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How to size Weil McC indirect tank?

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scott w.
scott w. Member Posts: 208
Current tank has to be replaced. Capacity is a 45 gal tank with 8. WM does not make this size tank any longer.   Old tank provided adequate hot water.  Do I go up a size or shrink it down? The boiler is an ultra.  See series 2 and three advertised. Much difference in the two?

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,037
    edited May 2023
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    You will need to determine the amount of hot water required. One way is to calculate your requirements based on normal usage using a chart like this to determine the first hour rating required. With that information you can select the tank based on the specifications of the tank you are selecting.

    Most indirect tanks have some sort of capacity based on the BTUh output of the boiler it is connected to. make sure the connecting piping is large enough to transfer the capacity. I have found 140K BTHh boiler connected to an indirect with 3/4" supply and return pipe. The only thing is that 3/4" copper can only convey about 40,000 BTUh. (4 GPM @ 20° ∆T) you might be able to squeeze more than that but it might be a little noisy.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    random12345
  • JohnNY
    JohnNY Member Posts: 3,231
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    Or you can treat this like an EDR calculation. The surface area of the heat exchanger on the Gold Plus 60 is 20 square feet/EDR with a 46-gallon domestic water capacity. If you can match those values closely, you'll match your hot water recovery and output. Indirect water heater published ratings are an exercise in smoke and mirrors based on usage flow rates, incoming domestic and boiler supply water temperatures, available BTUs from the boiler side, stored water temperatures, and capacity.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    mattmia2
  • Karl Reynolds
    Karl Reynolds Member Posts: 63
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    The Gold Plus tanks were re-branded Triangle tanks. A model Smart 50 would be a direct replacement, assuming that you were satisfied with the performance of the existing tank.
    Larry Weingarten
  • JohnNY
    JohnNY Member Posts: 3,231
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    The Gold Plus tanks were re-branded Triangle tanks. A model Smart 50 would be a direct replacement, assuming that you were satisfied with the performance of the existing tank.

    Was that the tank-in-tank design, popular in its time? I think that fell out of favor. For what it's worth, the Turbomax design is intriguing.
    https://www.thermo2000.com/en/
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
  • Karl Reynolds
    Karl Reynolds Member Posts: 63
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    Triangle Smart series indirects are the "tank in tank" design. Still being made, still selling 15-20 per month . Serving high-end homes in the Colorado mountains, the majority that we sell are 80, 100, an 119 gallon
    models.
  • JohnNY
    JohnNY Member Posts: 3,231
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    Triangle Smart series indirects are the "tank in tank" design. Still being made, still selling 15-20 per month . Serving high-end homes in the Colorado mountains, the majority that we sell are 80, 100, an 119 gallon
    models.

    Great. They worked well as far as I know. I think there was an issue with how to drain them but "How often does that come up?" was always my reply to that.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
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  • Karl Reynolds
    Karl Reynolds Member Posts: 63
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    Best way to drain is to plumb a Schrader valve into the piping and blow them out with air. My first generation soft jacked Smart 60 is twenty-two years old. Never had to drain it and still cranking out more than adequate hot water for a family of six with four teen agers.
  • mattmia2
    mattmia2 Member Posts: 9,734
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    Dies the rebanded version have the lifetime warranty to the original owner and are you the original owner?

    Just remember, no one ever complained about too much hot water.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,037
    edited May 2023
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    mattmia2 said:

    Dies the rebanded version have the lifetime warranty to the original owner and are you the original owner?

    Just remember, no one ever complained about too much hot water.

    Let me be the first then>>>

    Darn water heater makes too much hot water... we never run out... How am I supposed to curb those teenagers from wasting all the energy... if it would only run out when they were in the shower, that will teach 'em.

    I guess this makes me the exception to the rule.

    I always thought I was exceptional!

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    pecmsgmattmia2CTOilHeat
  • mattmia2
    mattmia2 Member Posts: 9,734
    edited May 2023
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    Larger well insulated tanks can be more efficient too. The standby losses in a well insulated tank are less than the losses involved in heating up the boiler and having it cool down again so storing more water and having fewer cycles for small and moderate loads is more efficient. If it is a mod con you might even be able to run it in its condensing range(but I suspect that it is a conventional CI boiler since it is a WM branded tank)

    EDIT: I see it is a WM Ultra so it is a mod con so the losses involved in heating the boiler to make hot water are less but still not trivial.
  • scott w.
    scott w. Member Posts: 208
    edited May 2023
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    Thanks all for the replies.  The current WM  tank  I think leaks internally at times.  Would like to replace current  WM tank again with WM. Unfortunately WM does not make the same size hot water tank any longer.

    I hear a strange noise inside the tank like a drip drip drip sound with a hiss like the water is hitting something hot. The sound does not occur all the time. Never happens when the plummer is visiting.  The current tank works flawlessly but did notice over time I needed to turn up the tempature dial a notch or two over the last 12 years to fill the spa tub. Only use the big tub after a day  of difficult  yard work such as digging,  planting and trimming .

     Since I am hearing the drip drip drip, need to be proactive and change the tank out before it quits on a Friday night.   Just one person in the household. Only wash clothes in cold water and normally use the dish washer right before bed time. Trying to figure out if I can go down in size and still have enough hot water for any overnight guests.   Rare that guests take a shower at same time or right in a row. The recovery on current tank is well within about 15 minutes.  Maybe can save a few bucks on the summer gas bill if going down in size of hot water tank. Still want close to the same functionality as I have.

    I found that if you have someone taking  way to long of a time in the shower, ( a half hour is ridiculous) slip to the basement and slowly slowly turn off the valve to the hot water tank. A quick  exit from the shower will happen shortly. Works every time and no one is the wiser. Used this idea to get my  kid sister out of the shower when I needed to get cleaned up quickly and get out of the house on a Saturday night.
  • JohnNY
    JohnNY Member Posts: 3,231
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    There's nothing in that tank that would make an internal dripping sound so I wouldn't let that be the reason to change the tank. But, you know. Do whatever makes you happy.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 9,734
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    JohnNY said:

    There's nothing in that tank that would make an internal dripping sound so I wouldn't let that be the reason to change the tank. But, you know. Do whatever makes you happy.

    But it could be something like scale rubbing on something as it expands and contracts(or maybe even the tank on the foam or the plastic cover). I think i would try cleaning the DHW side with acid before buying a new tank. Actually, thinking some more, I would clean it out with acid, mainly because reduced output is reported, then I would pressure test each side and let it sit over night if possible, that will tell you if there is a leak somewhere.

    A smaller tank is likely to cost you a bit more in fuel. The smaller tank will run more and shorter boiler cycles to keep it hot and there are some loses as the boiler gets up to temp at the beginning of each cycle and as heat that is in the boiler and the water that doesn't get transferred to the tank after the cycle ends is lost to the ambient air.
  • Karl Reynolds
    Karl Reynolds Member Posts: 63
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    With the tank-in-tank design, the flexing of the inner tank between heating and cooling cycles is supposed to prevent scale build up, in theory. Again, that is a Triangle Tube Smart tank in Weil Mc Lain clothes. The equivalent in Triangle is the Smart 50. You could likely get away with a Smart 40 or even a Smart 30 based on you habits posted above.
  • tim smith
    tim smith Member Posts: 2,765
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    I really like the Lochinvar SIT050 as long as single wall is ok in your jurisdiction.