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Rinnai help needed

MtjagMtjag Member Posts: 3
edited April 2016 in THE MAIN WALL
I have a Rinnai R75LSi that I've had up and running for 7 years. I've descaled four times. Four years ago, I put a plate exchanger in front of it that is in front of my outdoor wood furnace. Everything has worked fine for four years. About three weeks ago, I notice the water was not as hot and the flow was about 60% of my cold water flow. Even though the Rinnai hadn't signaled me to descale, I thought I would descale both the Rinnai and the plate exchanger....separately. I did the plate exchange, then went to the Rinnai. I flushed the Rinnai for about 45 minutes and then I think I messed up. I decided to swap the hoses around on the Rinnai to make sure it was flushed well. The flush pump wouldn't pump through the Rinnai after about 10 seconds, I shut the pump off and disconnected. However, I think I may have messed up a check value or something on the inside of the Rinnai as now the external check value is leaking water when I plugged it back in and I have virtually no water pressure. In fact, the Rinnai won't even come on when I hope a hot water spigot in the house and will only come on when I open the check value located under the Rinnai. On the Rinnai troubleshooting it shows the following: "Nothing happens when water flow is activated.
Check for cold to hot cross over. Isolate circulating system if present. Turn off cold water to the unit, open pressure relief valve; if water continues to flow, there is bleed over in your plumbing."
Mine is doing that, but it doesn't tell you what to do if that is the case.

Does anybody have any ideas?
Rinnai is closed for the weekend.


  • JackJack Member Posts: 1,045
    By reversing the hoses and pumping backwards you have taken debris back into the turbine in the cold water inlet. If that turbine doesn't turn, the unit will not start. With the cover off, locate the cold water inlet valve and remove it. Disassemble the valve and there is a small black cylinder inside the inlet. The turbine wheel is mounted inside that black cylinder. That cylinder will come apart. Disassemble...paying attention to the orientation, clean, reassemble, flush on a more regular basis and don't do this again. Rinnai isn't closed for the weekend, but limited tech staff.
  • MtjagMtjag Member Posts: 3
    Thanks much for that advice. The Rinnai is now working, though it seems I have a problem with water pressure from my heat exchanger that seems to be clogged. I tried to flush this yesterday, but couldn't get enough through put with vinegar. I thought I would try it again with muriatic acid. Any suggestions otherwise?
    Thanks again for your help!
  • JackJack Member Posts: 1,045
    I would not use muriatic. Keep pumping the vinegar. Also take a woman's stocking and put it on the outlet hose to filter the debris. Going forward, get a thorough water test done and compare it to the specs in the 75 install manual. You have decisions to make based upon those results.
  • MtjagMtjag Member Posts: 3
    Ok, thanks for that. I will get some more vinegar tomorrow and give that a go. I guess I should just keep it running for a few hours to see if it improves on the flow.

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