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Flue gas reversion or "bad propane"?

SuperTechSuperTech Posts: 350Member
edited April 6 in Gas Heating
I just finished up a really lousy week of work with a really aggravating service call.
Due to the colder than normal weather we have been experiencing here in NY we haven't made the transition into A/C season yet, and as a result work has been slow and my boss has been sending two guys out on what are normally one man service calls.
Usually this is a good thing and makes the day go by faster, but today I was paired up with a technician who is older and more experience than myself. He likes to rush through everything so he can get an early start on getting drunk, and he thinks I get "too crazy" about "minor details like combustion analysis". He thinks CA isn't necessary and his experience gives him all the answers.

Anyway, we were sent out on a no heat call. The customer has a five year old Bosch Greenstar Combi unit fired by LP. My wizard co-worker doesn't even look for the fault code (EA, no flame detected) and just starts opening up the gas pipe union, assuming the customer is out of propane. I pulled the igniter and flame sensor out and was quite surprised by my discovery. The flame sensor was extremely corroded, greenish colored and broke off the porcelain as soon as it was touched. The electrodes appear to have been meltedand have a gap the size of the grand canyon. The first thing I thought of was to check how the boiler was vented, because the only other time I have seen anything like this was on Munchkin/Purefire boilers that were vented concentrically. I found the intake and exhaust were separate 3" PVC pipes terminated right next to each other. The vent was installed correctly according to the manual, but not what I considered the best way. After picking up the part I took out my Testo 320 to check combustion. Of course this angered Einstein, he considered the job done after the boiler fired up. It's Miller time!
That didn't deter me, I put the unit into high fire and took a flue sample. My Testo shut down on sensor protection because CO production was in excess of 4000 PPM. The professor didn't consider this to be a problem and concluded that it was a result of "bad propane"! He became very angry when I suggested that the boiler was unsafe to operate. He thought that even with "bad propane" the equipment was fine because it's only five years old....

What do you guys think? All thoughts, opinions and suggestions are welcome.
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Comments

  • Jamie HallJamie Hall Posts: 8,021Member
    Bad propane?

    What is that @Steamhead says? Something about "you can't fix..." Can't teach 'em, either, sometimes.
    Jamie



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



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • the_donutthe_donut Posts: 333Member
    Don’t leave us hanging...what happened next? Boiler running for the weekend and coming back Monday...
  • SuperTechSuperTech Posts: 350Member
    edited April 6
    > @the_donut said:
    > Don’t leave us hanging...what happened next? Boiler running for the weekend and coming back Monday...

    I told my boss about the situation. I'm the type of guy that can't sleep at night if I'm worried about the safety of a customer. Even though I wasn't by myself or the senior tech on the job I would feel responsible if something happened. Sure, it functioned for five years previously but that doesn't make it right.

    Carbon monoxide scares the sh*t out me.

    I know many technicians go their whole career without performing combustion analysis, but once I became aware of the potential for death due to negligence I can no longer ignore it.

    I know nothing I say or do will change my co-workers attitude towards combustion analysis. He has that special type of vision that allows him to tune a boiler by eyeballing the flame. He was also blessed with the ability to measure superheat by comparing the how the suction line feels compared to a cold beer....but he makes the boss money therefore I have to do my best to get along with him.

    I will probably end up going back to clean and tune the boiler, change the pressure reducing valve and install a backflow preventer. And if the homeowner decides to pay for it I will move the flue pipe termination away from the intake. Or if they can't afford it I would rather have make up air come from inside the basement.

    Does anyone else agree that what I found looks like the result of flue gas reversion?
  • kcoppkcopp Posts: 3,026Member
    I don't think cross contamination is the issue....
    I wonder if it was properly converted. That can be a bit tricky w/ Greenstars... Need the chip card and properly adjusted.
  • SuperTechSuperTech Posts: 350Member
    > @kcopp said:
    > I don't think cross contamination is the issue....
    > I wonder if it was properly converted. That can be a bit tricky w/ Greenstars... Need the chip card and properly adjusted.

    Thanks! I will have to do some research on the LP conversion procedure. My company didn't do the installation and I'm not familiar with this boiler. That would explain the condition of the electrodes and flame sensor, as well as the high CO production.
  • SuperTechSuperTech Posts: 350Member
    Another thing that really bothered me about this call, the homeowner was an old widow living there by herself and her dog. She was a hoarder, I couldn't tell if she had baseboard or radiators, the house was packed. The company that sold her the boiler ripped out a perfectly good 12 year old cast iron oil fired boiler and sold her the mod con by using scare tactics. They told her she would have to replace the tank soon and that she wouldn't be able to afford the oil soon. The tank is still there, looked fine to me.
    They abandoned the existing indirect tank, did not connect the outdoor sensor and jacked up the water temperature settings to the max.

    As a result she says now she spends much more money on LP with the mod con than she ever did with the Peerless oil fired boiler! The Peerless would have outlived her, now she's stuck with a trashed five year old mod con that blows noxious steam out next to the door that she uses to go in and out of her house.

    Nice, right?
  • Stephen MinnichStephen Minnich Posts: 1,860Member
    I don't think it is the vent terminations either. Props to you for standing up to the knuckle dragging tech. I would have shut it down right now. No heat is better than no pulse. My suggestion, like Kevin's, would be to get the manual and do every step over for the conversion, check gas pressure, and then another combustion analysis.
    Stephen Minnich
    Minnich Mechanical Design
    708-305-5748
    www.minnichmech.com
  • lchmblchmb Posts: 2,746Member
    edited April 7
    memory serves me right on the greenstar, turn the throttle all the way in and back it out roughly 3/4 to one turn (be gentle on this that you dont break it) . Turn the gas valve in and back it out 4 to 5 turns. dial it in high and then drop it to low fire and test..it takes a couple high/low cycles to dial it in.. Give Bosch a call and ask for Mike. He's excellent on this unit.. your co reading should be less than 50 with that unit..
  • SuperTechSuperTech Posts: 350Member
    @lchmb Thank you so much for the great advice. I will definitely follow it. It's always good to have someone at the manufacturer to ask for. I downloaded the manual earlier, but between The Professor testing my patience and my Testo getting whacked with 4000 PPM CO I didn't have the opportunity to check the details of the boiler setup.
    It wouldn't surprise me if the installer the customer described didn't bother to set it up properly. If they thought using the tankless coil with the temperature setpoint jacked to the maximum was superior to the indirect tank and the outdoor reset was not necessary, that really makes me question everything. Obviously they didn't have the best interests of the homeowner (or the boiler) in mind.

    Is anyone else surprised that the Greenstar is more expensive to operate on LP than the oil fired Peerless?

    Has anyone ever heard of "bad propane"? Or was Einstein just blowing smoke up my @$$?
  • lchmblchmb Posts: 2,746Member
    "bad propane" is the excuse we hear when the installer has no clue how to set the system up. The starting settings were worked out by Bosch in their NH location. When you switch oil to propane you will of course use more gallons of propane than oil.. that's just the difference in product. But if you use outdoor reset and size the unit properly it should cut down on this difference... I would start by checking inlet gas pressures, check line size, set up the unit per spec's for co, co2 and then add outdoor reset. With an elderly person I dont stretch the settings to far..she's used to warm, but you can eek out some savings...
  • captaincocaptainco Posts: 371Member
    Based on current oil and propane prices in Ohio, a 72% efficient oil furnace/boiler would use 80% less dollars in fuel than a 90% propane furnace/boiler.
  • SuperTechSuperTech Posts: 350Member
    > @captainco said:
    > Based on current oil and propane prices in Ohio, a 72% efficient oil furnace/boiler would use 80% less dollars in fuel than a 90% propane furnace/boiler.

    I'm not sure of the propane prices here in NY, but that makes me feel better about keeping my current oil fired boiler. Higher AFUE always sounds great, but as we know there's much more involved in seasonal efficiency than AFUE

    I found out that the boiler in question was installed by a local oil/LP supplier. No wonder they didn't care about connecting ODR or properly sizing the boiler.
  • captaincocaptainco Posts: 371Member
    I'm not sure of the propane prices here in NY, but that makes me feel better about keeping my current oil fired boiler.

    As of Feb 2018 Propane = $3.52 gal. or $3.91 per 100,000 btu
    Oil = $3.38 gal. or 2.41 per 100,000 btu
  • LeonardLeonard Posts: 278Member
    edited April 10
    Engineer, not a heating guy, but I'ld wonder a bit about using indoor air for combustion. By placing both in and out pipes together as they are on same side of house you might not get wind driven pressure differential between them.

    Inlet and outlet appear to be far enough apart, plus hot air rises.

    Inlet seems close to ground, we sometimes get deep snow fall and drifts here in southern NH.
  • captaincocaptainco Posts: 371Member
    We recommend adding an open Tee on the combustion air pipe just inside the wall. If the outside gets covered you still have plenty of combustion air. Also, having tempered air when it is zero outside helps too.
  • SuperTechSuperTech Posts: 350Member
    > @captainco said:
    > We recommend adding an open Tee on the combustion air pipe just inside the wall. If the outside gets covered you still have plenty of combustion air. Also, having tempered air when it is zero outside helps too.

    I like this idea. I've never seen it before, but I can see the logic behind it.
  • RichRich Posts: 2,446Member
    edited April 10
    captainco said:

    We recommend adding an open Tee on the combustion air pipe just inside the wall. If the outside gets covered you still have plenty of combustion air. Also, having tempered air when it is zero outside helps too.

    This would depend upon the buildings construction . Tight house could equal dead folks inside .
    Not so tight house could possibly pull in too much cold air and increase load .

    Neither is preferable
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • SuperTechSuperTech Posts: 350Member
    How would the combustion air supply endanger a homeowner?
  • DZoroDZoro Posts: 287Member
    No, a open tee next to exhaust might just as well be a open window next to your exhaust.

    Don't do it.
  • DZoroDZoro Posts: 287Member
    In @Supertech's case had there been a tee there the home would have been potentially filled with 4000ppm co.
    That be bad news.
    D
  • ratioratio Posts: 1,380Member
    captainco said the tee was in the "combustion air pipe just inside the wall." I took that as inside the building. I'm sure I don't understand the hydrodynamics of the whole system, but I don't see how flue gas could reenter that way without some other serious problem coinciding.
  • lchmblchmb Posts: 2,746Member
    Need to remember if you take air for combustion from inside it is no longer a direct vent appliance and clearances to openings change. The air intake shouldnt have any issues and one would think the owner can keep an eye on it for snow load since it's next to the door...
  • Jamie HallJamie Hall Posts: 8,021Member
    On a T being inside the building... I can envision at least one risky scenario. Not saying it would happen, but... let's suppose a common arrangement with the intake and exhaust located outside. Perhaps four feet apart, but at more or less the same elevation. Now... we block the intake, and the furnace takes air from inside. But -- if the intake is blocked, there's a good chance the outlet will be too, no? So now where is the exhaust going to go? We have negative pressure inside the space -- air being sucked up by the burner. Are you quite sure your rollout switch or whatever is going to be enough to shut down the system?
    Jamie



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



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • SuperTechSuperTech Posts: 350Member
    edited April 11
    Maybe that's why I have never seen that done?

    I see plenty of condensing gas equipment where they don't bother to connect a combustion air supply. Even when I see an Energy Kinetics oil fired boiler without it I get annoyed. The few times I have seen flue gas reversion on munchkins and pinnacle boilers it was due to use of concentrically vents. Not sure why they are ok to use in the manual. I've corrected the gas reversion by adding some extra PVC pipe to exhaust, but I would rather see the two pipes installed a few feet away from each other.
  • SteamheadSteamhead Posts: 11,829Member

    Bad propane?

    What is that @Steamhead says? Something about "you can't fix..." Can't teach 'em, either, sometimes.

    >:)
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
    https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
  • captaincocaptainco Posts: 371Member
    There have been two cases of CO deaths at least where both the flue and intake on a condensing appliance was covered with snow. There was not enough air for combustion so the equipment went bonkers on CO. The CO was trapped near the house and migrated back in. Had there been an open T inside the equipment would of had plenty of combustion air and wouldn't have made excessive CO.

    If houses ever get that tight we are all going to suffocate because we breathe in O2 and exhale CO2. I think most are confused about how much combustion air is really needed. Unless you have a totally foamed house the odds of the heating equipment using up all the air are somewhat negligible.

    Unless you have encountered one of my students from the past 30 years you probably haven't seen this done. The key is that if there is the slightest chance this could cause a problem, it would not be recommended and so far that hasn't happened.

    It works better than a sign.
  • DZoroDZoro Posts: 287Member
    Code around here is exhaust must be 10' or more from any fresh air intake to the home. A tee in a intake pipe coming into a building would be considered fresh air intake. Air from that tee is free to enter and leave as it wishes. So as long as that intake is further than 10' from the exhaust, I guess that would be ok.
    I have seen too many mod. boilers ingesting their own gases over the years, mainly happening during low firing. The exhaust goes out so slowly that it hangs around, and re-enters the intake piping especially with horizontal concentric venting. I would be very concerned in these cases.

    IMO
    D
  • captaincocaptainco Posts: 371Member
    It had to take a real mechanical wizard to come up with the idea that putting combustion air intakes and flue exhausts close together is a good idea.

    I also found out years ago if you terminate the flue with a tee, it nullifies most of the wind effect that everyone is concerned with and the intake doesn't have to be that close.

    Condensing equipment has the strongest inducers of any equipment. I have not found any negative pressure (even a whole house fan), that could affect the venting on a 1-pipe condensing appliance, much less suck in through a tee on the intake of a 2-pipe. I have tried! Again, if there would be any chance of failure, we would not recommend it ever.
  • ZmanZman Posts: 3,988Member
    edited April 12
    @SuperTech
    I like the way you are handling this and appreciate the position you are in. If you follow the advise above and your solid instincts you will have this one figured out and running safely in no time.

    You certainly cannot fix Mr 4,000, smorethousand. I don't recommend trying. If folks would just stop letting all that dirt get in the propane....

    I agree with @Rich 's concerns with interior CA Tee. Because it is mechanically induced, the CA piping in sized very small for condensing boilers compared the code openings required for atmospheric equipment. Once you add a Tee to the mix to the mix, the air will come from whatever source provides the least resistance. In most homes, most will come from the house and a little will come through the exterior termination. It doesn't sound particularly dangerous to me. I just don't see much upside and plenty of downside.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SuperTechSuperTech Posts: 350Member
    A tee will be installed now. I like it! Thank you everyone for your advice. @captainco how can I become one of your students? I'm always looking to learn from an expert.
  • HomerJSmithHomerJSmith Posts: 440Member
    edited April 12
    Once you pull combustion air from inside the structure, you no longer have a Category IV appliance. Air like any flow is going to flow in a path of least resistance and that is going to be thru the "T" in the interior of the structure.

    Last yr we got 18' of snow thru several storms, this yr we only got about 8' that was meaningful, like 4' in a 5 days. We have on very rare occasions had 22' of sno.

    I always climb the vent up the exterior wall to the point where I think the terminations would be about 1 1/2' above the average worse case scenario. I don't ever use concentric venting, having seen so many problems with it.

    The way I do it is to run the air supply vent out the exterior wall and put a "T" at the exit if it is close to the ground like your picture shows and run the air vent up the wall. I put a screen on the exposed, bottom, part of the "T" to keep critters out and terminate the raised air vent with a 90 deg. Any sno or water that enters the air vent will exit the open end of the tee before it get to the boiler. Most of the combustion air will be drawn in from the "T", under normal conditions, but, when the sno covers the "T", the combustion air will be drawn from the 90 deg.

    The exhaust flue is set 18" above the combustion air vent and out from the 90 deg air vent, which against the wall, with a 45 deg fitting.

    Works for me.
  • lchmblchmb Posts: 2,746Member
    supertech can I strongly suggest you contact the NH office of Bosch. Run it by their tech support and see what they recommend. As pointed out, this changes all your codes and it is not something in the manual....
  • captaincocaptainco Posts: 371Member
    So far there have been at least two known deaths from 2-pipe condensing equipment installed according to Code and somewhat vague mfg instructions. So far after 25+ years there have been no injuries or deaths from adding an indoor combustion air tee. Of course there is some additional information that identifies how much combustion air you really need, not the made up industry standards and also how to control it.
    Apparently controlling combustion air is against industry standards and Code.
  • lchmblchmb Posts: 2,746Member
    edited April 12
    I've never said it's against code. I'm saying i would prefer to have the manufacturer agree with my changes to their system. The codes are very specific in clearances for direct vent and vent only appliances. It also give's a clearance for an intake into the building, which this would now be. The other concern would be AHJ. Will he approve something that is not in the manual and if something goes sour, who is going to back you on it. It may have nothing to do with the tee but it's something that you did and the manual does not approve.. I've been around a couple days.. even though i may have sufficient air in the space provided, I still prefer to gain it all from outside... Plus..if I feel strong enough to do it, why wouldnt I run it by them?
  • captaincocaptainco Posts: 371Member
    Did you know that all flue gases including CO are heavier than air below 32 degree? And according to Code and manufacturers recommendation, what vent termination is allowed to be closest to a door or window? On top if it -stupid-stupid-stupid. We are smarter than manufacturers and Code officials when it comes to actual performance of equipment in the field, or at least we should be. The manufacturer doesn't supply the plastic pipe so he has no say! Can't fix stupid!!

    If I can't fool an AHJ then I am not very creative. Also AHJ never support contractors in court cases only themselves, plus they aren't liable.

    I am liable for hundreds of thousands of equipment all over the country and Canada that would not be allowed by the manufacturer or Code. But it has all been upgraded to be safer than its original design and many families have been grateful.

    lchmb - you are way too smart and experienced to be shy and scared. Good conversation!!

  • lchmblchmb Posts: 2,746Member
    edited April 12
    shy? god no...scared..nope..cautious..hell ya have a family that comes first..and I've made many many decisions i will stand behind every day of the week. And some (alot) are not written in a book.. Our experience and training allows us to make that decision. We can back it up. But can this newer tech make that same call. Can he say he did it right. And what if he misses something you and I would have seen... My fear is for what may happen to the less experienced.. and our the homeowner who reads this and takes it on himself because it must work... knowledge is power..and power can burn... and yes..it is a pleasure to have a good conversation!! I enjoy these greatly
  • ShalomShalom Posts: 90Member
    All this discussion of where the combustion air comes from is starting to make me wonder. I have two hot water heaters and two boilers (well one's broken right now) and they get all their combustion air from whatever happens to be in the basement, and exhaust into a chimney. As far as I know there's no intake from the outside, other than what comes in through a naturally leaky 98 year old house. Should I be concerned about this?
  • lchmblchmb Posts: 2,746Member
    edited April 13
    it never hurts to have an inspection done by a reputable service provider. Request they check for sign's of spillage and of course install and maintain a good quality co detector(s) in your house Shalom. You would be surprised how much space is needed for combustion so it never hurts to check... At the same time have a chimney inspection done to make sure it is in good shape.. btw more than one detector never hurts..
  • captaincocaptainco Posts: 371Member
    lchmb - I agree but there is no way to add an indoor tee to your combustion air pipe and screw up.

    Shalom - Its all a matter of whether the flues can overcome the house or the house can overcome the flues. Signs of rust and corrosion point out intermittent problems but not just combustion air. A continuous draft test and combustion test of each can determine what problems might need to be fixed. Draft in the flue does mean you are getting combustion air to the equipment or at least the flue. The combustion tests determines if the air is getting to the burner.

    Sometimes things work perfect for all the wrong reasons. It doesn't hurt to have a CO alarm in your house near the bedrooms.
  • Jamie HallJamie Hall Posts: 8,021Member
    As @lchmb says, @Shalom , it never hurts to check. However, in an older house such as yours, it is rather unlikely that your house is tight enough to cause a problem -- and equally unlikely, if your chimney is in decent shape, for that to cause a problem. The problems which folks are seeing -- which are very real -- are the results of a combination of very tight houses (which cause other problems as well with air quality) and various combinations of forced or induced draught through what would have been regarded 30 years ago as ridiculously small pipes.
    Jamie



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



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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