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Buderus GB-142

Entropic Member Posts: 3
Have 2 Buderus condensing gas boilers, Model GB-142 Logamax Plus that I need some help with.

Went to clean out the condensate tank at the left rear of the boiler, and it was pretty full of a grey mud like material. Removed and cleaned the tank. Took the bottom cover plate off after undoing the spring snap clips and just about had to pry it loose. Well, I did have to pry the cover enough to get the top portion to come loose, then carefully get the rest off. The gasket/seal seems to stay with the boiler section except where it pulled free at the back and bottom right corner. The lid was completely encrusted with white and grey buildup especially where the condensate would flow through the hole at the bottom left. The hole was completely jammed and nothing could get out to the condensate tank. I chopped away at it with a flat edged screwdriver end, and got it opened up and almost all the gunk off most of the lid. I did the same to the flat plate between the tubes with coils/fins and tried to wire brush off the coils mostly of calcium? deposits. Put her back together and it's running.

My questions are:

1). soft water- the installer said we could NOT use our softened water so they plumbed it with the high iron/calcium water. It looks like the hard water is killing the boiler fins/coils everything it comes in contact with?!

Is there something to use, a spray or chemical to dissolve this hardness from the fins? It's like concrete! Wire brush isn't cutting it. BTW, the second boiler in my barn DOES have softened water being supplied to it, I believe, because that is what we ran over to the barn from the house. In both cases we have Pex tube radiant heat. Is the softened water going to do harm to the barn system?

2). Is the silicone like gasket supposed to be replaced whenever one removes the cover to clean the boiler fins, etc?

3). How often do these boilers need to be taken apart and cleaned, and does the condensate holding tank often jam up with the lava like mud? Is this just a byproduct of the combustion process?

4). If I had to, can I buy just the outer door cover that has the holding tank orifice, or am I screwed if the gasket sealing flange gets chipped and the seal leaks?


  • Hydro
    Hydro Member Posts: 20

    Finding a plugged up condensate, means your boiler has been severely neglected. This boiler should be cleaned annually, or at least semiannually to avoid this problem in the future. If the condensate is plugged up to the extent which you are describing, you can bet your heat exchanger fins are blocked also. I am willing to bet your gas bill has gone up significantly. For this much scale to take place, (and I have seen it more than once) at least the lower part of your heat exchanger is surrounded by condensate water and the flu passages are at the very least, partially blocked, as they are located on the bottom. You should have this boiler serviced immediately by a qualified technician. The flue passage on the bottom is very narrow, and you will need to dismantle the boiler almost completely to access the rear flue, and properly clean it. The burner must also be serviced, and tuned with a new combustion analysis. The bottom gasket is designed to be reused, you can repair it with silicone if you rip it while you wait for a new one, but that is the least of your problems right now. I have run into this a few times and it is a long process to get that boiler back into shape. Luckily the burner is on top, but that poor boiler was still running? If so, not for much longer. Imagine the burner trying to heat the HX and the condensate that was surrounding it!!! And the fan trying to force the flue gasses through all of that mess!!! I'm sure I have a picture I can post.
    "If you don't know where you are going, any road will get you there"
  • Ironman
    Ironman Member Posts: 6,555

    The buildup on the heat exchanger is a byproduct of combustion from when the flue gasses condense. It's on the fire side of the heat exchanger and has nothing to do with mineral content of the water on the inside of the HX.

    The grayish muck in the condensate trap is normal for an aluminum block boiler, also.

    You suffering from a sever lack of maintenance and should get a pro who's familiar with the GB142 to service it immediately.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Hydro
    Hydro Member Posts: 20
    edited January 2014
    GB 142

    Here it is! took me a while to find it. Plugged solid, even when I made this hole with my finger it still held water.
    "If you don't know where you are going, any road will get you there"
  • Entropic
    Entropic Member Posts: 3
    reply & questions...

    Thanks for the responses, So am I to understand that the soft water is NOT an issue with these boilers, or is it?

    I get it now that the scale and sludge are not a result of the soft or hard water, instead it is a lack of maintenance. Is there a way, or ways to bring it back to spec with a through cleaning?

    I have been trying to find an independent to service the boilers but there are few gas certified guys out on their own in my area and a few companies like the installer use a gas guy to supervise the install, then move on to other new jobs, and service gets a backseat. Can I do the cleaning portion myself and then bring someone in for the gas/air setup, etc.?

    Thanks again guys, and for the pictures!
  • Hydro
    Hydro Member Posts: 20

    I am assuming by your questions that you are not a tech.. My personal feeling is to get a Bedurus tech out there immediately, that boiler needs professional service. When that pipe in the bottom plate plugs up, even partially, the scale and water (which is corrosive), will climb up into the lower part of the flu gas collector, which is located only inches above that bottom plate. This boiler forces flue gasses through a very narrow passage in the bottom of that flue collector, and if it is not 100% clear, it will not run right, at the very least. Removal of that collector is not an easy task, and the entire boiler has to be stripped down, cleaned and reassembled, then tuned. This is not a job for a handyman. If you have trouble finding a competent tech. in your area, go to the Bedurus website, and choose from the menu " find a contractor", enter your zip code, and a list of factory trained companies will come up, and will even show specific equipment that they specialize in.

    Good Luck
    "If you don't know where you are going, any road will get you there"
  • Entropic
    Entropic Member Posts: 3
    Questions remain..... Please some answers

    I agree the boilers need competent service and preventive maintenance, and I will accomplish that ASAP.

    No, I'm not a boiler tech, BUT I am a former foreign auto shop owner, who has also done solar and off peak storage R&D, so taking things apart and cleaning/fixing all kinds of technology is like breathing for me. :)

    I do need to get answers to the following: I have often gotten a P6 error code, indicating low pressure in the house boiler, long before the need to clean/service this boiler. I use the lever on the pressure regulator valve and it comes up to within range. What might be likely causes? A failed pressure relief/control valve diaphragm?

    And again, is softened water an issue, or not, for these boilers? And if non-softened mineral laden water is flowing through the radiant above floor PEX tubing and the boiler's heat exchanger, isn't that going to buildup over time and reduce efficiency/heat output?

  • RobG
    RobG Member Posts: 1,850

    Hydo, not to nitpick but semi-annually means twice a year, bi-annually would be every two years.

  • SWEI
    SWEI Member Posts: 7,356
    Mineral build-up

    will not happen unless the system is using a lot of make-up water.  Do check the manufacturers' specs on hardness and pH, though.  We frequently blend with RO water here in order to meet those.
  • Hydro
    Hydro Member Posts: 20
    edited January 2014

    I stand corrected, thanks Rob. And also on that GB142, I have found a common problem with these boilers leaking through the air vent very slowly, and not something that would jump right out at you unless you look for it. The supply house sells a replacement kit to rebuild it, also, and no disrespect to you as an auto mechanic, I am sure you have a great deal of mechanical ability, I feel that when it comes to a HE boiler, with a potentially blocked flue collector, you can have a dangerous situation, with the possibility of carbon monoxide entering the space and should not be taken lightly. Maybe its not blocked, and its fine, however, when it goes that far, without service and the lower plate,plugs up even a little, the scale will enter the flue collector, and stick to the sides and actually harden like cement, and cause at least some restriction in the exhaust. This is probably the hardest part on the boiler to fully access, and the entire boiler needs to be torn down to get to this part, I would consider myself a junkyard auto mech., I do my own brakes, but I wouldn't try to rebuild my own engine, and dyno test it. Good luck to you whatever you decide.
    "If you don't know where you are going, any road will get you there"