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Using a Rheem water heater for hydronic and hot water

AndrewHern Member Posts: 7
Hi everyone. Do you think I can use a gas Rheem water heater for simultaneous hydronic heating and hot water? The model number is xh40t06pv40uo. According to this models use and care manual (page 31), it says that yes, you certainly could. But you have to make sure that every valve etc is suitable for use with drinking water. Also you have to set a timer and make sure the system turns on every 6 hours for 1 minute for the purpose of keeping microbes from growing. 
I live in northern New Jersey and l own a two family 2000sqft home. I was thinking of buying one water heater tank for each 1000sqft family dwelling. Any advice would be greatly appreciated. Thank you. 


  • Jamie Hall
    Jamie Hall Member Posts: 20,840
    Well, yes, technically you can, provided the water heater has the power to heat the house. Do I recommend it? No, I don't. A water heater -- particularly a tank type -- is intended to heat and store hot water, providing it for occasional relatively high flow but relatively short duration domestic use. A boiler, such as might be used to heat a house, is intended for a lower flow, usually, of hot water -- continuously. Very different demands.

    And I do NOT recommend mixing your heating water and your domestic drinking water. Ever.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • AndrewHern
    AndrewHern Member Posts: 7
    Thank you Jamie for your comment. I really appreciate it. Wouldn’t having a timer run the system every six hours for 1 minute Eliminate the microbes in the system? 
  • hot_rod
    hot_rod Member Posts: 18,900
    Legally yes, if the manufacturer has it listed. In addition to Jamies comments, they are not very efficient, maybe high 70%.

    2000 su feet could require as little as 20,000 btu/ hr, maybe as high as 60,000. So a heat load would be needed to see if it even has the btu needed to cover the loads
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jumper
    jumper Member Posts: 1,990
    Copper is not supposed to scale but....
  • Jon_blaney
    Jon_blaney Member Posts: 298
    I have been doing it for 20 years, no problem. I use a hydroair system on an oil fired tank. I do not think you can find radiators or baseboard that is compatable with DHW. You would need a heat exchanger. System becomes more complicated. Check the First Company and Bock website for info. Run the take at 140 deg to kill the bugs.
  • This company has a lot of good options for heating with water heaters:

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hourTwo btu/ per sq ft for degree difference for a slab