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  1. #1
    Join Date
    Jan 2008
    Posts
    16

    Rinnai tankless water heater problem

    We have installed a bunch of Rinnai units without problems. One exception has a problem no one can figure out. When a shower is in progress, after about 1 minute the heater shuts down for a few seconds, which delivers a few seconds of cold water (not fun for the occupant) then ramps back up and doesn't do it again. We have checked everything 4-5 times and redone the flue once. Nothing changes. The Rinnai factory guy can' figure it out. Anybody else have this problem?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,064
    When you talked to the factory tech, did he address the safety recall on them.

    Sorry, I can't help you with the intermitant hot water problem.
    If it happens every time. Have one guy go up stairs and run the showe, and you stay at the heater, and check for what ever device is dropping ouot.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jan 2008
    Posts
    89
    Could be a couple of things. A sudden drop in water pressure or gas pressure is most likely.

    The rinnai wants a certain water pressure level to run, could be your supply has erratic pressure and at some points you're dropping below its level to stay on.

    A gas blockage or drop in gas pressure could produce similar results.

    I also heard that some of the Rinnai's have problems with condensate from the duct backing up into the unit and when it senses that, it temporarily cuts the flame. Theres supposed to be an integrated system to eliminate excess condensate, but it may not be functioning properly.

    You've discovered some of the many issues with a real-time system...

    Get a water pressure gauge (ten bucks) hook it to the end of a hose and drag it over to the WH. Have someone turn the shower on. See if the flame drop is accompanied by a water pressure drop on the gauge.

  4. #4
    Join Date
    Dec 2007
    Posts
    132
    had that problem with the shower going cold , customer had temp of water to high triggering scald guard in the mixing valve in shower causing it to go cold for a few seconds turn temp down

  5. #5
    Join Date
    Jul 2006
    Location
    Southern Ca, Elkton Md
    Posts
    7,572
    Quote Originally Posted by beenthere View Post
    When you talked to the factory tech, did he address the safety recall on them.

    Sorry, I can't help you with the intermitant hot water problem.
    If it happens every time. Have one guy go up stairs and run the showe, and you stay at the heater, and check for what ever device is dropping ouot.
    What saftey recall?
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,064

  7. #7
    Join Date
    Jul 2006
    Location
    Southern Ca, Elkton Md
    Posts
    7,572
    Those are wall furnaces, not water heaters?
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  8. #8
    Join Date
    Dec 2007
    Posts
    132
    Yes I thought it was just the wall furnaces also

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,064
    Sorry, just caught the name.
    Never read the article.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Jan 2008
    Posts
    16
    I thought it might be the shower mixing valve but we tried turning the temp down and that affected nothing. I even changed out the Rinnai. It worked OK for a couple of days then same thing. The plumber says its not in the pipeing so everyone points at the Rinnai. Something in the house is causing the fluctuations, not gas or water pressure, we checked that. Not the flue, we replaced that. I'm HVAC not plumbing, how do you check a house?

  11. #11
    Join Date
    Sep 2006
    Location
    Rhode Island
    Posts
    17
    Washing machines have internal mixing valves that have been known to cause problems with Rinnai's. Try shutting the water to the washing machine off and see if that fixes the problem.

    We've had similar problems and found that to be the issue

  12. #12
    Join Date
    Jan 2008
    Posts
    89
    Where's it mounted? Inside the house or outside somewhere? Whats the intake venting look like?

    Is this just a problem with the shower or with any h/w usage?

  13. #13
    Join Date
    Jul 2006
    Location
    Southern Ca, Elkton Md
    Posts
    7,572
    Ok, I had a same problem reported yesterday.

    Complaint, durring shower loss of hot water a slight pressure problem. Also noticed that they are not saving as much as expected.

    Here is what I found was the problem:

    Sorry, I just remembered what forum this is, and cant post technical information.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

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