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thermal mass

I've seen a number of systems like this in WI, and I really don't see an advantage. By using your dom tank coil, or with triangle tube the outer tank, you've increased the thermal mass of your primary loop by a few gallons at best. granted you will get some exchange within the domestic tank back to your smaller zones, but when those BTU's are gone you ask your boiler to go to high fire to replace them. The real advantage to a mod-con is the condensation at low return temperatures. Using the domestic tank not only depletes your ability to provide plenty of hot water,it costs more to run those small zones. Just install a 50 gallon tank in the primary and deplete that before asking the boiler to fire.


  • Big WillBig Will Member Posts: 394
    Thermal mass

    I have been putting together systems using knight boilers with Superstore water heaters. The systems are all zoned some of the
    zones have been quite small. So my thought is to change my primary primary loop to include the indirect as a thermal storage tank to reduce cycling. The inderect would need a mixing valve but my system runs a max of 160 deg for design temp. It seems that this would help the boiler on the days when the first floor bathroom is the only zone calling. I read the posts here a lot and have not seen someone do this. Am I missing something.
  • CouderayCouderay Member Posts: 314

    You would only be gaining the volume of the coil in that style tank. They do make tanks where the tank is in the boiler loop and the domestic runs thru a coil. Could be wrong here, but it might not work as your thinking.
  • jp_2jp_2 Member Posts: 1,935
    would work

    you could use the superstore as a buffer, as long as theres decent delta T you have the whole tanks volume at your use.

    don't quite understand your piping scheme though?

    I would tie those little zones together though.
  • kamneykamney Member Posts: 15
    Buffer Tank

    "Am I missing something?"

    Yes... with outdoor reset, you will be looking at supply temps at or under 100° in the shoulder seasons. You should keep the domestic's temperature better separated. Why not use a buffer tank at your P/S intersection?
  • hot_rodhot_rod Member Posts: 13,518
    I have done a few

    my favorite one was done with a Triangle Tube indirect tank. I used the inner tank 40 ga capacity as the boiler side. The outer 5 gallons or so was a glycol snowmelt. The 140 Munchkin piped right to that inner tank. No primary secondary loop, just boiler to tank.

    An indirect with coils as the buffer doesn't buffer quite as well as the tank capacity but it does help.

    On another one I have the Ultra boiler connected directly to the coils of an 80 gallon Peerless indirect tank. I run it at 150F. Then the radiant pulls off closely spaced tees with a 3 way thermostatic to mix down to 120F. Three years on that system without a problem.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Big WillBig Will Member Posts: 394
    believe me

    I would love to tie the zones together or slave them so they couldn't run alone. These are high end homes in sanfransisco and the coustomer could care less about my concerns. great peaple but give them what they want and dont ask why.

    to the question about the domestic water getting to cold. If I wire the tank thermostat to the DHW termanal in a knight it will run a higher temp until the tank is satisfied. With the mass of the tank and the fack that the sysytem is staple up Running at a 110 deg minumum I think that won't be a problem.
  • big willy big willy Member Posts: 92
    another job

    So I am going to use a super store 60 as a buffer in one house in SF. I have another home where I am worried about short cycling but I am using a amtroll 80gal that has 3/4" lines for the H/X this is more head than I really want for my boiler loop. I have looked around and dont see much in the way of small tanks for thermal storage that have large enough water ways.
  • scott markle_2scott markle_2 Member Posts: 611
    HX buffer?

    Why use a coil at all , what is the reason for a HX?, why not just use a tank with multiple tapings or an electric tank with the elements removed. I could imagine using a two coil indirect tank and pulling heat from the tank via extra coil. But I don't see how a single coil indirect could supply dhw and heat unless you are talking about an open loop system.

    The only reason I can see for hx separation would be if there was glycol involved and you wanted to keep it out of the boiler loop.

    Edit: I reread the original post, did not understand the idea at first. I don't think this will offer much buffering once the dhw tank reaches 160 which it will do frequently from it's connection to the primary loop and the other larger zones. It's also it's wasteful to keep the tank this hot. As already mentioned if the system is full odr reset (as any condensing unit should be) your primary loop temps. will be to cool much of the time.
  • Al Corelli_2Al Corelli_2 Member Posts: 395
    What about...

    Hows about a Boiler Buddy?

    Saw these at AHR. They are made for Boiler Buddy by the same people that make Ultra SuperStors. They look a heck of a lot like them, so I asked the guy there and he told me they make the tanks for him.

    I am not affiliated with them, I do not receive money, nor beer from these guys. I just think the product has merit.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    Al Corelli, NY

  • big willy big willy Member Posts: 92
    that my friend

    is just the thing I think that would fit the bill nicely. I will call for a quote when the normal peaple wake up.
    Also if they do offer you beer take it. Wink Wink.
This discussion has been closed.


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