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Buderus won't run on generator

TwistedtreeTwistedtree Member Posts: 1
I, along with a number of other people, have been unable to get a Buderus GB boiler to fire on generator AC power. They work fine on grid power, and even on an inverter, but fail to fire when powered by a generator. This of course comes as a great surprise to people who install a backup generator with a goal of maintaining heat during a power outage.

I've sent multiple inquiries to Buderus about this and the silence is deafening. I've received no response at all. I've tried various forms of power conditioning, frequency control, grounding and isolation, etc. with no success.

My first question is whether there is anyone out there who has been successful running a Buderus off a generator? Maybe your success will help the rest of us. My other objective, quite frankly, is to generate some pressure on Buderus to address this problem. At this point I steer people away from them if they have any plans for backup power. It's very unfortunate since the Buderus is otherwise a very attractive product.


  • seabee570seabee570 Member Posts: 89

    It is most likely not the fault of the boiler,but the generator.You possibly need a very good ground on the generator.Here is what happened to me.I was replacing the electrical service in my dads house in january.when I hooked up the furnace to generator it would just start the cycle but would not attempt to light off.I had to use the ground wire going back to the panel and it worked.CAUTION-THIS CAN BE A DANGEROUS SITUATION.I would try grounding the generator and then using a dedicated ground back to the generatror for the boiler.....
  • seabee570seabee570 Member Posts: 89

    you might have answered your own question...if it runs off of an inverter you might need to feed an inverter with the generator, and then from inverter to boiler...or an inverter duty generator
  • klausklaus Member Posts: 183

    Did you check your AC frequency output???

    This is one of the most common things I see when it comes to generators and electronics. The output frequecy of small generators seems to vary more than largesr counterparts as the flywheels have less kinetic energy to stabilize the output to the changing load and rley on the throttle govenor to adjust and maintain engine RPM which usually isn't quick enough to respond to a sudden load change.
  • Jamie HallJamie Hall Member Posts: 6,708
    You might have a point...

    Hadn't thought of that. The generator should be wired so that when the transfer switch is thrown to it, its ground and neutral are connected to the ground and neutral of the house switchgear, as well as, obviously, both hot lines. If that is the case, and the voltage is reasonably close to line (120/240 or possibly 120/208 3 phase) and the frequency is reasonably close to 60 hz, it really should work...


    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Genny specs?

    Is this a 3600 or 1800 rpm generator? The 2 pole generators that run at 3600rpm for 60 Hz create a crappy sine wave. It can look more like a stepped square wave with noise on top of it. 4 pole 1800 rpm units are better but still not as clean as house AC.

    I would not even recommend a 2 pole unit.

    You might try conditioning the output of the 1800rpm unit or as suggested using an inverter to clean it up.

    Is the generator on a transfer switch which if wired correctly completely isolates the house from the powerline AC and provides a proper ground. The generator ground may require additional external ground rods when it is not connected to the neutral/ground bus that normally would be wired to the powerline AC (interrupted by the transfer switch).

    Is the boiler circuit and some other circuits just a partial house load for the generator? A smaller generator may have a transfer switch but be wired to just some of the loads like fridge, some lighting and the boiler. In this case I would look at how the wiring was handled. There may be some ground loops because the partial loads are not properly isolated.

    Is this a case where the partial loads are on a sub-panel off the main panel with a transfer switch between? A sub-panel has its neutral/ground jumper removed when fed by a main panel. When run off the generator, it can be acting as a "main" panel and need the neutral/ground reconnected now that it is isolated from the house main panel.

    In the case of the Buderus, they must either checking for correct power or just sensitive to incorrect power.
  • Steve EbelsSteve Ebels Member Posts: 1,287

    The Freq is the thing that screws up electronics. All the internal "clocks" in circuit boards look for that 60 cycle AC and when it's off by even 2-3% they are often programmed to shut down. You need to get the RPM on the generator dialed in to 3600 exactly and then hope it has a good enough governor to maintain it as loads vary. Often times a portable genset such as found in HD, Lowes or the like are not going to cut it. The worst/cheapest are some of the units from Northern Hydraulics and Harbor Freight.

    If the owner doesn't want to pop for a home standby unit like a Generac he will have to buy a UPS that is capable of handling the load of the boiler and wire that inbetween the genset and the boiler control. I've run your problem before and that solution works. Problem is the UPS may cost him more than he spent on the genset depending on the amp draw of his boiler system.
  • Honda

    makes a true sine wave generator. It is an inverter unit and runs at varying rpm to satisfy load. They are quiet and they work great. I put a constant pressure pump in my home and was told it was the only generator that would run it. I would rent one and check before buying.
  • Ron HuberRon Huber Member Posts: 127
    same problem

    With a few Triangle Tube Prestige boilers, had to adjust the speed of the back up generators to fix the problem.
  • Darin CookDarin Cook Member Posts: 45
    Twisted Tree

    Buderus has different versions of the UBA control out there. Your customer obviously has the version that will not recognize the "dirty" voltage. If you replace the UBA with the correct version, the boiler will run with no issues on generator power. I had the same issue with one boiler in an area that got pounded by our bad ice storm in upstate NY. Contact your local Buderus product rep and tell him that you need to upgrade your UBA control. Oh yeah - it was free to boot!

    Problem solved!!!

  • geniustimegeniustime Member Posts: 1
    The Buderus service man

    If you have a GB142 Buderus boiler and it wont run on your generator or you keep getting error codes you need to check your UBA board. If your UBA doesn't say 3.6 your boiler will not run on a generator or you will keep getting error codes.
  • heatpro02920heatpro02920 Member Posts: 991
    4 year old post, lol

    I came across this problem in the past, just installed a line conditioner and FIXED.... I believe it was a tripplight or something like that, I haven't had any issues lately..
  • Lali77Lali77 Member Posts: 1
    Munchkin boiler didn't start on generator. Problem solved.

    I had the exact problem on my Munchkin T50 boiler, it's similar technology to the Buderus. I spent lots of time on these forums and researching UPS' and inverters and other technology I thought might work. The problem was all in a twist of a screw. FYI on that issue with the Munchkin Boiler faulting (f-19) on the Generator

    I got it. It works perfect now and with all 10 circuits on the transfer switch switched on and everything powerd up. Munchkin boiler, Tv laundry. Comp. all lights. Even a space heater. Etc...

    The Speed Control (a spring loaded screw) on the generator needs to be set balanced to maximize power and still keep the frequency under control. Too much speed creates spikes above 60hz, too little speed not enough power and under 60hz.


    GENERAC GP5000

    3. Connect an AC frequency meter to one of the AC output receptacles. No-load frequency should be between 62.0 - 62.5 hertz.

    4. If the frequency/RPM are incorrect, turn the speed adjust screw until frequency/RPM is within limits. Turn clockwise to increase frequency/RPM, counter clockwise to decrease the frequency/RPM (see Figure 19).

    5. After adjustment is complete add a drop of removable loctite (Loctite 241) to the threads of the speed adjust screw (see Figure 19
  • LAG1VTLAG1VT Member Posts: 9
    UBA 3.6 repair part needed

    Hi ,

    I have a UBA 3  V3.6 that needs to be repaired. The entire fuse socket dropped down inside the enclosure when trying to replace the fuse. Is there any way I can get a replacement part? The socket appears to just push into the housing and make contact with the  circuit board.  That is, there are no wires actually attached to the fuse socket that I can see.  Possibly someone out there that has replaced an old UBA V3.5 with the V3.6 still has the 3.5 laying around. I would assume the fuse socket is the same.

    If anyone can help let me know.
  • ZmanZman Member Posts: 3,517

    What in the world does this have to do with the original post?

    If you have a question about buderous parts, make a new post.

    It would help if you gave the model of the boiler and the area of the country you are in.


    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • LAG1VTLAG1VT Member Posts: 9
    UBA 3.6 repair part needed

    Sorry ZMAN,

    This is my first time on the forum and I guess I didn't do it properly. I will start a new post as soon as I figure out how to do it. I put it here because my whole problem started when my Buderus GB142 would not run on my generator during the recent power outages caused by the ice storms here in Jericho, VT. Recommended fix was to replace UBA 3 V3.5 with UBA 3 V3.6.  I got the 3.6 but the fuse assembly is damaged.
  • SWEISWEI Member Posts: 7,356
    How to do it

    There's a button at the top right of each forum labeled "+ Add New Thread"

    For this forum, it links to
  • LAG1VTLAG1VT Member Posts: 9

    SWEI, thanks for the help.
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