Installing Wood Gassification Boiler With 1000 Gallon Thermal Storage

[Sid]

Hello all, I've been reading around the forums and planning for some time now, but it's about that time for my first post so here it goes.

New Wood Boiler - Attack DPX 45 Profi

Thermal Storage - Two 500 gallon 're-purposed' propane tanks stacked horizontally on top of each other.

New Chimney - Haven't ordered it yet but planing on doing DuraTech double-wall stainless. Installed inside house (just have to go up through one bedroom then out top (bedroom has cathedral ceilings)).

Existing Setup - Buderus Logano G115 Oil Boiler, Buderus Logalux ST150 Indirect Fired Domestic Hot Water Tank, 1 Circulator with 4 zones on zone valves, 1 zone for DHW and, 2 for each bedroom, and 1 for the living room.

Plans: I plan to install and configure controls the way Nofossil explains:

https://www.hearth.com/talk/wiki/pressurized-storage-solution-for-biomass-boilers/


What I have done so far (with video explination):

Got the new boiler in house: https://www.youtube.com/watch?v=DLBbsgTeluo

Video of existing setup: https://www.youtube.com/watch?v=X-Z9NZzMufc

Cleaned and placed bottom tank: https://www.youtube.com/watch?v=wLK8x8mm5dw

Cleaned and plan to place top tank tonight (wish me luck...) https://www.youtube.com/watch?v=zlSDzZypNUY

Cleaned, Painted and placed stand: https://www.youtube.com/watch?v=wrtbwT1wsfM

I found the three 500 gal tanks and stand on craigslist and paid $1200 (super lucky find I think). They are a little rusty but the guy I bought them from said they did work and he seemed like a decent guy. The tanks have ports all over the place as the video and drawing illustrates. He basically told me he simply out-grew the system for his heating needs and for how long he is away from home for extended periods of time.

I only have room to stack two tanks on top of each other. I know ideally I would like them vertical but don't have space for that either.

The above YouTube videos explain all of the tanks' and port locations and sizes. I have also attached some pictures and a very rough drawing of tanks with dimensions. I plan to 3D Model the tanks and stand with dimensions, but haven't gotten around to it yet. I also plan to modify Nofossil's plumbing schematic and electrical schematic to better fit my needs, basically just add another zone like I have and use Caleffi's ThermoBloc.

I'm no HVAC technician but do consider myself somewhat competent of a handyman. I can weld, solder, do basic carpentry, and went to school for engineering. I work as a teacher (IT) in a vocational high school and am friends with the HVAC instructor who has many years of experience. Once the final tank is in place and boiler is in place and I install the chimney, I may leave the rest of the work in the hands of that HVAC teacher or my brother from Colorado who is a hydronics engineer (if he is willing to make the trip).

One issue I hope to receive feedback about is that of the expansion tank. Along with the three 500 gallon tanks and stand, there is a custom made expansion tank he had made from what seems to be about a 150-200 gal propane tank. This would technically be considered a 'compression tank' since there is no bladder. Since there is no bladder both my brother and HVAC teacher don't think it is wise to use due to air and corrosion over the long term (I don't care about the periodic maintenance of checking level and draining/charging). This is a shame since an Extrol style expansion tank with bladder is not cheap for this size system.

I will take pics and a video of the expansion/compression tank and try to post later tonight.

Any thoughts, suggestions, criticisms, and concerns are greatly appreciated. I will keep this post as up to date as I can, thanks.

 

[maple1]

Do you have a high place you could put that expansion tank?

I am heading into winter 3 with just an ordinary 110 gallon LP tank for an expansion (compression) tank, sitting upright on the floor beside my storage. But I have an SX90V sized bladder tank ordered that I will be shoehorning into that space for next winter. I do find I get some air moving into my system from the 110 over time - it's not much and happens very slowly but it seems to make a beeline for my upstairs zones and creates an airlock, which I then have to bleed back out. That airlock seems to happen a couple times a winter. IF I had a place to put my current tank up high (like the highest point on my system or higher), I would do that. But I don't. I did it this way originally because of the high cost of a 'proper' bladder tank of the right size and the place I got my tanks at ahd a mountain of them for cheap. I have since decided to do a hybrid thing. I also have a 20 gallon compression tank in the joists above my boiler that was there for my old one - I just left it there & piped it in to top of boiler. I also picked up a 15 gallon one that I will plumb into top of storage, and I can locate that one up high, against the ceiling of my basement stairway. So between those two compression tanks, and replacing the 100 gallon LP tank with the 90V, I should have enough expansion & eliminate the airlock situation. My boiler manual has provision for installing an open expansion tank, 8' above the highest system point. So I'm pretty sure my 110 gallon LP tank would work up there too - but even after 3 years of thinking about it, I just don't have a place that high to put it.

 

[Sid]

Do you have a high place you could put that expansion tank?

I am heading into winter 3 with just an ordinary 110 gallon LP tank for an expansion (compression) tank, sitting upright on the floor beside my storage. But I have an SX90V sized bladder tank ordered that I will be shoehorning into that space for next winter. I do find I get some air moving into my system from the 110 over time - it's not much and happens very slowly but it seems to make a beeline for my upstairs zones and creates an airlock, which I then have to bleed back out. That airlock seems to happen a couple times a winter. IF I had a place to put my current tank up high (like the highest point on my system or higher), I would do that. But I don't. I did it this way originally because of the high cost of a 'proper' bladder tank of the right size and the place I got my tanks at ahd a mountain of them for cheap. I have since decided to do a hybrid thing. I also have a 20 gallon compression tank in the joists above my boiler that was there for my old one - I just left it there & piped it in to top of boiler. I also picked up a 15 gallon one that I will plumb into top of storage, and I can locate that one up high, against the ceiling of my basement stairway. So between those two compression tanks, and replacing the 100 gallon LP tank with the 90V, I should have enough expansion & eliminate the airlock situation. My boiler manual has provision for installing an open expansion tank, 8' above the highest system point. So I'm pretty sure my 110 gallon LP tank would work up there too - but even after 3 years of thinking about it, I just don't have a place that high to put it.

I could fit the tank in a closet upstairs, but could probably only get it a few feet above the highest point in the system (not the 8' like your manual is looking for). If you and others chime in and think that is a good idea I would be willing to give it a go. I just really don't want to ruin 2 nice boilers and storage tanks to corrosion/air. The house is a log home with only 2 levels. One ground level where boilers are (walk out basement on slab) and a living level above that. 8' ceilings in basement and cathedrals upstairs/main level.

 

[ewdudley]

I could fit the tank in a closet upstairs, but could probably only get it a few feet above the highest point in the system (not the 8' like your manual is looking for).

The 4'-8' above highest point is for an open expansion cistern that is at atmospheric pressure, not a compression tank (or bladder tank).

Since you've got a compression tank that is sealed you can simply try to get the tank above the top of storage. If the water leaving the boiler goes uphill directly to to top of storage, and the top of storage is connected directly to your compression tank somewhere above the top of storage, then any gas that comes out of solution in the hot boiler will find its way to the top of storage and then to the compression tank. Since the supply line from the top of storage that feeds your loads will be flooded at all times then there won't be any gas migration from storage into your heating system.

 

[Tennman]

I regret not going to see a properly running system. As a DIY'er I got lots of great advice here during my learning years (which is now 6 years and ongoing) but it would have been very productive if I had actually seen what a healthy gasification flame looked like, heard the roar first hand, and understood the importance of seasoned wood early. Being in the NE it's likely there's someone not far away who would be glad to show their system operating at the peak of the heating season. Sounds like you're making great choices and have lots of help. Congrats

 

[cityboy172]

I regret not going to see a properly running system. As a DIY'er I got lots of great advice here during my learning years (which is now 6 years and ongoing) but it would have been very productive if I had actually seen what a healthy gasification flame looked like, heard the roar first hand, and understood the importance of seasoned wood early. Being in the NE it's likely there's someone not far away who would be glad to show their system operating at the peak of the heating season. Sounds like you're making great choices and have lots of help. Congrats

This. I wish there was someone closer for me to look at. I'm in week 1.5, and it's a little nerve racking, especially with this bitter cold snap. I'm a nervous wreck right now.Would of liked a couple more weeks before we got into sub zero temps.

 

[Sid]

I was able to finally get that top propane tank on top of the stand last night. Surprisingly it went on fairly easy.
Check out the video and pictures below if you'd like.

Top Tank on Stand: https://www.youtube.com/watch?v=eeIWldZ2x4k

 

[brant2000]

I've never really heard it mentioned before (maybe it has), but what do you all think about using the top void space of storage tanks for expansion? I actually just did this the other day, and all has been working well (albeit my tank is much smaller than these). The idea is that as long as you have dead space above the top tank port and a vent above that, I was able to use the vent to force an air bubble into the top of the tank. I just connected an air hose with about 25 PSI and pushed a few gallons out of a system drain.

 

[ewdudley]

I've never really heard it mentioned before (maybe it has), but what do you all think about using the top void space of storage tanks for expansion? I actually just did this the other day, and all has been working well (albeit my tank is much smaller than these). The idea is that as long as you have dead space above the top tank port and a vent above that, I was able to use the vent to force an air bubble into the top of the tank. I just connected an air hose with about 25 PSI and pushed a few gallons out of a system drain.

You bet, it works the same as having a compression tank connected to the top of storage. I think you would want the air vent connection and a clear or translucent sight pipe (oxygen barrier PEX works well enough) outside the insulation so you could keep an eye on it, and to be able to maintain the system if you ever needed to make a change.

Keep in mind that you will need on the order of 10% or more of dead space above the upper port.

 

[Sid]

You bet, it works the same as having a compression tank connected to the top of storage. I think you would want the air vent connection and a clear or translucent sight pipe (oxygen barrier PEX works well enough) outside the insulation so you could keep an eye on it, and to be able to maintain the system if you ever needed to make a change.

Keep in mind that you will need on the order of 100 gallons of dead space above the upper port.

brant2000, that seems like a good idea and would be quite easy since my top tank has 2 large out ports. Not sure how well the pics show it but there is one 2" pipe out on very top and another 2" slightly lower on side. Like ewdudley states, I will need to make sure there is enough of a cavity above side out for the 100 gal necessary.

Can anybody speak to the issue of dissolved oxygen causing problems over time in the system? This is one of the main issues why bladders are used now and compression tanks are considered a thing of the past (I know another issue was the lower maintenance of a bladder system, but that isn't really too large of a concern for me). Also, what if the cavity was charged with something inert like argon or something like CO2 that doesn't propagate oxidation/rust. I'm no chemist but maybe there is one here in these great forums. Just because it doesn't let rust/oxidation doesn't make it a solve all...for example there is the issue of acidity, etc.

 

[brant2000]

brant2000, that seems like a good idea and would be quite easy since my top tank has 2 large out ports. Not sure how well the pics show it but there is one 2" pipe out on very top and another 2" slightly lower on side. Like ewdudley states, I will need to make sure there is enough of a cavity above side out for the 100 gal necessary..

Exactly, and in either case, you'll want to use the ports that enter horizontally, rather than the top/bottom mounted ports (for less mixing/better stratification). Theoretically, you could put air bubbles in both tanks, if one doesn't provide enough capacity.

Others may have a much better understanding of the chemistry than I do, but I believe the oxygen within that bubble of air will continue to migrate into the water until it is all disolved. Since hot water cannot support dissolved oxygen; however, it should progressively precipitate (I know this isn't the correct term) out and should be removed by a scoop/air vent.

 

[ewdudley]

With a bladder expansion tank system the dissolved gases that come out of solution in the boiler should find their way to the air eliminator and should leave the system forever.

The old compression tank systems had a vent in the top of the boiler and a vent at the top of the air separator, both of which were piped up to the compression tank with no venting to atmosphere. The compression tank was typically located in the floor joists above the boiler. These systems can run for decades with all gases accumulated in the compression tank.

In a system with a [solid fuel] boiler and storage a compression tank can work well if the tank is situated such that all gases that come out of solution in the boiler can find their way up to a compression tank, and such that any gases that go back into solution stay in solution until they come back around to the boiler. In this case there generally is no need for an air eliminator, and if one is used it should be closed off after the system is up running.

Where a compression tank does not work quite as well is where the tank sits off to the side and cool water dissolves gases that are then taken out of solution in the boiler, and then are vented to atmosphere by an air eliminator, or find their way to be trapped in high points of the system.

 

[DaveBP]

Don't use CO2. When it is dissolved into water it becomes an acid and you want just the opposite in your boiler water.

Nitrogen is pretty inert under these conditions and is probably cheaper than Argon.

I just used the same chemicals used by Garn boilers (open to atmosphere) because my brain was starting to lockup trying to decide what to do. Cheaper than buying a nitrogen tank and regulator.

 

[maple1]

When I reset my pressures this fall, I took my little 5 gallon air pig to my local tire guy, and he filled it with nitrogen. That turned out to be just enough to recharge my compression tank. (BTW that whole nitrogen-in-tires thing seems a bit hokey to me - he just stuck some sort of magic 'nitrogen wand' on the end of his ordinary compressor hose & used that. Assume it scrubs nitrogen from the air?).

Anyway, on a somewhat related note & in the strange coincidence category - after posting what I did above last night about dealing with an airlock in one zone a couple times a winter, a couple hours later I was dealing with it. Noticed that one upstairs zone was cold on the far end - rads were warm at the front of it, guess it was airlocked to a trickle. It was easy to fix, got a system down and leave short hoses attached to hose bibs so just had to close one valve & open another for a few moments. But in doing that, I studied my expansion (compression) tank location & tie-in again, and came to the conclusion/revelation that this airlock issue was being caused by air migrating out of the expansion tank through the water - and when it was hitting its T just upstream of the load circ, was migrating the other way, up the zone return pipe backwards, right into that zone return pipe. That problem zone return pipe is last back to the manifold, so would be the first the air would hit if it was seeping/bubbling up the return pipe against the flow. I suspect this happens when zone flows are very low or stopped (like when charging storage but zones not calling for heat) - which is more often now since I installed the Alpha and reduced my flows. And also explains why the air scoop on the supply side of the zone piping wasn't helping with it.

Already looking forward to getting the new bladder tank put in for next winter (but not the install process) - good thing I don't need it right away, ordered it a month ago & still no word on it. Just wish I had a high place for the tank I have now, pretty sure it would work fine if I could get it up on the second floor somewhere.

EDIT: Forgot to add, the 5 gallon nitrogen fill was free.

 

[DaveBP]

magic 'nitrogen wand'

Yes, magic. And free was the honest price.

 

[Fred61]

Forgot to add, the 5 gallon nitrogen fill was free

Great price if it was truly nitrogen. I didn't know it was that easy to separate nitrogen from the other elements in air. I used to pay big money for pure nitrogen when I was applying spray coatings.

 

[maple1]

Was a gizmo something like this:

(broken link removed)

(Sorry for the thread derail - my last nitrogen comment...)

 

[Bob Rohr]

I've never really heard it mentioned before (maybe it has), but what do you all think about using the top void space of storage tanks for expansion? I actually just did this the other day, and all has been working well (albeit my tank is much smaller than these). The idea is that as long as you have dead space above the top tank port and a vent above that, I was able to use the vent to force an air bubble into the top of the tank. I just connected an air hose with about 25 PSI and pushed a few gallons out of a system drain.

That's basically how a solar drainback system operates, captivating an air bubble in the upper portion of a tank, it could be a separate drawback tank, or the upper portion of the buffer, really doesn't matter.

You do want a sight glass to watch and maintain that bubble, and yes it can still be a pressurized system and have that air bubble trapped.

You may need to replenish some air from time to time as it can re-absorb into the hot fluid. Also use a B&G airtrol fitting that puts any air eliminated from the piping up into the "space" or compression tank.

Compression tank systems are considered air management, while bladder tanks are air elimination systems.

Be sure to run the calcs how much expansion "space" is required, it's much larger than a bladder or diaphragm tank.

The Wessel tank site has a free calculator for compression tank sizing. Convert that answer into the space in your tank.

 

[Sid]

Thank you all for all the great tips/info. I plan to really look into the idea of using the top cavity of my top storage tank as the necessary 'cushion'. I'll need to do some measurements and calculations to make sure I have the volume above the port.

DaveBP, I actually considered installing the Garn Jr. a while back but with my needs it didn't seem as good of a fit (having to heat storage first then demand.) The concept of using the chemicals (which is necessary for un-pressurized systems) had been a thought of mine but when mentioned to my brother and HVAC instructor, they both didn't seem to have much experience with that. My brother has experience with glycol systems but that might end up costing as much as a bladder tank when talking about 1000 gallon plus system.

Bob Rohr, a sight glass indeed (actually clear pex for me [home made]) would be for sure happening if I were to do it that way. And filling/charging once and a while is no problem for me.

Still, the big question I have is...with 100 gal or so of 'air', being sometimes dissolved and then going through new boiler, steel tanks, and expensive existing cast iron Buderus boiler, is that air going to cause issues (corrosion, sludge, dirty water, air pockets, etc.) over time? I know the little bit of air that gets through the wrong type (non oxygen barrier) of Pex can cause issues ...what will 100 gal space of it do? Some theories say that once the steel get's their 'glaze' of rust and no other air is added, there shouldn't be any issues (not enough O2 to cause issues)...others say no good - that's why compression tanks are not used anymore. Chemicals may be good, but do they expire or become less effective over time; and where does the cost of bladder expansion tank come close to that of chemicals?

Sorry for all the questions, I can go on and on with the questions...this is great forum and I already greatly appreciate the help already. Wife is kicking me off computer but I'll be back soon. Thanks again.

 

[Energy]

Just browsing around fourm. Been thinking of installing a wood boiler for quite some time. Considering similar but maybe outdoor wood boiler. Came across this thread. Excited to see how this all works out!! One question is what do you mean by "Cushion" of air in the top tank? Is this not going to be a presurized system? Maybe just reading wrong?

 

[brant2000]

One question is what do you mean by "Cushion" of air in the top tank? Is this not going to be a presurized system? Maybe just reading wrong?

It is a pressurized system...the "cushion" is just a pocket of gas (air) that allows for the hot water in the system to expand. Since liquids effectively cannot be compressed, yet they will expand as the temperature increases, they will take up more volume...that "cushion" provides the volume for the expanded liquid.

 

[Energy]

I'm assuming this 1000 gallon plus everything else lets say 1050-1100 is the total system volume. Using the storage tanks (top tank specifically) as a Compression Tank would result in needing about double the amount of space as compared to a typical bladder or Diaphragm expansion tank. Rule of thumb for closed loop expansion tank sizing with a bladder is 8-10 percent based off typical boiler temps. Other systems with larger operating temp deltas may require even more. Open systems are also different. Basically you would need 160+ gallons of a non disturbed air pocket at the top of your storage tank which is not vertical. This is not achievable from what I can see. Your main horizontal inlet coming from the top tank ( from what i can see from pics) would be way to close to not disturb the air and most likely pull air from the storage even if you were to install a vertical "straw" using the union looking top port. But lets make another observation....this is a completely ferrous metal system. That amount of air in a tank will rot it out so fast. Even with a crazy high ph level this will rust. Black iron pipe can have dissolved oxygen in the piping because the inner pipe will form an oxidized layer of magnetite and will be "protected" by the thin layer. Having a completely air filled cavity in a steel tank with boiler water and high temps just sounds foolish. Do you not see rust pour out of the bottom port of your air compressor when you drain it?

 

[brant2000]

In a non presurized system this 1000 gallon plus everything else lets say 1050-1100 total system volume. Using the storage tanks (top tank specifically) as a Compression Tank would result in needing about double the amount of space as compared to a typical bladder or Diaphragm expansion tank. Rule of thumb for closed loop expansion tank sizing with a bladder is 8-10 percent based off typical boiler temps. Other systems with larger operating temp deltas may require even more. Open systems are also different. Basically you would need 160+ gallons of a non disturbed air pocket at the top of your storage tank which is not vertical. This is not achievable from what I can see. Your main horizontal inlet coming from the top tank ( from what i can see from pics) would be way to close to not disturb the air and most likely pull air from the storage even if you were to install a vertical "straw" using the union looking top port. But lets make another observation....this is a completely ferrous metal system. That amount of air in a tank will rot it out so fast. Even with a crazy high ph level this will rust. Black iron pipe can have disolved oxygen in the piping because the inner pipe will form an oxidized layer of magnetite and will be "protected" by the thin layer. Having a completely air filled cavity in a steel tank with boiler water and high temps just sounds foolish. Do you not see rust pour out of the bottom port of your air compressor when you drain it?

Please take a look at some of the previous comments/discussion regarding dissolved oxygen/corrosion. It may still be of a slight concern (personally I would expect this to present no real issues), but that would be up to the system owner/installer to determine.

Regarding the volume available... you wouldn't want to use the immediate top port, as that would introduce too much mixing in the tank. The OP would have to determine how much available there would be above the other top port.

 

[Energy]

Sid is also correct in reading that non oxygen barrier pex can allow air to get into the tubing and into the loop. Many issues with that. Non oxygen barrier for domestic water such as AquaPex brand. HePex brand for ferrous apps. Domestic water is filled with air yet all the components and plumbing for the domestic use non ferrous material such as the copper in the pipes, the ceramic in the heater tank, the brass ball valves, the bronze heat exchangers, the stainless fittings. Bring on the air,...just not in boiler loops,,,,unless of course everything is stainless and copper including the circs...now that would be pretty to look at.

 

[Energy]

Regarding the volume available... you wouldn't want to use the immediate top port, as that would introduce too much mixing in the tank. The OP would have to determine how much available there would be above the other top port.

I agree completely with the theory that this will introduce more thermal mixing around the immediate area yet I do not believe that you will lose much stratification even in a small 500 gallon tank. these 2in ports will cut the flow significantly especially if sid was to extend the 2in ports a little further.