Rinnai hotwater producing hot bath but only lukewarm everything else

Hi

Hoping that someone else might have seen this and have an easy fix before I call in the repairman.

This rinnai gas hot water system appears from the electronic display to be working but the temperature doesn’t match what is displayed.

The auto bath function will fill the bath with hot water of the right temperature. Eg set to 40 degrees, produces 40 degrees.

However hot water in kitchen, basin and shower is only lukewarm despite being set to scalding. eg set to 60, produces about 25-30? If set to 50, then output temp is lower.

I’ve tried turning off power to outside system, but no luck. Seems like a hardware sensor issue. Anyone else seen this before?

4 comments
  1. There should be 3 temp settings: 1) the bath water temp, 2) temp set from display in the bath which is used for hot water sent to non-bath faucets around the house, and 3) temp set from the display in the kitchen which is used for hot water sent to non-bath faucets around the house.

    The “優先” button in the bathroom display overrides the temp set in the kitchen display. I wonder if you have the temp set in the bathroom to a low temp, and “優先” is on?

  2. The bath will have its own electric heating element to maintain the set temperature.

    So even if the incoming water is too cold it will just top it up and even reheat it back to that temperature if required.

  3. Double check the settings as some units have three settings for hot water, bath and other taps.
    If they are all set correctly, then the boiler may have an issue and the landlord should be consulted.

    The same happened to me two months before the boiler died completely.

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