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IBC 20-125 Fault Code 29, 30

Crispy Member Posts: 17
2 year old combi. Had a HW failure. Am not using space heat right and have not tested that. Saw a 29 and reset. HW fine. Failed again with a 30. Manual says for 29, 30 - Gas Valve relay faulty- Replace Controller. Reading other areas for no HW, the flow sensor and temp sensor come up. When I reset, the HW comes back and will operate properly for several cycles or for
a whole shower. It has failed 8-10 minutes into a shower. Wondering about the flow sensor. Manual does mention cleaning as a solution. If it is listed as a 12k ohm sensor, does that mean it should read 12k ohms when probed? Anyone find HW flow sensors need maintenance? Thanks in advance, C. 


  • 109A_5
    109A_5 Member Posts: 1,344
    edited August 2022
    Crispy said:

    2 year old combi.

    I'd think I would let the 5 year warranty take care of it. A controller board sounds expensive.

    Sounds like a failing relay or a failing solder connection on the controller board.

    "Manual says for 29, 30 - Gas Valve relay faulty- Replace Controller ". Not sure about the association to the any sensors with this type of failure.

    With the AC power to the boiler turned off, I suppose you could disconnect and re-connect connector X1 to the gas valve and see if it makes any difference. "Replace Controller" sounds pretty specific to me.

    As far as the resistance of the thermistor type sensors. The nominal resistance value 10KΩ or 12KΩ is at 77℉ or 25℃. If the sensor is at another temperature use the chart in the manual to determine the resistance at that temperature.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    GGrossAlan (California Radiant) Forbes
  • I'd call technical support IBC at (844)432-8422.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • pedmec
    pedmec Member Posts: 936
    if its 10k then it is 10,000 ohms @ 76 degrees. 12k is 12,000 @76 degrees. k represents one thousand
  • Crispy
    Crispy Member Posts: 17
    edited October 2022
    Follow up: Five year old DC 20-125 throwing 29 and/or 30 code…. A very helpful IBC representative was quick to say the trouble-shooting guide suggesting “replace control board” is wrong. The problem 9/10 times is the Spark Module. There’s a kit that includes the module, an igniter probe and gasket but I needed only the module. I simply switched out the module with a pigtail to the terminal block. Problem solved, all boiler functions restored. Hope this helps, C
    Alan (California Radiant) Forbes