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alliance running cold

I have 2 Burnham Alliance 55  piped to Apline condensing boilers. Both run cold after running a shower for 10 minutes. I understand that it maybe that I'm drawing 5gpm that the system can't keep up (as advertised) but here is my question....the water from the tank has run cold even though the supply & return pipes are too hot to hold. Why is there no heat transfer? Shouldn't the water be at least lukewarm?Seems that the tank only heats when there is no demand?


  • Zman
    Zman Member Posts: 7,572

    Both the alpine and the burnham have high head losses. Is the circulator sized correctly? Is it piped with DHW priority?

    What is the output of the boiler during a dhw call? What is the delta t?

    Could the coil be calcified?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kcopp
    kcopp Member Posts: 4,438
    I have run....

    into a "limed" coils on the Top Performers before....(same as the alliance) This was on city water. It may have not been calcium but it sure did effect heat transfer. Nice thing is that the coil is removable and you can clean it up.
  • bluemoon
    bluemoon Member Posts: 40

    Both brand new

    Tried all 3 speeds on grundfos

    Piped directly off header with priority

    Supply & return both red hot
  • jonny88
    jonny88 Member Posts: 1,139

    you need a minimum of 1" piping and if using grundfoss use the 26-99.