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Thread: HVAC Company Recommends Removing Burners To Fix Overheating Furnace?

  1. #1
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    HVAC Company Recommends Removing Burners To Fix Overheating Furnace?

    Here's the short story, my furnace is overheating and shutting itself off and the HVAC company is suggesting to remove a burner so that it doesn't run so hot because they think my furnace is over sized for my 2100 sqft home. Is this really a typical thing to do?

    Here's the long story with more background:
    My York GY9S100C16DH11H furnace (2006/2007 92% efficiency model) shows 4 blinking red lights for high limit switch open. I tested the limit switch myself with a multi meter to confirm that it is opening when the furnace shuts itself off which it was, then I tested the limit switch in a pot of boiling water while monitoring the water temp with a meat thermometer to confirm that the limit switch is not opening prematurely. It opened right at 180F as designed, so the limit switch is not faulty. Furnace filter is also not the problem.
    Due to the design of my furnace model, further troubleshooting would require partial disassembly to open up the furnace to get to the blower motor/housing which I'm not comfortable with so I called an HVAC company. They got into the blower housing area and found that the capacitor for the blower motor was going bad, resulting in the blower not blowing enough hot air through to keep the furnace from overheating. I asked them if the blower motor and other internals like the coils all looked good and they said yes. They replaced the capacitor and called it good, but after they had already left the furnace eventually overheated again and shut itself off with limit switch open error.
    They came back out and lowered the gas pressure in the furnace and took some temperature readings with a digital thermometer at different parts of the furnace and eventually concluded that the furnace is over sized for my home and they recommended removing one of the 5 burners from the furnace so that it doesn't put out as much heat and hence overheat itself. I found this conclusion perplexing because the furnace did not have any overheating issues previously so if it was really over sized for my home wouldn't it have had over heating issues to start? To me this comes off as a band aid solution that doesn't address the real cause of why the furnace is overheating. Is removing a burner from a furnace really a typical thing done to address overheating issues?

  2. #2
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    Not anymore. There is a lot more testing to do. What type air filter are you using. Is it new? Are all registers open and return grilles clear? Any other recent changes to the house or system?
    Climate Control Solutions for your Home or Office

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  3. #3
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    If you have central A/C, it could be that the A/C coil is dirty and restricting air flow.
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    How many times must one fix something before it is fixed?

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    The filter is a 3M Filtrete 800 MPR in ceiling filter. I could not find a filter at the furnace return which I thought was strange based on what I was reading online, but the HVAC tech confirmed it didn't have one and that it's not unusual to only have the ceiling filter so I took him at his word about that. The ceiling filter is pretty new and clean. I actually tried running the furnace with the ceiling filter removed as a test but it still overheated and shut itself off.

    All the registers/vents are open and it's just the one return grill in the ceiling that has the filter I mentioned. No other changes to the house or furnace/AC that I could think of that would cause the overheating. Furnace is original to the house which was built in 2006 so it's only 14 years old. We've had the house for 3 years now and have not had any issues with the furnace up until this fall. The HVAC tech basically put it to me as the furnace just running hotter with age, combined with it being over sized for my home is causing it to overheat and removing a burner to lower the BTU's would prevent it from overheating and tripping the limit switch. I honestly don't know how true either of those things are. Do furnaces tend to run hotter over time as they age? I would think this would be manufacturer defect/warranty claim territory if that is the case?

  5. #5
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    Have a tech inspect the A/C coil. A dirty coil can cause the problem your having.
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    How many times must one fix something before it is fixed?

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  7. #6
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    UPDATE: So apparently my furnace now runs without overheating/shutting itself off.


    When the HVAC company originally replaced the capacitor for the blower motor, the furnace ran for awhile and then turned itself off normally because my house was already warm so it didn't need to run long to pass the 70 degree temp I set on the thermostat. I shut the heater off and didn't run it until the next morning so I could observe the control board/diagnostic lights and it was at this time that the furnace overheated after about 10-15 minutes, so I shut it off and didn't run it at all until the HVAC company could come back to investigate.


    When they came back, they turned the gas pressure down (they said it was set too high for what the manufacturer suggested) and ran it for 20-30 minutes without it overheating/shutting itself off, but they recommended removing a burner to 1. prevent anymore overheating and 2. prevent more problems down the road since they concluded after taking temperature measurements with a digital thermometer that the furnace overall was running too hot internally and over time internal components will fail sooner etc.


    It was at this point that I was unsure what to do and posted here asking for advice and considered calling another HVAC company to investigate further. I didn't bother running the furnace at all thinking that it would continue to overheat. Yesterday I decided to give it a shot and ran it in the late morning when my house was pretty cold. I monitored the furnace and had eyes on the burner flames and control board diagnostic light to watch if it shut itself off with an overheating error, but it ran for about an hour or so without issue which was surprising and encouraging so I turned it off to give it a break. From what I remember it raised the temp in the house from 64 degrees to 66/67, don't remember exactly.


    Since then I've run it few more times during the day so I can monitor it and so far it hasn't overheated and shut itself off, so I'm glad about that but also confused as to why it would have overheated on that one run the next day after the capacitor was replaced but not anymore? Could it be that the capacitor maybe just needed to get tuned in with the blower motor or something like that? From a technical perspective, I'm not sure what factors could be in play when a capacitor is initially swapped. Could it have just been a fluke and it's probably fine now? While I've been running it during the day, I've gone to all the vents in my house to feel for airflow and they're all blowing fine. What do you all think?

  8. #7
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    When they came back, they turned the gas pressure down (they said it was set too high for what the manufacturer suggested) and ran it for 20-30 minutes without it overheating/shutting itself off.

    Who to say they just didn’t under fire the gas valve a tad instead of what it was. Not saying that’s the case but it’s a possibility.

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  10. #8
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    With them saying that removing a burner will help prevent trouble down the road. Sounds like they realize the furnace is too big for the duct work its connected to.
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  12. #9
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    Since the limit switch doesn't "average" the discharge air temp, but measures it from the burners it's closest to, removing a burner won't solve anything. It's usually located near the middle burner(s) which cannot be removed as that would prevent proper ignition upon startup.

    A large portion of proper diagnostics is just using plain old common since. As you mentioned, the furnace didn't trip the limit for 14 years with all of the burners it now has. How is it that it's now necessary to remove one? Which is also against code. And no, furnaces don't just run hotter with time if everything is functioning correctly.

    As Beenthere has pointed out, your a/c coil is probably dirty and needs cleaning because it's restricting airflow. Also, your blower motor may be wearing out and not moving sufficient airflow. You have an airflow issue and taking a simple delta T measurement between supply and return should have been one of the first steps. The allowable delta T (temp rise) is clearly stated on the furnace tag.

    The gas manifold pressure MAY have been too high and contributed to the problem, but under no circumstances should it have been set below what's listed on the furnace tag. Doing so will cause flue gas condensation in the primary heat exchanger which will destroy it.

    The furnace is no doubt over-sized for your house, but the only way to correct that is with a properly sized one.
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    ​You can choose to do what you want, but you cannot choose the consequences.

  13. #10
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    All york single stage furnaces on natural gas must be set to 3.5 " wc. If they turned it down below that to keep the furnace from overheating this will cause another problem. My advice is pull the furnace if it's too big. You'll have chronic issues forever until you do

  14. #11
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    I'm wondering if at 14 years old anyone even bothered to check the blower motor capacitor.
    If a capacitor gets far enough out of range you can easily lose a couple hundred rpms. And with a little less airflow it's pretty easy to trip a high limit.
    And as mentioned above, check the evap coil as it can certainly restrict airflow.
    Did anyone even bother to see what the amp draw of the blower motor was?
    You don't squat with your spurs on.
    And you NEVER put the torches away before pressure testing.

  15. #12
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    UPDATE - INDUCER MOTOR DIED! Apologies for the long post again but would appreciate anyone's thoughts on my current furnace developments...at a minimum it would make for a good troubleshooting exercise for you experienced HVAC folks

    As I mentioned before, my furnace stopped shutting itself off due to overheating/high limit switch tripping so I continued to use it when one night I heard a loud grinding sound coming from the furnace which obviously was a motor seizing up. I shut the furnace off for the night and later confirmed it was indeed the inducer motor that died. I'm going to buy a replacement and install it myself, but now I'm questioning the cause of the original over heating problem I had. Could it have been the inducer motor going out that was leading to the over heating? If not, could it have been excessive heat from over heating (caused by something else) on the inducer motor that sped up its demise and killed it?

    Since some folks mentioned the AC coils getting clogged with dust as a cause for poor airflow and hence over heating, I bought a camera scope and snaked it inside the furnace through the high limit switch hole to get a look at the AC coils and the furnace coils and as far as I could tell, there doesn't seem to be excessive caked on dust on the coils to be causing air flow/over heating issues in my opinion. What do you all think?

    Here's a link of pictures I took of the coils h ttps://ibb.co/album/FkSj6D (copy/paste the URL into a browser and remove the extra space between h and t. The forum doesn't allow me to post links yet.)

    So assuming that clogged coils isn't the cause for air flow restriction/over heating, then the next logical assumption I think would be that it was indeed the capacitor for the blower motor going out leading to lower blower RPM's causing insufficient airflow/over heating. This would line up with the fact that the furnace stopped over heating/tripping the high limit switch after the new capacitor was installed by the HVAC company. To rule out the high limit switch being faulty again, I took it out and tested it again in a pot of boiling water and it tripped at the temperature it's supposed to so the switch is still good.

    So could it be that the blower motor capacitor and inducer motor unluckily started going out due to age (14 year old furnace) around the same time leading to overheating issues and eventual death of the inducer motor or maybe just the blower motor capacitor going out causing over heating issues and that over heating lead to the death of the inducer motor? This all had me confused because the inducer motor has a temperature limit switch of its own built right into the housing so I would think if the inducer motor was starting to go bad and not blowing enough to sufficiently blow exhaust out I would think that limit switch in the housing would have been tripped but it never was. After I removed the dead inducer motor assembly from the furnace, out of curiosity I removed the limit switch from it and found that the switch still had the black plastic cover on it from the factory, similar to this picture: h ttps://i.ibb.co/z715H36/limitswitchcover.png (copy/paste the URL into a browser and remove the extra space between h and t. The forum doesn't allow me to post links yet.)

    This would explain why this switch never tripped because it had that plastic cover shielding it from the heat inside. All these years with that plastic cover on the limit switch! I guess the installers never thought to look if it had it on or not? Maybe they assumed the manufacturer removed them since it comes pre-installed in the housing?

    In any case, I'm dumbfounded at the real causes of my furnace issues but also surprised at how much I've learned about HVAC because of all of this lol! My next step is to order a replacement inducer motor and install it and see how everything works after that and go from there and I'll make sure to check if the housing limit switch still has its plastic cover on! I think I may also buy a manometer to double check that the HVAC company didn't screw up the gas pressure and set it lower than what it's spec'd for. I'd love to hear everyone's thoughts and opinions on this latest update. Thank you!

  16. #13
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    We'd love to respond, but you have admittedly gone into the realm of DIY and that prevents us from replying per the site rules. Good luck.

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  18. #14
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    Dang, that's too bad because I was looking forward to hearing any input given the new info I found with the coils not being clogged and the limit switch on the inducer motor housing being covered this whole time. From a technical troubleshooting perspective, I thought it was kind of a neat twist in the story (but still very unfortunate since I have no heat lol!) so thought it would be good to hear what others could make of it.

  19. #15
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    Sorry, this is not a DIY site

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