470 gallons of storage, in 550 gallon tank - Dooh!

peakbagger Posted By peakbagger, Nov 13, 2017 at 8:19 AM

  1. peakbagger

    peakbagger
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    Jul 11, 2008
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    One thing with an open non pressurized storage tank is that it is vented, not by much and the vent configuration tends to minimize venting of vapor but they are vented. My AST tank has a 1/2" PVC vent and I use it to hang a temperature probe down into the top of the tank so I had not checked the water level in the tank in a few years. I was down prepping for the season and I removed the sensor and "sticked" the tank. First try with a short stick didn't reveal any water when I pulled it out. I got a longer stick and did find a water line but it looked real low so I repeated, I got the same result. I was about 10" down on water level. Dooh! I figure I was down at least 80 gallons maybe a bit more. Every BTU stored counts especially since I cant justify swapping over to radiant baseboard.

    I ran with the low tank for the first run of the season but need to get the hose out and top it up.
     
  2. sardo_67

    sardo_67
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    Sep 19, 2017
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    can you tell me more about your storage system? I am looking to DIY my own for my new house.
     
  3. peakbagger

    peakbagger
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    Its the standard AST design.http://www.americansolartechnics.com/products/heat-bank-storage-tanks/ Its roughly square and made our of iso-foam slabs reinforced with sheetmetal on the corners and held together with self drilling screws. Super strong and lightweight. I carried everything down a set of stairs and installed it myself in an evening. The big thing I would strongly suggest is contacting AST and having him make a custom liner. He and others have learned expensive lessons that the only liner that lasts is heat welded PVC. There are all sort of other materials mostly from the roofing industry that claim to work but they are not designed for long term submersion with elevated temps. ASTs tank is super efficient but he doesnt mind if you DIY a tank and he just supplies the liner and top cover liner to your dimensions. He also sells heat transfer coils.

    IMHO unless you have real good floor drain and dont mind changing out a liner in a couple of years have AST make you a liner. Its pay me now or pay me later.

    Give Tom a call at AST or look around on Youtube for his videos. A great guy to talk to
     
  4. sardo_67

    sardo_67
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    ok that's who I looked at a while ago and couldn't find it again.

    after more reading I think a propane tank would be best so I don't have to do the heat transfer coil and all that extra stuff, I was under the assumption they all worked like a pressurized system.

    now that I think about it what kid of PSI do the closes systems get to?
     
  5. Fred61

    Fred61
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    I have a 500 gallon cylindrical For the first two years I had a 3/4 inch pex tube about 5 inches long for a vent. It extended out of the insulation about a half inch. I had to add water a couple times over each heating season. I am able to keep a pretty close eye on the water level because I had a sight glass plumbed into it while I was having all the connections and wells welded in during installation. With the tank being in the basement I realized that all that water was going into my house.

    I added a snorkel to it and extended it across the basement and vented it to the outside. Now I only need to add a small amount of water every two years or so. I can only assume that the water is condensing in the longer pex run and draining back into the tank. Perhaps the cold outside air also plays a part.

    The tank exhales every time we top off the heat. It's breathing through a single pex nostril and pumping out an immense amount of moisture. I noticed a big change in the humidity and condensation on the windows.
     
  6. Hydronics

    Hydronics
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    Closed systems are typically designed for about 15 PSI, the relief valve is typically set at 30 PSI. To accommodate the expansion for the temperature swing you will need a large expansion tank on a closed system.
     
  7. peakbagger

    peakbagger
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    I don't mind a bit of humidity in my basement during burning season. As it is when heating the house I have plenty of evidence of low humidity. With double panes and cellular blinds with side seals that are closed at night, I dont get much frost on my windows.

    Its a never ending discussion on what is better pressurized or pressurized storage each has their pros and their cons. In my case my system is set up so that with the flip of a switch or low storage temp, my heating system is a plain old easy to understand and diagnose oil fired hydronic system.Any boiler tech can walk in an diagnose it. I have relays on some wires like the circ pumps but they are all designed to fail closed if the power to the wood boiler goes away. I use the oil heating systems thermostats and controller to run everything all the time. Someday someone else will own this house and if they dont want the wood boiler and the storage, I just shut a couple of valves and I can yank the wood system including disassembling the tank and moving it to my next house. My sense is a pressurized system is more of an integrated system that is far less easy to split off but I will let the pressurized folks make their case if they care to.

    Practically in my case a square tank that could be assembled in place is the way to go. It takes up less room volume than a circular tank for the same capacity. Its made out of 99% foam so hard to beat the R value. I could bring it down my stairs in pieces and installed it myself. With a lot of rigging I may have been able to get a single piece tank in the basement but it wouldnt have been pretty and once there I would have needed to insulate it with foam somehow.

    The biggest issue to me is that a large percentage of folks are using non code/certified tanks for pressurized systems. They may have been coded/certified once but its highly unlikely that when it was altered to use as a heating storage tank that the paperwork was done to keep it code. Yes there are some firms that do go to that trouble and sell properly altered tanks and you pay for it but most folks appear to skip the code implications. In the back of my mind I am willing to pay a possible premium to make sure that all the components of my system are used as designed and intended to reduce my future liability. I am a PE and have seen the consequences of misapplied equipment in court and it is not pretty. I seriously doubt any professional is going to supply and install a pressurized storage tank that was improperly altered as they own that liability for it as long as that tank is in service. I have heard of the wink/wink/nod method of a contractor installing everything up to the tank but letting the owner supply the tank but that is something the contractor/owner had better hope never goes to court against an insurance company. On the other hand a non pressurized storage tank is outside of any code as its atmospheric. The only pressurized component is the heat exchanger and if it fails it dumps into the tank. Sure the non pressurized tank can flood due to its failure just as pressurized tank can but if an insurance company gets involved they will most likely pay the claim and if it the claim is high enough, go after the company that supplied the tank . An altered pressurized tank failure is another story, even though the damage is the same they have plenty of basis to not pay.
     
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  8. Fred61

    Fred61
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    My house has been tightened up so much in the last few years it's bordering on needing an air exchanger if I'm not super careful about using exhaust fans when showering, cooking and activities such as shampooing carpets. I would need an exchanger if I had not reached under the ceiling insulation and pulled out the vapor barrier from the fiberglass batt insulation before I topped it off with cellulose fiber. Putting an extra 10 or twenty gallons of water into my living space was a disaster waiting to happen. Picture mold growing on the interior of the exterior sheathing due to condensation. I've seen it happen.
     
  9. Hydronics

    Hydronics
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    I do understand your stance, I'm a licensed professional engineer also.
    Bear in mind that the propane pressure vessels guys are using were designed for at least 100 psi. In a hydronic application they'll never see over 30 psi. That's quite a safety factor.
    Obviously, you wouldn't want to specify one for this use without CYA certifications but for your own use, I wouldn't be concerned.
    Open and pressurized each have advantages and disadvantages as you noted.
     
  10. Fred61

    Fred61
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    If I can believe what I read on the internet it takes 177 psi to keep propane liquid so I'd say that they would need to be thoroughly abused not to hold 30 psi.
     
  11. peakbagger

    peakbagger
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    Not worried in the least about the original tank design, far more worried about the guy who stick welded on a couple of nozzles with a low hydrogen rod that had been sitting on a shelf for a few months sucking up moisture. Since the tank is full of water I am not worried about it exploding, just leaking at an inopportune moment, but then again its someone else basement. Usually its not that hard to seal off the leak, the PITA is to get to the leak, removing insulation, rewelding and then re-insulating. At this pressure I would be tempted to wire brush it and JB Weld it.

    As long as folks go into this knowing the risks versus the cost savings more power to them.
     
  12. Fred61

    Fred61
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    Certifying the tank ain't gonna change the welding rod.
     
  13. peakbagger

    peakbagger
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    I agree certifying the tank is generally just over pressurizing it and seeing if it will leak Code alternations to a coded vessel by a shop with stamp is going to make sure its done right of they wont have a stamp very long. There will be materials traceability, a weld procedure laid out in advance, a certified welder and then someone is going to inspect the alteration to see if it comply s with a plan
     
  14. Marshy

    Marshy
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    @peakbagger, I emailed AST but habe yet to hear from them. I was considering starting an AST tank thread so all the owners have a common thread to share tips with, kind of like the BK and other stove owners do.

    One of my questions for AST was, does the water in the tank need to be treated?
     
  15. peakbagger

    peakbagger
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    I didn't treat mine, Unless your water is really aggressive and would attack copper, I dont see a need to and dont remember any instructions to do so . I had to pull my tank cover after two years and the water was crystal clear. Its routinely heated to sterilizing temperature so nothing is going to live in it. The only weird thing is the water damaged the tie wraps used to make the nest of tubes easier to handle when its dropped in the tank. Hindsight is I could have put some stainless steel ones to replace them. They are not needed once the exchanger is in place but without them its a bundle of snakes to get in and out
     
  16. sardo_67

    sardo_67
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    so is yours a closed pressurized system?
     
  17. Fred61

    Fred61
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    It's a retired thick wall stainless 4 ft. diameter x 6.5 foot high chemical tank. It is unpressurized with two large coils for heat and DHW and 1 smaller coil in the bottom that activates when or if the boiler overheats. Tank water is heated by a 30 plate heat exchanger.
     
  18. NateB

    NateB
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    AST has youtube videos on how to assemble the tanks. I think they would be informative for you. It is call hotandcoldtv on youtube. I use an 820 heat bank. My system is pressurized, but the tank is not. The tank is just thermal mass. If you are looking at pressurized vs unpressurized from a cost perspective, I think it is about the same. The benefit of pressurized is you can store more heat, and unpressurized is you can modify the system without expensive tools. For example, I added a heat pump water heater to my tank for DHW in the summer. In a pressurized tank system that would have been a significant project for me, but unpressurized tank/thermal mass system. I was able to do it with a pipe cutter and some pipe glue.
     
  19. tom in maine

    tom in maine
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    Tom from AST here.
    Sorry I missed this thread. Been busy with things at the shop.
    If one of our tanks is sealed (including having the cap on the tube we use for checking level, there is very little evaporative loss and room humidity is not affected.
    That being said, sometimes things get missed during sealing. In most cases, it can be corrected after the initial assembly.

    We recently made a change on our tank liners. We are still using the same material but went 50% thicker. And also went to a liner that is folded in place.
    This eliminates welded corners which can be stress points. We mark the liners for easy installation. And they are perfectly fitted to the tank shell, so any variance in the tank size during assembly is not an issue.

    We also have changed over to stainless steel heat exchangers. These are stronger than copper and seem to tolerate pH issues that seem to affect copper DHW coils. AND, they are less expensive.

    If anyone is trying to reach us, my email is tom@americansolartechnics.com
     
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