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Hot water not so hot...

I have a 17 year old Thermo Dynamics tank less boiler; hard water and partially restricted coil. The copper pipe leaving the coil is hot to touch but the pipe leaving the mixing valve is not so hot. New mixing valve has been installed. The only time I seem to get good hot water is after the boiler reaches 180 after calling for baseboard heat. Regardless of my hard water and restricted coil I would think the pipe exiting the mixing valve should be almost as hot as the pipe exiting the coil. The valve is all the way open.  Any help here!


  • billtwocase
    billtwocase Member Posts: 2,385
    aquastat settings

    Where are they set? Tankless coils are rated at 200 degrees. You should be LO 180 degrees, and close to 200 degrees HI limit with a tankless coil that has a mixing valve. You cut drop the Lo to about 160 in warmer weather, but winter setting, it needs to be closer to 180