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IBC DC 20-125 Error Code 5

Stag Member Posts: 1
edited November 2021 in Radiant Heating
I have an IBC boiler for my domestic hot water and radiator heating.
It's been cutting out and showing error code 5 which the manual says is a poor flame signal. With possible solutions being:
• Condensate drain blocked
• Gas supply pressure too low or drooping under load
• Check ignitor and ignition cable
• Check gas valve adjustment
• Check grounding of all parts of the installation
• Check combustion air supply and flue gas exhaust piping and terminations, possible flue gas recirculation in the system.

We've had the technician from the company that installed it out to us maybe two or three times per week for the last 3 weeks.
They've changed out the flame sensor.
They've adjusted the exhaust and inlet piping.
They've taken off and cleaned out the condensate drain.
They've done other checks for things like gas valve, ignition cable and such.

They keep telling me this is very rare in these boilers, but we don't seem anyway close to a solution.
Has anyone on this forum had something similar that could point to a solution?

Last night I altered the domestic hot water mode from eco to comfort. I believe eco is a mode that tries to learn when you need hot water and tries to keep the domestic hot water in the boiler at temperature during those times. Whereas the comfort mode is less efficient by keeping the water in the boiler at temperature all of the time.
Since changing these modes last night, this is the first morning in 3 weeks we've woken up to warm radiators and hot water available at the faucet. I'm hoping the boiler doesn't error out in this mode, especially with winter getting closer.
Would this mean a circuit board or computer inside the boiler has a fault if one of the modes doesn't work?
If the boiler doesn't error out in comfort mode, is it worth bothering our installer/technicians with this information?


  • kcopp
    kcopp Member Posts: 4,443
    How about the little grounding spring in the burner plate... that in there securely?
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,055
    edited November 2021
    It's pretty rare to have problems like this - good boiler.

    Have they checked the gas pressure with a manometer? Ideally, the static pressure (boiler not running) for natural gas should be 7" wc; propane 11" wc. The dynamic pressure (when the boiler fires and is running) should not drop more than 1" wc.

    If your gas pressure is not correct, it could be a problem with the regulator on your gas meter or the pipe size to the boiler may be too small.

    Negative pressure gas valves are very finicky.

    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