Looking for some input on storage

[jeffesonm]

I've been shopping for tanks for pressurized storage for my EKO 40 install... shooting for 500-1000 gallons total. Whatever I get needs to fit through a 35" opening into my basement (which has a 7' ceiling), so that has been somewhat limiting.

I recently got a lead on some tanks nearby that are ~265 gallons (1000L?) and were used to transport some type of alcohol for industrial processing. They came from Europe and have two 3/4" British pipe thread holes at one end, each of which connects to a dip tube that goes about half way across the tanks as depicted below. The guy says the tanks were held horizontal and they would blow nitrogen in the top to purge the alcohol out the bottom. These tanks are attractive because they fit in the door, can fit standing up, are reasonably priced and very clean.

I considered buying two and racking them horizontally with pallet racking, similar to this setup. This would let me use the existing ports/dip tubes, however not sure 3/4" would cut it... 137,000 / 500 x 20 = 13.7 gpm and max gpm for 3/4" is only 6.5, so two tanks wouldn't cut it. I could add a third but that would be some odd racking, or a fourth for symmetry but now that's a lot of fittings, connections, flow to equalize, etc...

What seems better would be to get three of these tanks, abandon the existing ports and have someone weld up new fittings. I like the layout from the Effecta Lambda brochure, depicted below. Seems like it simplifies controls too... EKO charges storage, circs draw from storage. I'm eyeing up Floydian's constant circulation/iValve/ODR setup but haven't seen anyone use this with baseboard yet.

The Effecta tanks sure have a lot of tappings... some are for electric backup elements so I can forgo those. How does it work when you're drawing heat from the tanks? How do you draw heat equally from all three, or do those three horizontal connections between the tanks equalize the temps between them?

 

[ewdudley]

Usually reverse return piping is used to equalize flows:



For storage with a wood boiler you can have the boiler connected as shown above, then the load can connect to the opposite end of each manifold so it is connected with reverse return as well.

I don't know why the manufacturer drawing above uses so many ports, maybe for solar system or something. They wouldn't be useful for a normal wood boiler storage setup.

(And as I usually point out, all tank volume above a top side port, and all tank volume below a bottom side port is lost for heat storage purposes unless there is an internal riser/dip tube arrangement.)

Here's a discussion:

https://www.hearth.com/talk/threads/how-to-install-3-seperate-300-gallon-water-storage-tanks.76474/

[Edit:] Agree with Bob below, 3/4" port is not necessarily a problem, it's just another restriction. It's not like a weakest link in the chain type situation, instead all the resistances add up and if the pressure drop is acceptable when all the restrictions are accounted for then you're good to go.

 

[Bob Rohr]

I've been shopping for tanks for pressurized storage for my EKO 40 install... shooting for 500-1000 gallons total. Whatever I get needs to fit through a 35" opening into my basement (which has a 7' ceiling), so that has been somewhat limiting.

I recently got a lead on some tanks nearby that are ~265 gallons (1000L?) and were used to transport some type of alcohol for industrial processing. They came from Europe and have two 3/4" British pipe thread holes at one end, each of which connects to a dip tube that goes about half way across the tanks as depicted below. The guy says the tanks were held horizontal and they would blow nitrogen in the top to purge the alcohol out the bottom. These tanks are attractive because they fit in the door, can fit standing up, are reasonably priced and very clean.

I considered buying two and racking them horizontally with pallet racking, similar to this setup. This would let me use the existing ports/dip tubes, however not sure 3/4" would cut it... 137,000 / 500 x 20 = 13.7 gpm and max gpm for 3/4" is only 6.5, so two tanks wouldn't cut it. I could add a third but that would be some odd racking, or a fourth for symmetry but now that's a lot of fittings, connections, flow to equalize, etc...

What seems better would be to get three of these tanks, abandon the existing ports and have someone weld up new fittings. I like the layout from the Effecta Lambda brochure, depicted below. Seems like it simplifies controls too... EKO charges storage, circs draw from storage. I'm eyeing up Floydian's constant circulation/iValve/ODR setup but haven't seen anyone use this with baseboard yet.

The Effecta tanks sure have a lot of tappings... some are for electric backup elements so I can forgo those. How does it work when you're drawing heat from the tanks? How do you draw heat equally from all three, or do those three horizontal connections between the tanks equalize the temps between them?

View attachment 124300

Are you considering a pressurized system? Check and see if those tanks were designed to be pressurized.

That 3/4 port, while not ideal, would not be a deal breaker. Most control valves like zone valves and balancing valves have ports that are reduced.

A 3/4 flapper type zone valve with a 7.5 cv typically has a 5/8" orfice. Flowing 13 gpm thru a 7.5 Cv valve give you about a 3 PSI drop.

I suspect those taps have a larger id compared to a ZV or control valve, more in line with a 3/4 ball valve with a Cv typically around 13.

Cv meaning the gpm flow rate that produces a 1 psi drop across the valve.

For balanced flow, either reverse return, or headers built with equal length piping would work. Google around the HW storage tank manufacturers websites and find some piping schematics for multiple tanks.

 

[jeffesonm]

Usually reverse return piping is used to equalize flows:

View attachment 124313

For storage with a wood boiler you can have the boiler connected as shown above, then the load can connect to the opposite end of each manifold so it is connected with reverse return as well.

I don't know why the manufacturer drawing above uses so many ports, maybe for solar system or something. They wouldn't be useful for a normal wood boiler storage setup.

(And as I usually point out, all tank volume above a top side port, and all tank volume below a bottom side port is lost for heat storage purposes unless there is an internal riser/dip tube arrangement.)

Yes I think some of the connections on the Effecta tanks are for solar. I wonder why they are connected together at the middle.

The return reverse piping makes sense. I was thinking to have separate taps for loading/drawing from storage so the boiler circulator and load circulator do not interfere with each other, sort of hydraulic separator-ish. I know this would mean some delay between when the boiler makes heat and when I can use it, but if the supply tappings are near the top I am hoping it would be minimal.

 

[jeffesonm]

Are you considering a pressurized system? Check and see if those tanks were designed to be pressurized.

That 3/4 port, while not ideal, would not be a deal breaker. Most control valves like zone valves and balancing valves have ports that are reduced.

A 3/4 flapper type zone valve with a 7.5 cv typically has a 5/8" orfice. Flowing 13 gpm thru a 7.5 Cv valve give you about a 3 PSI drop.

I suspect those taps have a larger id compared to a ZV or control valve, more in line with a 3/4 ball valve with a Cv typically around 13.

Cv meaning the gpm flow rate that produces a 1 psi drop across the valve.

For balanced flow, either reverse return, or headers built with equal length piping would work. Google around the HW storage tank manufacturers websites and find some piping schematics for multiple tanks.

Yes I would like pressurized storage so I can run higher temps and skip the heat exchanger. Here is a photo of the tank... it has domed ends but I will have to check and see if there's a tag or something for pressure rating.



Thank you for explaining Cv, I never understood what that meant. Return reverse sounds like a good solution for 3+ tanks.

 

[ewdudley]

I was thinking to have separate taps for loading/drawing from storage so the boiler circulator and load circulator do not interfere with each other, sort of hydraulic separator-ish.

If boiler and load are on opposite ends of the upper and lower manifolds you get the both the desired hydraulic separator effect and the desired circuit isolation effect.

Indeed you can even tee the load into the manifolds on the same ends of the manifold as the boiler connections and it will work out fine because the pressure of hot water rising will make all load flow come from the tanks without any parallel flow through the boiler.

(Borrowed from other thread)

                  boiler ----|----|----|----load
                             T    T    T
                     load----|----|----|----boiler



load  ---------------------|
                           |
boiler --------------------|---|----|----|
                               T    T    T
                               |----|----|----|--------------------boiler
                                              |
                                              |--------------------load

 

[jeffesonm]

If boiler and load are on opposite ends of the upper and lower manifolds you get the both the desired hydraulic separator effect and the desired circuit isolation effect.

Indeed you can even tee the load into the manifolds on the same ends of the manifold as the boiler connections and it will work out fine because the pressure of hot water rising will make all load flow come from the tanks without any parallel flow through the boiler.

Okay I after looking at the other thread I think I understand what you're saying. I tried copying your diagram but couldn't figure out how so I made another one:


*edit* - looks like you figured out how to bring that one over here...


When both the boiler circulator and the load circulator are running, some of the flow would go past storage and to the loads, correct?

 

[ewdudley]

When both the boiler circulator and the load circulator are running, some of the flow would go past storage and to the loads, correct?

(Nice diagram, sure beats the old 1980's ascii art!)

As boiler works through the burn cycle -- due to boiler being offline, return temperature protection, and/or variation in load flow -- the flow from boiler can be less than, equal to, or greater than load flow. In all cases load will get the hottest water available whether completely from storage, partially from storage, or completely directly from the boiler. Likewise flow from boiler will go completely to storage, partially to storage, or completely directly to load.

 

[maple1]

Mine is set up pretty close to what that second 'acscii art' one shows.

It works great. My boiler circ flows more than my zone circ, so the zones just pull off what they need & the rest goes to storage. I was having some issues with ghost flow through a cold boiler when heating DHW just from storage, but since I replaced my 15-58 three speed zone circ with an alpha, that issue seems to have gone away, because the Alpha can be made to flow slower. That situation could also be alleviated just by provided a more direct flow between storage/loads than between boiler/loads. For example, in that second 'ascii' drawing, if the load/boiler positions were switched at each of their common Ts, the loads would have a more direct path stright thru the T to/from storage which should help reduce ghost flow through the boiler - the boiler circuit would see more head from the extra bend it would have to go around. But, mine are like that and I still got ghost flow through the boiler when my 15-58 was pumping through my sidearm.

Lots of little intricacies to this stuff, it seems.

 

[Coal Reaper]

Okay I after looking at the other thread I think I understand what you're saying. I tried copying your diagram but couldn't figure out how so I made another one:

View attachment 124318
*edit* - looks like you figured out how to bring that one over here...


When both the boiler circulator and the load circulator are running, some of the flow would go past storage and to the loads, correct?

Thats how i set mine up. I felt is was the simplest/cheapest way to go about getting the hottest water to zones. The return water helps keep your loading unit open so the boiler can make more hot water. Pic of x300 is about an hour after lighting fire. Top and bottom tank sensors are actually on the Tees. Storage loop does need to pump harder than load loop. I am using set point of 120* but when boiler is running return temp is higher even though pump is only moving 3gpm. Consideration needs to be given as storage approaches full charge AND load is returning that is close to supply temp. In this case it continues to push the supply temp higher and higher. For this reason i dont charge my storage higher than 170* bottom unless i am there to increase flow in boiler loop to lower temp increase through boiler.

 

[jeffesonm]

Thanks for the input guys, going to check out the tanks this week... will look for a tag/pressure rating before pulling the trigger.

 

[Hansson]

Effecta has some drawings on systems on the swedish site.
Unfortunately only in swedish

(broken link removed to http://www.effecta.se/images/principer.pdf)

 

[jeffesonm]

Picked up three tanks this week at $100/each. Based on the tag they held ethyl chloride, but the guy said they use nitrogen @100psi to purge them so I think they should be both empty and clean. They turned out to be 800 liters which is a little smaller than I was expecting, but 2400 liters = 630 gallons which should be a good match for my EKO 40. Not sure what TP or WP mean, but 1 MPa = 145 psi so they should be good for pressure.



In addition to the drip tubes mentioned in the first post, each tank also has one 3/4 tapping at one end and two 3/4 in tappings at the other end. Any more thoughts on whether I should squeeze 137,000 btu through three 3/4 holes, vs getting someone to weld on some 1 1/2" fittings?

 

[ewdudley]

Any more thoughts on whether I should squeeze 137,000 btu through three 3/4 holes, vs getting someone to weld on some 1 1/2" fittings?

Assuming at least 40 degF deltaT through the system (hopefully you can get more deltaT and even less gpm) then system gpm would be 140000 / (500 * 40), or 7 gpm.

Flow through each tank would be:

((7.0/3.0) gpm) / (((0.75/2.0)^2 * pi) in^2) = 1.69 feet / second

Which is pretty slow, but pointed vertically into each end of the tank it's maybe somewhat a little fast if you're a perfectionist.

However, when charging the tanks I don't see mixing at the top to be such a big deal, the system will get first pick of the hottest water, and by the time the tanks are fully charged the mixed layer goes away.

When drawing for load, flow rates should be much lower, so mixing on the bottom should be even less of a problem, and by the time you're into a minor mixed layer it's time to be lighting a new fire anyway.

 

[Coal Reaper]

Test pressure and working pressure

 

[Vizsla]

Don't let that effecta picture confuse you, that's not how they would really pipe it. Its worth the $50 to have a couple 2" ports welded on. I wouldn't mess with the 3/4" taps with that size tank. At 7.5GPM in a 3/4" threaded tap is over 6 mph, ideally you'd like to be under 2-3mph or atleast under 4'/sec to protect stratification. Not a must, but taking a look at storage or buffer tanks of similar or smaller size and note the port sizes.

 

[ewdudley]

At 7.5GPM in a 3/4" threaded tap is over 6 mph, ideally you'd like to be under 2-3mph

Sounds right, but aren't there three tanks? So I think that would be about 7 gpm shared by three ports, about 1.7 feet per second, or 1.1 mph when charging, much less when drawing.

 

[jeffesonm]

That all makes sense and sounds quite reasonable. It would be nice to avoid cutting/welding these tanks... for one, I'm cheap, and for another, I'd like to avoid the headaches around cutting, lining up the holes perfectly, welding, testing, rewelding, etc...

I'm planning a constant circulation distribution system so even during charging some flow will be diverted to the loads. From what I've read I can also do weighed burns so as the tanks approach max temp and deltaT closes, the BTUs will have dropped and the flow can stay steadyish. And as you point out ewd the mixing won't really matter then since they'll be pretty hot top to bottom.

I read this thread to estimate my expansion tank size. System is 630 storage + 22 boiler + piping = 675. Ranch house, boiler in basement, all baseboard... 10' x .434 = 4.3 psi, plus 5 = 9 psi minimum static pressure. Max design pressure = 30 psi. Tank on floor. p_lo = 9, p_high = 30, t_hi 210 and I get 9% of 675 = 61 gallons. Did I do that right?

 

[ewdudley]

I read this thread to estimate my expansion tank size. System is 630 storage + 22 boiler + piping = 675. Ranch house, boiler in basement, all baseboard... 10' x .434 = 4.3 psi, plus 5 = 9 psi minimum static pressure. Max design pressure = 30 psi. Tank on floor. p_lo = 9, p_high = 30, t_hi 210 and I get 9% of 675 = 61 gallons. Did I do that right?

Yes, that's right. Normally it comes out at 8% to 10%. t_hi is the average temperature for the whole system, so 210 degF seems a little extreme. Using t_hi 190 degF gets you down to 7.31% or 50 gallons. Also if you shave off 2 psi by using static pressure plus 3 psi instead of static pressure plus 5 that brings cold system pressure down to 7 psi and a 6.67% tank, or 45 gallons. But oversized can't hurt if it's affordable.