Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Join Date
    Apr 2006
    Posts
    329

    checking a heat exchanger

    Am I correct in thinking that if I used my combustion analyzer and put it the supply air stream, that a high CO reading would indicate a bad heat exchanger? Would anything above 0 ppm mean a bad heat exchanger?

  2. #2
    Join Date
    Dec 2010
    Location
    The Colony, TX.
    Posts
    15
    absolutely correct there should be no co detected in the supply air and the only thing i have ever seen that would cause that would be a cracked heat exchanger.

  3. #3
    Join Date
    Dec 2009
    Location
    Southern US
    Posts
    504
    Well................

    When the unit first fires CO2 would be present but when the blower starts it would usually force supply air back into the exchanger. Thats why the rollout switch trips.
    I'm good at making things cold...You can ask my first two wives!

  4. #4
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    I dont think with a draft inducer any CO would leak into the supply duct at all regardless, even with a gravity system is kind rare to have CO leaking from the HX into the conditioned air, just check the combustion byproducts for o2 increase after the blower kicks in.

  5. #5
    Join Date
    Dec 2009
    Location
    Southern US
    Posts
    504
    Quote Originally Posted by hvacpope View Post
    I dont think with a draft inducer any CO would leak into the supply duct at all regardless, even with a gravity system is kind rare to have CO leaking from the HX into the conditioned air, just check the combustion byproducts for o2 increase after the blower kicks in.
    You know I had never really looked at it that way, I think your right!
    I'm good at making things cold...You can ask my first two wives!

  6. #6
    Join Date
    Jun 2009
    Location
    Bakersfield, Ca
    Posts
    1,716
    Couldn't CO be released from oil burning off of a fresh h/x? Dust?

  7. #7
    Join Date
    Aug 2010
    Location
    Chicago, IL.
    Posts
    135
    Quote Originally Posted by hvacpope View Post
    I dont think with a draft inducer any CO would leak into the supply duct at all regardless, even with a gravity system is kind rare to have CO leaking from the HX into the conditioned air, just check the combustion byproducts for o2 increase after the blower kicks in.
    If this is true then we're replacing units with a cracked HX because of what? High combustion chamber temperatures only? I taught CO leaking into the supply stream was a major concern also?
    Learn to live, so that you may live to learn.

  8. #8
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,614
    if the gas x changer is bad it prolly will be opened up on the top, or supply side creating a negative at that spot, drawing out combustion air, but if on bottom it will be pressurizing the chamber causing roll out. Yes No?

  9. #9
    Join Date
    May 2008
    Location
    Central Pennsylvania
    Posts
    438
    Quote Originally Posted by hvacpope View Post
    I dont think with a draft inducer any CO would leak into the supply duct at all regardless, even with a gravity system is kind rare to have CO leaking from the HX into the conditioned air, just check the combustion byproducts for o2 increase after the blower kicks in.
    I've never tried using a combustion analyzer on an RTU, but I would think if the HX was cracked you would probably pick up CO in the supply side. Yes you have a draft inducer but the supply fan moves a lot more air.

  10. #10
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,614
    Quote Originally Posted by chillerguy81 View Post
    I've never tried using a combustion analyzer on an RTU, but I would think if the HX was cracked you would probably pick up CO in the supply side. Yes you have a draft inducer but the supply fan moves a lot more air.
    you have never used one to set up valves and dampers to see how it was burning from stack measurement's?

  11. #11
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    very simple rule, high pressure moves to low pressure, a cracked HX would mess the combustion efficiency big time but very rarely would do more than that, where is captain CO when you need him?

  12. #12
    Join Date
    Dec 2009
    Location
    Southern US
    Posts
    504
    Interesting!

    I think the next PM's I do on one of our older buildings where there is a good chance of heat exchanger problems, I'll try to take one of our analyzers and run some checks.
    I'm good at making things cold...You can ask my first two wives!

  13. #13
    timebuilder's Avatar
    timebuilder is online now AOP Committee/Professional Member*
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,814
    Quote Originally Posted by hvacpope View Post
    I dont think with a draft inducer any CO would leak into the supply duct at all regardless, even with a gravity system is kind rare to have CO leaking from the HX into the conditioned air, just check the combustion byproducts for o2 increase after the blower kicks in.

    That was my opinion until last week, when I had a call for a "gas smell" at one of the few remaining video stores outside Philly. The manager said the smell was coming from the register in the entrance alcove.

    On the roof, there was an old york 150 with a perforated hx. Inducer ran great, but combustion byproducts WERE finding their way into the supply air.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event