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Indirect DHW tank recommendations for Prestige Solo 110

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Installed a (propane fired) TT Prestige Solo 110 in 2011, for central heating, intending to add an indirect tank for DHW in future.
2400 SF house with radiant subfloors on ground floor and full bath, panel radiators for remaining (1866 vintage) 2nd/ 3rd floors.

My current electric storage tank is beginning to fail, and I do NOT want another one…
At one time I’d considered the TT “tank in tank” model but am open to suggestions.
2 residents here, with occasional 1-2 weekend guests.

Well water here, latest test in April 2022: Iron 0.013 mG/L, Manganese 0.010 mG/L,Chlorides 16.9 mG/L, Hardness (CaCO3) 80mG/L, Nitrates <1 mG/L. These are “straight from the well” measurements, before the water is treated as follows:
sediment spin down ahead of pressure tank, pleated sediment, iron reduction, and carbon block filters, Watts TAC tank, ALL downstream of pressure tank.

1.5 baths (main bath has (2) 2.5 GPM shower heads), dishwasher. Clothes washer self-heats water and has only a cold water connection at present. Cellar laundry tub periodically sees HW use for cleaning garden tools, litter boxes, etc. All suggestions welcomed, especially from those familiar with the Solo 110 used for both heating and DHW. Thanks !

Comments

  • hot_rod
    hot_rod Member Posts: 22,382
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    Performance -wise I think you will fine all the brands of the same capacity perform about the same. A 40- 50 gallon should be adequate if you are currently using an electric tank of that size.

    Once you look at several brands pay attention to the water spec in their manuals (available online). If in fact you are out of range on any, officially you do not have any warranty on the tank.

    Over the years my best experience has been with the glass lined steel tanks. They are less sensitive to out of spec water. With stainless tanks, the chloride levels are the deal breaker.

    Most all the boiler and tank manufacturers have a choice now of stainless or steel.

    There are some tanks with lifetime warranty, read the fine print :) I think Viessmann offers lifetime warranty on their stainless tanks, built into the selling price, of course.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EdTheHeaterMan
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Thanks Hot Rod! There are quite a few options on the market……want to avoid the heavier units, due to a tight and awkward load-in here.
  • hot_rod
    hot_rod Member Posts: 22,382
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    The stone lined tanks will be heavy, 3- 400 lb range. But steel or stainless are manageable by one person 

    While there are dozens of brands available, many are made in the same factory or with the same tank heads, coils, etc

    It may come down to availability.
    Lochinvar, Bock, Bradford White, Ao Smith are some of the glass lined tanks, many models still built in the US.020

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    I’m leaning towards a Thermo 2000 Turbo Max (model 34 or 44, since my TT Solo 110 has a net output of 87000 BTU/Hr ), the head loss is fine, and my well water chemistry is within the acceptable limits.The counter-flow heat-exchanger design is appealing, since it will (theoretically) be more efficient than a storage type indirect. Thoughts? Thanks again!
    The WALL really helped me back in 2003, when I bought an 1860’s vintage house with single-pipe steam heat. I grew up in a house with hot water cast iron rads but knew nothing about steam….electrical engineering is my beat.
    You Guys (and Gals) are the best!
  • GGross
    GGross Member Posts: 1,075
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    I have sold Triangle Tube and Viessmann for quite a long time. Both tanks are quite nice. The Viessmann gets a bit pricey but they keep the 42 gallon model at a competitive price point (no built in aquastat though) both have a limited lifetime warranty to the original owner in a residential application.


    https://triangletube.com/products/smart-316-residential

    https://www.viessmann-us.com/en/products/vitocell/vitocell-300-v.html
    Alan (California Radiant) Forbes
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Thank You, GGross: I had been looking at Viessmann as well. Don’t want to say this out loud, but my TT Prestige has been in service 11 years this month, and its SS heat exchanger has been trouble free with this water. I have cleaned/descaled it twice.
  • hot_rod
    hot_rod Member Posts: 22,382
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    The Thermo 2000 is a reverse indirect. The tank holds the boiler water And a mass of copper coils hold the potable water. So it basically heats the cold water as it is flowing through the coils
    So it only stores a few gallons of DHW
    The energy is stored in the 30 or 40 gallons of boiler water 


    Same caution applies with hard water scaling



    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • flat_twin
    flat_twin Member Posts: 352
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    We have five years on our 40 gallon glass lined Bock indirect. The glass lined heat exchanger coil is large bore with quick recovery times even at 160 degree supply water temps. We don't run out of hot water even with consecutive showers.
  • Zman
    Zman Member Posts: 7,588
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    The TT Smart tanks have more than their share of failures. I am not a big fan of Amtrol's "self-clogging" coils. Your chlorides don't look bad to me, my vote would be the Lochinvar Squire 040.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Alan (California Radiant) Forbes
  • heathead
    heathead Member Posts: 234
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    When I looked at the tank in tank or the reverse indirect designs, I always though higher temperatures near the outer shell would mean more heat-loss. Probably so little it doesn't mater.
    Zman
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Thanks for all of your comments. The only thing that gives me pause about the Thermo 2000 Turbo Max is the carbon steel tank: I like the efficiency of the copper HX and (reported ) fast “recovery time”. Stainless has been a good bet here, while carbon steel, glass lined “big box brand” electrics, not so much. Again, thanks for your observations and advice, all welcomed. One cat sleeps in the cellar, and I’ve fitted her for a life-jacket ‘till we get this resolved…….
  • pedmec
    pedmec Member Posts: 994
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    the turbomaxx is an instantaneous. that is all boiler water sitting in the tank, not potable.
  • mattmia2
    mattmia2 Member Posts: 9,843
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    Because the tank is exposed to the closed system water, not the potable water, it won't rust through the way it would constantly seeing fresh potable water.
    MikeAmann
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Thanks! Yes I’m aware that the tank itself holds only boiler water, the exchanger holds the potable.
    So, the boiler water is NOT a corrosion liability, even if the tank is carbon steel rather than stainless? It is a “closed” heating system; I plumbed it in PEX-Al-PEX, the boiler loop is copper, the circulator pumps are cast iron, manifolds are EP
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    ….and the panel rads are steel…..
  • hot_rod
    hot_rod Member Posts: 22,382
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    I am a proponent of
    #1 good quality fill water, ph, TDS, hardness in range
    #2 add a hydronic. conditioner. Even with perfect fill water the conditioners give you film providers, oxygen scavengers and ph buffers should the DI water be low ph.

    With thin steel radiators and a large carbon steel tank, a hydronic condition plan conditioners would be a wise investment.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGross
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Thanks, Bob, that is a very good suggestion. When I first cleaned this system I’d researched cleaners and conditioners. TT had a specific recommended cleaner to flush the HX, which I did use.The Fernox cleaner I used for the system was OK with Uponor only because it wouldn’t remain in there, but the Fernox conditioner would play well with all components EXCEPT Uponor’s EP manifolds (think the O-rings could be damaged) so I was advised to use an alternative product.
    Time to clean the HX again anyway, and I will add the recommended conditioner. Thanks again!
  • pedmec
    pedmec Member Posts: 994
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    I personally like turbomaxx as i just installed 8 of them and they worked great. but my concern is the size of your boiler for a turbomaxx. As with any instantaneous hot water coil it depends on the ability of the boiler to maintain that 180 degree target as close as it can. lets say your supply domestic water temperature is 140 and you will temper it down with a mixing valve. for every gpm that you use, and i'm assuming a 80 degree temperature rise. you need:

    80 delta (60+80=140)
    1 gpm = 8.33 btu per degree rise
    80 x 8.33 = 666.4 btu gpm
    666.4 x 60 = 39,984 btu/hr

    Obviously this is a cold start. The problem becomes the recovery of the boiler water in the tank. You have to maintain that 180 to get the temperature rise never mind trying to use 3,4, maybe 5 gallons of hot water a minute. Instantaneous works best with higher output btu boilers as they can keep the boiler water temperature UP during high demands. Which is why i use tfi instantaneous hot water tanks in all the apartment buildings i worked on.

    my recommendation would be an indirect as you have storage of hot water. very little heat lose thru the jacket. you seem to be on top of the water conditions and with hot rods input with that a trouble free hot water system.
    mattmia2
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Hi Pedmec, thanks for your observations. I know the Turbomaxx is a different animal than a conventional indirect, but you sort of put it into perspective by calling it an “instantaneous” unit. The specs looked appealing, including the copper heat exchanger.
    At a minimum, we’d be drawing 5GPM with our 2 shower-head setup, from a propane fired boiler that is spec’ed at 87000 BTU/Hr flat out. The Viessmann Vitocell vertical units spec. well, although right now they seem to have a 30 day lead time. I can find very few complaints about them on-line. Thanks again!
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,361
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    Hi, Just to play with numbers a bit, you say 5 gpm with two showerheads. Modern showers are 2.5 gpm, so 5 gpm is total flow. A good percent to use is 70% hot and 30% cold for what comes out of a showerhead. That reduces your total hot flow to 3.5 gpm. Now if you wanted, you could install good lower flow, 1.5 gpm heads. That would mean your total hot draw would be 2.1 gpm. All that should make it easier to find equipment that will fill the need.

    Yours, Larry
    Alan (California Radiant) ForbesMikeAmann
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    Hi Larry: Thanks for the advice; you make a good point about ratio of hot to cold. The Turbomaxx and Vitodens each seemed to be (on paper) within the abilities of my TT boiler, but Pedmec seems to be saying that because it’s a reverse flow “instantaneous” type unit I might be pushing things to keep up with my minimum flow requirements.
    Will investigate lower flow shower heads, these have been here since 2012 and could be upgraded to low(er) flow units. My criteria is that boiler water to indirect should be no more than 180 F, potable output 140 F, tempered down to
    125 F output, which we currently use here. It’s only 125 to the kitchen sink and dishwasher, loses a little bit to the Floor. 2 fixtures (though I ran insulated PEX everywhere). The shower has an anti-scald temp valve which never lets us see more than about 112 F anyway (because I set it low). Thank you for your input and advice, I greatly appreciate it.
  • Zman
    Zman Member Posts: 7,588
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    In my mind, reverse indirects and condensing boilers with outdoor reset are not a perfect match. You will need to maintain the reverse indirect tank at a pretty hot temp in order to have instantaneous hot water.

    You also need to be meticulous in maintaining the anti scald valve because of the very high temps of the initial slug of water or during low flow conditions.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    And this (like that from previous contributors to this discussion) is information only the pros who have seen it can provide! My boiler does use outdoor reset for the panel rads (though my radiant floors are fed from a set-point mix valve, after much research, and advice from Warmboard’s engineer, American Wood flooring trade groups, etc and others). Thanks again. Either way I plan to keep a close eye on the anti-scald / tempering valve. Any recommendations on one? Triangle Tube recommended Apollo / Conbraco products back when I took their maintenance course in 2011…
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    The Vitocell EVIB-300 42 gallon tank was installed last Wednesday / Thursday. Hired the local mechanical contractor (who also tag-teamed one of our Unico cooling systems with me here, back in 2015). They did an excellent job, and, so far it works very well. Installers gave me a little good-natured ****: “if we bid the job with all this stuff we’d never have gotten it…” because I gave them Webstone ball valve / drain/fill combos, plus unions, on DHW and Boiler supplies and returns. I said “boys, it doesn’t matter, ‘ cause I’m buying, and I like easy access to everything…”
    The only “squirrley” part was getting the (TT) 12k NTC thermistor into Viessmann’s tank temp. sensor clamp, and keeping it there.
    Verified it’s accuracy with a thermocouple on the DHW Hot output, and my Flir camera. Wife commented that her shower stayed warm all the way through. It’s the little things….thanks to everyone for your advice and recommendations.
    MikeAmann
  • Novagen_Ed
    Novagen_Ed Member Posts: 45
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    (I might have mis spelled “squirrelly” :D )