# My Tank construction and experimental Hex



## sparke (Mar 1, 2008)

I have been working on the tank part time for a few weeks. I am getting close to putting the pieces together and filling it up with water. I made the L shape for 2 reasons. 1. You cant see in the pics but there is concrete on the bottom 1/3 of 3 walls. 2 walls are againts foundation wall. I only need to reinforce the front wall. I will reinforce the walls that have concrete holding the bottoms. The concrete was part of the existing basement.

Ambient Temperature in Basement 60* - 70*

Volume - Approx. 760 Gallons
Tank Material - 2x4 studs, 3/4" Vantek plywood, 16 penny galv. spiral nails, 2.5" & 3" deck screws.
Insulation - R 11 Fiberglass, 1" Styrofoam, 2" Foil faced , bubble wrap.
Liner - Polypropylene 45 Mil reinforced.
Hex - 800' 1/2" non barrier pex (should probably use barrier pex) ( 4 coils - 200" each), 2 - Zurn Pex manifolds,
80' 1/2 copper pipe for support, 6" uv rated Panduit tie wraps ( used UV rated because the temp. limitation was 210* instead of 175* for white tie wraps.


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## NHFarmer (Mar 1, 2008)

Where did you get the liner?What is the temp.rating?


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## sparke (Mar 1, 2008)

https://www.hearth.com/econtent/index.php/forums/viewthread/15568/

The people at Water Saver said it was good for higher temps then EPDM but I could not get a straight answer...  The EPDM was not any more expensive so I dont think they were trying to make extra$$$


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## antknee2 (Mar 3, 2008)

Hi Sparky I am very impressed with your incredible ability to get right into a project , design ,construct ,test ,improve . Do you have a crew  ? Your back yard looks great for a solar project . Anthony


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## sparke (Mar 3, 2008)

No, it is a solo project except the wife helps me hold the frame while we make the coils.  Two down two to go.  The second one came out much better.  It took me a while to figure out how to support the pex.  I hope it works because it takes a while to make the coils.  As far as the Solar goes.  I am sure I am going to get the bug to do do that in the summer.  Then I will be asking lots of questions   It is my goal to be 100% oil free.  I have not burned a drop since I put in the new boiler : )


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## Nofossil (Mar 3, 2008)

You might want a bit more insulation once it's done to reduce standby loss - especially in the summer.

Two questions:

1) What provides the 'hoop' strength to resist the water pressure?

2) How will you prevent evaporation?


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## sparke (Mar 3, 2008)

nofossil said:
			
		

> You might want a bit more insulation once it's done to reduce standby loss - especially in the summer.
> 
> Two questions:
> 
> ...



1. Do you mean system pressure? If so, the hoops are tie wrapped every 2 inches on the 3 vertical supports. The tensile strength of the tie wraps are 40lbs. 
Do you think this is going to be a problem??

2. The lid will be made of insulation wrapped in polypropylene and it will be siliconed to the top of the tank. It will also be covered with plywood for safety. 

I do plan on more insulation later.


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## MarcM (Mar 3, 2008)

sparke said:
			
		

> nofossil said:
> 
> 
> 
> ...



I believe he's asking what will provide resistance against the sides of your tank falling outwards when it is filled with water.  The taller the tank, the more hydrostatic pressure is exerted.


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## MarcM (Mar 3, 2008)

Just a little advice regarding the insulation... any foil faced insulation should be facing out towards an air barrier.  Remember, aluminum has a very high thermal conductivity... so if it is in physical contact with another solid it will promote heat transfer from your tank.

The reason it is used against an air gap is, air has such a low thermal conductivity, heat conduction does not represent a large loss even with the increased conductivity of the foil.  The foil, however, has a very low radiative emissivity, meaning it will radiate very little heat to its surroundings.  So the idea of foil faced insulation is, by putting it adjacent to an air space, the air itself prevents against conductive losses, and the foil reduces radiative losses.


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## sparke (Mar 3, 2008)

The bubble wrap is foiled on both sides... The tank support is described in original post (even if my thoughts don't translate to paper well)... Basically the tank has foundation support on 5 of the 6 walls. The remaining wall will be bolted to the floor with 1/2' anchor bolts. Then it will have "whalers" (horizontal bracing). The horizontals will then be backed by vertical bracing as well. I don't think the tank is going anywhere : )  Also the pics dont show the 2" of foil wrapped polyisosyanurate styrofoam. Also foiled on both sides...


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## sparke (Mar 4, 2008)

Mark,  The 2" styrofoam is indeed backwards.    The back side is foiled but it is different then the shiny side.  I wonder how much efficiency it will cost me?  It is too late to change it.


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## MarcM (Mar 4, 2008)

Probably not a tremendous amount... it just won't help any, but having a thing layer of very conductive material in your insulation should be much penalty being surrounded by very thermally insulative materials.


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## SteveJ (Mar 8, 2008)

sparke,

Why did you chose 800' of 1/2" pex? Did you compare heat transfer rates with copper?

Are all four 200' coils reversible - used for both heat in and heat out?

Did you research the "submersible" quality of the pex?

For my 600 gallons of unpressurized storage, I am thinking of using 1000' of 1/2" pex for $290 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200205852489 instead of 180' of 1/2" copper for about the same price (actually more for completed auctions) http://cgi.ebay.com/1-2-60-ft-TYPE-L-WATER-Copper-Tubing-Coil_W0QQitemZ140212959413QQihZ004QQcategoryZ63902QQssPageNameZWDVWQQrdZ1QQcmdZViewItem.

Very cool setup and thanks for posting,
Steve


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## jebatty (Mar 8, 2008)

sparke said:
			
		

> Liner - Polypropylene 45 Mil



Before you install your tank lining, I suggest you research independently and carefully the temperature rating of the poly liner. My quick research on polypropylene liners, including 45 mil, shows very good low temperature performance but most specs do not even indicate a hight limit, as this material seems to be principally sold as a pond liner or similar application.

This site shows a melting temp as low as 142F and a softening temp as low as 95F. The site also indicates the poly extends into much higher temp ratings, so different grades of poly appear to exist. Check out your liner specifically, just to be sure. http://www.polymerprocessing.com/polymers/PP.html

You would not want to find that your liner was dissolving into your hot water return line, to congeal or be deposited (if that happens) in your plumbing/boiler, etc.

This cite talks about poly liners for steel tanks. Since the focus is for this specific purpose, I would be cautious about giving the temp rating too much credence, if your liner is for ponds and not tanks. Also take a look at the info on stress as the temp changes. http://www.fisherutah.com/technical-docs_files/Polypropylene.pdf

I investigated polypropylene tanks for my hot water storage and decided against poly tanks. I found that most of the tanks within a reasonable price range softened at around 120F and could start melting at 140F, which is consistent with the above cite. I did find that high temp poly tanks were available, but they were very expensive and way outside the price range I was willing to pay.

Unless you are sure about your poly grade temp rating, think again about EPDM, which appears to be fine in temp rating for boiler tank lining. https://www.hearth.com/econtent/index.php/forums/viewthread/14864/


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## sparke (Mar 8, 2008)

SteveJ,

Why did you chose 800’ of 1/2” pex? Did you compare heat transfer rates with copper? 

*When STSS did a quote for me , they quoted 240' of copper(2-120' coils).  I think copper transfers around 3X that of pex.  So that was 720' fo pex and I just rounded up a bit.    200' per coil worked out perfect with the height of my tank.*

Are all four 200’ coils reversible - used for both heat in and heat out? 

*Yes, I will post a schematic later. I am changing my system from series to parallel.  The project got a bit more time consuming when I decided to do that.*

Did you research the “submersible” quality of the pex? 

*No, I got the idea from EricJeeper who uses pex in his tank.*


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## sparke (Mar 8, 2008)

jebatty,  Thanks for the info.  I did research it before I purchased. You are right most specs show low temp tolerance only.  Scroll down and see where it was tested at 176* C 
http://www.google.com/search?source...=1T4SUNA_en___US257&q=firestone+Polypropylene   (third link down-open Adobe document)

I will be the guinea pig for this material.  EPDM is rated for 175* that is the only reason I went with this material.


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## SciGuy (Mar 8, 2008)

sparke said:
			
		

> SteveJ,
> 
> Why did you chose 800’ of 1/2” pex? Did you compare heat transfer rates with copper?
> 
> ...



That 3 times number just doesn't seem correct to me for conduction. If the the link I've attached is an indicator it would seem like they vary by a factor of ~ 800 times. Perhaps I'm missing something ....over or underthinking as usual.

Hugh

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html


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## sparke (Mar 8, 2008)

Were you using the polyethylene? I agree that math does not work but something is awry. Maybe because they are just comparing the material in its raw form, not cross linked, or anything else they do while manufacturing, etc... 

EricJeeper says his 500' of 1/2" pex in a 600 gallon tank works like a champ. 

Since there is no hard data besides peoples experiences - This is why I am calling it experimental


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## SciGuy (Mar 8, 2008)

sparke said:
			
		

> Were you using the polyethylene? I agree that math does not work but something is awry. Maybe because they are just comparing the material in its raw form, not cross linked, or anything else they do while manufacturing, etc...
> 
> EricJeeper says his 500' of 1/2" pex in a 600 gallon tank works like a champ.
> 
> Since there is no hard data besides peoples experiences - This is why I am calling it experimental



sparke,

All of the "plastic" types seem pretty consistant in regards to their conductivity. Cross linking is used for strength purposes not heat transfer purposes. 
That said, I have always thought that the copper heat exchangers were often way oversized if there is a fair amount of convection going on near the tubing in the tank. If this is so then if might account for Eric not having problems with pex his installation. 

I would love to see a link to a reliable source that shows copper only having 3 times the conductivity of PEX.

Hugh


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## sparke (Mar 8, 2008)

Sciguy, 

I do not remember exactly where I read that. For sure on this site and possibly on "builditsolar". I know I have read it at least on 3 sites... I have studied so much on the net I could not possibly begin to tell you where I saw it. I saw cases where pex hex's failed miserably. In those cases the installer used the same amount of pex as they would have copper. Then I have come across success stories like EricJeeper. As you know, there is more involved then just the pex. There are flow rates, head pressure, friction losses, etc...
I made the decision to go for it and see if it works. If it does great I saved about $800. If not I lose about $200 and alot of time. Just look at it this way. If it fails I am taking one for the team  I think it it going to work fine.


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## jebatty (Mar 8, 2008)

I continue to have trouble understanding why the choice to go with a big coil hx when a flat plate for about 1/3 the cost can perform so well. I know an extra pump is needed, but pumps today are very economical. The flat plate 5 x 12 x 30 plate I use (pd $200) will load my 800 gallons of storage from 80 to 150-160 in about 6 hours, and at the low end and until storage input to hx reaches above about 130 can take all the heat my Tarm Solo Plus 40 can deliver without idling. 

What are the benefits of the coil hx over the flat plate?


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## EForest (Mar 8, 2008)

Jim,
Is your 800 gals open or pressurized?


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## sparke (Mar 8, 2008)

I want to maximize stratification.  If you explain how to do that with a plate hex and an un-pressurized system I would be very interested.


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## jebatty (Mar 8, 2008)

I am moving from unpressurized to pressurized. The boiler side is pressurized already. Storage will be soon, as I move to a 1000 gal LP tank.

My plate hx feeds hot water into the top and draws cold water out of the bottom of the tank, which should result in about as much stratification as one can get. I intend to do the same with the pressurized LP tank.


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## EForest (Mar 9, 2008)

Jim,
Have you thought about welding a tankless DHW coil such as you get with an oil boiler into you propane tank?
Just something I'm thinking about.

Ed


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## sparke (Mar 9, 2008)

Jebatty, Do you use dip tubes?  Turbulence in the tank?


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## jebatty (Mar 9, 2008)

gasifierwanabee said:
			
		

> Have you thought about welding a tankless DHW coil such as you get with an oil boiler into you propane tank?


Have not because don't currently heat DHW with the boiler, but will consider in the future. I'm finishing my first season with the Tarm. I'm waiting for the LP tank to be delivered, and I'm not sure of the maximum opening into the tank that could be used to insert a coil. What do you suggest?



			
				sparke said:
			
		

> Jebatty, Do you use dip tubes?  Turbulence in the tank?


I do not on the open system tank currently used because the tank had an inlet fitting on the top and a drain fitting on the bottom. Also, I do nothing to create turbulence. Hot water in on the top and cold out the bottom results in very heavy stratification, which seems to be most desirable. A really good part of the heavy stratification is that the return to the hx is coolest possible, which also results in the highest rate of heat transfer through the hx. I get as much as an 80F heat rise through the hx.

On the soon to be pressurized system, as I don't have the tank yet, I may have to use a dip tube on the return side to draw cool water from the bottom of the tank but I don't think I will need one on the top side for supply hot water. What do you have in mind?


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## sparke (Mar 9, 2008)

I am trying to educate myself on that method. If I had known you could use a plate hex with an open tank I am sure I would have gone that route... That's why I am here, to learn! If the ole pex trick don't work, we will be talking soon : )


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## slowzuki (Mar 10, 2008)

The main benefit of the closed coil is reducing the number of pumps.  Every pump costs money to run.


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## sparke (Mar 12, 2008)

Finally got this thing up and running.  The tank made it from 50* (guess) to 120* overnight.  The tank was only heating when the boiler overheated.  I temporarily hooked tank pump to overheat aquastat.  Right now I am running a dedicated load through the tank.  As the Delta narrows I am not sure how well it will go from 150* to 180*.. So far so good on the experimental hex...  Here's a few pics before I sealed it with the cover.














For all you code freaks, I am going to remove the light fixture... someday... : )


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## MikeF (Mar 13, 2008)

Well Sparke...how did Day 2 go? Were you able to hit the temperatures in the storage tank that you desired as well as keep the house warm? Any obvious issues thus far?


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## sparke (Mar 14, 2008)

Day 2:  Lit the fire at about 5:00 P.M.  Loaded the boiler about 1/2 to 3/4 full.  Got up at 5:00 a.m and switched over to the tank.  Warm day - it was about 35 -38*  but the tank supplied 3 showers and kept the house at 72* (set point).  I relit the fire at 9:00 p.m.  I dont have controls hooked up.  So the operation is not automatic yet.  So far so good...


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## antknee2 (Mar 14, 2008)

sparke said:
			
		

> Day 2:  Lit the fire at about 5:00 P.M.  Loaded the boiler about 1/2 to 3/4 full.  Got up at 5:00 a.m and switched over to the tank.  Warm day - it was about 35 -38*  but the tank supplied 3 showers and kept the house at 72* (set point).  I relit the fire at 9:00 p.m.  I dont have controls hooked up.  So the operation is not automatic yet.  So far so good...



Congratulations Sparky on great job .


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## MikeF (Mar 14, 2008)

Sparke,

What temps are you hitting in your tank?


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## sparke (Mar 14, 2008)

Thanks Anthony.  I can honestly say I learned the majority of the information for storage tanks from this site.  Thanks guys!!  Also Chris Holley who is the Garn Dealer in this area sent me a drawing to plumb the tank. 

Mike,  I do not have an answer for you because I do not have the sensors hooked up yet. I was checking it with a meat thermometer but now the tank is sealed.  I plan on installing a pipe through the lid tomorrow.  Then I will install 2 maybe 3 sensors in the tank.  Top, middle, bottom.  I have not purchased them yet...


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## SteveJ (Mar 15, 2008)

sparke,

Great job - looking to do similar setup.

What temperture sensors are you going to use and where (through the ouside or on a vertical pipe or other) are you going to mount them?

Please keep the update coming,
Steve


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## sparke (Mar 15, 2008)

The sensors are going to be submersible (if I can find some) and they will enter the tank through a pipe in the lid. I may go with traditional thermometer with long stems like this one: http://www.marshallinstruments.com/products/GJ.cfm The stems range from 2.5" to 84" but I don't know if the temp. reading is on the tip or the whole stem. If the whole stem is reading temp. then that model will do no good for middle and bottom readings. I am also looking at 10K sensors but the ones I have found have to be sealed. They can not get wet...


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## sparke (Apr 1, 2008)

I finally found a gauge. I got it at a Johnstone supply. Even though they said they did not have anything for this application over the phone - I found this hanging on a display wall. The bottom pic is the supply gauge from the tank/wood boiler which ever is running. In this case this is the temp from the tank.  The other pic is where the sensing bulb goes through a pipe into top of tank.  The sensing bulb is attached to a 48" capillary tube.


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## MikeF (Apr 1, 2008)

Great job, Sparke. I didn't think that a pex hx would work this well, but it obviously does. Keep us posted on your progress. One question...What is the average temp difference going into and coming out of the hx? 

By the way got an e-mail from Greenfire about the changes they are making. Sounds good.


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## sparke (Apr 1, 2008)

MikeF said:
			
		

> Great job, Sparke. I didn't think that a pex hx would work this well, but it obviously does. Keep us posted on your progress. One question...What is the average temp difference going into and coming out of the hx?


Charging tank:
That all depends on how far I draw the tank down. If I run the tank down to 120* When I start to recharge with 190* water, I will get return temps of 120-130* Of coarse I am circulating cold water in the pipes at this point too. I would say a 20*-30* difference is average until the temp in tank starts to approach 180* Then the supply and return temps get closer to each other... 
Drawing from tank:
This depends on ambient room temp. 
Right now I am lighting one fire a day. Burning about a load and a half through the boiler. That supplies all domestic use and heat for about 24 hours.( Five people live here all take at least one shower a day). The tank really shines in warmer weather.


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## gimmeWood (Apr 1, 2008)

very intriguing - I may have to consider using pex for the tank I am planning.  Do you have any experience with a copper hex?  Do you think your pex works as good as a shorter copper hex?


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## sparke (Apr 1, 2008)

No experience with a copper Hx.  But if the 3x ratio is correct (this is open to debate).  Then I have the equivalent of 266' of 1/2" copper.  For 700 gallons.  ( The tank held about 750 before the lost space of the Hx's.  I have no idea how much space in gallons is wasted).  What I will say is I can charge the tank from 120* to 180* in about 6-8 hours while still drawing domestic and heat.  However it is not cold outside.  Probably around 30 to 35* at night.


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## Willman (Apr 1, 2008)

> I finally found a gauge. I got it at a Johnstone supply. Even though they said they did not have anything for this application over the phone - I found this hanging on a display wall. The bottom pic is the supply gauge from the tank/wood boiler which ever is running. In this case this is the temp from the tank.  The other pic is where the sensing bulb goes through a pipe into top of tank.  The sensing bulb is attached to a 48” capillary tube.



Sparke, I was wondering how after market automotive temp gauges would work. They have capillary tubes fairly long.
Thanks for the updates.
Will


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## sparke (Apr 1, 2008)

The ones I have seen would probably work fine except you would need a 12 volt  DC power source.  Actually they may run on less signal like 5 volts DC but I am not sure...


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## sweetheat (Apr 1, 2008)

Nice job! I'll be interested to here how the polypropylene reacts with the hot water. Is EPDM sold in large enough sheets to avoid lap joints and glue. Any thoughts on fiberglass lined DIY storage tanks. Can you reline your tank without a major rebuild sparke? I'm trying to get all the info I can before I buy or build storage for my tarm solo 40 thanks sweetheat


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## Richardin52 (Apr 2, 2008)

Your tank gives me a lot of ideas about building a tank.  I'm not clear on how you reinforced your tank so it can support the pressure of the water.  I'm sure I could build a tank and support it with steel like angle iron bolted together.  

The box would be made of ¾ inch plywood or even advantec if supported correctly.  The corners supported by vertical strips of angle iron.  The sides would be supported by horizontal straps of angle iron running around the box say at 2 foot intervals from top to bottom.  Then insulate the inside and the outside.  

  The liner is key, what does Tarm us for a liner on their tank?


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## sparke (Apr 2, 2008)

No problem yet with the polypropelene.  Yes you can buy it in large sheets but anything over 10' will have a glued seam from the factory.  I can not replace the liner easily. The tank was built under a stairway in a corner.  All components were installed before the last wall was put on.  The liner and Hx are performing quite well but the real test will be time.


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## sparke (Apr 2, 2008)

Rich, The tank has support on 2 foundation walls. Three walls are againts foundation footing.. The front wall is supported by 2- 45* braces cleated to 2-2x4 nailed together and bolted to the floor with concrete anchors. 

I thought of doing something similar to the box you are describing. I think it would work if you banded the box using thin metal straps. I am not sure where you can get the banding or the tool to tighten/lock the end. In another thread someone mentioned using aircraft cable... Check out http://users.telenet.be/hagim/zonne_energie/hot water storage.htm.


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## SteveJ (Apr 2, 2008)

sparke,

Great job and please keep the updates coming...

Do you have any feel for how much wood you are using now compared to before the tank?

Thanks,
Steve


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## sparke (Apr 2, 2008)

It is really hard to say because the weather turned warm just about the time I finished the tank.  Right now I am making 1 fire a day, about a full wheelbarrow.  But that is green wood.  When it was cold, I was burning 24/7...


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## sweetheat (Apr 2, 2008)

Any hardware or building supply would have form banding. It comes in a long roll with holes punched every inch for nailing to the form boards. It works quite well for major concrete pours. Should work OK for storage tanks. It's not rust proof though. Steel wailers around on 4 sides would also work. Lumber banding would work too, their's a special tool used to tighten them up. Rich, I beleive tarm uses EPDM. I have questions about drain holes in the tank. Do they make fittings designed for EPDM? Does the tank water stay put or will it circulate? Is it just the heat storage medium? And the exchangers do the water circulating? Plumbing term for heat exchanger is hx? correct? How far are you from coastal downeast sparke? I would like to come and look at your set up some day. A day closer to clean heating. sweetheat


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## jebatty (Apr 2, 2008)

Sparke - what is the flow rate gpm between boiler and tank?


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## sparke (Apr 2, 2008)

jbatty, I am not sure on gpm. I tried to address this issue in another thread but got no responses. I am currently using a taco 007. I just purchased a 3 speed Grundfos UP26-99. I think some of my heat zones need a bigger pump as well. I eliminated the pump at the wood boiler all pumping is done from heat zone pumps or tank pump. It is working very well. I would like to know the professional way of sizing pumps but know one wants to part with that info...

Sweetheat, I live 20 minutes north of Augusta. You are welcome to check it out anytime. The water in tank is "dead water". Just a transfer medium.


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## slowzuki (Apr 2, 2008)

Maybe I should start a thread on pump sizing?  Oh well in short heres a few tips.  You size the pump for the friction loss and how many gpm you need to move around a loop.  The gpm is set by the heat loss in the loop. So:

1) Say you have a rad loop designed to give a temp drop of 30 F at 5 gpm to get the right BTU's for the coldest day.
2) Say your loop is an inline rad loop using finned copper, you add up for each size the total lenght of pipe and number of each type of fitting.  Convert the fittings to equivalent pipe lengths using tables.  Use a friction loss calc or table to solve the friction loss at 5 gpm.  Lets assume there is 13 feet of head loss (13 feet of head loss is not 13 feet of pipe, it refers to a 13 ft tall water column which is about 0.44 or something psi per foot).
3) Go to a collection of pump curves and mark the point 5 gpms/13 feet.  Any pump curve below that will not move enough water.  Any curve above will move enough.  If you oversize the pump it costs you extra money to run the pump and it will circulate more water than needed, maybe with velocity noise depending on pipe sizes etc.
4) In a backwards way, you can size pipe based on a pump by reversing the process.
5) It is bad practice to size a pump near its static / shutoff pressure if it has a flat curve out to high flow. The pump will not last as long.


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## Dave T (Apr 2, 2008)

Hi sweetheat I am a commercial roofer and work with EPDM on a regular basis .045 and .060 when we make a penatration through a roof that we want water to flow through we ues a drain hub and run the EPDM right across it,using a mastic caulk with constant,consistant compression the EPDM is clamped between two pieces of metal with the caulk sealing the EPDM to the drain hub.This is on a commercial roof I am not fimilar with lined tanks but would think it has to be very similar.


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## sparke (Apr 2, 2008)

Thanks for the interpretation Slowz. I have a book coming from Grundfos so hopefully it will have the tables in them. I will post a schematic when I have the chance to draw it. I have an interesting set up...


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## Der Fuirmeister (Feb 1, 2009)

Sparke,

It's been awhile since this post paused for summer....how did your tank liner and pex hx work out?

I have a lot of 5/8" pex left over and might consider this over copper.


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## sparke (Feb 3, 2009)

It works great!.  My hx can easily sink all the BTU's the boiler puts out.  The boiler runs wide open until the tank hits about 170*  I have had the tank over 200* a few times (not on purpose).  Again the jury is out on how long it will last but so far so good!  On a side note - I have had problems with the cover.  The combination of odd shape & location make it hard to get a good fit...


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## Der Fuirmeister (Feb 3, 2009)

Thanks.  I have lots of 5/8 pex left over from the radiant floor installation.  Think I'll try your pex hx.

Have you tried using silicone adhesive to adhere foam backer rod (or similar type) to the EPDM on you tank top?

Did you ever find the submersible temp sensors?  If not I might be able to locate a source.


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## jebatty (Feb 3, 2009)

> I am currently using a taco 007. I just purchased a 3 speed Grundfos UP26-99.



Something that works also has to mean that the physics are pretty good too. I did a line loss calc on 200' - 1/2", and pump head at 2 gpm is about 27'-28'; at 1.5 gpm pump head is about 16'-17'; at 1.1 gpm pump head is a little over 9'. Head at over 2 gpm quickly gets extremely high. Mutlitply the gpm x 4 for the four coils. At 9' head a 007 will move about 5 gpm, so it appears that you are moving about 4.5 gpm. At a delta-T of 20, your gross btuh is about 45000 with the 007.

Based on the above, for its pump curve my estimate is that a UP26-99 (single speed) likely will move about 2 gpm or a little more, x 4 = 8 gpm total = 80,000 btuh at delta-T = 20.

Your btuh will drop off as tank temp closes to within 20 and less of your boiler input temp. If boiler input is 190 and tank is 180, at 100% heat transfer your delta-T is only 10, and maximum btuh is 22500 at 4.5 gpm or 40000 btuh at 8 gpm. 

Are you still using the 007? Do these calcs seem to fit what you are experiencing?


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## sparke (Feb 3, 2009)

I am just using the one probe in the pictures.  It has a 4' lead on it which gets me down to the lower 1/3 of the tank.  I charge that part of the tank to 180*.  I have measured the difference before.  It is about 10* hotter at the top.  So I charge the tank  170/180/190.  This is a subjective guess based on readings at different lvls in the tank.  As far as the cover goes - I have it fixed for the time being.  I used Hardy board(concrete board used on floors and shower spaces for tile work).  I then sealed the cracks with high temp silicone.  This cover is inside the tank held up by supports.  Over that - across the top is bubble wrap.  Since the cover is in the tank the bubble wrap has a 2" air void.  2" polyiso. and r -24" fiberglass insulation over the top.  Working well for a month now.


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## sparke (Feb 3, 2009)

jebatty,  It is funny you mention the pumps.  I just posted yesterday in a different thread about us hearth.com folks always seeking better efficiency.  The pumps are my next area of concentration.

 I have more concerns about my heat loop pumps then anything else at the moment.  Can you dumb it down a bit for me?  I believe the way to size a pump properly is to figure out run length, size pipe, friction in fittings, etc...   Is there an easier way to figure head loss?  If you have temp gauges on supply and return and know the ambient temp of rooms being heated... I assume you can figure out whether or not your pumps are adequate?  I have a difference of 10-20* from return and supply. depending on the room temp.   Any quick rule of thumb?  Maybe we should start another thread about pump sizing.  I know there are other threads kicking around but since we are on the subject...


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## jebatty (Feb 3, 2009)

sparke said:
			
		

> Any quick rule of thumb?  Maybe we should start another thread about pump sizing.  I know there are other threads kicking around but since we are on the subject...



There are some rules of thumb which have appeared in various threads. For heat transfer, maximum gpm: 1/2" - 1.5 gpm, 3/4" - 4 gpm, 1" - 8 gpm, 1-1/4" - 14-17 gpm, 1-1/2" - 22-25 gpm, 2" - 45-50 gpm. For btuh calculation: gpm x delta-T x 500. For line head, total pipe run length (round trip + equivalent for fittings, etc.) and then use the calculator at Pipe Friction Loss. For calc of additional pipe length to add for fittings: see attachment. Once you've calculated pump head at target gpm, then look at the pump curves from Taco, Grundfos, B&G;etc., and find a pump that provides the target gpm at the calculated pump head, and you want your target gpm/pump head to fall about in the middle of the curve.

If your pump head is too high, you need to go to larger pipe size or shorten your run. As a practical matter, pump head 5'-30' is about the operable range, I think, for most home applications, and the lower the pump head the more flexibility you have for system design.

Hope this helps. If I made an error or someone can do this more simply, add what you can.


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## sparke (Feb 6, 2009)

That is a big help.  Thank You very much !


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## Duetech (Feb 6, 2009)

Yes that is a lot of help thanks jebatty.


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