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Buderus GB142-30 Soft 6A (sub 227) only when cold.

Paul WolfPaul Wolf Posts: 14Member

Similar to my post of July 2017, I have noticed that (when cold) my GB142 tries to light 3 times (soft 6A each time) before finally catching and working fine. It rarely makes it to a 4th time and a HARD/lockout 6A.

This happens ONLY after the boiler has cooled to ambient temperature. Like overnight when not in use, or during warmer months when there is no call for heat ot DHW for along periods of time. If the boiler does not have time to COMPLETELY cool down, it will start the FIRST TIME on the next call for DHW or heat. No 6A. The 3 tries thing only happens after it cools completely.

Even though I am in the northeast, it doesn't get the same use as most in this region as I supplement with wood heat.

It has had fairly regular maintenance. About 18 months ago I did the following: replaced the HSI and ionization rod, cleaned the heat exchanger and checked gas pressure and ratio. The gas inlet pressure was 10.10 in h20. The gas/air ratio was at the very positive limit of spec -.04 to 0.00.

I have a spare UBA3 to test with and that didn't make a difference. (I didn't think it would. It was a "I have it, why not try it" type of thing)

Any thoughts?




  • HVACNUTHVACNUT Posts: 2,127Member
    6A as you know is no ionization.
    In order for the UBA3 to clear, the reset button must be held for 5 seconds.
    Can you see the HSI glowing?
    Is there voltage to the gas valve?
    Unless you have the correct instruments, you'll need a pro to diagnose and repair. There's a lot to check on a 6A code.
  • ZmanZman Posts: 4,867Member
    Has a combustion analysis been performed? If so, what were the numbers?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • IronmanIronman Posts: 5,010Member
    Is this on natural or LP?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Paul WolfPaul Wolf Posts: 14Member
    edited April 6
    Gents, thanks for the replies.

    Bob, thanks for the reply. LP.

    A combustion analysis was done when the heat exchanger was replaced in 2015. I do not remember the findings, but the tech did not have to make any adjustments.

    Gas valve has voltage, HSI glows. During each of the 3 failed attempts, the HSI glows, and the flame "puffs" blue for less than a second. Just a quick puff. Not enough to light the "proof of flame" indicator. The third time is always a charm. :-)

    Thanks for the replies.

  • ZmanZman Posts: 4,867Member
    Those exchangers have a tendency to plug up, particularly when the combustion is incorrect.
    The HX should be inspected and cleaned and combustion analysis performed. Don't assume that the tech knows how to perform an analysis without seeing results.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HVACNUTHVACNUT Posts: 2,127Member
    On the next reset try blocking some, not all the air on the intake pipe with your hand immediately after ignition. If it stays lit, theres a combustion issue. HX, gas valve, fan not coming up to speed. Call a pro. It's been 4 years since the last maintenance anyway. And get combustion test results printed out.
    This is not a job for a HO.
  • IronmanIronman Posts: 5,010Member
    In addition to all that's been said:
    1. Make sure the condensate trap, collector pan, drain line are clear.
    2. You may be getting some air in the gas train. Could be a gas valve not seating, small leak on a fitting, etc.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
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