Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Rinnai R85e, no power to controller, no hot water

I thought I would share my experience hoping it helps others. I have a 2005 Rinnai R85e instant water heater that went dead between showers. No power to the controller, removing the controller wires from the board didn't help. Confirmed 120VAC to unit, checked continuity of both fuses, confirmed power going to transformer 120VAC and 100VAC on secondary side of the transformer (had to use small wires since my tester was too big but don't let them touch! Or get ready to buy new fuses, how do you think I learned). Once power to the control board is confirmed, unplug everything from the control board (leave the small power supply screwed to the front of the control board plugged in) except for the plug coming from the secondary side of the transformer. If you have power to the board but no power (24 VDC) at the terminals going to the wall mounted controller it's a bad board. I bought a new one from Rinnai through a local dealer for $200 overnight shipped and have hot water again. Make sure to check the 2 DIP switch settings and set the new board to the same settings. Hope this helps someone. Rinnai tech support was outstanding and walked me through the last steps when I hit a diagnosis wall but wasn't ready to sink the $200 yet.


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,391
    Hi @Robert_Sorenson , Welcome to HH, and thanks for sharing your experience. It sounds like aside from that pesky fuse, things went well. Might it be useful to have the heater on a surge suppressor? I'm just wondering why the board died...

    Yours, Larry
    Alan (California Radiant) Forbeskcopp
  • Cjones232
    Cjones232 Member Posts: 1
    I am having the same problem with unit no power is going to it. Checked my panel big and breaker is not blown. Power unit on wall is blank and tankless heater does not seem to show any power as well. I need help trying to figure it out
  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    That is an electrical problem -- particularly if both the boiler and the tankless heater are out. Are they on the same circuit (they shouldn't be, but we'll overlook that)? The breaker is not tripped -- but are there any emergency switches which might have gotten turned off (there should be at least one -- but there may be two)?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England