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Acidic condensate + CO test fails = cracked heat exchanger?

HeloDogHeloDog Member Posts: 34
I had a HVAC tech tell me my boiler heat exchanger is cracked. He based this on performing a carbon monoxide test (over 10 ppm detected near the boiler hood) and evidence of acidic condensate (dust/soot/whatever) on the top of the boiler by the hood. He said that in his experience, the presence of these two things always means the heat exchanger is cracked. There is no evidence of water leaking.

Do you think his conclusion was reasonable?

FYI: The boiler is suffering from delayed ignition and flames shoot out the side when the boiler is started (this is why he was troubleshooting it). Two techs from two companies have said it's dangerous and one said he personally wouldn't feel comfortable turning it on again to troubleshoot it. So it's shutdown and I'm going to replace it. Now I'm just trying to find somebody that will do a good job.


  • mattmia2mattmia2 Member Posts: 1,180
    You have draft and combustion issues. Whatever is causing the delayed ignition is very likely also what is causing the high co readings and spill out of the draft hood.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,930
    your techs don't have a clue. If it was a warm air furnace a cracked heat exchanger could cause co & combustion problems.

    With a boiler a cracked heat exchanger would leak water.

    Depending on it's age the co problem can likley be fixed and the ignition problem could be fixed if parts are available

    10 ppm in the boiler flue gas is not an issue, so you may not have a co issue

    Check 'find a contractor" on this site. Don't give the boiler replacement job to those knuckleheads
  • unclejohnunclejohn Member Posts: 1,525
    If you have flame roll out you need to have the boiler cleaned and that my be the end to your troubles. On the other hand if your boiler is 35 to 40 years old a new boiler might not be a bad idea. And yes it sounds like who ever you had there dosent want to get his hands dirty. Also tell the one tech he has to tuen it on to troublr shot it. Just because.
  • JUGHNEJUGHNE Member Posts: 6,788
    So a guy looks at your water boiler that has 12-15 PSI showing on a gauge and tells you that your heat exchanger is cracked....and the floor is dry?
    I looked back at your other posting, you are the 6000' altitude person.
    You are really striking out on boiler people in that area.
    This makes 3 or 4 that seem lost.
  • HeloDogHeloDog Member Posts: 34
    Damn. It didn’t make much sense to me but I was kinda hoping the pros here would say, “Yep, you bet. That’s what that means”.

    Jughne: Yep, that's me. It's been a struggle.

    The Find A Contractor feature on this web site list NO contractors in the entire state of New Mexico. And of the four companies I’ve been in touch with so far, the results have been dismal. One tech didn’t know how to clean the burners (or was to lazy), one partially closed the gas shut-off valve to prevent the delayed ignition problem, another told me it didn’t matter that the gas pressure from the propane tank was 1.5” w.c. lower than the minimum input specified for the boiler, another asked me to send them pictures of my boiler instead of coming out to the house to get info for their new boiler proposal, one came out to the house to get information for their proposal (and to give me their sales pitch) but then never got around to sending me their proposal (even after I called them to remind them) and now this guy with the cracked heat exchanger diagnosis. Dismal.

    Anybody have any thoughts on how I might find a decent HVAC tech in the Santa Fe area? I’ve exhausted the recommendations from neighbors and companies with strong reviews on Angie’s List or Google/Yelp. Searching this forum for New Mexico didn’t yield a recommendation either. I'm down to throwing darts at a board.

    Oh, and now I'm also worried about having anybody troubleshoot the boiler if there's a risk it's dangerous to even turn the thing on. This is my first house with gas appliances. I'm not enjoying it.

  • unclejohnunclejohn Member Posts: 1,525
    Maybe start with your propane distributer and get the pressure right at all your applainces. Then call the boiler manufacture and see if they have a factory rep. who can help.
  • mattmia2mattmia2 Member Posts: 1,180
    Do the flame at the draft hood test with nothing firing and see if it is going up. if it is blowing out of the draft hood you need to fix that first. open a window and see if you get positive draft that way.

    also fix the propane pressures as @unclejohn said.
  • HeloDogHeloDog Member Posts: 34
    It's interesting that nobody on the forum has given the slightest hint that they agree with the HVAC tech about it being unsafe to perform diagnostics on my boiler. Keep in mind, on this Raypak, you have to reach in to light the pilot. It puts your hand, arm and face pretty close to the burners and a potentially explosive start-up.

    Instead, everybody immediately skipped over that concern and moved immediately to continued troubleshooting.

    What am I missing? Again, I'm new to gas appliances. Help me understand the thinking here. I'm pretty sure safety is a top priority with the pros here - based on comments I've read on other threads. So I'm guessing people aren't seeing this situation as a safety concern - just a HVAC tech trying to scare a customer into buying a new boiler. Is that about right?
  • unclejohnunclejohn Member Posts: 1,525
    Once you are aware of delayed ignition you go about the work of remending the problem. So pull and clean the pilot and make sure you have a good strong pilot flame. Pull and clean the burners. Thats for the delay. For the roll out you first put the flame roll out switch that was bent back away from the burner rack, dead give away by sight that you have a heat exchanger that needs cleaning. And then you clean the heat exchanger. The Ray Pac is a copper tube boiler if Im not mistaken so you carefully soft brush the HX. Sometimes a wet vac helps with the flushing. You can get the burner rack completely out in less then 15 mins and then blast away.
  • JUGHNEJUGHNE Member Posts: 6,788
    For me any gas burner in question or on my first visit, I make the power switch is off, then light the pilot if needed.

    You usually can light the pilot without the possibility of the main burner coming on. You would hear the main burner gas if pushing the pilot button down were to somehow open the gas valve.

    Then stand off to the side and turn the power on....your hand stays on the switch just in case.

    I would guess that standing to the side is just second nature to most techs.
    mattmia2delta T
  • Tim McElwainTim McElwain Member Posts: 4,357
    Try this company in Albuquerque [email protected]
  • HeloDogHeloDog Member Posts: 34
    Okay, I just wanted to be sure I wasn’t going to get a tech killed or blow up my house.

    So basically I need to change my approach. When I make arrangements for the next service call I need to tell them explicitly what tasks I require the tech to do (thanks unclejohn), have them confirm the tech they send can do these tasks and then I need to watch them do it when the service the boiler. Simple enough. It's heavy handed but letting the tech troubleshoot or do maintenance unattended isn’t getting me anywhere.

    Unclejohn: I had the propane distributer scheduled to come out last week to replace my single stage with a 2 stage regulator system (they said it was the only way to get the pressure up to 12" w.c. (minimum input for my boiler)). I postponed the work because of what the last tech said about it being unsafe to work on the boiler and to replace it. I’ll reschedule to have them come out.

    JUGHNE: The last tech wanted to see the burners ignite so he had me command heat from the thermostats and then positioned himself down on the ground so he could watch what happened. His face was a few feet away at ground level when it ignited and went BOOM. Standing aside wasn't second nature to him I guess.

    Mattmia2: Did the draft test and the smoke was pulled up into the hood. Also I’ve confirmed that there are two pipes that provide fresh air to the utility room. Both are sized correctly for a 135,000 btuh boiler. One pipe goes from the roof to a foot above the ground and it's inside a shorter pipe that stops a foot below the ceiling. I didn't realize that and it probably wasn’t obvious in the pictures I posted previously.

    Tim McElwain: Didn’t find an AllAroundPropane company in Albuquerque. I did see somebody raving about a company in Albuquerque that only works on boilers called Outlaw Mechanicals and their web talks about northern NM and southern Colorado. However, it would be about a two hour drive by highway to reach me and I find it hard to believe they would come this far but I may give them a call anyway.
  • Tim McElwainTim McElwain Member Posts: 4,357
    The phone number for All Around Propane is 505-598-5660.
  • Tim McElwainTim McElwain Member Posts: 4,357
    All Around Propne
    Propane supplier in Kirtland, New Mexico
    Address: 3991 US-64, Kirtland, NM 87416
    Closed ⋅ Opens 8AM Mon

    Phone: (505) 598-5660
  • HeloDogHeloDog Member Posts: 34
    Tim McElwain: Right, but they are about 160 miles from me. And 190 miles from Albuquerque.

    Mattmia2: Correction. The pipe within a pipe configuration is with the exhaust pipe. The inner pipe is for the exhaust gases and the outer pipe appears to be open to the outside air.

    unclejohn: Not sure what you mean about a "roll switch that was bent way back". Are you talking about something you're seeing on my boiler? The manual only talks about a “roll-out sensor”. It’s to the left of the gas valve assembly and looks orientated correctly and not bent.

    By the way, the manual says you clean the flue gas passages by removing the hood, flue collector & burner tray, then use a garden hose to rinse soot from between the fins. Yikes! Not sure how they would do that in my utility room without making a huge mess. A soft brushes sounds like a better idea.

    FYI: I stuck my phone under the hood and took this picture of the heat exchanger. It looks a little dirty but at least the fins don’t look totally clogged. You can see the gaps between the fins pretty well. Could probably use a good cleaning anyway I bet. I would love to see inside the tubes to see how much scaling has built up because the water here is very hard (450 mg/L). But that sounds much more involved. Maybe something to look into later. Right now just want to get it working.

  • Tim McElwainTim McElwain Member Posts: 4,357
    If you call that number they can hook you up with someone near you 505-598-5660. Propane people all know one another.
  • JUGHNEJUGHNE Member Posts: 6,788
    If that is the bottom of the heat exchanger then there should be no problem with lack of draft because of restriction thru that.
    The inside of the tubes could have issues but will not affect the draft thru the boiler. It would make the boiler water run hotter and possibly eventually shut down on high limit earlier than usual.
    My guess is back to gas pressure, orifice size and that 6000' altitude.

    Just a story concerning the "stand to the side" lesson.
    Years ago I was checking out problems with a LP furnace.
    I check the pressure on the manifold, that is the pressure right to the burner. This unit had an 1/8 plug in the manifold.
    That is where you put your manometer gauge.
    So after adjusting pressure, I remove the gauge, pack it away and start the furnace again. The main valve opens and the burner starts, within 2 seconds the flame comes roaring out the front of the burner compartment. Immediately know what was the problem and shut the switch off. I had not replaced the 1/8" manifold test plug. The gas came spewing out of that hole on top of the manifold and being heavy LP it settled down and found the flame of the main burners.
    I was kneeling right in front of the furnace in a closet. I had a beard earlier that has since grown back.
    That might have been 20 years ago but these are things that are programmed into your survival subconsciousness and you retain as "second nature"......have never forgotten to replace those plugs since and always stand to the side. B)
  • HeloDogHeloDog Member Posts: 34
    JUGHNE: It's a picture from above looking down at the top of the heat exchanger. I took a several pictures and in them you can see the tubes on the far left and right have fins that look pretty clear. Can't really tell about the middle ones unfortunately.

    The 10.5" w.c. measured at the tank vs the 12" w.c. minimum requirement for the boiler seems like a big red flag to me too. The propane company tried to talk me out of having it adjusted ("it's been working for 13 years why would you want to change it now..."). So did one of the HVAC techs. My understanding is low gas pressure is one contributor to delayed ignition so getting the low input pressure within spec seems like an obvious first step. May not fix it but it at least removes one possible root cause.

    Your business isn't very forgiving. One of the techs that came by told me a similar story that's "burned" into his memory. He told a client to turn down all the thermostats before the tech lite the pilot. But he didn't realize that the client had turned one of them back up for reasons unknown. When he lit the pilot, the thermostat commanded heat and the boilers were lit too. Scared the crap out of him and he got burned a little bit. At my house he walked with me and visually confirmed every thermostat was turned down. Lesson learned.
  • Tim McElwainTim McElwain Member Posts: 4,357
    The truth is the tech should have controlled the equipment coming on or off by the switch at the equipment that way thermostats could all be turned up to call for heat.
    mattmia2JUGHNEdelta T
  • mattmia2mattmia2 Member Posts: 1,180
    Not to mention any gas burner correctly installed since at least the 50's will have separate valves for the main burner and pilot burner, either in separate physical valves or a combination valve that will allow the gas to the main burner to be turned off while lighting the pilot.
  • Tim McElwainTim McElwain Member Posts: 4,357
    How did you come to the requirement for 12" W.C. on this boiler? That seems a little high most LP systems work with 10" W.C. inlet and outlet on the gas valve?
  • HeloDogHeloDog Member Posts: 34
    Being able to turn off the gas to the burners at the boiler would be useful. But there doesn't appear to be a valve that lets you turn off the flow to just the burner. The gas valve is a Robertshaw 7200 and the only adjustment I see on it is a pilot adjust screw. As far as electrical power, the only way to control power is by pulling the plug at the outlet (as far as I can tell).

    Tim: I"m getting the pressure requirements from the rating plate for propane. Setting it too 12" will satisfy the boiler and water heater requirements. My GE gas range/oven only states a manifold pressure of 10" (no input min/max). Searched the internet without luck so may need to call GE to verify it will accept 12" on the input side.

  • mattmia2mattmia2 Member Posts: 1,180
    That boiler has a combination valve (as does almost everything manufactured after total shutoff became a requirement in the 60's.). When you move the lever to the pilot position it turns off the main burner supply.

    @Tim McElwain take a look at @HeloDog 's other posts, there is another thread with the pictures of the boiler in question and answers to a number of other questions.
  • HeloDogHeloDog Member Posts: 34
    mattmia2: okay, that makes sense.
  • JUGHNEJUGHNE Member Posts: 6,788
    Tim, just another note....OP is at 6000' elevation.
  • HeloDogHeloDog Member Posts: 34
    Anybody: Does this mean anything to anybody?
    It occurs to me that when the last tech turned on the boiler from cold iron, it did the big "Woosh" and flames came out the side when the burners ignited. And during the next two hours while he was doing CO testing, it didn't do it at all. I know because we both sat in the closet watching it most of that time.

    The time before that, it also happened when a tech started it from cold iron (because I had shut it down the week earlier).
    Prior to that, I know it happened while we were using it to heat the house. But it's likely there were long periods when the burners were allowed to cool down between being called for heat because it was late September, pretty warm outside and our wood burning stove was providing most of the heat. The burners probably only ignited between midnight and 10am when it was kind of cool outside.

    So if it only happens when the system is cold or at least when the burners are allowed to cool down a bit before being called upon for heat, does that point to a root cause(s)?

    Tim: Called All Around Propane in Kirkland. Unfortunately he wasn’t able to recommend anybody in the Santa Fe area. But he asked about my boiler problem, seemed knowledgeable and his thinking was similar to what I’ve been hearing here. And he said he had heard about my problem in a Linkedin post. That’s pretty funny.

    I learned more about pressure regulators today because he was suspicious of the propane company for saying they needed to come out and replace my single regulator with two separate regulators. He thought they should be able to simply adjust the existing tank regulator. I had wondered about that too and his concern pushed me into looking deeper. I found the data sheet for the regulator on my tank (Type R632 Integral Two-Stage Regulator). At first I thought he was right because it says the Output Pressure Spring Range is 9-13” wc. But after I studied their pressure / Flow Capacity chart, I decided that probably the propane company was being truthful, darn it. If I’m reading it right, as the output pressure approaches 12” w.c. the flow rate approaches zero. So I guess they really do need to change it.

    Unclejohn: Find a manufacturer rep for RayPak in Albuquerque. They pointed me to a HVAC company in Albuquerque they said was good with RayPak equipment. Made an appointment for them to come out Nov 20th. It’s a four hour drive (up and back) and they charge drive time at their regular labor rate. So they were very understanding when I told them I might cancel if I found somebody I closer.

    Called GE Support to see if 12” wc. will be a problem for my gas range/oven. They said they didn’t know but would get back to me in a few days with an answer. Maybe they even will.

    So I’ll wait for their answer before having somebody mess with the tank outlet pressure. Breaking the range/oven while fixing the boiler wouldn’t be an improvement to my situation.
  • mattmia2mattmia2 Member Posts: 1,180
    The problem only existing when the boiler is cold makes sense. it isn't the burner but the boiler and flue. When the boiler and especially the flue is still warm from the boiler running it will draft more easily. to figure out if there is a design problem or something collapsed, blocked, or damaged will take someone looking at the length of the flue out through the roof and how it is connected to the boiler and the size to see if it is correct.
  • mattmia2mattmia2 Member Posts: 1,180
    If the bottom part of the boiler or even the burner is restricted the extra draft could help it work right
  • HeloDogHeloDog Member Posts: 34
    That makes sense. I'm not much of a DIYer so I'll leave pulling the burner tray out to a tech. But I can at least look around the burners to see if anything is obstructing things. And accessing the pipes on the roof is easy (flat roof) so maybe I can look down it with a flashlight to see if it's clear. If I can figure out how to remove the cap. Didn't see any screws so maybe it's a friction fit kind of thing.

    Thanks for the help mattmia2. I appreciate it. Eventually I'll have another tech out here to inspect and service it. In the meantime, learning about the system and checking off things that don't require a tech is helpful.

  • neilcneilc Member Posts: 805
    Is the house drafty ?
    or is it well sealed for air infiltration? (especially the attic, or 2nd floor ceilings)
    When that boiler, and the flue, is cold,
    is cold air dropping down the flue, and becoming makeup air for "stack affect" in the house?(the warm air in the house rises, vents out the attic, and draws cold air in where it can, including dropping down a cold flue)
    Next cold boiler and flue opportunity, try holding a lighter, smoke stick, or candle, by the draft hood or barometric damper,
    and see if the flame or smoke are pulled into the stack, or pushed back, into the house.
    No crazy exhaust fans pulling ?
    or an imbalanced HRV / ERV, with the intake fan not operating ?
  • JUGHNEJUGHNE Member Posts: 6,788
    Has that combustion air inlet cap been foam sprayed....maybe closed up?
  • hot_rodhot_rod Member Posts: 13,184
    Bristol Stickney or Boaz Soifer are a couple solar radiant guys in Santa Fe, might run them down And ask for a recommend.
    The local wholesalers usually know who is experienced in the area also, Dahl Santa Fe for example
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • HeloDogHeloDog Member Posts: 34
    Got a call back from Outlaw Mechanical, the company in Albuquerque that only services boilers. They don’t service my area but he asked me to describe my problem. He said he was pretty sure he knew what was going on. He said it’s actually pretty common probably here in New Mexico. The call was pretty short because he was driving, reception was spotty and I had someplace I had to be, but here’s what I think he was telling me before he had to hang up.

    Installers will often install a primary loop system instead of a primary/secondary loop system like they should. As a result, the return water is often a little too cool for non-condensating boilers. The result is the flue gases aren’t hot enough to successfully escape out the exhaust pipe. Some of it condenses and falls down on the heat exchanger and leaves a calcium deposit. These build up on the heat exchanger and make it difficult for the flue gases to escape. Vinegar will work to clean them - unless it doesn't. I told him my photos of the top of the heat exchanger looked pretty clean. He suggested getting a picture from the bottom and explained that on my Raypak getting the burner tray out was super simple. So tonight I took pictures of the bottom of heat exchanger. I’ll have to text them to him tomorrow and see if this is what he was expecting to see.

    If I dampen the highlights and bring out the shadows, the tubes are a little easier to see.

    Here's a close-up:

    neilc: It’s a single story, adobe brick house, spray foam flat roof. Between the ceiling and roof is a 2’ tall crawl space stuffed with insulation. I can definitely say that cold air is not coming down from the flue when the boiler is cold. I thought to check that while I was taking pictures tonight. The area beneath the heat exchanger was room temperature and I didn’t feel air moving against my skin in any direction. Seemed dead calm in there. Should it be? By comparison, the combustion air vent that ends a foot above the floor had a little cool air coming down. Outside the temperature was about 35F by the way. I lite a match beside the draft hood (cold boiler) the other day, the smoke was pulled into the hood (lazily). No crazy exhaust fans or HRV / ERVs (had to look those up). However, I do have a wood burning stove in the living room that is usually burning wood if its cold enough to have the boiler running, and there’s usually a pedestal fan and ceiling fan in the living room to help move some of the stove’s hot air to the other rooms in the house. And sometimes we’ll open a window for a while if the stove gets the living room too hot.

    JUGHNE: Where the flat roof meets a vertical surface, the spray foam roofers spray the transition area with a waterproof UV protective coating. Pretty sure that’s what you’re seeing along the bottom of the exhaust vent and the majority of the combustion air vent pipe.

    hot_rod: Thanks for the recommendations.
  • mattmia2mattmia2 Member Posts: 1,180
    Does the stove have combustion air ducted in from outside or is the stove drafting room air? If it is room air, it probably isn't all of the problem but it certainly isn't helping.
  • HeloDogHeloDog Member Posts: 34
    The stove is getting room air. It's pretty far from the room where the boiler is. Plus the pedestal fan in the living room is pushing air towards the boiler room. That fan is usually running if the stove is hot.
  • ZmanZman Member Posts: 5,734
    The top of the heat exchanger is usually worse. Can you sneak the camera in the draft hood and take a picture?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HeloDogHeloDog Member Posts: 34
    top of the heat exchanger:

  • mattmia2mattmia2 Member Posts: 1,180
    Did you take some pictures of the burners while you had them out? Something could be clogged there, there has to be a scheme to make the flame carry over from the burner with the pilot to the other burners but that is about the limit of my knowledge of burner cleaning and adjustment.
  • HeloDogHeloDog Member Posts: 34
    I did take some pictures and also tried to figure out how it all works. Near as I can tell, the gas flows from the gas valve into a manifold that spans across the header of all nine burner tubes. The head of each tube is connected to the manifold. I don't see any physical connection between the tubes. The pilot sits next to and slightly above tube 1. So I think that when the gas is allowed to flow, it gets to all the tube headers at the same time and the pressure pushes the gas down each tube. The first tube gets lit by the pilot. Tube 2 gets lit because gas comes out of the holes along its top and because it's in close proximity to tube 1. And so on. Does that sound right?

    Next time somebody fires it up, maybe I can rig a mirror near the ground so I can safely video the start-up sequence of a delayed ignition and a normal ignition. Might shed some light on why they are different. For now, it's shut down until a tech works on it.

    Also, I noticed there is a bracket that should be providing support to the gas valve. It's not screwed into the tray and it's not attached to the gas valve either. So no joy there. The gas valve seems extremely well supported by the manifold regardless.

  • HeloDogHeloDog Member Posts: 34
    Reading over some of the earlier post, I realized I may have unintentionally mislead people about the type of CO test that was done in the title. To be clear, the tech did an ambient CO test. Sorry if that confused anybody. In case it provides insight to anybody, here’s more information about the tests he performed.

    He set the thermostats to command heat and then used a combustion analyzer with a probe to sniff on the outside of the flue collector, under the draft hood. He performed the test three times. The test results were very similar. He got readings of 0 -1 ppm for about 14 minutes on each test, then the reading would climb up and stabilize at a higher reading for a minute or two and the test ended. On the first test, it had climbed to 24ppm, on the 2nd test it climbed to 12ppm and on the third test it climbed to 5 ppm.

    So is an increase in ambient carbon monoxide associated with a cracked boiler heat exchange in some way? If so, how? I can understand why you might see water dripping or a drop in water pressure, eventually performance issues in the radiators, etc. But I don’t any connection with ambient CO. In a furnace, maybe. But a boiler? To uneducated me, it sounds like a vent/draft issue that's occasionally lets a whiff of flue gases escape but then it dissipates or gets sucked back into the exhaust vent.
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