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Differential Setting for Indirect DHW


I have a new Lochinvar KHB 199 Condensing Boiler with a SIT80 indirect tank. The factory differential setting is 6 degrees, which seems low. The installer has left all settings unchanged. (The boiler sends 170 degrees to the tank and tank temp set to 140).

Should I leave the 6 degree differential or do you recommend going to a larger number? My thought is to have a few less cycles.




  • hot_rod
    hot_rod Member Posts: 22,256

    the aquastat that come with some tanks are typically 15.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MikeAmann
    MikeAmann Member Posts: 998

    My Honeywell L4006A has a built-in 8 degree differential.

    HVACNUT Member Posts: 5,863

    If there's a .5° standby heat loss per hour, then big whoop. Twice a day to recover wont break you. If there's a big demand, you'll like that tight differential.

    With the tank set to 140°, I'm sure there's a mixing valve tempering down to 120°, right? So going to a 10° diff should be fine in this case as long as everything is piped and sized correctly.

  • MarkC
    MarkC Member Posts: 18
    edited October 2023
    Just a small thank you to all in this post. I had the same question and got an answer here! FYI, my HTP ELU85WBN default dhw differential temp setting was zero!