NHB 150 making DHW at 165 supply temp?

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DIYorBust
DIYorBust Posts: 95
in THE MAIN WALL

After replacing the PCB board in this navien NHB 150, I noticed that when making DHW it is down modulating to keep the supply water temp going to the indirect water heater at around 165. I feel like it should be supplying 180, to maximize the DHW water supply and recovering time. Are we missing something with the settings or jumpers? Thanks!

Comments

  • HVACNUT
    HVACNUT Posts: 7,785

    How do we know if you missed something if we don’t know what you didn't miss? I'll blindly throw a dart anyway.

    Screenshot_20260116_053306_Samsung Notes.jpg
  • DIYorBust
    DIYorBust Posts: 95

    Thanks, I figured it out, dip switch 8 on the PCB for exhaust temp limit was in the wrong position. This boiler has a polypropylene vent and it is safe to operate at 180, but the boiler was limiting the vent temp for PVC.

  • hot_rod
    hot_rod Posts: 28,708

    Generating DHW with the lowest boiler supply temperature increases efficiency of the boiler.

    So if 160 boiler temperature was providing adequate DHW, why boost it to 180?

    A lot of recovery time has to do with boiler capacity, piping and pump sizing and the size of the coil in the indirect.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGrossbjohnhy
  • DIYorBust
    DIYorBust Posts: 95

    160 does not supply enough hot water.

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