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Rinnai 120CN not reaching temp setting

cfar Member Posts: 13
I have a Rinnai 120CN combi boiler which won't hit the desired boiler temp.

I'm using room air, natural gas and with a single zone layout.

I current have the DHW temp set to 120* which works perfectly.

However, the boiler is set at 165*, but it will only get to 143* and then "cycle" back down to 130* and then do it all over again. Ive played qith temp settings  but I can't get the boiler to reach anywhere close to its target. And as you can imagine,  this is not optimal with the current weather situation most of are experiencing.

Thank you.


  • cfar
    cfar Member Posts: 13
    Once it gets to ~140* the fuel seems to run out and begins to sputter.

    I played with the settings giving the boiler portion priority.  It's been hovering around 130* for a couple hours now.
  • Jamie Hall
    Jamie Hall Member Posts: 23,567
    You may have a gas pressure problem -- but that takes specialized training to check. It wouldn't be surprising, since everybody and their uncle is using gas on days like this.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England