Rinnai Tankless Error LC Code

    Your Rinnai will build up a scale on the inside of the heat exchanger significantly reducing efficiency.  If it becomes too much the Rinnai tankless will produce an error code LC (or 00 when previewing error history).

    How to Fix Error LC on your Rinnai

    As a temporary fix if you simply unplug the unit and wait 60 seconds then plug it back in the tankless should work for a little while.  The Rinnai may work for up to a week before the error shows up again so it’s important you address the issue as soon as possible.

    To properly fix the problem the tankless needs to be flushed to remove the scale buildup.  Toronto and surrounding areas serviced by municipal water (from lake Ontario) have reasonable water hardness. Thats to say you can probably get away with flushing your tankless once every two years.  If your home is serviced by well water there is a good chance you are prone to higher water hardness and greater scale buildup in your tankless.  A simple water test can tell you your water hardness and help determin the frequency your flush your tankless.

    The LC code is signaling your tankless has too much scale so it needs to be flushed.  You can hire a company to perform the service which will cost roughly $100-$150, or you can do the flush yourself but you will need a few things.

    We have put together detailed instructions on how to flush your Rinnai Tankless but you will need a flush kit, you can grab one off Amazon for fairly cheap here.

    See how to properly flush your tankless at home

    Check out our tankless flushing service for Toronto and surrounding areas.

    Reset Rinnai LC Error Code After Flush

    Scale build-up in Heat Exchanger (when checking maintenance code history. “00” is substituted for “LC”)

    1. Flush heat exchanger per recommended flushing procedure found in water heater’s owner’s manual.
    2. NOTE: The LC, LC0 –LC9 codes are the only codes that will allow a water heater to continue to operate. The display will alternate between the LC codes and the temperature setting. The controller will continue to beep.
    3. On older products, you can reset the LC code by turning off the power and then turning it back on.
    4. On newer products, there is a shutdown feature built into the product to prevent damage caused by the water heater scaling up. See reset function for these water heaters below:

    •LC, 00, or LC0 –LC9 indicates that there is a scale build-up in the heat exchanger and that it needs to be flushed to prevent damage. Refer to the flushing instructions in the owner’s manual. Hard water must be treated to prevent scale build-up or damage to the heat exchanger. The above codes will lock the water heater out, requiring a reset function. See below how to reset.

    •To operate the water heater temporarily until the heat exchanger can be flushed, push the on/off button on temperature controller five times. (Water heater will operate for 70hrs and lock out with another LC code) Example: LC2 indicates water heater has been reset for 3 -70hr periods without flush and hard reset. After temporarily reset, controller will cycle between set temperature and LC#.  After flushing water heater, the procedure to reset LC codes:

    •Push the two switches (A and B) on PC Board at the same time for five seconds.

    •Water heater will return to normal operation and LC# count returns to 0. This hard reset procedure is not in owners/installation manual or tech sheet.

    Author: administrator

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    1. I have the RL75i tankless water heater. After flushing it I pushed the two buttons for over 5 seconds and the error code 79 will not reset.


    3. Thank you so much , I was able to go turkey hunting , after a quick flush of the system and reset.

    4. If you do NOT have the A and B buttons on your pc board, you locate the series of 5 buttons running vertically down pc board.first is white, second black then white, white and white.. You hold the third and fourth buttons for 5 seconds and release. That will reset your lc code.

    5. If you dont have the a and b switches 0n your rinai hot water heater and instead you have a series of five buttons running vertically down your pc board right above the little digital screen, you hold buttons 3 and 4 for five seconds and release. This should reset your lc code.


    7. Thank you for posting this!

      It saved me a $200 plumbers bill. 🙂

    8. how to fix the error code 17 in model RUR199N Rinnai.

    9. are the reset switches just below all the dip switches

    10. Code LC1 after 2 descalings
      How do I remove the code?
      Rinnai RL75e
      Control unit MC-91-2us-s

    11. Thank you for posting this!

      It saved me a $150 plumbers bill. 🙂

    12. To do the hard reset you need to take the cover panel off. You unsnap the strip on each side of the panel and unsrew the panel. When removed there are two very small buttons located on the bottom right. Press those for five seconds and it will reset the code.

    13. To turn your Rinnai Tankless back on temporarily until the heat exchanger can be flushed, push the on/off button on temperature controller five times. Your system will now operate for 70hrs before it locks you out with another LC code.

      After a flush is completed you need to do a hard reset on the Rinnai.
      — Push the two switches (A and B) on PC Board at the same time for five seconds. This will reset the LC error codes.

    14. how to reset LC2 code after flushing unit

    15. how do yo9u reset the lc code after flushing

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