On-demand H2O heater shuts off

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Davelux, Feb 3, 2007.

  1. Davelux

    Davelux New Member

    Messages:
    7
    Location:
    California
    My on demand water heater shuts off when I turn on the cold water valve or adjust the temp at the shower knob. It turns on and heats the water to the set temp when I turn on only hot water valve at the sink or the shower (set all the way to hot). If I turn on the cold water valve or adjust the shower temp knob the on demand water heater shuts off. I have had to turn down the water temp so the family can just use the hot water.

    Any thoughts on how to be able to turn the temp up and adjust the temp by adjusting the valve at the facuet or shower?
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    What brand is it?

    Tankless, will be by and may be able to help but he also will want to know the brand
  3. Davelux

    Davelux New Member

    Messages:
    7
    Location:
    California
    Rheem Pronto

    RTG-42PVN

    Thanks
  4. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    2 other questions, how long have you had it and are you in a hard water area?
  5. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Have you tried this number for trouble shooting?


    1-866-720-2076 for Rheem Direct
    Available between 7AM - 7PM Central Time
    7 days a week
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,263
    Location:
    Cave Creek, Arizona
    heater

    Without being able to actually see what is happening when the situation occurs we are just guessing. But your description implies that once you turn on the cold water side, its pressure overwhelms the hot and thus reduces the hot flow below the point where the tankless will activate, shutting it down.
  7. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    An experiment...
    Try to leave the hot water in the lav running and then try to use the hot and cold in the shower...
    If it works then you might have a problem with the flow switch...
    The hot water in the lav forces more water through the heater and if the flow switch is not being triggered by the shower's flow whem mixed, it might trigger with the lav's flow added...
    Tankless will be able to give you a better answer though....
  8. this should be interesting

    this thread should be very interesting

    when things get heated up over this Rheem tankless

    to say the least......LOL


    super bowl sunday and all, my bet is it wont get

    fixed till Wednesday....
  9. Davelux

    Davelux New Member

    Messages:
    7
    Location:
    California
    I have had it less than a year and it has always worked this way. No hard H2O.

    Yes. If I leave the faucet on, I can adjust the shower temp.

    I have not callled Rheem. I will call them on Monday. Sounds like the "flow switch" is bad.

    Any other thoughts?

    Thank you

    Dave
  10. Last edited: Feb 3, 2007
  11. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA
    First off, check the filter and clean as necessary. I suspect that your trouble is related to your shower head. If you are using an older shower head that may be restrictive, replace it with a new 2.5 gpm model. Your Pronto is going to deliver 2.4 gpm at an 80 degree rise. You need a minimum of .66 gpm to trigger and operate the heater, and the pressure must not fall below 14psi. I'll assume you aren't getting any error codes on the controller since you didnt mention that. Refer to your owners manual to determine how to use the controller to check the flow. If that info isn't in there, the tech support people can walk you through that.

    As for temp, remember that it makes no sense to heat the water higher than you want in the shower. If you do, you are cooling it back off immediately before you use it.

    If you are in Seattle, we can service your heater immediately. Private message me your phone number and I wil be glad to walk you through any other possibilities.
  12. hourley rates.....

    I am sorry, Tankless
    but I just have to be an a-hole here......
    ( I just cant help myself )

    If this fellow were lucky enough to be in Seattle,
    and you were able to service his
    Rheem 1 year old tankless heater, sometime
    next week after the super bowl......

    I understand that you did not install the thing,
    and I know that Rheem dont pay squat on warranty
    service repairs so

    what is the hourley rate for working on them???

    just give me a ballpark guess what the billl might
    mushroom into,

    best case and worst case????
    Last edited: Feb 4, 2007
  13. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA
    In this case, we're betting this is not related to a malfunctioning heater. Its a flow issue. But it will be interesting to see how it shakes out.

    Our hourly rate is no more on tankless than if we were coming to repair a tank heater. Our service call is $99.00 and that buys you 30 minutes, then we bill at 100/hr. I can't answer the question of how much it may cost, since we have only done a handfull of service calls in the past 3 years. We are anxious to do service work on them, but they are just do dependable that we don't get much. (ok, that sounds like a sales pitch, but it is true) The calls we have had were mostly related to non-heater issues. One I repaired last week for instance had been improperly winterized at a vacation cabin. a small 30.00 part froze and cracked. I had that one back in service in about 10 minutes (not counting all the driving). We did have a legitimate part failure the other day on a Noritz, but it is extremely rare at this point.

    Tankless heater are fairly simple, if you learn the way they work, and have the parts, you can do just about anything to them in an hour or less.

    And if a customer calls us today, and wants us today, we go today. That's just the way we do business here. He'll pay for sure... but we are available.
  14. srdenny

    srdenny Plumbing Contractor

    Messages:
    361
    Location:
    SF Peninsula
    Just curious, Tankless. What was the defective Noritz part? And how does one accumulate all the parts needed to service a wide variety of tankless brands?
  15. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA

    It was an ignitor. Thankfully, this was a double install, and the cust was getting by on one heater. We don't yet stock many parts, but we always have a good stock of different models of heaters. If a cust is in dire straits, we would just "borrow" a part, and replace it when we get the part from the manufacturer.
  16. Davelux

    Davelux New Member

    Messages:
    7
    Location:
    California
    Problem Solved, I think.

    Problem Solved, I think.

    Tankless was right, it was a flow problem. Not enough hot water being able to flow through the faucet or the shower head.

    At the sink, I reduced the cold water inlet valve below the sink to 3/4 open. This reduced the cold water flow at the sink faucet, allowing the hot water enough throughput to keep the on-demand heater running.

    At the shower, the restrictor bushing was still in the shower head. It seemed if it were manufactured in place, so I drilled thru it. Works great!! Now I’m looking to replace the screen that was on the other side of the restrictor.

    What a difference that makes. Shower rocks!

    Take home message.......Low-flow and On-demand do not mix

    Thanks for the help
  17. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    If that is the case the tankless heater people will have to change the flow sensor.
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