Buderus GB142 emitting fumes in basement, and propane meter detects propane at exhaust outside house

DyedInTheWool

I heard gurgling at the exhaust (outside house) when our Buderus GB142 came on for hot water. We have had a lot of rain, including some torrential rains that were a bit horizontal, so my first thought was water in the exhaust pipe. I ran downstairs and noticed fumes in the basement. I opened up the boiler and found the condensate trap had melted and deformed, was disconnected from the drain and totally dry, so I replaced that and filled it with water. And restarted the boiler. No error code (still). But I still smell fumes in the basement (though they don't set off the CO alarm which is just recently replaced) and my gas detector (Toptes PT520A) detects propane at the exhaust pipe outdoors (it does not detect flammable gas anywhere indoors, around the machine or at any level of the basement). Are these symptoms consistent with water in the exhaust impeding normal operation? The drain pump is working, so I'm not sure why we'd have water in the line, about to go down into the crawl space to explore... Thanks for any ideas!

Steamhead

Shut that thing down NOW and call a pro!

Where are you located? We might know someone...........

DyedInTheWool

Thanks for your reply. I shut it down immediately, days ago. Technician is coming tomorrow morning and he's worked on our machine before. We've been living with cold water showers for several days.

What I'm wondering is whether I should make an effort to clean out the exhaust line before the technician arrives -- could water in the exhaust line cause my symptoms?

DyedInTheWool

Oh, and: I noticed there's a gap in the exhaust collar and the alligator clamp is rusty, so there has been some exhaust leakage for a while. Our service company installed the collar (it's the replacement flue assembly Buderus made available for free as the original ones had a high failure rate). And one of the condenser clamps is off, so the seal on the condenser isn't perfect either. I'll be bringing all of this to the attention of our technician. I'm just fretting that they may not think checking the exhaust piping to the outside is part of their remit.

HVACNUT

DyedInTheWool said:

What I'm wondering is whether I should make an effort to clean out the exhaust line before the technician arrives -- could water in the exhaust line cause my symptoms?

No. Leave it for the tech. There should be NO standing water, or low spots in the exhaust venting. 
You had a spare condensate trap?

DyedInTheWool

OK, thanks.
No, I didn't have a spare condensate trap. I noticed the condensate trap was completely warped/fried/disconnected -- "fried" -- and called my service company (the company that does annual service on my Buderus, which was last performed in December 2022) to ask whether the technician would have one on the truck. They said no, "special order". So I called FW Webb and drove to the warehouse where they had one in stock and picked it up myself. I thought it was pointless to have the technician out before I had that obviously-required spare part in hand.

Mad Dog_2

Those crappy plastic "Milk Container" quality condensate traps don't hold up very long.  Have you been having this fully serviced once a year?  Don't sound like it.  This GB needs a Complete Tear down and cleaning, new Gaskets, DO NOT TOUCH OR RUN...No showers for a few days is better than THE ALTERNATIVE..........Mad Dog 🐕 

DyedInTheWool

It has been serviced annually, like clockwork.

Something happened that caused the exhaust to overheat. As I heard gurgling from the exhaust outside, my bet is the heavy rain has plugged the exhaust, maybe we have a low spot, it's a little difficult to check as it's a crawl space and the exhaust is insulated, but we'll check it, and the drain of course.

As I wrote, the machine itself isn't throwing any error codes. I don't see why it needs a complete tear down! If the exhaust overheating is due to a blockage, that would likely explain my symptoms.

And for the third time, I am NOT running the system. I am NOT touching the system. We have been taking cold showers (as I already wrote!)

All I did was replace the condensate trap, which does not require any expertise or really much in the way of brains. What would have been pretty stupid, imo, would be having a technician arrive without the replacement trap on his truck. Ergo, I went and got one.

JUGHNE

This is not to be critical of the OP, but we have come to rely upon electronics and their read outs that we

ignore our nose smelling gas.

This is a WAG on my part, I am interested in the actual cause of this situation.

I have never seen this type of unit, but from this distance I would make a guess that your gas valve is not shutting off 100% and burning (sometimes) within the chamber. Without the benefit of the blower/fan to remove the exhaust it melts the cond drain and some fumes may flow by gravity out the exhaust pipe.

If the flame is extinguished then raw gas could be smelled inside and at the exhaust pipe outside.

It has to be a very small passing of LP gas or you and the basement would not be here to post.
IMHO.

DyedInTheWool

I was right, the problem is water in the exhaust line. There's a little belly in the line where the PVC pipe exits the 90 elbow that's seated in the collar. I had noticed that segment had turned tan (from heat, obviously). Anyhow, when we got a few days of downpours, including rain driven horizontally towards the open end of the exhaust pipe (which is straight up/down, not slanted down), we accrued extra moisture in the line.

So we will replumb that last little stretch to the boiler to fix the pitch. The margins are very tight as it is, and when the original Buderus collar had to be replaced, it seems the replacement collar was just a hair taller than the original piping, so pitch is tight there to begin with. And the PVC that was code when our Buderus was installed in 2010 was less heat tolerant than today's spec (my tech says the replacement pipe will hold up much better to heat). The collar connection to the straight 90 should also have been siliconed (oops! bad on the installer!) and perhaps a long straight 90 will give us a chance to pare a little more off the bottom of the elbow to lower that last leg a hair more, further improving the pitch without more invasive pipe work. And he'll install a new collar, of course, as that rusted alligator clamp can't be replaced (not to mention the gasket is no doubt shot too).

My tech says the machine will tolerate quite a bit before it throws a fault, he's not surprised that it still ran with water in the line. (By "ran", I mean it functioned up until I discovered there was something amiss and shut it off.) Also, I had noticed the drain pump ran for a few minutes after shutting off the furnace, and he said that tells him the pump needs a major cleaning, but because it's 13 years old it really needs to be replaced as in his experience the parts deform under all the crud and they tend to fall apart when you attempt to clean them once the buildup has gotten bad. No one ever said anything about cleaning the pump, so that has never been done. I forgot to ask how long the drain pumps will last if they get regular cleaning, but 13 years seems like a pretty good run. I'll also ask whether cleaning the drain pump isn't part of annual maintenance, and if not whether it's a homeowner task or an addon they can do periodically.

He will test for propane with his fancy meter when he returns for the repair work. He told me 200 is the limit, as measured at the exhaust. I'll be sure to ask him whether the gas valve is shutting off properly. Thank you very much for this!! I sometimes smell a faint whiff of gas when the unit comes on if I'm outdoors. I've been told I have an overly sensitive nose -- I'm regularly kidded about that -- and I've noticed my nose is much more sensitive than my 50-10,000 ppm meter. Hopefully, with a clear exhaust line and the other repairs/adjustments, I won't experience any other whiffs, no matter how faint. It probably didn't help matters that one of the heat exchanger clips had fallen off; and the heat exchanger also needs a new gasket (and it looks like last time my tech replaced parts, a couple of years ago, he put on a gasket for the GB142-45 instead of the GB142-30, so this time we'll use the right gasket). I also replaced the CO detector in the ceiling above the furnace last week. Should be just a few more days of cold showers. It's just dawned on me that we used to have a black bag for heating water in the sun when camping. Heading to the attic to try to find that!

HVACNUT

If the exhaust is collecting water, it isn't piped right. Rain or no rain. 

Mad Dog_2

Exactly, that would never happen if its installed and pitched the right way.   PVC is no longer allowed on Mod Con Vents (NYS/NYC and most manufacturers haven't allowed it in years.  It should be replaced with PP.  Is that what you mean by the "new spec" ?   Mad Dog 🐕 

Mad Dog_2

Didn't I tell you above, the unit needs a complete tear down and going over...new gaskets, et al???  If your "tech" used the wrong sized GB-142 Gasket (I don't know how you make that mistake??), then  how thorough has he cleaned it or how well is he familiar with the GB-142?  Just wondering... Matt NYC 

Mad Dog_2

A true, thorough annual cleaning of a GB-142 will take 2 1/2 to 3 1/2 hours.  Mad Dog 🐕 

DyedInTheWool

Good question re how he managed to install a GB142-45 gasket on my GB142-30! He and I looked at pix of parts on SupplyHouse and he said he thought the picture for the heat exchanger gasket for the GC142-30 was wrong, he said the one I wanted had the notches at the corners, and he pointed to what is currently installed on our machine. And looking through my notes, he's the one who installed what's currently on there, it was the first time it was replaced (after 11 1/2 years of operation). I called Bosch today to confirm the 30 takes the smooth round gasket. So, looks like he erred.

He's the best Buderus tech they have at the company I've been using (maybe the only one). Maybe I can find someone better. I'm sure the last cleaning, in December (not done by him, alas, but by another tech at the same company) was probably deficient. I'm in eastern MA in case you know someone good in my area.

It could very well be the pitch was a problem from the beginning and that's why the original collar failed after 9 years. Buderus saw a lot of collar failures, though, so it's hard to know. The plumber who installed this no longer does this kind of work and I don't think he was an A player. Do I have it right that we need 1/4" pitch per foot of pipe? I'll measure myself and see what the pitch over this little ~3' segment is. We shouldn't have to cut off some of the straight end of the elbow to get the pitch right, imo... that just leaves a gap where the elbow enters the collar. My tech claims high temp silicone will fill that gap fine, but I would rather have a clean join. With silicone too, I guess.

I probably misspoke calling the existing piping PVC. It's white plastic pipe, I don't know exactly what it is. It was to code in 2010 but is not up to 2023's code. My tech can tell me what the before and after pipe types are, he was explicit that the currently mandated pipe won't warp in future. I'll ask him.

Mad Dog_2

No...You're probably right....PVC is usually White AND was Kosher for the venting until the Industry and manufacturers decided it really wasn't the ideal material for this.  Polypropylene (PP) then became the better standard.  I remember when that changed. I had dozens of GBs installed with PVC vents and was like ...oh thats just great!  In any case,  I've never seen as issue on any of those installs.  Mad Dog 🐕 

Mad Dog_2

Don't beat yourself up.  You've stayed on top of the maintenance alot more than most HO's.  Mad Dog 🐕 

Mad Dog_2

Try Charlie from Mass.  He's on here as a Find a contractor and a is top notch plumbing & heating man.  Even if he just just for a paid consult, he'd set you straight.  Mad Dog 🐕 

HVACNUT

I don't remember the exact details, but I once met a Bosch/Buderus rep on site for venting issues with a GB. We wound up installing a drain Tee in the vent so the excess condensate didn't go back to the boiler. The drain was 3/8 loop trapped vinyl tubing and was routed to the boiler condensate before the neutralizer.
If you think that is the only out, check with Bosch/Buderus first. Maybe see if the tech can get a rep out to you.

Mad Dog_2

Yes...I put that drain tee on most of my GB installs..irrespective.  Mad Dog 🐕 

DyedInTheWool

We already have a drain T. It drops to the condensate pump, which we also need to replace as it's on its last legs. I'm thinking we should replace it with a neutralizing condensate pump, as we don't currently have a neutralizer on this line (not strictly required in our situation, as the condensate drips into our sump which maybe needs to be pumped 3 times in 25 years when we get epic rains before the ground thaws, in which case the condensate is vastly diluted by what pours into the sump hole). So I'd love any opinions about that!

Meanwhile, the tech insisted the water in the line problem was caused by that little 1'+ segment of pipe closest to the furnace. But no! I finally went into the crawl space and lo and behold there are two giant bellies in the exhaust line there, which he declined to look at. I feel foolish for not checking that out sooner (inhibitions of a 72-year-old female homeowner who has no mechanical training, I guess). Anyhow, that's really where the problem is! So a question: We need to replace that entire line, which is PVC (code in 2010, no longer code in MA in 2023, as of 2-3 years ago, I'm told). And the existing PVC pipe is insulated -- like a black rubberlike sleeve over it -- as it runs through an unheated crawl space, and we're talking 30' of pipe in that unheated crawl space. So: should that exhaust line be insulated? The tech says no, not necessary. But I thought I read somewhere that it does need to be insulated?

Who is Charlie from MA and how do I get ahold of him? Is he a Buderus expert?

Thank you, all, for your advice!!!

Big Ed_4

You clean the heat exchanger fins with butcher block oil . When changing the trap also check and make sure the top seal is still good and fit forms to the top of the trap. Normal mistake made .

JUGHNE

That "belly" in the pipe might not come out with added supports.

The bend may be in the memory of the PVC.

However, it would be worth a try.

DyedInTheWool

The PVC pipe appears to have supports about 6' apart in the badly deformed 15' run, not enough. And the pipe has sagged so much that the top of one of the bellies is nearly level with the bottom of the original pipe! It would be a miracle if attempting to pull it up resulted in a fix...

Clearly, this is a situation that has been in the making for a very long time, i.e. the 13 years since this was all installed. What a shame, as this might have been avoided with a few more supports! The pipe is hung from floor joists, it would have taken maybe 5-10 more minutes to secure it better. Now it's a very expensive repair.

If you were me, would you have a general contractor replace the exhaust line or would you have a plumber do it? My GC builds entire houses, this is not a complicated repair in his book. But he isn't a licensed plumber. We would be using grey CentroTherm, I guess. The benefit of having my GC do it is he can also replace the insulation in the ceiling of the crawl space while he's down there. The current insulation is fiberglass and it's full of rodent nests and sagging. We need to address this too before the weather gets cold as it insulates the radiant hydroponic pipes that are fastened to the bottom of the subfloor. He's saying rock wool would be better than fiberglass.

JUGHNE

IMO, that should be adequate hangers for 3" sch 40 PVC.

It sound like it has been overheated over the years.

Often you see the pipe discolored near the boiler buy not enough to soften the PVC.

I think you have a firing problem.

This is LP, I don't know about that particular boiler but most are shipped with NG sized orifices.

The installer usually has to change the orifice in the field from NG to LP.

DyedInTheWool

It has definitely been overheated over the years. The pipe is discolored near the boiler but not in the crawl space, which is about 5' and 2 elbows away from the boiler. The pipe in the crawl space is wrapped in a black rubber-like sleeve. Maybe that caused it to retain more of the flue heat, helping it to soften and sag over the years? Our Buderus doesn't just heat our water, it heats the entire first floor all winter and we're in MA. And we don't use the upstairs heating system (steam radiators heated by a Burnham IN3) very much, so all winter long the Buderus works hard.

The LP to propane conversion kit was installed when the Buderus was installed. There is a dated sticker on the boiler affirming this with our installer's signature.

I'll ask our current tech to verify that the orifice is the LP orifice. That would be a shocking miss, imo, but worth asking about. Thank you for the tip.

Re contractors, we're near Boston so I'm afraid Charlie is 2 hours away.

I'm still struggling to find out whether the exhaust pipe in an unheated space must be insulated per MA code. Our tech says no, they've never heard such a thing.

DyedInTheWool

Thanks for the tips re how to clean the heat exchanger. I've so far left this to a service person. I don't know how they clean it, or what they use to clean it. So far, I'm reading clean it with butcher block oil or mineral oil. Apparently, it has been really caked with condensate every year (and, more rethe furnace's overall functioning and efficiency. With a new exhaust line, properly pitched and clean and free of obstruction, maybe it won't get so dirty between annual cleanings. Or maybe I need to learn how to clean it so I can do a touchup at 6 months. I'll talk to my tech about this and ask him to show me how to do it.

I've purchased some spare parts "just in case" including an extra heat exchanger gasket, an igniter, and an ionization electrode, on the advice of my tech. Anything else I should have on hand for "insurance" as we head into winter?

I'm a little impressed that our Buderus soldiered on given the completely dysfunctional exhaust line, actually. Hoping the new exhaust line will make it happy;)

JUGHNE

There is a cheaper less quality 3" PVC pipe that should not be used for Exhaust.

(Some areas do not approve PVC exhaust at all. Although that is what I have in my house and is on every boiler & furnace I have installed.)

It is lightweight "Cell core" that is a sandwich of pvc with maybe fiber glass in the middle.

It is marked for DWV only.....not pressure rated....you might see the markings on the exposed pipe at the boiler. It is considered OK for air inlet to the boiler as there is no heat involved.

Mad Dog_2

PVC is no longer allowed on Flue pipe in NYS.  You need to replace with PP polypropylene.  Its not that expensive, yiu can pitch it the correct way and you'll bring up to code.  Mad Dog 🐕 

DyedInTheWool

PVC is no longer allowed in MA either, and I've been told MA was the first state to disallow it, about 3 years ago. (Europe stopped using PVC even longer ago.) We are repiping with CentroTherm (a polypropylene product) with support hangers every 3'. Insulated to R6 in the unheated part of the run. Also installing a combo condensate/neutralizer pump. Hope I never have to worry about this line again! (And hope the Buderus outlasts its average lifespan!)

DyedInTheWool

The original exhaust line was PVC Sched 40 with a thick black insulation sleeve. Looks like it was to code. Which begs the question: Why did it sag? I'm wondering about the overall pitch and will try to measure that tomorrow in the crawl space.

Meanwhile, I tried drilling small holes in the two big bellies to drain out any water, and got probably a gallon from each hole, then taped them both with several wraps of duct tape and turned the Buderus back on to see if the 3L error cleared. It did not! Which means water in the exhaust line is not the cause of the fault. I get a 214 when I press the wrench icon to see the drill-down code, and then P17 when I press it again. The first time I tried to start the furnace, the fan unit seemed to wobble and made a noise. After that it seemed to function smoothly, but it starts, then stops, then starts again, a few times, maybe 2-3 times. I don't know what startup looks like -- what the series of startup tests looks like.

Anyhow, it looks like there is more to my problem than just the exhaust line. This is such a miserable experience. If anyone has advice for me, please weigh in. I just want to avoid being left with an non-functioning Buderus when my service company is done plumbing the new exhaust line, and if I need a new blower I want to have that on hand before they get here.

Mad Dog_2

PVC, depending on the diameter needs alot of hangars...Every 3 - 4 feet to stop sags.  NYS outlawed PVC on flue exhaust 10-12 yrs ago.  Mad Dog 🐕 

DyedInTheWool

I found this notice that says NYS outlawed PVC in 2014 https://www.nyc.gov/assets/buildings/bldgs_bulletins/bb_2021-001_highlights.pdf Very sensible decision!

Apparently, MA only made this important change 2-3 years ago! https://theboilersmith.com/blog/pvc

I'll bet plenty of folks already knew PVC was a poor choice back in 2010 when my system was installed. Too bad the code didn't keep up with sensible best practices. Here I am stuck with no hot water for weeks and a very expensive rip-replace, all because of poor materials -- and shoddy work too, if hangers should have been spaced every 3-4 feet! Makes me wonder how people in the trade, and our town building inspector, overlooked all this. I expect service people to know what they're doing, they're making a living off this! And yet...

When I called my service company (when I noticed fumes in the basement, could smell and detect propane outside at the exhaust exit), my Buderus was still running! Now it throws a 3L/214. Seems like so far my service company has just fumbled around, fixing the wrong thing, failing to diagnose, and now going from bad to worse with the Buderus throwing an error. This is so frustrating!

DyedInTheWool

PS, our PVC Sched 40 exhaust pipe is 3".

Mad Dog_2

Yes, that's what I seem to remember as far as the Ban.  Keep in mind, though, it was bandied about for about a year, so 2013 I knew.  It was a punch 👊 in the gut, considering all the GB-142s I had installed in the previous years. Water 💧 🚰 🚿 under the bridge.  The reason was that IF.....The Mod-Con malfunctioned and put out much higher than normal temp Flue effluent, the PVC could become soft, weak and fail. First, several years before they banned Cell-core PVC,  the real light, ersatz pvc. 

I see my old installs quite often, being in the homes.  The older installs with PVC are fine, but then again, these were supported early-abd-often and pitched properly AND are maintained, so they likely never saw a high temp effluent for long.  Mad Dog 🐕 

DyedInTheWool

After three visits and new exhaust line, flue collar, condensate traps, blower, ionization rod, and gaskets the service company claimed we were all set! Well, they weren't gone an hour when the system kicked in to heat our water while I was in the house and I smelled gas! So I shut it off and they sent a 3rd tech the following week who said the CO was measuring 800ppm in the basement at the machine (yikes!), that the fuel/air mix was all wrong, and that although he'd gotten the CO down substantially (teens) the pressure was unstable so there was still a leak and he thought the leak was at the midline of the HX and the HX needed to be replaced.

The next day I got a call from the service manager pulling the plug and saying they don't replace HXs and would not work on my Buderus further. After calling around I could only find one company willing to consider doing a HX replacement; I paid $99 for a dispatch call but their tech, who wasn't very familiar with Buderus after all (and I'd been very clear with the dispatcher I wanted an expert!), refused to turn it on or run any diagnostics (afraid of CO exposure) and never followed up with the quotes he promised (either for the HX replacement or the new boiler he urged I get instead), basically a paid sales call for nothing.

So, we have just replaced the Buderus with a Viessman Vitodens 100-W. And changed service companies! A month without hot water really makes one appreciate the comforts:)

GGross

Sounds like you really got put through the wringer on this one. Viessmann is a good boiler, with a good warranty. Main thing to keep up on is cleaning the heat exchanger on LP gas, you just don't want the "coffee grounds" to build up inside the heat exchanger (once year, or every other year), that goes a long way toward keeping the boiler running in tip-top shape.

One advantage with that one is that it has a self tuning combustion system, so it makes it very difficult for some knucklehead to leave you burning at 800ppm CO. Techs should still use an analyzer annually to confirm proper combustion