Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Buderus GB 142/30 Intermittent 6A (sub 227) error code "SOLVED"

Paul Wolf
Paul Wolf Member Posts: 35
edited July 2017 in THE MAIN WALL

Sorry for the long post, but I want to provide as much information as possible. I have 10 year old LP fired GB 142/30. It is giving me intermittent 6A (sub code 227) some soft, some lockout. By intermittent I mean (recently) about every other call for heat or DHW. Luckily it is summer and I have the time to deal with it.

The heat exchanger was replaced under warranty 18 months ago for a leaking issue.

In the past, when it has started doing this, it was (at first) very infrequent (once every 1-2 months) and a simple reset would take care of it. As time went on it would get progressively more frequent (2-3 times per week) until I took action. My action consisted of removing the ionization rod, cleaning it with a scotch-brite pad (there wasn't much of anything on it and it wasn't deformed or looked like it was overfired), and reinstalling it. The boiler was then good for 6-7 months. It did this periodically for 3-4 years up to now. June 2017.

So I am at the point I in my first paragraph. Intermittent 6A. What I observe. On a call for burner (either heat or DHW) It goes though its boot up sequence, 1. Purge chamber, 2. OC Energize HSI (glows brightly), 3. OL Gas solenoid/valve opens, 4. stays like this for a few seconds, then a very gentle puff of blue flame in the inspection glass for much less than a second, the green flame-on LED on the BC10 flickers once VERY quickly, then HSI de-energizes and a soft 6A appears. It tries this 4 times, then lockout code (flashing) 6A. After 1-2 times of this 4x sequence it will usually start. Green flame LED will be on solid and display shows =H (DHW call). After it starts once, it will stay running until the call is satisfied. Then I can test it using flue gas test mode and It will usually start the first time until it cools completely to basement temperature (several hours). Then it will most likely be a hard start again.

I did notice that this time was the first time that the HSI has been hard to pull out. I have to twist and pull to get it out. Significant friction in between the heat exchanger casting and the shield (I presume), of the HSI. In the past seven years I've never had this issue. It has always slid right out with no resistance at all. I suspect this is due to the deformity of the HSI.

What have I done? Per the manual, both devices (electrode and HSI) check out for resistance and current/voltage specs respectively. When cleaning the ionization rod I also examine the HSI and shield. Up to this point all has been well. Over the past few weeks I have replaced individually: 1. Ionization rod. No difference. 2. HSI and shield. No difference. I had a spare UBA3 so I tried that. No difference. The new devices (electrode and HSI) still check out for resistance and current/voltage specs. This morning I checked gas inlet pressure. 10.10 in h20. (well within spec for LP fired). and gas/air ratio 0.00 in h20. This gas/air ratio is at the very positive limit of spec -.04 to 0.00. I would like to get it to -.02 if possible. The one thing that has me puzzled and may be related to my issue is that I can not seem to adjust the gas air ratio. With the manometer properly connected and zeroed out and then starting the unit in L30 service mode (30% load) I get 0.00 in h20. Turning the adjustment 4 mm allen under the protective screw cap, makes no difference. I did not turn it more than 1/2 turn in either direction as the manual cautions about large adjustments. I returned it to its original setting and put the protective cap back on.

I have also checked the condensate trap and stuck my finger in the condensate outlet at the bottom to be sure it was clear. it does not appear to be a blocked air intake as it doesn't matter if the case is on or off. I can't inpect the entire exhaust, but it is very short and can flash a bright light in from the outside, and see it reflect on the PVC exhaust outlet at the top of the boiler.

This is where I am. Intermittent 6A (227).

I need some further guidance. Any thoughts of what I might be missing? The fact that it is intermittent makes it really hard to diagnose. But fortunately, I can reproduce it pretty easily. Thanks in advance.

Thanks in advance. P...


    HVACNUT Member Posts: 4,213
    Trouble shooting says check contacts on the UBA 3 and mounting plate and BC10 base plate.
    What's your lock up gas pressure?
  • Paul Wolf
    Paul Wolf Member Posts: 35
    edited June 2017
    HVACNUT, Thanks for the reply. Which manual are you looking at? I didn't see that in the troubleshooting section, but my manual is from 2007 (It came with the boiler). It may have been updated. UBA3 has been replaced. By checking the contacts does it mean just visually looking for aberrations? Or ? Also, it it talking about the UBA 3 mounting plate or the HSI/Ionization assembly mounting plate?

    The short answer is: I don't know what my lockup pressure is. Where can I find/measure lockup pressure? On the LP tank regulator?

    Is your train of thought that excess pressure may be exerting pressure on the inlet valve to the GB 142 and thus it takes a few (several) times of restarting to relieve the pressure enough to allow the valve to open completely? Just curious. Again, thanks for the reply.
    HVACNUT Member Posts: 4,213
    Here's the service manual for the GB142.
    Your lock up pressure is the incoming gas pressure at the gas valve. You need a manometer to check and adjust. I didn't read your whole post again, but for ANY adjustments, I would recommend a certified technician with a digital combustion analyzer to bring everything within specs.
  • Paul Wolf
    Paul Wolf Member Posts: 35
    Thank you. That is a newer version than I have. I'll go through it. Inlet gas pressure is 10.10 in H2O. Well within spec.(8-13). According to both versions of the manual. As my post mentions, the gas/air ratio is at the far positive end of spec, and from what I can tell will not adjust. My post mentions what I did to try and adjust it. Thanks.

  • Big Ed_4
    Big Ed_4 Member Posts: 1,778
    On the ohm reading on the HSI .. If its' close to the end of the range replace it .. You need to sit with tech support on this ...Noel up there I feel is the best ....

    I have enough experience to know , that I dont know it all
  • Paul Wolf
    Paul Wolf Member Posts: 35
    So judging by the way the flame looked when it TRIED to start. See my first post where I said
    "then a very gentle puff of blue flame appears in the inspection glass for much less than a second"

    I thought it might be a draft issue. I checked the exhaust, all clear. I decided to take the top and bottom covers off of the heat exchanger. what I found was that after 1.5 years the heat exchanger was pretty much plugged. Lots of white deposits on the bottom of many of the fins and the condensation trap (lower HX cover). I was surprised to find this as my last heat exchanger was in service 7+ years, and when I replaced (for leaking at one of the seams) it wasn't anywhere near as plugged as this one. What changed? Fuel formulation (LP) ?.

    A scaling/cleaning of the larger deposits on all of the fins I could reach worked great. I put it back together and it has been running for a week. Starts on the first attempt on a call for heat or DHW EVERY TIME !!! No more 6A (227).

    I also learned that there is a TSB that requires the corrugated stainless steel gas line to be replaced with a black coated one free of charge.

    I hope this helps someone.
  • Ironman
    Ironman Member Posts: 6,600
    Buderus recommends spraying mineral oil on the fins to remove the deposits. Let it sit for a while, then rinse off.

    The fire side deposits occur when the boiler is condensing. The lower the water temp, the more they occur. It happens in all condensing boilers, but the deposits stick more to the ones with aluminum heat exchangers.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Paul Wolf
    Paul Wolf Member Posts: 35
    Ironman, Thanks for the reply. Yes, I looked up Buderus' suggested method of cleaning the HX. On a cool HX, remove top and bottom covers. Cover/protect HSI and Ionization rod with something. Spray or baste mineral oil on as much of the HX as you have access to. Let it sit/soak for a while. In service mode fire it at 100% for 10-15 mins. Let it cool. Spray down with water. Clean off excess debris from lower cover, flush condensation trap. Repeat if necessary.

    Looks like they recommend every two years.
  • Happywife
    Happywife Member Posts: 1
    Thank you for your post. My husband had already cleaned the boiler, top and bottom. The mention of checking the flue hit home. Like yours, ours is a very short pipe out the side of the building. Upon checking said pipe ... sure enough -a bird's nest. After most of 2 weeks of diagnosing, replacing a part, & cleaning , he was puzzled, as you were. Now - hot water and a happy wife! (Always check the basics) Thanks again!
    HVACNUT Member Posts: 4,213
    Occam's razor strikes again.
  • pace
    pace Member Posts: 1
    We had a very similar problem (13 years old unit, no maintenance). Error 6A 227. It happened only in the winter, and more so in colder temperatures. Manually turning the unit off, then on, would restart the heating, but it would take increasingly more tries. And the lower the temperature got, the more tries it took. A year ago we replaced the hot surface igniter and the ionization electrode. It worked ok for the rest of the winter. Now we had the error code again. An HVAC specialist came and checked the heat exchanger. It was covered in LOTS of debris. It looked like pieces of cement. And the condensate trap was filled with the same material. He cleaned everything out, replaced again the hot surface igniter and ignition electrode (they were overheating and got damaged again withing the past year). We didn't do the mineral oil spraying this time, but our Buderus is working again!
    HVACNUT Member Posts: 4,213
    13 years with no maintenance will do that? Weird.
  • Paul Wolf
    Paul Wolf Member Posts: 35
    Should my Buderus GB142/30 boiler light on the first attempt ?every time? If not, what is an acceptable rate of retries/lockouts.

    If i recall correctly, when I first installed it, it lit the first time, every time. I didn't concern myself with it again until it started acting up many years later.

    UPDATE: See history above in this post. Back in April of this year I got fed up with the unit fairly regularly going out on 6A/6L lockout (227). I called a firm that came highly recommended. He cleaned the HX, and went though a set of diags. I presume it was combustion, pressure and smoke testing.

    For the next 30 or so days I monitored the startup sequence when calling for heat (not DHW). Usually in the morning when we first get up. I have 29 recordings in my sheet. Out of the 29 starts, only 10 "lit" on the first attempt. The others are varying attempts of 1-3 tries, usually getting a soft 6A or 6L. Of those 29 attempts, it eventually started. It NEVER turned to a hard lock-out. I figured it was "par for the course" for a 12 year old unit and stopped monitoring and left it alone.

    We don't use our heat much during the "shoulder months" early spring and late fall. We have auxiliary heating for that. We use the boiler (for heat) from about mid November to Mid April. The boiler only fires up for maintaining DHW the rest of the time.

    It wasn't until last week, when we had a cold snap up here in the Northeast that we started using the heat. Since then (and I haven't been monitoring it THAT closely) We've used the heat a fair amount. I have seen it several times do 1 or two attempts and then light. However, in the last 7 days, it has hard locked out on 6A. twice. A power on/off resolves it, usually within 1-2 attempts of lighting.

    Back to my initial question. What is an acceptable amount of retries for this boiler before it eventually lights ?

    Should I call the tech back ? Maybe try a different tech? I'm done trying to figure this out myself. I don't mind paying someone to fix it, but I don't think it's unreasonable to expect a somewhat permanent (more than a few months) fix.

    Thoughts ?
  • DeBow
    DeBow Member Posts: 4
    just spent several days working on a Buderus GB142-24 with a 6a code. Boiler hadn't been clean since installed in 2012. I ended up cleaning it twice as recommended with the mineral oil, replaced the hot surface ignitor and flame sensor back in February. Now ,months later had the same 6a code lockout. Micro DC amps at flame sensing rod 3, power 189 volts AC. HSI 186 ohms cold, 246 ohms hot. Pins on gas valve ohms 74 left and center then 188 center and right pin. Propane gas inlet, boiler off 9.2"wc. the problem regulator at tank had be replaced with the wrong size. Propane company replace it again. Now gas 12.68"wc boiler off, 11.45 high fire and 11.88 at 30% boiler speed in the L30 mode. Next day locks out again, call Buderus again. Fan starts at -4.29"wc, pause pre-purge -.98 to -1.06, too low advised to replace gas valve. Replace gas valve next day, same results. Call Buderus, they advise I replace the fan motor even though the -4.29 is with in specifications. Then Buderus gives me another phone number to call. That guy tells me the same thing. I replace the fan, it's working now. Fan test -4.30 to -4.45"wc, pre-purge is at -1.06 to -1.12" wc as tested at the gas valve outlet port. Here is what I learned.... if the gas can not be adjusted for it's fuel and air ratio on the L30 mode don't be so quick to agree the regulator in the valve is bad, it could simply be the meter your using isn't able to have that stability for that test. The gas valve is blamed for a worn fan motor. The fan motor may have a slight enough change in it's rpm to cause the pressure pulling gas through that valve to be insufficient. I will see as time goes by if the 6a code comes back.
  • dpeshkin
    dpeshkin Member Posts: 1
    My GB142 (2006) is having the exact same problem as the previous poster (Paul Wolf). "On a call for burner (either heat or DHW) It goes though its boot up sequence, 1. Purge chamber, 2. OC Energize HSI (glows brightly), 3. OL Gas solenoid/valve opens, 4. stays like this for a few seconds, then a very gentle puff of blue flame in the inspection glass for much less than a second, the green flame-on LED on the BC10 flickers once VERY quickly, then HSI de-energizes and a soft 6A appears. It tries this 4 times, then lockout code (flashing) 6A. "
    I noticed that the condensation trap is full with water. Once I dump the water out the condensation trap and reset it, the boiler fires right up on the first attempt.

    Does anyone know how this may be resolved?

    Thank you in advance.
  • It sounds as though your condensate drain is clogged.
    Often wrong, never in doubt.
  • FB
    FB Member Posts: 30
    According to my manual, the condensate trap should be removed and cleaned as part of the annual cleaning. Then it should be filled with clean water and reinstalled. When I clean ours, it typically has some charcoal looking chunks and gunk floating in the water. We burn natural gas. Our GB142-24 has been in service for 13 years.
    Paul Wolf
  • The trap might be clear, but check the drain to make sure it's not clogged. The drain is the part downstream of the trap. Pour some water down it and make sure it runs free without backing up.
    Often wrong, never in doubt.
    Paul Wolf
  • Paul Wolf
    Paul Wolf Member Posts: 35
    DeBow, Thanks for the update.
  • Paul Wolf
    Paul Wolf Member Posts: 35
    UPDATE: After many techs have had a stab at this issue at significant cost to me. I finally found a competent one that REALLY knew his stuff with these GB's. Bottom line, he didn't find anything conclusive with the initial ignition multiple attempt issue, but he DID find out why the boiler would occasionally flame out (6L) mid cycle. Hx is cracked right where the finned tube goes in to the casting (this is a warranty replaced Hx (2015)). Watching closely in the sight glass as the boiler modulates up, the flame is normal for a while, then a "puff" comes out of the area by the crack and extinguishes the flame. The boiler relights the first time and usually continues on to complete the cycle but with a VERY high CO measurement (over 600 ppm). After the relight, the flame wavers in the area of the crack, but not enough to drop the current on the ionization rod below the 1.4 microamp threshold so it stays lit.

    New boiler time.
  • KennyCatbox
    KennyCatbox Member Posts: 15
    Anyone know of a good Buderus tech in Hudson Valley area?
    HVACNUT Member Posts: 4,213
    Have you tried the "Find a contractor" link at the top of the page?
  • Paul Wolf
    Paul Wolf Member Posts: 35
    Pardon my tardiness in updating my post/issue. I thought I did, but apparently not.

    I have resolved my issue. I gave gave up on the Buderus a year ago and installed a run-of-the-mill PurePro from FW Webb. Not as efficient, but I don't use much fuel. I supplement with wood and a mini-split. It's been an absolute dream for the past year. Not a single issue. Very simple, basic unit. My only complaint is that the draft inducer has a bit of a vibration to it. I've not been able to figure out how to balance it. And It's not bad enough to warrant replacing it. Though I would bet if I made enough "noise" with Webb, they might warranty it.