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  1. #1
    Join Date
    Jan 2020
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    Seeking 2nd Opinion Bryant furnace overheating

    Hey guys, Iíve been reading a lot of threads here and Iím glad I found this site. Tons of awesome info! I was hoping to reach out for some additional opinions, I disagree with the HVAC tech that ďdiagnosedĒ my unit and would like some of your thoughts.

    I have a Bryant Plus 90 Furnace that was installed in my home in 1996 (I know, itís aging but until now has ran flawlessly, Iíve lived here three years but am in contact with previous owner, purchased from a friend).
    Model: 350MAV036040
    Serial: 3693A04335

    About a week ago the furnace turned off in the middle of the night, tripping a code 33 for the rollout switch.

    The furnace will turn on, the burners will ignite and it will run 4 to 4.5 minutes then trip the code and kill the burners, but leave the blower on to cool the unit.

    I did a quick check over, thereís no blocked vents in the house anywhere (currently have all the grates off also just Bc). It has a brand new, cheap Mert4 filter in it so I donít think itís restricting the air flow there. I located the intake/exhaust which comes out the back of my house (furnace in basement). Thereís no restriction in the piping (Visually) and I can feel air coming out of the exhaust and the intake side is sucking air in. There are no abnormal smells near the exhaust/intake and the HVAC tech checked the exhaust pipe with his CO meter and said it read fine, I donít know what it read though.

    So I called a Pro, he came out and inspected the unit. He bypassed the limit switch, the unit ran about 7 minutes and he deemed that to be my problem. Great, ordered the part and he returned the next day. Installed the new limit switch, fired up the furnace, it ran about 4 minutes and tripped the code 33 again. The HVAC tech checked the A coils ontop, they're clean (unit is serviced annually), he checked the blower motor settings, capacitor, checked the flame rod, cleaned all water vents/hoses, then finally replaced the roll out switch on the side of the burner box. Turned the furnace back on, ran for almost 4.5 minutes and tripped the code again.

    AFTER he spent almost six hours in total on my unit, he told me that my problem is when the builder built the house (IN 1996) they installed a 14inch evaporator coil on top of a 17inch Bryant furnace. He is claiming the reduction to 14inch coils on the 17inch furnace is causing the furnace to overheat and shut itself down. He recommended I replace the entire unit. Furnace and air conditioner. WHAT? And he charged me for everything, I feel totally ripped off.

    If the unit needs replaced, it needs replaced. Iím okay with that. Iím not okay with being expected to believe itís ran fine for 25 years but all of a sudden the evaporator coils on the furnace is the issue.

    I know these units had issues with their Secondary Heat Exchangers. This unit DID have that replaced under warranty in the mid 2000s, we're still trying to locate the paperwork for the exact date.

    Any and all opinions are appreciated. I plan on calling another tech out but if it needs replaced I am going to have to wait a little while. I have 3 gas fireplaces in the house so I have plenty of heat for now.

    Thanks,

    Ralph

  2. #2
    Join Date
    Jan 2004
    Location
    PA
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    Its probably the secondary heat exchanger.

    Carrier/Bryant units had a problem with their secondary heat exchangers.
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    How many times must one fix something before it is fixed?

  3. #3
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    Jan 2020
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    Thread Starter
    Thanks beenthere but the secondary HE has already been replaced under warranty. Do you believe itís going again?

  4. #4
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
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    Quote Originally Posted by Ralphc01 View Post
    Thanks beenthere but the secondary HE has already been replaced under warranty. Do you believe it’s going again?
    Could be.
    If it was replaced in the 2000's, lets say 2009, that makes 10 years.
    Been another 10 years.....

    If you did lose another heat exchanger, someone needs to do a complete evaluation of your duct system.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  5. #5
    Join Date
    Jan 2020
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    Thread Starter
    Iíll have another company check the secondary out again, this guy removed the bottom blower and inspected it looking upwards, he said it looked ďclean and newĒ but there was no other testing done to it from what I saw.

    For the duct system, what are they checking for? Just that the air flow readings....

    Iím a car guy so I know nothing about HVAC. If the secondary is bad then Iím fine replacing the system, I just didnít believe the size of the evaporator caused this breakdown all of a sudden.

    Thanks

  6. #6
    Join Date
    Sep 2007
    Location
    edmonds wa
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    At that age and design of furnace ,i would bet the secondary starting to plug up. Does the exhaust have a foul odor from it?
    UA Local 32 retired as of Jan 2020

  7. #7
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    I wouldn't invest any serious money into that furnace at its age but definetly dont give that first guy any more of your money! Ask your friends, family and employers who they trust and use

  8. #8
    Join Date
    Sep 2007
    Location
    edmonds wa
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    As i remember you could pull the inducer motor and look thru to the ends of the secondarys.
    UA Local 32 retired as of Jan 2020

  9. #9
    Join Date
    Jan 2020
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    Thread Starter
    No foul odor from the exhaust, secondary was replaced under warranty once. Could be plugging up again thought I guess.

  10. #10
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    Jan 2020
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    Thread Starter
    No plans to sink an major money into it Makeitcold, but if o could get some more time out of it for a few hundred bucks I wouldnít of minded. lol

  11. #11
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    The smaller coil is fine, IF it's done correctly, this usually requires a transition in between the two to direct the airflow into the smaller coil, manufacturers will usually list a minimum length of transition in the install literature. If the smaller coil is just slapped on top of a larger furnace it will often have airflow issues that cause the furnace to run hot. Your static pressure should be measured on your highest used speed and compared to the blower performance chart to determine how much airflow your ducting can move efficiently and then a manual j should be done to determine the load on the building. Loadcalc.net allows you to do a free block load version of manual j, a contractor that's worth your money will do a more detailed, room-by-room load calculation, but it's good enough to give you an idea if your correctly sized or not. Oversized equipment on undersized ducting is so common it's the norm.

  12. #12
    Join Date
    Dec 2007
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    I'd bet a paycheck on failed secondary!!!

    Just because it was replaced does not mean it can't fail again. what do you think it was replaced with? Yes, the same type that had the failure.

    A combustion analysis will confirm it.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  13. #13
    Join Date
    Jan 2020
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    Thread Starter
    Thanks Makeitcold - there is a transition between the evaporator and furnace, but not much. Maybe 3-4 inches by eyeing it. Iíll check out the website you provided, but Iíll likely leave it to the pros though.

    Side note - my house did have an addition built on to the back of it, adding about 1000 square feet roughly. The contractor at that time did add two additional vents into the added space. He ran them with the flexible duct stuff thatís easier to run. Could this have affected the furnace operating properly by changing the air flow in the ducts? The addition was built roughly 8 years ago.

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