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Buderus GB142 ... multiple corrosion issues.

woobagoobawoobagooba Posts: 4Member
A noob here, thanks for all the terrific advice. Hoping to get your views on the following. Pics attached.

I've got a new-to-me, approximately 10 year old, natural gas fired GB142 w/ indirect Buderus HW tank. 3500 sq ft house with cast base boards and radiators. The issues ...

- the pump manifold is rotting away. Why? Particularly concerned with the related corrosion within the boiler. I read the manifold is a problematic original, and there was a replacement offered at some point?

- the vent piping seems to be discolored, and the 90 degree elbow just before the turn to go outside the house appears to be leaking. Condensate not draining correctly and caused failure of the PVC cement joint? Seems a slope issue with the exhaust line? Exhaust too hot?

- can't see it in the photos, but their is a hole (1" round ) rotted through the back of the (aluminum?) exhaust vent adapter (no worries, the unit is shut off). It was leaking exhaust directly into the basement! I assume this was a condensate issue. New flue vent adapter kit (plastic) has arrived and is ready to go in.

HX has not yet been disassembled. No idea how often it was cleaned. Probably due for cleaning.

So I'm going through the math repair versus replace. Also need recommendation for good Buderus service tech in Eastern MA.

Much appreciate your opinions on of all this.



  • IronmanIronman Posts: 5,082Member
    I'd say a severe lack of maintenance. No excuse, that's the easiest mod/con to clean.

    Just go through and clean or replace whatever needs it.

    Is there an AM10 boiler reset control? The flue pipe deterioration leads me to believe not. Without it, the high limit on the boiler is 194* which is unnecessary and inefficient.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rodhot_rod Posts: 11,608Member
    Check your model number, see if any recalls are open.

    Water quality is critical in aluminum block boilers, a tight ph, below 7 gpg hardness, and chloride level below 100 for the fill water.
    Some installer like to add corrosion inhibitors to protect the HX. Conditioners buffer the ph, introduce oxygen scavengers, and add film providers to protect all the metals. Conditioners do need maintenance and occasional buffers added.

    Here are water specs, and approved aluminum friendly conditioners for one of the newer models.

    If you have a manual check it for cleaning and service info,
    if not, download the manual for your exact model.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Posts: 3,416Member
    Seems like you may have anti freeze in the system.

    That pipe is showing corrosion in an odd spot, is there something dripping on it?

    The manifolds have been a pain at times:

    The “flue adapter” has also been a problem. We do a couple a year, 1/d day project

    when we get new customers calling us for GB142 service, we have them read our GB142 letter and acknowledge it. It’s filled with items that can come back and haunt us

    If it has antifreeze and it hasn’t been serviced in a while, start saving for a new boiler.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • woobagoobawoobagooba Posts: 4Member
    edited August 14
    @Ironman ... yes an AM10 is installed and I see the the outside temp sensor mounted a few feet below the exhaust.

    @ Hotrod. I did locate the Buderus water chemistry guidelines. I will check with the town (I am on muni water), or better yet do a Rhomar test. And also will check on that recall notice.

    @ GW. Unlikely there is antifreeze in system ... I will check.

    PO claims unit was serviced annually in Fall. Service tag indicates it was serviced Fall 17 and 18. I popped open the HX burner fan and condensate collector plate. I ask you, is this one heating season of scale buildup?

  • woobagoobawoobagooba Posts: 4Member
    edited August 14
    Just noticed corrosion in the condenser plate corners? Cause of the corrosive leak on the supply and return lines to the lower right inside the enclosure?
  • IronmanIronman Posts: 5,082Member
    edited August 14
    Clean the heat exchanger by spraying mineral oil on it, then turn it on. Avoid getting it on the ignitor and flame rod. Repeat if needed (very likely).
    Get a new gasket for the collector plate and maybe a new trap. Clean they flame rod with a dollar bill or replace it.

    As, mentioned: it's suffering from a severe lack of maintenance. The previous owner may have paid someone to maintain it, but they grossly failed to do so.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • ZmanZman Posts: 4,969Member
    A few quick thoughts:

    The vent piping in the picture has some issues. One of the pipes is definitely cellular core, confirm that the exhaust pipe is not.
    The vent pipe does not appear to be sloped correctly back to the boiler. Zip ties off of domestic piping is not a proper support. If the vent pipe is yellowed from excessive heat, it needs to be replaced.

    The HX with that level of fouling is and indication of neglect. I would also wager that a combustion analysis has never been performed.

    The water chemistry is critical with that boiler. What are the levels now and what impact has that had on the internals.

    When you consider what it will take to get this boiler back in operation (for a little while before something else goes bad), how does that compare to the cost of installing a new boiler?

    In my experience, 10 years life expectancy is about average for that model boiler (local water quality and maintenance play a huge factor). I would sawzall it out and get a new stainless steel firetube boiler.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • woobagoobawoobagooba Posts: 4Member
    Thank you. Re: the water quality. I intend to have Rhomar do a test. From what point in the system should I extract the sample? The make-up water supply is from the muni water feed.
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