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Not enough hot water..

Looking for some opinions.

I have a customer who we installed a bosch zbr 151,000 BTU boiler this summer.  He did alot of research before buying and was unsure if he wanted to have a superstor 45 gallon or 60 gallon indirect water heater attached to the system.  He opted not to have the combi unit installed due to his high water demands and thinking it would be a good idea to have a 45 gallon head start.

His problem is that he sometimes runs out of hot water.  He used to have an atmospherically fired 75 gallon unit.  My suggestion is to go to the 80 gallon superstor just to make sure.  He wants to know if we could add an on demand water heater to supplement during high demand but not sure that's a good idea.... or how to marry the two in the correct way could this or should this be done??



  • NYplumber
    NYplumber Member Posts: 503

    What is the temperature of the indirect, is it on priority, and what is the boiler water circulating through the indirect on a call from the dhw aquastat?
  • SWEI
    SWEI Member Posts: 7,356
    Atmospherically fired 75 gallon unit

    what was the burner capacity on that unit?
  • Tim Schram_2
    Tim Schram_2 Member Posts: 17
    more info

    The old unit was a 75,000 but burner. The new one is set for domestic priority at 130 degrees using a thermistor in the tanks well connected directly to the boilers circuit board. I also tightened up the differential on the boilers dhw programming
  • SWEI
    SWEI Member Posts: 7,356
    Large loads

    Is there a large soaker tub or whirlpool bath?  A multi-head shower?

    Following an indirect with a tankless can work well if the tankless can handle preheated water and is set to come on ~5ºF lower than the tempering valve.  Doing this with electric tankless on some solar systems now.
  • Rich_49
    Rich_49 Member Posts: 2,703
    How much

    demand is there in this house and as others have asked what kind of flow from showerheads , tubs ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Tim Schram_2
    Tim Schram_2 Member Posts: 17

    The house does have a soaker tub and has about a 8 gpm faucet.  The system in place gives what it is capable of.  He's just outrunning it.  He was given the choice of what size tank and has underestimated how much the tub would be used.  I'm just inquiring mostly about adding a tankless to supplement.  I've heard that feeding hot water into a tankless is not recommended so was possibly thinking about feeding the tankless into the indirect, but also concerned with additional pressure drop.
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