DIY heat storage

sardo_67 Posted By sardo_67, Nov 13, 2017 at 2:16 PM

  1. sardo_67

    sardo_67
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    Sep 19, 2017
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    Tarm B55 here and house around 1600sq feet along with a non insulated 24x24 garage with open celling to rafters I would like to heat this winter. located in CT

    house is baseboard with some under floor in the living room, most of the walls are not insulated as It was built in 59 and I guess it was an option but has new windows.

    garage will be heated directly from the boiler with 2 45kBTU modie heaters and also set up as the emergency head dump zone if my boiler gets too hot. only looking to keep the garage at like 40/50 unless I'm actually working in there

    I have seen some of the DIY hot storage tanks from wood and plastic liners which for me seems the best bet as moving large heavy tanks into my basement isn't really possible.

    what can you guys recommend for me, 400/500 plenty or 1,000 really needed? I've seen a lot of different set ups.
     
  2. peakbagger

    peakbagger
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    Jul 11, 2008
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    See my reply in the other thread.

    Tank sizing is related to a lot of things. My boilers nameplate is 90,000 btus. A 500 gallon tank holds roughly 4000 pounds of water. I have standard baseboard so i pretty much run out of heat around 140 deg F. I can run my tank up to 190 deg F so the maximum temperature difference in the tank is 50 degrees. Water stores 1 btu per pound per degree F so my tank can in theory store 200,000 useful (to me)Btus. You should have run a heating calculation on your new home so look it up and see how many btus per hour you need on the coldest day. Divide by the storage but capacity and that tells you how long a charge will last you. My boiler can put out 90,000 btus so it takes me a little over 2 hours (2.22) to heat the tank up (its closer to 3 hours). That lines up well with my lifestyle which is start heating the boiler prior to supper and then run it until the tanks up to temp. Once the tank is up to temp my boiler is also heated up with plenty of water with no place to go. I have an external hot water maker so I charge that up with the hot water in the boiler and then run the house heat off of the boiler until I go to bed. I then switch the system over to running on storage when the house calls for heat. I can usually run a day in cold weather and possibly up to three in shoulder seasons but for the last few years I have been heating the house with a minisplit in shoulder season with excess net metered solar.

    So if you put in a bigger tank you can go more days between running the boiler but at some point when you need to charge it back up you will need to run it longer. IIf you are just building the house and install radiant emitters in place of baseboard or radiant heat you can heat down to as low as 90 degrees. So the same size 500 gallon tank with radiant can be just as effective as 1000 gallon tank on regular baseboard as there is use for that warm water. Ideally everything is more efficient the lower temperature you can utilize for heating. There are higher output boilers than mine so if you want larger storage you probably want a higher output boiler.
     
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  3. sardo_67

    sardo_67
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    Sep 19, 2017
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    I bought the house in June and have not been in it long enough to really see how well heating it is, cost is an issue to me right now as I spent around 30k since getting the house on remodeling and upgrading stuff. I just know that having only a boiler and no storage isn't the best idea unless I am going to be using a lot of heat, the 55 is rated at 140k on wood so it is way over kill for a use like that.

    I read more and saw in the other thread I need to make a close pressurized system as I do not want to deal with making heat exchangers and such in an open tank.

    however I am looking into that a lot more so it may be a possibility, I still have like 700ft of 1/2' pex left over from my under floor heating installation.
     
  4. hobbyheater

    hobbyheater
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    Nov 14, 2011
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    This Pdf file is on a home made storage tank. Use pressure treated lumber, stainless steel fasteners, and AST's Liner.
     

    Attached Files:

  5. stee6043

    stee6043
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    Aug 22, 2008
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    500 gallon propane tanks can be surprisingly easy to move with two guys and a dolly on each end.

    Mine were 37" in diameter. Strategically about 2" bigger than my walk-out slider door. Other than the door issue moving them in/out was pretty straight forward...

    Just thought I'd share.
     
  6. sardo_67

    sardo_67
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    Sep 19, 2017
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    is there a reason 55gal plastic tanks aren't used? or the other various types of plastic tanks available on CL for somewhat cheap, mostly agriculture use ones?
     
  7. peakbagger

    peakbagger
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    Plastic tanks are typically limited to 140 to 160 degrees F. Any more than that and the tank will lose integrity. Too low of temp for storage.
     
  8. Bob Rohr

    Bob Rohr
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    Take a look at the tanks that Tom builds at www.americansolartechnics.com He has spent many years perfecting the open tank design and components.
     
  9. Fred61

    Fred61
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    Both pressurized and unpressurized have their advantages and disadvantages. One particular thing I like about unpressurized is that unlike pressurized it's simple to get domestic hot water without screwing around with side arms, pumps, etc.
     
  10. Sparky

    Sparky
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    Feb 24, 2012
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    I built a unpressurized storage system like the one in the instructions hobbyheater gave you, Approx. 1200 gallons 8x8 I used copper coils for my heat exchanger (most expensive part) It works quite well. I also used EPDM as a liner. I have a 2400 sq foot house in VT well insulated. In shoulder seasons I can a couple of days between firing. The first tank I built was half the size, That worked ok but the bigger tank is much better. If you need any details or help PM me and I will give you my number and I will help you any way I can
     
  11. peakbagger

    peakbagger
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    Although the Kerr design that was linked has some great reference value it sadly advocates an EPDM liner. As many have found out EPDM or various strains of modified EPDM is not and never been rated for elevated hot water storage. Some people have been lucky and perhaps the prior poster was one of them but do yourself a favor and use another material. Sure there are more exotic systems that could work well, the cost and installation hassle is far higher than the cost to get a custom PVC liner built which has been proved in the long term.

    There were at least two possibly more manufacturers licensed by University of Maine to make the Richard Hill boiler design. This was the first design wood boiler that required external hot water storage. Sadly many of these installations failed when various home built storage solutions failed. The boilers were costly and storage tank longevity was regarded as an afterthought so many options were tried and many failed. AST had worked with Dick Hill for years to come up with their current design and is probably the best resource on what worked and didnt work.

    Ultimately its your call and as long as you go in realizing that an EPDM DIY liner is a science experiment, have at it. Personally I would buy or build a stainless steel tank unpressurized and be done with it if you dont want to go with heat welded PVC.
     
  12. Nofossil

    Nofossil
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    I'm a huge fan of pressurized storage (I have unpressurized). Major advantages:
    1. Propane tanks are really heavy duty - no failure worries.
    2. No heat exchangers. When charging from your boiler at 185, water in the top of storage is 185. When heating from storage, baseboard water temp is the same as top of storage.
    3. No evaporation loss or condensation in insulation.
    Bottom line, gallon for gallon, pressurized storage provides more usable capacity.
     

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