brace it against the other tank wall. also along the top you can run rod thru and tie it together.

I had to brace mine up more. I knew that there was alot of weight there but still it wanted to give. A round tank is alot easier to hold. Mine is made out of walkin freezer panels, steel inter and outer panels with 4in foam between. They are bolted together with rod running thru all the way around. I had them braced at the bottem. When I started to fill it I relized that I had to add more so I ran rod thru the top in 4 places and bolted them together. Then when I started to heat it the sides started to bow from top to bottem and I had to add a middle brace. I've got it done now but relize now the pressure that all that water holds. You should be ok if you brace against the other wall and when you put water in the other tank you will not have a problem.
leaddog


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## Nofossil

I think I may have posted this picture somewhere, but it's not in this thread. I used an 880 gallon stainless tank from a local stainless scrap dealer / fab shop. I think I paid $350 for it. I put in three HX coils:

1) Domestic hot water preheat (cold well water gets heated on it's way to the hot water heater).
2) EKO boiler / zone coil with rectangular hard copper grids top & bottom.
3) Solar panel rectangular hard copper spiral.

The EKO / zone coil is bidirectional. When th EKO is heating it, it flows top-to-bottom driven by the EKO's circulator. It acts as another zone, in effect. When it's being used to provide heat, it flows bottom-to-top, driven by its own circulator. In that mode, it's effectively another heat source plumbed in parallel to the EKO and the oil boiler. Description of the plumbing here.

It's enclosed in an insulated 'doghouse' under the deck just outside the boiler room.

More description here.


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## pbvermont

why is everyone building elaborate concrete and wood-based structures for storing large volumes of water?  Why is no one using the variations on the method that the Tarm heat storage tanks are made from?  Its essentially several 4'x8' aluminum sheets riveted end to end and forming a large circular tension ring, insulated w/ foam foil board and lined w/ epdm.  All materials available at local home-building supply store and EASILY moved and put together.  AND in whatever size that fits your needs.


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## Eric Johnson

That's a good idea. I think the answer (at least in my case) is twofold: 1.) I assume that anything that costs $3,000+ from a vendor is going to cost at least half that for me to build. That sounds like an erroneous assumption from what you say. And, 2, sometimes these projects can get out of control: Let's see, I've got a concrete tank in my basement already, all I need is some foam board insulation and a liner. It turns out to be a little more complicated than that, but once you get started, you really don't want to start from scratch. Recently, I've also wondered about using a small above ground pool.

So welcome to the Boiler Room, pbvermont. Have you actually built a tank this way? If so, how much did it cost?


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## Nofossil

pbvermont said:
			
		

> why is everyone building elaborate concrete and wood-based structures for storing large volumes of water?  Why is no one using the variations on the method that the Tarm heat storage tanks are made from?  Its essentially several 4'x8' aluminum sheets riveted end to end and forming a large circular tension ring, insulated w/ foam foil board and lined w/ epdm.  All materials available at local home-building supply store and EASILY moved and put together.  AND in whatever size that fits your needs.



From your screen name, I'm assuming that you're from Vermont as well. I would like to welcome you as a forum member and as a fellow Vermonter. Where are you, if I might ask?

To answer your question for my situation, I needed more water storage than I could accomplish with a round tank. I actually needed more than I did accomplish with my oval tank, but that's life.


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## pbvermont

Thanks for the welcome.  I have been reading many of the posts here for several months, and have benefitted greatly.  
   I live in Washington Co. in Vermont.  I am presently installing a 1979 Buderus woodboiler (83K BTU) of which I have 3 in number (in various states of repair...2 were free and the good one was $400). 
  And yes, I built my own heat storage tank for $700 worth of materials from my local lumber store...no wood, no concrete, in the manner described in my previous post.    It is 4' tall and 7.5' in diameter (approx 965 gal), insulated w/2" of foil-foam board under, around and on top.  Lined w/ .45mil epdm "pond-liner"/roofing material.  It has 3/4" copper pipe for lid support.  This includes the pvc plumbing bits for the pass-through plumbing for my eventual hookups.   It's essentially an indoor, above-ground swimming pool that sits in my basement, under the cellar-stairs. This price does NOT include any heat exchange element. 
    I'm going to depart radically from anything I've encountered on this site, (because I can, having the "item" I need) and install a 200 gal. heavy-walled old, copper boiler-tank INSIDE my main heat-storage tank.  Essentially a tank-in-tank heat exchanger.  Unlike a coil-in-tank that others are working with.  This will be a closed system, boiler to copper tank for heat IN, and reverse flow from copper tank to CI radiators for heat OUT.
  My system like others on this site is somewhat designed around the principal components I have "garnered."
  I could use some help planning my piping and circ. sizing  and placement etc.


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## Eric Johnson

Sounds like an interesting project. I really admire the innovative ideas people come up with when it comes to setting up hydronic wood-fired heating systems. Reminds me of the logging business--everyone innovates to accommodate their situation. As you probably know, some of us have thought about using cast iron radiators for in-tank heat exchange. Pretty cool idea with the tank; kind of a similar approach. Does it have tapping top and bottom? How much does it weigh? At today's scrap prices, that's got some value.


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## pbvermont

I've certainly thought of its scrap value, but it is a thing of beauty from a bygone industrial era that I don't want to destroy.  It has found a new useful home.  It has tappings all over it.  Six, to be exact.  Sizes ranging from 3/4" to 4".  I am about to move it into the "swimming pool" and guess that it weighs in the 4-500 lb. range.  I'll be ramping and rolling it up on top of the "pool", then head scratching, and figuring a way to lower it in(prob. a couple of come-a-longs hanging from basement ceiling joists).


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## Nofossil

I love the intersection of technology and old-fashioned scrounging.

In this case, I'd be a little worried about the effectiveness of heat exchange between the two tanks. Lots of the water in both tanks would be some relatively far away from the HX surface, so you'd have to depend on convection to spread the heat. I haven't got the energy at this moment to compare surface area with other designs.


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## pbvermont

My inner tank has roughly 48 sq. ft. of copper  surface area.  More than 180' of 3/4" copper pipe does,  that I know is rated to transfer 39,600 BTU/hr. at 4.5 gpm. What's wrong w/ relying on convection currents?  I'm not sure why you say "much of the water in each tank is not near convection surface."  Is this not also true of coil systems?


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## leaddog

:wow:  guess that it weighs in the 4-500 lb. range

The last scrap copper I took in I got $3.00 a pound. If that thing is 4500lbs that would buy you a complete heating set up with storage. I run into some good deals with scrap but not that good.
I do think it will do the job for you but make sure you have some cold water return protection for the boiler as it would take a long time to get all that water up to temp when it was doen on heat.
leaddog


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## Nofossil

pbvermont said:
			
		

> My inner tank has roughly 48 sq. ft. of copper  surface area.  More than 180' of 3/4" copper pipe does,  that I know is rated to transfer 39,600 BTU/hr. at 4.5 gpm. What's wrong w/ relying on convection currents?  I'm not sure why you say "much of the water in each tank is not near convection surface."  Is this not also true of coil systems?



Thanks - saved me the effort of doing the math. Math on Saturday mornings doesn't always happen.

There's nothing wrong with relying on convection - that's how indirect hot water heaters work, also. My only question is how well this configuration accomplishes it. Coils spread the surface area over a larger volume.

I'll gladly admit that I don't know the science - please take my question as curiosity rather than criticism. I'm truly interested in how this works.


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## pbvermont

Sorry, my bad typing.  I meant "in the 400-500 lb. range."  It doesn't weigh 4500 lbs.  Yes I will put cold water return protection on it, thanks.  The boiler will have its own preheat loop w/ a Termovar valve and dedicated circulator.  I hope that generally, once I get the big tank temp up, the little one will just need to boost it now and then.
  Nofossil.  Thanks for your critique and questions.  Its all grist for the mill.   Dialogue can help towards greater knowledge.  Again, because I HAVE this tank, and its a LOT of copper, I am interested in using it.  Being the scrounger that I am, there's no way I can go out a buy comparable amounts of copper at this point.  
    I believe Eric said a while back that anything (metallic) with a lot of surface area, in the storage tank, is going to exchange heat.  How it does it, exactly are all finer points of thermo and fluid dynamics. 
  Two  types of smaller indirect tanks are made to go next to regular oil and gas boilers for DHW:  coil-in-tank, and tank-in-tank.  Mine is just a large version of tank-in-tank.


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## WRVERMONT

Another crazy Vermonter.  I like the copper tank within your swimming pool concept.  Useing what you have is efficiency in itself.


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## hkobus

I love the "pool" idea. I the round shape has more strength to begin with. Not sure if I like aluminum, but roofing steel is high tensile, easily riveted and cheap (cover-sheets are very cheap if you don't care about color) I am thinking about using load ty-down straps, with ratchets to tension the outside. 
My question is, how do you make a round liner from EPDM. I have seen the tape they use to attach flat surfaces, but I would think you would have to deal with some creasing where the sides meet the bottom. Any experience on this anyone? I appreciate any thoughts here, thanks.

Henk.


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## pbvermont

I actually didn't use aluminum.  I used 4x8 sheets of Tuff-liner, readily avail. at the lumber store for $35/sheet. It's white and has a nubby surface and is used around here to line the walls of milking parlors, food processing rooms.  I overlapped the sheets 4" at the ends, put construction adhesive between and a double row of large autobody rivets.  Your idea of reinforcing tension straps is a good idea, but when you put these materials together you may see that they would be overkill.  Save them for a better purpose.
  As for the Epdm liner in a round container.  Not a problem.  I bought 15' square pondliner on the internet  for the inside of the tank, AND a 10' square piece to make a lid.  These were standard sized pieces that were...ON SALE!  They are heavy.  The inside liner weighed 65 lbs.  I just draped the 15' piece in the tank, tucked it well around the bottom joint with my feet, and here's the trick for the side-walls....made lots of regularly spaced small pleats.(consult a seamstress or tailor).  These pleats are "pinned" on the top edge with 8 or 10d gal. or alum. nails punched through the liner into the foam insul.  Trim the excess rubber around the edge.  Then cut your top "lid" piece using a great big compass.  Make sure you don't undersize it.  It needs to go all the way out over the edge.  It gets sealed to the tank liner w/ silicone caulk.  Done.


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## Eric Johnson

I stapled my liner into the wooden toprails on the top perimeter of my concrete tank. Silicone the joint where the liner used for the lid and the liner used for the tank meet.


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## ISeeDeadBTUs

Nick said:
			
		

> Greenwood does not sugest storage ?
> 
> Nick



I have the GW with no storage, other than the amount in the oil boiler 20 gal(?) and the DHW tank 50gal.

I am thinking pretty seriously about going to a two-coil 160gal DHW tank to replace the 50-plate HX, and eventually incorporate solar. We haven't had the sub-zero nights with all 6 radiant zones calling yet, but last year they tended to overwhelm the GW. But I think I calculated already that 160 gal of 160 deg water only gives me a buffer of like 20 minutes? Anyway, since the dog and I NEED it cool to survive, the tank don't go in until I figure out how to move the stand-by losses outside once it warms up outside.

And a warm basement does mean a warm house - within reason! I set my walk-out basement stat at 65 deg, keep my DHW between 135-145 deg. The standby losses keep the basement warm, thanks to concrete and polystyrene insulation . . . oh, and dirt!! But trust me, ones it gets sub-zero at night and max of 20 during the day, the basement slab will start circulating.

Jimbo


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