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Buderus GB142, doesn't answer call for heat

I had a Buderus GB142 boiler installed in 2008. DHW and 3 zone hot water heat. Saturday morning (two days ago) thermostats on 70, house at 63 and scrolling through the Service button shows code OH (standby/no call for heat). The circulator pump was running, all three zones are calling for heat yet the boiler does not receive/answer the call. DHW is fine, no issues.

The Chimney Sweep button will fire the boiler and run for 30 minutes, as expected per the service manual. Once the 30 minute cycle completes the zones continue to call for heat but the boiler does not fire and the control panel displays OH/no call for heat (Heating System Status LED off, Burner Operation LED off)

This AM the house was at 60 and stats at 70. Same story as above re: pump running, OH code, etc. Switched one stat to off, the other two as low as they would go (they are heat only, no on/off). Waited 30 minutes and moved the stats back on/to 70 and unit now fires and operates as it should, with both Heating System Status and Burner Operation LEDs lit. All zones receiving 151 degree heating water (current outside temp @35F).

My installer/service guy had to leave the business due to health issues and I've had difficulty finding a qualified tech (Monroe, CT and interested in recommendations). I'd like to get some feedback here to help me understand what may be going on with the unit so I can have a productive and intelligent conversation with service techs I call.

Thanks in advance!

Comments

  • Ironman
    Ironman Member Posts: 7,367
    Does the 142 have an AM10 outdoor reset control installed?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • kcopp
    kcopp Member Posts: 4,419
    Start simple. Is there an issue w/ the t-stat? ...batteries new? Wire cut? Screw off a terminal?
  • Manny3636
    Manny3636 Member Posts: 6
    Yes it does.
  • Manny3636
    Manny3636 Member Posts: 6
    Just watched it go through the process of receiving the call for heat. The HW Heat LED lights, the code goes to OA, the blower will run for a few seconds, the boiler does not fire, and the HW Heat LED goes off. Tries to cycle/fire a few times then gives up. Zone valves remain open, relay indicates it is sending signal to boiler, but the boiler remains in OH and does not try to fire again.

    Watched this go for about 20 minutes, with outside temp dropping to 30F and HW heat water temp going down to 80...still no firing of the boiler.

    Eventually shut off unit, waited 5 minutes, and switched it back on. This time the boiler picked up the call for heat, OA code/HW heat LED lit, and after about 2.5 minutes the boiler fired. Been running for about 90 minutes without issue now.
  • Manny3636
    Manny3636 Member Posts: 6
    Sorry kcopp...missed your question...

    Wires/connections/terminals all solid. Old thermostats, no batteries.
  • Ironman
    Ironman Member Posts: 7,367
    edited November 2015
    The AM10 may be acting up.

    If you have a zone control panel, you can try temporarily connecting the end switch terminals (XX) directly to the "WA" (green) terminals on the boiler. Doing this should cause the boiler to fire and go to the water temp setting on the space heating dial (up to 194*). The ODR function will be bypassed, but you'll have heat - if the AM10 was the problem.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • GW
    GW Member Posts: 4,691
    Outdoor sensor acting up? See what temp the am 10 says the outdoor temp is.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • Manny3636
    Manny3636 Member Posts: 6
    AM 10 is reading correct outside temp. 25F on AM 10, 26F on thermometer outside .

    Seems like it'll go for a few hours as it should. Answers call for heat, fires the boiler when HW heat water drops to around 90, etc. Then it will just refuse to fire when called upon and the HW heat water temp crashes. After a few unanswered calls for heat by the boiler it stops trying to get it to fire and just stays in OH no matter how cold the stat or return water are.
  • kcopp
    kcopp Member Posts: 4,419
    I would still pull the wires for the outdoor sensor off and see what happens.
  • richrsd14
    richrsd14 Member Posts: 2
    edited March 2018
    My 2012 GB142-45 has exact same problem. After 5 years of no problems, would not answer heat call in am after night setback or period of lower thermostat setting. “OH” reading & no fire. Shutting power on/off from wall (not from gb unit) reset it fine. Temp reading on RC10 would be stuck at higher water temp than was real, but lower than AM10 minimum, & then drop to true lower temp with power reset & fire. Sensors tested OK, taco relay & pumps Ok, AM10 reading accurate outside temp. Bypassed AM10 & everything worked fine, except of course no more modulation- boiler went to high fire with every demand. Replaced AM10 & everything working perfectly for 1-2 months, now same problem starting again. Gradually happens more frequently over time. Appears to be AM10 again, but possibly something else causing it to malfunction. Internal voltage problem? Im in CT & use Air Inc for service. They do good job. Daniels energy maybe closer to you & also services Buderus. Original AM10 just out of warranty but I will see if Buderus in NH will make an exception. It practically broke on 5 years to the day. What have you done since posting?
    Oleg
  • Manny3636
    Manny3636 Member Posts: 6
    Hello richrsd14 -

    My issue turned out to be a bad switching relay (as kcopp suggested, something pretty simple vs more of a technology problem). Fair to say this was not a Buderus problem. Switched out the relay a year or so ago and have had no issues since. Well, other than condensate line freezing up in late Dec/early Jan when we were consistently below zero in CT and the water backing up through bottom of the unit and all over the floor of the basement (no, my installer did not run the line to an inside drain like he should have but instead out through the wall of the walkout basement, 90 degree down about 3 inches off the outside wall and maybe 3 feet or so above the ground...son of a gun froze a solid, crystal clear and thick 3 foot long icicle, requiring repeated trips per day with the missus' hair dryer to thaw it out). Again, I realize this was an installer mistake and not anything to do with the unit.

    Getting back to your issue, it does sound a lot like mine. We finally diagnosed the relay as the culprit b/c I wiggled the wires coming out if a few times out of frustration and suddenly the call for heat was sent/received properly. The tech that ultimately installed the new one said it was a bad circuit board and they replace them somewhat regularly. I'm just Joe Homeowner and not an expert by any means, but i would try to isolate/reconfirm these connections are working properly.

    I appreciate the input on techs in the CT area. I don't want to be overly critical of the ones that have attempted to provide me service but their area of expertise is really in the more traditional boilers in the market and not this technology.
  • richrsd14
    richrsd14 Member Posts: 2
    Thank you for that advice! I will look into the relay as possible culprit....
  • whoopsumbass
    whoopsumbass Member Posts: 2
    Folks if you are still monitoring this post, I have same issue on GB142 supplying 4 Zones of heat and DHW. Unit ignites to heat DHW BUT NOT for floor heat. Installer is very good thought it may be AM10 Controller, but his tech rep said to disconnect AM10 and see if the ARGOS CONTROLLER is not getting the demand for heat to the boiler. Trying to narrow problem to either Argos or AM10. Boiler never throws a code. If I turn off power to Argos and put it back on resets boiler and call for heat is recognized and it ignites. As soon as it satisfy heat shuts down and may not refine for floor heat but works ok for DHW. ANY COMMENTS OR INSIGHTS ARE APPRECIATED BEFORE I SEE INSTALLER TOMORROW AT 3 and spend more money.
  • whoopsumbass
    whoopsumbass Member Posts: 2
    Forgot to ask what relay was loose? Was it on something like Argos pump controller?
  • tomhorsky
    tomhorsky Member Posts: 5
    edited December 2020
    Hi, I'm new to forum, and I have the same problem with my Buderus GB142 boiler discussed above. I live west of Boston, MA, and have only found one local service company who maintains Buderus. Since my problem is intermittent, they have advised me it will be difficult to troubleshoot. I am about to order a replacement AM10 controller, found one on the internet, but learned that the AM10 has been discontinued. Anyone know if there is a new model, or is it just that Bosch wants to discontinue the GB142? Anyway, any advice as to how to diagnose which component or system is faulty is much appreciated. For now, I plan to ask my service company to install the replacement AM10 in hopes that that will solve the problem.
  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    It might not be the AM10. Look at what it is supposed to do. It modulates the boiler in accordance with the outdoor reset, and it has a warm weather shutdown.

    So... first thing to do is to see what outside temperature it thinks it is seeing. If this is correct, at least you know that the outdoor sensor is reading properly, and the AM10 is seeing it properly. If not, check the outdoor sensor and all the wiring associated with it (not a bad idea anyway -- a loose connection there could cause a very hard to diagnose intermittent)

    If it is, check and see if for some reason the warm weather shutdown temperature is correct. If not... fix it and see if that helps.

    If that is correct, then you can start worrying about the AM10 itself.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tomhorsky
    tomhorsky Member Posts: 5
    Jamie, thanks so much for the advice. I checked the settings on the AM10 and they look OK--outdoor temp reading about 5 deg high (reads 46 when the temp is 41), warm weather shutdown temp set at 75F. The supply temp setpoint was at 163F when there was demand, and 32F with no demand.
    The problem has been recurring in early AM, i.e., after thermostat setting of 62 overnight, the burner doesn't come on when the thermostat demands 68, although it looks like the circulator pumps are on. So this morning I pressed the chimney sweep button on the BC10 controller for 2 sec and the boiler came on in manual mode for 30 min, and heated the water to 194F. After one cycle, the unit has operated normally ever since.
    Maybe I will continue this manual intervention in AM until something changes...
  • GW
    GW Member Posts: 4,691
    No code? Normally there’s an error code when there’s a problem.

    AM10, That can be taken out of the picture, in several minutes. kind of surprised they’re recommending that without knowing for sure. Unless, their traveling costs are higher than the part itself, which happens sometimes. 

    Does it refire after reset every time?

    nat gas? LP? 

    You are pretty sure the boiler has been cleaned properly? Hate to say, some people should not be within 10 feet of this boiler.


    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • GW
    GW Member Posts: 4,691
    FW Webb has dozens of the AM10s 

    Slightly expensive part to be guessing at.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    After your little test there -- and having it come on after the chimney sweep function -- I'm even more inclined to think the problem is somewhere else....
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tomhorsky
    tomhorsky Member Posts: 5
    Gary, thank for your comment. No, replacing the AM10 was my idea, not the installer's. 2nd morning in a row I had to use the chimney sweep to get the boiler to fire. Yesterday it worked properly all day after using the chimney sweep. I have a 8-yr-old
    nat gas system. The service company seems to do a proper job cleaning and servicing the GB142, but says they cannot diagnose the problem if it is intermittent. If it persists, I will have them try anyway.
    Any thoughts on setting the BC10 control to auto, which I think bypasses the AM10 altogether?
  • tomhorsky
    tomhorsky Member Posts: 5
    Jamie, any guidance for troubleshooting? It seems to me that this problem of the unit "getting stuck" is fairly common, so must be susceptible to diagnosis. There are lots of troubleshooting procedures contained in the Servicing Instructions, but they seem to be used in response to an error code, as GW mentioned, but my unit doesn't report an error.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,540
    tomhorsky said:

    Hi, I'm new to forum, and I have the same problem with my Buderus GB142 boiler discussed above. I live west of Boston, MA, and have only found one local service company who maintains Buderus. Since my problem is intermittent, they have advised me it will be difficult to troubleshoot. I am about to order a replacement AM10 controller, found one on the internet, but learned that the AM10 has been discontinued. Anyone know if there is a new model, or is it just that Bosch wants to discontinue the GB142? Anyway, any advice as to how to diagnose which component or system is faulty is much appreciated. For now, I plan to ask my service company to install the replacement AM10 in hopes that that will solve the problem.

    GB142 is discontinued
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • GW
    GW Member Posts: 4,691
    Robert I have a brand new one of you need it 😀
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • GW
    GW Member Posts: 4,691
    This may help 


    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • tomhorsky
    tomhorsky Member Posts: 5
    Thank you, Gary. Do you suggest I check the external connection board to make sure the colors match the print?
  • GW
    GW Member Posts: 4,691
    Tom I was just thinking to wanted to bypass the AM10. This is how. If it’s too technical just have the service company do it. Hope it all works out 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    @tomhorsky , don't just check the colours. Verify which wire goes where. Electricity is colour blind, and you have no guarantee that the installer used the drawing colours.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GW
    GW Member Posts: 4,691
    Jamie that’s the color of the terminal plugs, it’s quite easy 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • GW
    GW Member Posts: 4,691
    In color 


    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • psb75
    psb75 Member Posts: 828
    Jamie,
    You are so "old school". And...that's not a 'bad' thing!