Takagi error 711 Gas Solenoid Valve drive circuit failure-HELP PLEASE!

Discussion in 'Tankless Water Heater Forum' started by JonD, Jan 19, 2012.

  1. JonD

    JonD New Member

    Jan 19, 2012
    I have a Takagi T-H2-DV-N tankless water heater. It's been in use for about 8 months now. It worked beautifully. Until this morning. I turned on my hot water, and it never got hot.

    The error message on the heater is 711-Gas Solenoid Valve drive circuit failure. First off: What does this even mean? Second: How can this be fixed? Third: What would cause this issue in heater in use for less than a year?

    Any help would be much appreciated!

    As of now (way too complicated to explain why we haven't had this fixed yet) we have no hot water, and we have two small children, and it would be VERY helpful if someone could explain what all this means.

    Thank you!

    Link to manual: http://takagi-usa.com/download/product_manuals/T-H2.pdf
    Last edited: Jan 19, 2012
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Well, a solonoid is an electrically operated on/off or adjustable valve. This particular one is connected to the gas valve that enables the fuel to get to the burner. A driver is the thing that controls the solonoid valve. The logic circuit board's diagnostics think that the thing that opens and closes that valve (the solonoid) is broken (failed).

    If it can't open the gas valve, it can't heat the water. Now, keep in mind that the diagnostics don't always point to the failure, but to a symptom. It could be the actual driver, or it could be the solonoid valve (maybe stuck), or the sensor that tells it where it is or even the circuit board itself.

    At under a year, it should be under warranty, so first thing is to call them. Certainly, it can be fixed, but not all plumbers are really trained on the things or carry parts like they would with a conventional water heater. It's one thing to plumb it in, it's another to fix it.
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  4. DonL

    DonL Jack of all trades Master of one

    Mar 30, 2011
    Rocket Scientist
    Houston, TX
    Sense that unit has a Micro-Computer, You may want to kill the electrical power to it for about 1 Minute, To reset the Computer. Just in case it is in a hosed mode.
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