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Bosch Combi 151 Overheated and melted wires C6 Fan Error

hibby50
hibby50 Member Posts: 15
edited January 2022 in Gas Heating
Hi everyone, I woke up this morning to no heat and hot water :/

I went down to check the combi and it had a C6 fan fault error on the screen. I power cycled the boiler and it came on and the fan was running with no errors. I ran an output test and saw it heating up. I went outside and confirmed the intake and exhaust were working. I came back in and saw the boiler smoking. I immediately cut the power and gas. I opened it up and found crispy wires and melted insulation.

I have someone coming out sometime today. But I'd really love an idea or second opinion of what the heck happened here since melting wires and gas are scary and I want to make sure this is fixed right.

Note: in the pictures i removed that wire to inspect the state of the wire's insulation, seemed ok but the connector is very crispy.





Comments

  • heathead
    heathead Member Posts: 237
    Looks like the sight glass window is broken? Flame coming out of that open hole now. Combustion numbers need to be check after the glass is replaced. Someone else will chime in if it's possible that it was shattered by a misfire.
    kcopp
  • hibby50
    hibby50 Member Posts: 15
    heathead said:

    Looks like the sight glass window is broken? Flame coming out of that open hole now. Combustion numbers need to be check after the glass is replaced. Someone else will chime in if it's possible that it was shattered by a misfire.

    I thought that could be the case but I wasn't sure. That's the viewer into the combustion chamber right? I wonder what could have caused it to shatter?
  • Big Ed_4
    Big Ed_4 Member Posts: 2,878
    edited January 2022
    Bad clean out plate gasket , is the shield missing behind it ? Some units came through with loose clean out door bolts... Extremely dirty boiler ?

    There was an error rendering this rich post.

  • hibby50
    hibby50 Member Posts: 15
    Big Ed_4 said:

    Bad clean out plate gasket , is the shield missing behind it ? Some units came through with loose clean out door bolts... Extremely dirty boiler ?

    It's possible it's extremely dirty. It was serviced a year ago and I asked if they were going to clean the heat exchanger and they said they can't? which didn't sound right to me. I have only owned the house 2 years and this was installed in 2015. I don't know the service history.

    I will ask the technician to check the clean out plate gasket, unsure where it is located to inspect it myself
  • Big Ed_4
    Big Ed_4 Member Posts: 2,878
    That front door , two bolts hold it to the boiler . The gasket fits into the grove in the door . Two spacers (don't loose) are used at the bolt holes not to over crush the gasket .. Behind the door to gain access there is a loose shield . To clean they make special flat brushes and a scraper that looks like a knife .... Your best off replacing the whole ingniter and flame sensor ..

    There was an error rendering this rich post.

  • hibby50
    hibby50 Member Posts: 15
    Big Ed_4 said:

    That front door , two bolts hold it to the boiler . The gasket fits into the grove in the door . Two spacers (don't loose) are used at the bolt holes not to over crush the gasket .. Behind the door to gain access there is a loose shield . To clean they make special flat brushes and a scraper that looks like a knife .... Your best off replacing the whole ingniter and flame sensor ..

    Gotcha, so the gasket you are referring to seals the plate that contains the flame sensor, igniter, and glass in my 2nd picture? I will ask about the shield when they remove it today.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,878
    edited January 2022
    The sensor ingniter has the broken sight glass , the gasket which looks like its leaking is the large door below the sensor igniter

    There was an error rendering this rich post.

  • hibby50
    hibby50 Member Posts: 15
    Big Ed_4 said:

    The sensor ingniter has the broken sight glass , the gasket which looks like its leaking is the large door below the sensor igniter

    Oh Isee now, thank you
  • hibby50
    hibby50 Member Posts: 15
    edited January 2022
    So the company came out. Could not get the parts for a week. I over nighted the parts to myself, they will not install them since I purchased them.

    I think I am going to attempt this repair myself. My plan is to swap the electrode assembly with the new style that has the different/no window, replace the wires, and clean the heat exchanger and replace that gasket.

    Anything else too look for/do?

    The flame sensor was only about a 1/4 inch long, the theory is that this caused the burner to cycle and got too much gas and misfired. Does that sound plausible to anyone? Only thing is this doesn't explain the fan error.
  • BoschGuy
    BoschGuy Member Posts: 5
    Looks like the inspection window glass on the boiler heat exchanger shattered allowing combustion gases and flames to escape the heat exchanger. Might have been caused by a combination of very high gas pressure, a fouled/dirty HX, incorrect combustion setting/analysis.

    What is the current state of the boiler?
    Sal Brunetto
    National Sales Manager
    Bosch Thermotechnology
  • Le John
    Le John Member Posts: 226
    That is pretty scary. First thing I did was to check the site glass on both mine and my tenant's Lochinvar Noble.

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