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Indirect DHW tank recommendations for Prestige Solo

Novagen_EdNovagen_Ed Member Posts: 30
We heat with a Prestige Solo 110: old type, MCBA controller, Propane fired. Outdoor reset water is mixed down to 114 degrees to feed Pex-Al-Pex in Warmboard . Remaining loads are Runtal panel rads that are fed ODR water from between 135-175 degrees. 10 degree design temp. here in northern Chester county PA.
A mixture of the two types of radiation is fed from all calls for central heat, to insure a minimum load of around 23K BTU/hr on the Prestige.

The plan for this year was to connect a "Smart" series tank to the unit for DHW, and ditch our electric storage unit.
Now I see the "Ginius" tanks advertised, all stainless construction. We have well water that falls within all of the requirements listed by ACV.
The Smart has had random issues reported, the Ginius is pretty new.....
(BTW, just cleaned the Prestige HX this year, first time. Efficiency improved a bit, no nasty surprises, except a slowly
leaking gasket on the outflow side of the HX, now replaced.)

Any recommendations are greatly appreciated. Thanks, to the most knowledgeable bunch of hydronics folks I'm aware of.
Ed

Comments

  • hot_rodhot_rod Member Posts: 11,378
    Ask around the area and see what types of tanks last the longest. In some water conditions the glass lined tanks last longer.

    Peak around the back lots of local plumbing wholesalers :)

    Chlorides are the number to watch with stainless tanks.

    if your water falls within the manufacturers spec, warranty will not be a problem.

    I suspect you will find equal thumbs up and thumbs down for almost any brand.

    The stone line tanks seem to last the longest from my experience.

    Higher tank operating temperatures generally reduce life expectancy, as minerals precipitate out more at elevated temperatures.

    140F should be an adequate tank temperature, lessen bacterial growth potential at 140F. Size the tank properly so you do not need to run higher temperatures then 140°
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Novagen_EdNovagen_Ed Member Posts: 30
    Thank you Hot Rod, greatly appreciate your advice.
    What's the best way to "extrapolate down" from the manufacturer's reference boiler temperature (usually 180 or 200 deg) to determine tank size for a minimum peak, first hour and continuous flow using a reduced boiler temperature?

    Thanks again
  • hot_rodhot_rod Member Posts: 11,378

    Thank you Hot Rod, greatly appreciate your advice.
    What's the best way to "extrapolate down" from the manufacturer's reference boiler temperature (usually 180 or 200 deg) to determine tank size for a minimum peak, first hour and continuous flow using a reduced boiler temperature?

    Thanks again

    Some manufacturers have or can calculate the outputs at various BTU inputs, temperatures and tank storage temperature desired.

    Some indirect tank manufacturers show performance at two or more stored temperature conditions, shown below is a Dunkirk reverse indirect.

    Thermo 2000 makers of the Turbomax have a nice software simulator, not sure if reps have access or just the factory? Here is an example of one of their tanks at low SWT.

    The program allows you to input boiler BTU, boiler SWT and DHW in and out temperature.

    Keep in mind this is a reverse indirect, boiler water in the tank, DHW in the copper coils. Nice for buffering and suppling DHW.
    I suspect the Dunkirk is a re-badged unit.

    It's a surface area game, the more surface area the better the performance, a dual coil indirect with coils piped in series is another way to get a low SWT performer. Look for a large coil diameter tank if you series the coils.

    http://www.thermo2000.com/pdf/en-US/specs/turbomax_43_en.pdf
    Screen Shot 2019-05-17 at 8.54.31 PM.png
    1822 x 1526 - 543K
    Screen Shot 2019-05-17 at 9.01.46 PM.png
    972 x 1156 - 1M
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • HVACNUTHVACNUT Member Posts: 2,120
    edited May 18
    Did TT finally put the Smart tank out to pasture? Man I hope so. The Ginius looks to have the conventional coil HX of most indirect water heaters.
    With well water, I believe that a stone lined tank like one offered by Vaugn would be best. We can assume regardless, a water filter system is in place?
  • hot_rodhot_rod Member Posts: 11,378
    Depends also on how much DHW you want or need. You have an electric tank now? What size? Unless it is 75 or larger I think any indirect will perform as well, better recovery no doubt.

    If you have large, fast fill tub loads, a larger tank volume give you dump capacity.

    Indirect recovery or instant production would be based on the 80,000 or so of actual boiler output capacity you have available. Efficiency of mod cons goes downs you know, when you run them 180- 190 for quick DHW recovery.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Novagen_EdNovagen_Ed Member Posts: 30
    Thanks for all of your comments. To address a few of them:
    Electric water heater is a 50 gallon unit (we had an 80, when it failed under "lifetime warranty" this was the manufacturer's replacement offering... ;) ).Recovery time is not stellar, plus we're adding standby power here next year, and the electric storage unit seemed like the first logical thing to remove.

    Well water here is filtered for sediment, iron reduction (iron content is low, around 0.010 ppm, this just hedges our bets) and then finally carbon block. Removed the old softener unit, no desire to put a new unit in. May add a Watts OneFlow to the system. We have moderately hard water (low 80 ppm each test). Ph is about 6.75

    Old top-loading water hog clothes washer was replaced by a front loading Asko, 240 volt, no hot water line, heats its own water. Dishwasher is Energy Star rated but has a hot water line. Otherwise a pair of 2.5 GPM shower heads and the usual stuff in a 1.5 bath home.

    I will look at the stone lined tanks. The Prestige and clothes washer each have stainless in them. Washer drum looks good, Prestige HX had only moderate scale when I cleaned it after 5 heating seasons (it was initially filled from our well, as were several radiant loops added in 2013).

    I have read mixed reviews of the Smart, Ginius doesn't have a track record yet (though I like that it's completely stainless), and I know there are lots of other choices out there. I considered the TT product first because of its low head loss, and, 'cause my Prestige has been trouble free since I installed it in 2011.

    Yes, I bought the Prestige for it's ModCon efficiency, and have no desire to run it at 180-200 F just for DHW. Sounds like bigger tank is the answer here.

    Thanks again, everyone, additional feedback and suggestions always welcomed. I'll post pictures when we install the unit, whatever it ends up being.....
  • modconwannabemodconwannabe Member Posts: 46
    edited May 20
    Hey Novagen, I'm a homeowner in northeast, have had a similar setup to you for 4 years now--TT prestige solo 110 primarysecondary, ODR, with 3 types of emitter--underfloor radiant, steel panel rads and cast iron radiant (each on different floor). We have a smart60, serving 2 apartments and seems either perfect or oversized for average 6-8 people (2 little kids). I have never run out of hot water with any combo of 2 people showering, or filling a tub with the dishwasher running and the heat cycling, mix and match that as you please. I keep water temp at 132 (and use the anti-legionnaire setting) and it rarely goes above 140 degrees for heating in the winter. The recovery rate has been plenty to handle all that. This link discusses the math behind what to expect (similar to above) but truly I think we'll replace with a 40 gallon when this thing expires some day (hopefully many years from now). https://www.contractormag.com/columns/yates/size-matters-indirect-water-0509
  • Novagen_EdNovagen_Ed Member Posts: 30
    Hi Modcon (hope you don't mind the contraction):

    Good article that you linked, thanks.
    I have had the feeling that a Smart 40 or Ginius 45 would be more than enough, even when we have a guest or two here for the week.
    Our highest demand scenario is a string of morning showers when guests are here. Otherwise, it's two of us, and we run the dishwasher late in the evening, when other HW demand is about zero. Plus it's better for the septic system's burden, IMO.

    Thanks for your "real-world" report of 6-8 folks getting by on a Smart60, with the mix of heat emitters you have, and average water temperature used ; much appreciated.

    I'm gonna assume you have the Smart set up for "priority" call, correct?

    Thanks again,
    Ed

  • modconwannabemodconwannabe Member Posts: 46
    It was setup as priority but then I turned it off at some point as there was no need and it was cold out and I wanted the heat up fast after the heat had been off while we were out of town;)

    I don't have the numbers in front of me, and there are a lot of variables I won't pretend to fully understand, but I believe the solo 110 is able to replace hot water at something like 2-4 gallons per minute, and our shower heads are all 2gpm, and our storage temp is like 132 or something. So even with no replacement from the boiler, with 2 showers going that's 30 minutes of hot water at minimum (in fact more since the water is mixed down by a third to ~100 degrees, minus heat loss along the line). It would suck to put in a 40 and have it be too little, which is why we oversized to 60, but check what the real world flow would be at maximum and do your numbers see what you get!
  • ZmanZman Member Posts: 4,855

    It was setup as priority but then I turned it off at some point as there was no need and it was cold out and I wanted the heat up fast after the heat had been off while we were out of town;)

    I don't have the numbers in front of me, and there are a lot of variables I won't pretend to fully understand, but I believe the solo 110 is able to replace hot water at something like 2-4 gallons per minute, and our shower heads are all 2gpm, and our storage temp is like 132 or something. So even with no replacement from the boiler, with 2 showers going that's 30 minutes of hot water at minimum (in fact more since the water is mixed down by a third to ~100 degrees, minus heat loss along the line). It would suck to put in a 40 and have it be too little, which is why we oversized to 60, but check what the real world flow would be at maximum and do your numbers see what you get!

    In this case you can figure the gpm capacity this way
    Btu/hr= delta t * gpm * 500.
    If your boiler has an output of 96,000 btu/hr and your are raising water from 40-110 degrees...
    Gpm = 96,000/70/500 = 2.74 gpm
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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