Takagi Flash T-K2 intermittently not heating

Discussion in 'Tankless Water Heater Forum' started by fmack12, Jul 11, 2012.

  1. fmack12

    fmack12 New Member

    Joined:
    Jul 11, 2012
    Location:
    Sacramento, CA
    Hello,
    I have a TAKAGI FLASH T-K2 tankless hot water heater. It is 9 years old.

    Intermittently: the water won't heat, or the water will start to heat and then stop heating, or it takes an escessively long time to heat. This happens at the faucet furthest from the water heater, which is a kitchen mixer valve faucet. The faucet worked fine for the first 9 years. Rarely, it has happen at other faucets - which have a dedicated hot valve.

    There is not a numeric error code panel on this unit; however, when the water is not heating the RED LED light is FLASHING and the GREEN LED light is OFF.

    The troubleshooting manual for this issue indicates this could be the: Igniter, Flame Detector, Main Gas Valve or Pre Post Check.
    When I unplug the unit and plug it back in at this time, the flame fires and everything works.
    This indicates to me that the Main Gas Valve is not the problem.

    Thus far I have cleaned the input water filter and flushed the system with vinegar, which turned the vinegar a light blue. I have also tested and there is not a plumbing cross flow.

    The toggles are set as follows: (for 122°)
    113 on
    104 on
    NG on
    LP off

    OUT off
    blank off
    IN off
    176 off

    Step by step instructions are always a plus. How do I proceed to fix this problem?

    Please Advise, Thanks.
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    It's easier to debug if you hook up the compatible remote so you can read the actual error code.

    On units this old flame-sensor varnish/crud is always suspect. Cleaning it up with a plastic scouring pad like a Scotch Brite (and NOT SANDPAPER) will often do the trick. Turn off the power and the gas to the unit before pulling it apart, but it's not a big project. Once you've done it once it's even quicker/easier to do again, if need be. (Air contamination issues make this an annual ritual for some installations, but if yours made it 9 years without a problem it's likely that you'd go years between cleanings.)

    Flow detector wear could be an issue too if it's only happening with lower flow faucets. IIRC the T-K2 needs to detect a bit over 1gpm to light up, and will flame out if flow drops below ~0.8gpm.
     
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  4. fmack12

    fmack12 New Member

    Joined:
    Jul 11, 2012
    Location:
    Sacramento, CA
    Dana, thanks for your reply. I will clean the flame-sensor, then install a Temperature Remote Controller TK-RE-02 for the error code if that doesn't work. It has been 105° here lately, and this thing is in the attic, so I am going to wait till it cools down a little before I get to this project. May take me a while, but I'll be back in touch. Thanks again.
     
  5. fmack12

    fmack12 New Member

    Joined:
    Jul 11, 2012
    Location:
    Sacramento, CA
    Hello Again,
    Cleaning the flame sensor seems to have done the trick - and it wasn't really visibly dirty or gummed - but the scotch bright pad has things working correctly . . . for now.
    Thanks for your help. :cool:
     
  6. Corbino

    Corbino New Member

    Joined:
    Sep 22, 2013
    Location:
    Milwaukee
    Dana, I have a similar issue going on and tried the flame sensor cleaning above, but no luck. I'm only having the problem with one shower in the house. Thoughts?
     
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    "I'm only having the problem with one shower in the house."

    If it works normally when other hot water taps are opened and only craps out when that shower is running, it's almost certainly an issue with the mixing valve in the offending shower, not in the tankless. The anti-scald valves develop leaks between the hot & cold sides, and when that happens the pressure drop of the heat exchanger in the tankless can cause all sorts of odd behaviors.

    Do you have the RE-02 remote, which will at least spit out the error code?
     
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  8. Corbino

    Corbino New Member

    Joined:
    Sep 22, 2013
    Location:
    Milwaukee
    Thanks for responding! I thought the same and replaced the mixing valve in that shower yesterday as well. I watched the unit when the shower requests hot water and it fires then stops right away. I also tried removing the shower head thinking it was reducing flow, but that didn't help. All other faucets get hot water, even the sink in the same bathroom as the shower (sink is actually a little further away). Other ideas? I do not have a RE-02 remote.
     
  9. Dana

    Dana In the trades

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    Location:
    01609
    It's clearly a plumbing-related issue if it only happens with one of the hot water taps, and fails reliably on that tap. The anti-scald portion of the think valve that is the most likely culprit- what kind of shape was the old one in?

    When the shower draws cause the failure, does it give you the blinky-blinky LED code as it hangs up? If yes, what it the blink pattern? I assume you already have the manual? See page 16 for interpreting the LED blink pattern.

    If you plan to own the thing for awhile, it's always worth installing the remote for debugging and re-setting the thing, since the codes are more specific.
     
  10. Corbino

    Corbino New Member

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    Sep 22, 2013
    Location:
    Milwaukee
    Glad you were so confident in your thinking! I swapped the NEW mix valve with one (9 years old) from another shower in the house with the same faucet and the darn thing gave me hot water. What's weird is I put the valve that gave trouble in the other shower and that works now too. Is that due to the closer distance to the heater?

    My mornings just got easier. AWESOME assistance on this!
     
  11. Dana

    Dana In the trades

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    Location:
    01609
    It's possible that the pressure differential across the anti-scald is different with different plumbing routing. But if the thing worked for awhile then crapped out in it's old location, it's probably going to eventually exhibit wierdness in the new location.

    It's also possible that scaling on the water side of the heat exchanger in the tankless is contributing to it by increasing the pressure drop across the tankless. If you've NEVER descaled the thing (in what, 8-10 years of service?) it's probably worth giving it the 30 minute pumped vinegar rinse. (There are several YouTube videos explaining how to descale a tankless.)
     
  12. Tosh

    Tosh New Member

    Joined:
    Oct 30, 2017
    Location:
    Texas
    We installed our tk3 approx 10 years ago and it has now began intermittently working. It especially doesn't work in the mornings when it's cold. Any suggestions. The price I got to service and trouble shoot was almost as much as we originally paid for the unit. I was hoping we could possibly attempt to fix or troubleshoot it on our own.
     
  13. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    Installing a wired remote compatible with your model goes a long way toward debugging these beasts. I believe the TM-RE30 is the right one for most TK3s, but it's worth a call to Takagi tech support to find out.
     
  14. Trung Vo

    Trung Vo New Member

    Joined:
    Aug 4, 2018
    Location:
    fremont
    Hi Dana,
    My model Takagi tankless is T-k4 - IN N and I have the same problem as the title mention in this article, I tried to clean the flame sensor as I see a lot of people in this thread resolved their issue, but the problem still persist for me. Next to the flame sensor is the ignite rode, I am not sure if I need to clean that rod as well? To be clear, when I open hot water to max, after 2-3 minutes, I got very hot water but when I tried to mix water to be able to shower, the water start to get cold and no more hot water. I do install the temp remote control, when I open hot water, I notice the light switch from standby to active and after 2-3 second, it switched back to standby and continue to be switch back and forth, that maybe the reason why the water could not heated continuously. The temp remote did not show any error code on the screen to be able to troubleshoot. Please advise thanks for your help.
     
  15. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    What is the temperature set to?

    There are two issues at play here that could be related to your symptoms- the minimum flow rate needed to keep the flame going, and the minimum temperature rise at that flow rate, which becomes more problematic in summer when incoming water temperatures are higher.


    The minimum firing rate of the TK4 is about 20,000 BTU/hr in, 16,000 BTU/hr out. At 16,000 BTU/hr (165 BTU/minute) at 2 gallons per minute (~16.5 lbs per minute) the minimum temperature rise through the unit would be 165 BTU/16.5 lbs = 10F. At 1 gpm the minimum temperature rise would be twice that, or 20F. The minimum flow rate for the heater to regulate temperature well is about 1 gpm, sometimes a bit less.

    A typical showering temperature is 105F at the shower head. If the incoming water in summer is 75F, that's still a 30F rise well above what a ~2gpm shower needs, so it would be able to regulate the temperature well if ALL of the water at the shower head is passing through the shower head.

    If the temperature is set to 120F and the incoming water is 75F a 105F shower at 2gpm would take in 1.4 gpm through the tankless, 0.6 gpm from the cold side of the shower mixer, and the tankless should be fine. With a very low flow 1.5gpm shower head it would be 0.5 gpm through the cold side, and only 1.0 gpm through the tankless, which could easily become an issue. A warmer slug of incoming water at 80F could cause the flow to the tankless to be low enough to cause it to flame out, and it might not be regulating temperature well at that low flow.

    Lowering the temp at the tankless to 115F the low-flow 1.5gpm shower would take 1.15 gpm through the tankless, 0.35 gpm through the cold side of the mixer, and the tankless would be better able to regulate temp.

    Lowering it still further to 110F out it becomes 0.2 gpm through the cold side of the mixer, 1.3gpm through the tankless, where it should be able to function just fine.

    But if the tankless is set for a scalding 130F a 1.5 gpm shower would be drawing about 0.65 gpm on the cold side, only 0.85 gpm through the tankless, a flow rate at which it won't regulate well (if at all), and very likely to flame-out.

    If you don't have the remote, and are setting the temperature with the DIP switches, the default setting from the factor is usually 122F, which could be a problem in summer at low flow. Try backing it off to 113F, which is then next lowest setting available. See page 41 of the manual for details.
     
  16. renteasternmarket

    renteasternmarket New Member

    Joined:
    Dec 10, 2018
    Location:
    Virginia
    Hi Dana,
    I have a Takagi Flash T-K2 which won’t stay lit. It is set at 140 degrees. It just started lighting, running for a few moments, shutting off, relighting, then shutting off and indicating error 12 on the display. I have removed and cleaned the flame detector. I’m guessing the unit is 10-15 years old. (We just bought the house this summer.) The unit also runs my radiant floor heating system. The shut off occurs when using any faucet, though initially I could use a colocated deepsink to modulate the flow when someone was in the shower. That no longer works either. I don’t know the maintence record, but I did notice it is missing a water filter and has no clean-out valves installed. As fortune would have it, after fighting with it all day, it has stopped doing it and has been running for nearly an hour as the heating system is starved for hot water in the 29 degree outside temps. Any insights are most appreciated.
     
  17. renteasternmarket

    renteasternmarket New Member

    Joined:
    Dec 10, 2018
    Location:
    Virginia
    Update: The radiant floor system ran all night. As soon as the shower was turned on the system read error 12. Turned off the heat and the system provides hot water for the shower. Can’t seem to run both at the same time?
     
  18. renteasternmarket

    renteasternmarket New Member

    Joined:
    Dec 10, 2018
    Location:
    Virginia
    Man this thing is finicky! Burner works but from 0 to 1.6 GPM I have no hot water even with the flame lit. Turn off all faucets and turn the heater back on it works with a 2.4 GPM flow rate.
     
  19. Scott Thibault

    Scott Thibault New Member

    Joined:
    Feb 13, 2019
    Location:
    Little Rock
    I have been struggling with a 12 yr old K2 for a few months. It usually works but at times won't light or just goes out. I have done many of the initial steps including installing the remote controller. It is giving both error 11 & 12. The thing that stands out to me is that before it lights, there is a series of three clicks. You also hear this click when an extra hot water faucet is turned on or off while running.
    When the unit doesn't light, this preemptive series of clicks do not occur. Therefore, i am focusing on this solenoid(?) or whatever triggers it.
    Any idea what creates that noise?
     
  20. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The clicking is the igniter rod, and that's normal to have it click more than once before firing off. I'm not sure if it should be clicking again when there is a sudden change of flow (as in turning a tap on/off.)

    Clipped from this page (for debugging the later TK4):

    11 (Three Times): Ignition failure

    1. Check gas supply and inlet gas pressure.
    2. Check if the Hi‐limit switch (Part #412) is properly functioning.
    3. Check for connection/breakage of wires (Part #413, 708, 709, 712), burn marks on the computer board (Part #701), and/or soot on the flame rod (Part #108). And then if O.H.C.F (Part #413) is breakage, Consult the manufacturer.
    4. Check if there is a buzzing spark ignition sound coming from the burner (Part #101) when water heater prepares for combustion.
    5. Listen for the double “clunk” sound coming from the gas valves assembly (Part #102) when water heater goes into combustion.
    6. (Only no sparking and/or kick sound) Check voltage on each wire to gas valves assembly (Part #102) and/or the igniter (Part #711). Refer to the “Appendix A” in Section C. *No sparking sound >>>>> Refer to the #1 at “Appendix A” in Section C. *No kick sound >>>>> Refer to the #2 at “Appendix A” in Section C.
    7. Check if there is leaking from heat exchanger (Part #401)
    8. Check if there is dust and lint in nozzles of the manifold (Part #102).
    9. Check current on the flame rod (Part #108). Refer to the #3 at “Appendix A” in Section C.

    12 (Three Times): Loss of flame

    1. Check gas supply and inlet gas pressure.
    2. Check if the Hi‐limit switch (Part #412) is properly functioning.
    3. Check for connection/breakage of wires (Part #413, 708, 709, 712), burn marks on the computer board (Part #701), and/or soot on the flame rod (Part #108). And then if O.H.C.F (Part #413) is breakage, Consult the manufacturer.
    4. Check if there is leakage from heat exchanger (Part #401).
    5. Check if there is dust and lint in nozzles of the manifold (Part #102).
    6. Check current on the flame rod (Part #108). Refer to the #3 at “Appendix A” in Section C.
     
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