Simpler Heat storage setup???

Vinced Posted By Vinced, Feb 12, 2018 at 12:39 PM

  1. Vinced

    Vinced
    Member 2.
    NULL
    

    Feb 17, 2008
    67
    3
    Loc:
    Central Wisconsin
    Ok, I've been around here since 2007. I've owned a outdoor wood boiler for 10 years and ever since I've read about adding heat storage I've been fascinated by it. The only problem is everytime I start reading about it and how to set it up I just get confused on how to set it up. My current set up is a primary/secondary piping and works great. My outdoor wood burner is a unsheltered type and is 40ft from my house in a 8'x12' shed. My primary loop goes from my shed to my house and over to my shop and back to the shed. I have a Taco 011 pump on my primary loop that runs all the time. In the house I have a side arm heater on the primary loop heating my electric water heater. It then runs over by my forced air LP furnace where I have 2 tees 6 inches apart with a Taco 007 pump on one tee controlled by a thermostat and a heat exchanger in the plentum. I have the same setup in my shop but don't use it much in my shop. This was all designed by a guy that designs heating and cooling systems for a living. My house is 1100 square feet and my unfinished basement is 28'x28'. I've come to the conclusion that I would need at least 500 gallons of storage to make it worth while. My boiler is a pressurized system and I'm thinking of making a wooden heat storage tank with the proper liner that is unpressurized. I've seen many storage tanks built this way and looks like the easiest setup to build. There is no way I can get a 500 gallon propane tank in my basement. Plus if in the future when I'm older or whatever and I decide not to have the boiler setup anymore it would be easier to remove it.
    So after all this babbling about my current setup now comes the question. What would be the simplest way to plumb a wooden rubber lined heat storage tank into my system? I seem to think if I build a copper piped heat exchanger and install it in the unpressurized tank then just plumb it into my primary circuit. Why wouldn't it work? I really want to batch burn has I can see all kinds of positive things about it. Like I said, I understand heat storage and how it works and I can see the advantages of it, but I just can't figure a good, simple, and cheap way to plumb it into my system.
     
  2. NateB

    NateB
    Burning Hunk 2.
    NULL
    

    Mar 5, 2013
    247
    67
    Loc:
    South Central Pennsylvania
    https://www.hearth.com/talk/threads/primary-secondary-piping-for-boilers.11837/

    Check out the first picture Bob Rohr post it is a good example of primary secondary plumbing. Your boiler, water heater, and storage, should be secondary loops. The circulator to your storage tank would be controlled by the: thermostats, tank temperature, and primary loop temperature. I use an aquastat, and a solar water heater control.

    If you want my 2 cents on the tank and HX buy one from American Solar Tech. The reason I say that is by the time you build it and it does not work well, and rebuild it to work better. You could just get one from Tom in Maine. I considered building my own tank, and I considered what 820 gallons of water would look like in my basement, and I thought maybe I should go with some who has done this before.
     
  3. Vinced

    Vinced
    Member 2.
    NULL
    

    Feb 17, 2008
    67
    3
    Loc:
    Central Wisconsin
    I've studied that diagram in the past. I understand the plumbing part where I get lost is in the controls. You mention "solar water heater control"? Do you have a reference to the part your using? Can you give me a brief run down of how your controls work?
     
  4. NateB

    NateB
    Burning Hunk 2.
    NULL
    

    Mar 5, 2013
    247
    67
    Loc:
    South Central Pennsylvania
    https://www.supplyhouse.com/Honeywell-L6006C1018-High-or-Low-Limit-Circulator-Strap-On-Aquastat-65-200F-range-5-30F-Adj-Differential-1738000-p

    This is the aquastat is powered when a thermostat calls for heat via a relay. (above 140 turn on the tank circ, below 140 turn on the oil boiler circ)

    https://www.supplyhouse.com/Tekmar-156-Difference-Setpoint-Control-On-Off-7954000-p

    I use this control to put heat into the tank. It has 2 temp probes one for the tank, one for the primary loop after all the loads, but before the tank. If the water is 20 deg warmer the tank circ turns on.

    Relays
    https://www.supplyhouse.com/Functional-Devices-RIBU1S-Enclosed-Relay-10-Amp-SPST-Override-w-10-30-VAC-DC-120-VAC-Coil

    I used 4 for 2 zones. One to feed the aqua stat, and one to turn on the zone circ.

    Hope this helps
     
  5. Karl_northwind

    Karl_northwind
    Feeling the Heat 2.
    NULL
    

    Feb 13, 2012
    496
    85
    Loc:
    Central Wi.
    Hi,
    Sometimes with an OWB storage is worth it, sometimes it's not. It really depends on the type of boiler, what sort of efficiency it burns at and how well it shuts down. If the boiler is crap efficiency and only runs at 40% if it's running well, don't bother. that is a function of boiler design, wood selection, and air control.

    if on the other hand it's capable of running at 65-70% when tuned and running well, storage might gain you something. pressurized storage is a pain, unpressurized storage is a pain.

    what sort of boiler is it? if it's outdoor and pressurized in this neighborhood I'm going to guess that it's an aquatherm. they all seem to be pretty bad combustion wise, and serious forest eaters, in which case adding storage probably won't get you much. the reason everyone here on hearth loves storage (and rightly so) is they are mostly burning low-mass gasifiers, which aren't designed to run without storage (mostly) and will run 80-90% efficiency when doing it right.

    If you smell a lot of "mostly" coming off my post, it's because the exception always is going to prove the rule here, as soon as I make a claim, someone will be doing it differently.

    There is a whole lot of "your-mileage-may-vary" in this solid fuel combustion world.

    cheers.
    karl
     
  6. Vinced

    Vinced
    Member 2.
    NULL
    

    Feb 17, 2008
    67
    3
    Loc:
    Central Wisconsin
    Thank you, yes this helps a bunch!
     
  7. Vinced

    Vinced
    Member 2.
    NULL
    

    Feb 17, 2008
    67
    3
    Loc:
    Central Wisconsin
    Yes I do have an Aquatherm. The reason I'm wanting storage is so I'm not tied to this boiler. I've operated this thing for 10 seasons now and have a pretty good handle on how to run it. My first season I used close to 10 full cords. I now use 5-6 full cords. This reduction in wood has come from learning the boiler and knowing how much wood to feed it. I also learned the first year that seasoned wood is the only kind of wood to burn. That being said, I'm not expecting any effiencey gains by adding storage but just convience in operating it and not feeling tied to it all winter. Take this week for example. Monday mourning got up to outdoor temperature of -1F. Tomorrow (Wednesday) is forecasted to be 42F. With temperature swings like this I'd be able to skip a day of adding wood or having a fire. Plus when it gets above 32F my stove idles too much and likes to get bad creosote build up.I know I can adjust the differential on my aquastat, but don't care too. I know my boiler will never be has efficient has a gasifier, but a little more convient would be nice.
     
  8. Karl_northwind

    Karl_northwind
    Feeling the Heat 2.
    NULL
    

    Feb 13, 2012
    496
    85
    Loc:
    Central Wi.
    If you have made that sort of improvement on an aquatherm you have done a lot! For cheap storage I'd do a flooded tank with either 2 pumps or a 4 way valve to change direction for loading/unloading. A copper coil will deliver and remove the heat nicely. you'll be looking at least at a couple thousand dollars by the time you're done. or you can buy a tank from american solartechnics for a couple thousand, plus another thousand for the coil/pumps to do it right. I'd consider a couple of their 200 gallon soft tanks for the ease and cost, especially if this addition is likely temporary. I have one for my small solar thermal and really like it. it's held up well over the 7 years I've had it.

    I usually size coils out of 1/2" copper, 60 foot loops, one per GPM you need to flow. 50 feet (splitting a 100 foot coil in 2) works ok too if efficiency is not too important. I usually get the best price on 60 foot coils though,so that's what I use.

    karl
     
  9. Chris Hoskin

    Chris Hoskin
    TarmSalesGuy 2.
    NULL
    

    Aug 29, 2008
    541
    67
    Loc:
    Lyme, NH
    Sounds like thermal storage will be a nice addition to your system. I recommend you do some math around how many btu you would like to store and how many gallons that takes. The size of your firebox (cubic feet or pounds of wood) will also play into this. My guess is that you would be happier with 1000 gallons than 500 and if you are building the tank that is not such a big deal (same copper coils regardless of tank size). Keep us posted. Chris
     
  10. Fred61

    Fred61
    Minister of Fire 2.
    NULL
    

    Nov 26, 2008
    2,347
    457
    Loc:
    Southeastern Vt.
    I don't want to be a spoiler here and hope I'm not but you said in your opening post that you would like to batch burn. Although this works for many it doesn't work for everyone. All the stars need to align in order to make use of stored heat. You mentioned that your distribution is a water to air HX. With that type of distribution you may not be able to use all the stored BTUs because of the higher temperatures needed to provide comfortable air.

    Those using radiant are able to make the best use of storage along with those with adequate convectors that make use of lower temperature water.
     

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