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By design hot water temp fluctuations

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STEAM DOCTOR
STEAM DOCTOR Member Posts: 1,968
Hi. Received call from potential customer. He is building house from scratch. He wants different hot water temps, different days of the week (don't ask why, long discussion). Is such a thing possible? Indirect with two auqastats controlled by timer???? Any thoughts or ideas would be greatly appreciated. FWIW, he is not looking for anything tankless. Its basically a weekday, weekend thing.

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  • ratio
    ratio Member Posts: 3,626
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    A T775 with a schedule to set the temp back would do it.
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    Thank you @ratio. Will give a look. New world for me.
  • hot_rod
    hot_rod Member Posts: 22,144
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    A motorized mixing valve? Maintain tank at 140F plus for legionella protection, motor valve to desired temperature.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    @hot_rod. Thanks for the suggestion. I am looking for something programmable. To allow for different temps on weekdays and weekends. Not sure if zone valve would accomplish that. My ears are open. Thanks.
  • hot_rod
    hot_rod Member Posts: 22,144
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    It's probably overkill but the Caleffi Legiomix allows you to program in a high temperature mode for legionella protection.
    It watches both supply and reciurc return for assurance, somehow you would need to use both sensors.
    Does the system have recirculation?

    https://www.caleffi.com/sites/default/files/file/h0002997-05_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    Thanks Hot Rod. Will take a look. System doesn't exist yet. They are building house from scratch.
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    Don't have any details or plans. I am assuming they are open minded.
  • hot_rod
    hot_rod Member Posts: 22,144
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    Without knowing his intent, it's hard to say which option would be best, but you have a number of workable options. Does he want a quick switch, or could the tank be depleted down to the lower temperature?

    If you do it with valves, they all need to be low lead of course.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    I think that he would prefer something that adjusts tank temperature
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,837
    edited May 2020
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    L4081 and L6081 controls have 2 sets of contacts with one sensing bulb. This is really old school but with the proper wiring design you could change the temperature with a switch upon arrival on the weekend, then return the switch to low temp on Monday..



    For automatic control, an Intermatic timer could be implemented.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics