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  1. #1
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30

    Carrier 48GS package unit Carbon Monoxide issue!

    I installed a new heat exchanger, inducer draft motor assembly, & the back plate for the draft motor today and after getting it done I started it up and everything came on fine. The 2 shot burners where burning blue and the outlet pressure was running around 3.2 to 3.3. However, after I was gone for about 2 hours the H/O called and said that there CO monitor was going off. When I got there I started it up and the gas valve didn't want to open up but after several attempts it finally did. The flames look great but i am getting a strong smell like a rich mixture but there is no adjustments that i can see on the burners for the air. i am getting an elevated reading in the house but i took the right side panel back off to check everything and it looks sealed up with no way of sucking the exhaust back into the system. I am stumped and can't think clearly at this point. I have never had this type of issue before after installing one before. The only thing I know of right now that doesn't seem right is the rich smell I am getting out of the flue and that is it!!!. Can someone help. Could a faulty gas valve cause this to happen?

  2. #2
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,790
    Maybe it's not the furnace and it's really the gas water heater in the basement not venting. draft diverters are DEADLY.

    If the CO monitor is going off then there is a really high level of CO in the home. It needs to be vented and the source determined and fixed.

    A faulty valve that leaked some gas on shutdown would cause CO to rise at shutdown.

    The only way to figure this one out is with a combustion analyzer.

    Did you install the regulator and flame retainer?

    Make sure your burners are aligned perfectly. They should point directly into the heat exchanger with no pitch up or down. make sure your burners are clean and the cones at the end of them are clear with no soot or stinkbugs in them.

    You could be producing so much CO and another source in the home is sucking in the exhaust fumes.

    Flame color tells you nothing about combustion. I had one on friday (48tjd009) that had nice "pretty blue" flames that was producing over 2000PPM out the flue.

    Ive had blue flames produce high CO, low CO
    orange flames produce high CO, low CO

  3. #3
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30
    Thank you for your response. The only other thing in the house that is on gas is the water heater and at this time it is not working itself. They have had it shut down for a while. Now on the regulator ,if I check the inlet and it is around 10 or 11 then I do not need a regulator right? To be honest, around here I have hardly ever seen an external reg on any unit for that matter at least when it comes to residential systems. The flame retainer is something I think this unit doesn't have on it and from the pictorial that came with the new heat exchanger it doesn't show it either. What was wrong with your unit (48td009) that was producing the CO, was it a cracked one? The alignment I might need to check on! It seems that when I install the gas nipple it doesn't align perfectly up with the hole and it causes it to shift a little but not very much though.

  4. #4
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    One other thing, seal the wiring hole to the indoor blower as this is under neg. press and can pull from burner comp..

  5. #5
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30
    great advice!

  6. #6
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,356
    Quote Originally Posted by helsonbm View Post
    Now on the regulator ,if I check the inlet and it is around 10 or 11 then I do not need a regulator right?
    the regulator he is talking about is part of the heat exchanger, not the gas system. it is a plate with holes in it.

    when you purchased the exchanger, you should have been sold 4 part numbers. heat exchanger, flame retainer, regulator, and support assembly.

    These are all the parts you need to build a brand new heat exchanger. If you reused any old parts, or left off any of these parts, that is likely your problem.

    Did you install 2 separate plates with holes onto the new heat exchanger? (the regulator and flame retainer)

  7. #7
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,790
    Quote Originally Posted by craig1 View Post
    the regulator he is talking about is part of the heat exchanger, not the gas system. it is a plate with holes in it.

    when you purchased the exchanger, you should have been sold 4 part numbers. heat exchanger, flame retainer, regulator, and support assembly.

    These are all the parts you need to build a brand new heat exchanger. If you reused any old parts, or left off any of these parts, that is likely your problem.

    Did you install 2 separate plates with holes onto the new heat exchanger? (the regulator and flame retainer)
    YUP^^^ That's what I'm talking about.

    My heat exchanger had a dirty combustion wheel, sooted burner plates, heat exchanger filled with stinkbugs and misaligned burners.

    When the burners don't line up with the h/x it will cause flame impingement which will cause CO to rise. also dirty burners cause CO to rise, a dirty combustion wheel will cause CO to rise as well. Before repairing the unit I had a "Pretty Blue" flame that was producing over 2000ppm CO.

    Just because "the flame" looks "good" means nothing about how much CO it's producing.

  8. #8
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30
    Just got home after going back out this call again. I replaced the gas valve due to an intermittent problem of not openning up when 24v was applied to the valve. After that, I just started it up after cheching the burners and the orfices which were fine but to no avail. So, I removed the heat exchanger again and took everything off of it and made sure everything was sealed and caulked to make sure no leaks then reinsalled and fired it back up but STILL the exact same problem. I am soo confused now because I not sure what to do. I did look over the heat exchanger while I had it out but didn't see anything abnormal.

  9. #9
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30
    Everything is basically new. New heat exchanger, inducer assembly, back plate, gas valve, and the 2 inshot burners. I called Carrier and there is no regulator or flame retainer for this piece of equipment. They doubled checked too. The alignment of the burner is right on as well. Sealed with high temp caulk, didn't go crazy with it but there is plenty to make a good seal. Not sure what else to check. The outlet pressure is a least 3.5 to 3.7. That model was a 48GS-030060301 by the way.

  10. #10
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    alignment is critical on this unit, so much so I like to use a flex connector on gas line to prevent it from changing. I hope newer units have better indexing pins to locate burner correctly.

  11. #11
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,356
    Quote Originally Posted by codgy View Post
    I hope newer units have better indexing pins to locate burner correctly.
    hahahaha.....no, nothings changed. Theres a reason that Carrier RTUs are the cheapest on the market. They're garbage and pretty much designed to fail in as many ways as possible.

    I like working on them though because they sure bring in the $$$$ with all those heat exchanger replacements.

  12. #12
    Join Date
    Sep 2012
    Location
    Ottawa, Canada
    Posts
    28
    I would check the install of the heat exchanger because its producing co. Checking seals and welds because it wasn't producing co before the install. I know it's a pain in the ass to take the furnace apart again, but may be needed. I've seen good techs install it upside down, I don't know how but try not to judge. Main thing is to make it safe.

  13. #13
    Join Date
    Sep 2007
    Location
    Nashville,Tn
    Posts
    30
    10-4

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