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Saunier Duval boiler just heat bathroom's rooms water but it doesn't heat radiator water

matlabo Member Posts: 2
edited November 2020 in Gas Heating
 Here we have a Saunier Duval Thema Fast F30 or F35 gas boiler and it turns out that the heating mode does not work while the domestic hot water production mode is working.

 At least the heating mode is triggered if I set the temperature to the maximum and again it's just for a few moments then it stops and the temperature rises much too quickly.

 According to the instructions to check the correct operation of the heating month you have to press simultaneously on the minus and the plus for 3 seconds and it showed me the code S 07, which means [B] HeatingCirculation mode [/ B] ...  .. What does it mean????

 So here I think that the problem comes from the 3-way valve, because when the boiler goes from the domestic water heating mode to the water heating of the radiators I saw nothing turned and also because the boiler in question remained about 7 months in  water heating position for bathrooms.

 So I unscrewed something from the 3-way valve:

 So what to do now?  How do I check that it works and how does the thing I photographed work?

 Thank you very much !


  • JohnNY
    JohnNY Member Posts: 3,244
    I don't know your boiler but your description of the problem suggests to me that your heating water circulator is not running. I'd check that next if I were you.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • matlabo
    matlabo Member Posts: 2
    Thankyou very munch but i have already solved the problem, i thinck that it was just the deviater valve which was gripped or blocked.