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not getting enough hot water from tankless coil

mortyb
mortyb Member Posts: 1
in Domestic Hot Water
When we moved into our house 8 years ago, we got great hot water for showers and baths from our Peerless WBV-03 boiler with tankless coil. Then after about 2-3 years it got much worse, temperature was fluctuating and unable to keep up for showers and even worse for baths. First we cleaned the coil, then we replaced it, but we never got back to the way it was when we moved in. Any thoughts on what might be going on? We have well water and scale has been a problem.

We have a L8124 Honeywell Triple Aquastat. The settings seem odd based on reading through other posts. HI is set to 195, LO is set to about 197, DIFF is set to 12.5.

I'm tempted to either remove the tankless and put in a Superstor indirect, although I'm not sure if this boiler will run the Superstor. Or put in an electric water heater in series with the tankless.

Any input would be appreciated.

Thank you!

Comments

  • psb75
    psb75 Member Posts: 894
    1.) Get a 65 gal. or an 80 gal heat pump water heater. Brad White, Rheem, or State/A.O. Smith. Not much sense in connecting it to a failing coil in the boiler.
    2.) Get an indirect tank and put a priorty zone on your boiler.
  • bburd
    bburd Member Posts: 1,011
    edited December 2023
    Those aquastat settings will cause trouble. The low needs to be at least 20° less than the high, and more if the differential is more than 10°. Any closer and they can interfere with each other, perhaps causing the symptoms you are experiencing.
    —
    Bburd
    MikeAmann
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,157
    edited December 2023
    The starting point for your L8124 aquastat should be 180°F high, 160°F low and 10°F Diff. If that does not get you where you want to be, then increase both the high and the low by 5°F Wait a few days before increasing the temperatures.


    When you replaced the Coil, Did you install a thermostatic mixing valve? That can help with overheating and temperature fluctuation that is always a problem with tankless coil water heaters. If you do not have a mixing valve, you will always have fluctuating temperatures based on the operation of the burner nad circulator pump during heating and non heating cycles.

    Here are 3 different boiler manufacturers instruction diagrams on tankless coil installation:
    This is the one I used when installing or repairing Tankless coil jobs: https://www.supplyhouse.com/Resideo-Braukmann-AM100-US-1LF-1-2-Lead-Free-Union-Sweat-Mixing-Valve-70-145F?_br_psugg_q=am100-us-1lf

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    bburd
  • MikeAmann
    MikeAmann Member Posts: 1,044
    edited December 2023
    mortyb said:

    We have a L8124 Honeywell Triple Aquastat. The settings seem odd based on reading through other posts. HI is set to 195, LO is set to about 197, DIFF is set to 12.5.

    A triple-acting aquastat does not work like a window where it cycles between 160 and 180.
    The LO limit is actually the HI limit in the summer, when there is no call for heat. Winter, when there is a CFH, you are running off of the HI limit minus it's built-in differential (10 degrees). Therefore the burner runs up to 180, shuts off, then fires again at 170.
    The LO limit is also the control for your circulator. The CIRC will not run until the temp reaches the LO limit. Your settings have locked out the heating circulator.

    Change your settings, watch the results, and report back.

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