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  1. #53
    Join Date
    Apr 2012
    Location
    Cleveland
    Posts
    611
    Yes it is. That was the worst of it, but it was cracked a few places. They were all where the secondary screws to the faceplate.

  2. #54
    Join Date
    Mar 2008
    Posts
    279
    Quote Originally Posted by Hvac216 View Post
    Yes it is. That was the worst of it, but it was cracked a few places. They were all where the secondary screws to the faceplate.

    Did u happen to check the plastic cover plate that have a dozen or so screws in in that covers the actual secondary hx when I find tail piece issue I usually see that but not always

    Sent from my BlackBerry using Tapatalk please excuse typographical errors
    If you can not do it right, Why even do it at all?

  3. #55
    Join Date
    Apr 2012
    Location
    Cleveland
    Posts
    611
    Quote Originally Posted by luv2cruiserccl View Post
    Did u happen to check the plastic cover plate that have a dozen or so screws in in that covers the actual secondary hx when I find tail piece issue I usually see that but not always

    Sent from my BlackBerry using Tapatalk please excuse typographical errors
    If I need to take the actual faceplate off then no. I'll pull it and look at it when I pull it off my van in the am.

  4. #56
    Join Date
    Mar 2008
    Posts
    279
    Quote Originally Posted by Hvac216 View Post
    If I need to take the actual faceplate off then no. I'll pull it and look at it when I pull it off my van in the am.
    Sounds good. I been wondering if a inspection camera thru the limit switch would work at all in helping to find these issues as well

    Sent from my BlackBerry using Tapatalk please excuse typographical errors
    If you can not do it right, Why even do it at all?

  5. #57
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,442
    I've found that Tranes are pretty consistent on O2 content. run 10% in flue. if its higher than that, likely a leak in hx. also, CO will be up sometimes as well.
    Col 3:23


    questions asked, answers received, ignorance abated

  6. #58
    Join Date
    Apr 2012
    Location
    Cleveland
    Posts
    611
    Quote Originally Posted by luv2cruiserccl View Post
    Sounds good. I been wondering if a inspection camera thru the limit switch would work at all in helping to find these issues as well

    Sent from my BlackBerry using Tapatalk please excuse typographical errors
    It should but it wod depend on the camera. My dewalt wouldn't fit.

  7. #59
    Everyone seems to be assuming that having a hairline crack in the heat exchanger is an extremely dangerous thing. Can combustion chamber air really get through a hairline crack when the combustion chamber is at a negative pressure relative to the house air? Reference - http://carbonmonoxidemyths.com/m/Myth-1.html.

    If this is such a dangerous thing, why aren't heat exchangers designed to be inspectable? Why are cracks so hard to find? Doesn't that suggest that cracks are likely to exist in many units out there that are thought to be good? Wouldn't this be a liability for furnace makers? (they've designed heat exchangers that can't be 100% reliably inspected for cracks that could lead to CO poisoning). The HVAC service guys (probably most reading this) are obviously worried about their part in this liability. What do the furnace design engineers have to say about this?

  8. #60
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,198
    I don't assume it is a dangerous thing,, I assume it could lead to a dangerous thing. If it is cracked it is condemned. If I make light of it and someone dies,,, it would be on me as I am the professional.
    ...

  9. #61
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,442
    Isn't there a "buy my book here" button on this site? sounds like one I saw yrs ago. Everyone is ripping you off, buy my book and I'll tell you what you want to hear, don't fix it.

    He states static pressure as proof that furnaces can't leak @ hx, but total pressure is full picture. Also, not seeing employees of manufacturers telling the public about furnace hxs is not proof that cracked hxs are safe.
    Col 3:23


    questions asked, answers received, ignorance abated

  10. #62
    Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

    My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

    Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.

  11. #63
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,224
    Quote Originally Posted by pairajacks View Post
    Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

    My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

    Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.
    When a crack gets to the point of leaking, it is hazardous to have air blowing into the HX. This affects the flame and can cause dangerous rollout and elevated CO levels. Wouldn't it be better to catch the crack before it gets to that point, even if it is not an immediate hazard?

    In most cases, just a visible crack in a HX is not sufficient reason to red tag and disable a furnace. To shut down and red tag requires there to be a problem that poses an immediate danger to the occupants of the building. A barely visible crack does not qualify but needs to be brought to the owner's attention and repair recommendations made.

  12. #64
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,589
    I had one last week, hairline crack, no rollouts. I told the lady, it's under warranty so I ordered a primary and secondary, left it running.

  13. #65
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,442
    Quote Originally Posted by pairajacks View Post
    Total pressure is static plus velocity pressure. As the blower air sees restrictions, the velocity pressure gets backed up and INCREASES static pressure. The bulk pressure in the blower - house area is higher than the combustion chamber. The only way to get reverse air flow through a crack is to have local eddies where the venturi effect dominates, sucking CO into the house air. (Can this happen? Or is it designed to be fail-safe?). The sited reference did talk (slightly) about this.

    My point is, if something is this unsafe, and potentially dangerous to just about everyone, wouldn't gas furnace heat exchangers be designed to be fail-safe? Does anyone KNOW that they are not designed to be fail-safe? Just about every other product under the sun IS fail-safe. Why isn't the un-attended roaring gas-fire in everyone's garage that we call a furnace fail-safe?

    Given how likely furnaces are to have a crack (I read some posts where 3 year old Trane furnaces were being replaced for cracks), the market should be moving in the direction of making furnaces fail-safe, not relying on service guys to make judgements about hard to inspect areas.
    manuf manual says annual maintenance required, and as part of that hx inspection. GAMA standard is industry guidline for hx inspection, and is repeated as addendum in international code book. that seems to be the method for keeping and eye on hxs.

    blocked flue switches are not hx hole detectors.

    I've seen furnaces that were positive static pressure in the cabinent, but soot all around the crack/hole in hx and in house.

    I'vbe tried contacting manufs/reps about the hx issue, how much too much crack, and they're rather evasive about giving straight answers. Have a Payne document about the steel secondary hxs that resulted in a class action lawsuit, and there was some spin on that.
    Col 3:23


    questions asked, answers received, ignorance abated

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