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Hot water tank temperature setting

tkos115 Member Posts: 87
I was wondering what the temperature setting should be for a hot water tank that is heated from my steam boiler. I may be mistaken but it seems to be set at 160F degrees. I might be looking at the wrong device but the one im looking at is on the side of my boiler, and when the boiler turns on to heat the water, if I turn it down it shuts off. I don't see any other controls on the tank other than what appears to be a pressure sensor.

Should this be set at a different setting, some people I was talking to think it should be set closer to 120F but I wanted to get some other options.

Thanks for your time and help all!


  • Jamie Hall
    Jamie Hall Member Posts: 19,380
    To be reasonably safe from bacterial contamination in the hot water, the hot water tank should be held at 140 -- not less. The 160 setting is most likely the aquastat for the boiler, which will ask it and the pump for the tank to run if the temperature is less than that, or rather less than that less any differential. Hopeuflly that is maintaining the tank at 140.;

    Now. 140 is hot enough to be actively dangerous from scalding. Therefore, to make sure that people -- particularly older, mobility impaired, or children -- there should be a mixing valve on the outlet of the tank which brings the water actually delivered to the taps and what have you down to 110 or so.

    A further minor advantage of all this is that it effectively increases the tank size.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,547
    edited June 2020
    The water temperature is controlled by a thermostat in or on the side of the actual tank. Think of it like a room thermostat for the water. You put 160° water from the boiler in the radiator inside the tank of water to make it hot. once the tank gets to the temperature set on the tank thermostat, the burner and circulator pump stops.

    Another way to look at it is...Steam is over 212°F going in to the pipes that heat the rooms... That does not make the rooms get too hot. The room thermostat turns off the burner so the boiler stops making steam when the thermostat is satisfied.

    The reason the setting on the boiler control is 160° is because that is all you need to efficiently heat the water in the tank. If you let the burner get any hotter to make hot water in the summer... you could start to make steam and heat the radiators. Now that would substantially effect the Air Conditioner performance.

    So look on the water tank for some type of dial or control or door or cover-plate. That is where the water temperature is set.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org