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Buderus GB142 - Code 7H

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Warm day out (79F) so not calling for space heat.
No hot water in the taps though, and the light is on for water heating mode, but the burner isn't lighting (or trying to light). The unit shows the following (scrolling through the menu):
7H
328
70
P23

Note its a 7H, not H7, so not low pressure (and 23 should be OK).
If I turn the unit off and then on, it runs the air system, but doesn't light the burner, goes straight to 7H.

FYI - replaced my UBA3 and transformer about 1.5 years ago.

Has anyone seen this error? I can't find it.

Comments

  • HVACNUT
    HVACNUT Member Posts: 5,865
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    P23 is boiler pressure. 
    70 is supply water temperature. 
    I don't see a main display code 7H or a sub display code 328. There are codes not in the manual that Bosch/Buderus will provide support for to a qualified tech. Can you see the HSI glow in the mirror?
  • kinderhund
    kinderhund Member Posts: 13
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    There is no HSI glow that I can see (tried having a look with the lights off as well.
  • HVACNUT
    HVACNUT Member Posts: 5,865
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    There is no HSI glow that I can see (tried having a look with the lights off as well.
    Even though it's not a 6A code, no ionization after ignition, it wouldn't hurt to check the igniter. It's only 2 screws.
    When was the last maintenance and is there a combustion report for it?
  • kinderhund
    kinderhund Member Posts: 13
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    Weird update. I missed the maintenance this spring due to COVID. So I decided to do it myself now. Took it apart, cleaned out all buildup. Nothing was plugged, but there was quite a lot of stuff in the condensate trap (which is partly cracked, and needs to be replaced), and there was a lot of sulphur-like buildup on the ionization electrode. The HSI and its shield looked ok.

    Put it back together, turned it back on and... same code. Frustrated, I went to bed.

    Got up the next day. All good, back to normal! It was idle ("0H"), but the outlet piping was hot leading to the hot water tank.

    Keeping an eye on it now to see if it reverts back again. Also going to get a tech in to do a proper combustion check and report.
  • Ironman
    Ironman Member Posts: 7,379
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    The 7H code deals with clean power and how the UBA control sees it. There could be a problem with either.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    kcopp
  • kinderhund
    kinderhund Member Posts: 13
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    Well, bad to worse. Got the 7H code again today. Turned off and on again, and now the screen is blank, and there's a loud buzzing coming from either the external connection circuit board or the transformer.
  • kinderhund
    kinderhund Member Posts: 13
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    Thought I'd provide another update. I noticed that there was some crud on the circuit board (the last time I had a technician out, he couldn't fit the cover over the circuit board, so left it on the floor). It was covering one of the external connectors, so I disconnected everything, and gently cleaned the connections on the circuit board.
    At the same time, I noticed that near that connection, there's what appears to be an arc burn in the plastic underneath.

    Plugged everything back in, and we're good to go! Guess water plus circuit boards is bad, huh? :#
  • SergeTheBelgian
    SergeTheBelgian Member Posts: 1
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    Hi Kinderhund,
    Same problem for me : 7H error.
    tell me how the story ends for you
    Serge
    Belgium