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Lochinvar Noble -- does space heat circuit deliver same MBH as DHW?

tc60045 Member Posts: 31
OK, @zman managed to turn my head on Lochinvar and I am confused by what appears to be very straight-forward math in a world where I had gotten used to bizarro math...

I have a *different* area (garage apartment) where a combi would work well for heating apt, garage with radiant-fed blower, and DHW to apartment.. In Navien land, if you need ~100K of heat from the space heating circuit, you have to buy a 199K Combi.

But it appears that Lochinvar 110 delivers 89K AHRI off a 110K BTU combi. Is this right? I feel unsettled...


  • Zman
    Zman Member Posts: 6,565
    You are correct.
    The navien has a smaller heat exchanger for the heating side.
    In the lochinvar unit, the heat exchanger can handle the full output of the boiler.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 14,786
    The Nobel is a fire tube design boiler, with a plate heat exchanger inside for DHW. The full boiler output can go to the heating load, or switch to the HX for DHW.

    Be aware of your coldest incoming water temperature when you look at available GPM on the domestic hot water side.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • tc60045
    tc60045 Member Posts: 31
    @zman & @hot_rod, thank you for confirming. Changes everything.

    Gotta say:
    (1) inside of these Lochinvars reminds me of my old Ford Explorer; inside of Naviens looks like a Lexus hybrid, where you need an MIT Comp Sci degree to diagnose. What is odd to me is that the Lochinvar is $1K more, despite its simplicity. Your $0.02-- Can I expect to make that back in lower service costs / peace of mind?
    (2) OMG, the app for Lochinvar is a nerd's dream come true. Every feature, set point, etc under the sun. Is it as good as it looks?

    thx both!!

  • tc60045
    tc60045 Member Posts: 31
    (note to mods: I am noting a rough difference in relative pricing above to understand up-front versus total cost of ownership. I will not discuss actual pricing and will remove that post if it violates the spirit of the board. Thank you!)
  • Zman
    Zman Member Posts: 6,565
    In my opinion, the Lochinvar is just a higher quality unit. Well worth the extra $
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • DZoro
    DZoro Member Posts: 1,049
    Loch is worth the price. You also can limit your boiler to the exact amount of btu's needed from your load calcs. While still having full power for your domestic hot water needs. Very simple and easy to work on = less fuss with maintenance and repair time. Parts also are properly priced if needed in the future.

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