Rheem Tankless Troubleshooting

Discussion in 'Tankless Water Heater Forum' started by Tommy Hager, Mar 2, 2021.

  1. Tommy Hager

    Tommy Hager New Member

    Joined:
    Mar 2, 2021
    Location:
    Parkersburg WV
    Hello,
    I'm having problems with my Rheem tankless RTG-95DVN as described below.

    Connector labels per SVC 820P pocket manual pgs 14, 15

    Initial state: branch circuit breaker tripped, unit inline 3a fuses both blown. Possibly associated with a power outage.
    Whole house protected by industrial grade Innovative Technology Surge Protector, indicators unit is OK. Rheem was plugged into a garden variety, point of use surge suppressor which failed, as noted by tone alarm.

    Action: replace 3a fuses, energize system.
    Result: both fuses blow.

    Action: replace 3a fuses, open all connectors on control board, energize system.
    Result: red led on control board flashes 4 times and repeats.

    Approach: with system deenergized, plug in 1 connector at a time, energize and note results

    Action: connect U only, energize.
    Result: 3a fuses remain intact, red led off not flashing.

    Action: connect G only, energize.
    Result: disc shaped component immediately to the right of G explodes, 3a fuses blow.

    Is there a common problem that is associated with the circumstances noted, that you could point me toward?

    How should i proceed to ensure that new control board is not damaged?

    I have a Fluke multimeter for taking measurements.

    Best Regards,
    Tommy Hager
     
  2. Tommy Hager

    Tommy Hager New Member

    Joined:
    Mar 2, 2021
    Location:
    Parkersburg WV
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  4. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Can't find a wiring diagram on line
     
  5. Tommy Hager

    Tommy Hager New Member

    Joined:
    Mar 2, 2021
    Location:
    Parkersburg WV
    Hi fitter30,
    Here is the wiring diagram and the service manual. Had to order needle point adapters for test leads in order to take any measurements at the connectors, should arrive tomorrow. Thought i was doing the right thing to isolate the problem when the component exploded. I doubt that i.ll be able to energize the board again without blowing the line fuses, so i think i.ll only be able to take resistance measurents. Any info or suggestions you might offer is appreciated.

    https://www.google.com/search?q=RTG-SERVICE-MANUAL-REV-2.PDF

    Service manual is the top result in this search at snowcrest.

    20210303_001419.jpg
     
    Last edited: Mar 2, 2021
  6. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    The board is toast, fan motor is a ecm- electronic controlled motor could be bad since plugging it in took out fuses and electronic part. Ecm motors are a dc motor that gets a pulse to determine speed. Page 17 service manual looks like water flow is the input of speed. Ecm motors and main control are not cheap and would take more sophisticated testing equipment and information.
     
  7. Tommy Hager

    Tommy Hager New Member

    Joined:
    Mar 2, 2021
    Location:
    Parkersburg WV
    Here's what i.ve got:

    ECM blower, black to red, where hi vdc gets applied, measures dead short, 0 ohms.

    The following measurements taken with connectors disconnected from control board: (correct procedure?)

    Connection U, overheat film, measures open. (It all looks undisturbed.)

    Connection R, all 4 thermistors measure open. (seems unusual for all to fail at once? I can't even imagine how access is possible to replace these.)

    Final insult: new control board is nonreturnable.

    Thanks for your input.

    Regards,
    Tommy
     
  8. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    It's not normal practice that manufacturers let you return electrical parts. Doesn't matter if it's printed circuit board or a motor and other parts come with a restocking charge.
     
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