Had routine furnace checkup - overheating problem


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Old 09-15-11, 04:02 PM
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Had routine furnace checkup - overheating problem

Ok, I scheduled a routine pre-heating season checkup of my natural gas furnace. I was told that the unit was overheating and shutting itself down. The fan continued to run and the thermostat was calling for heat but the unit itself was outputting 150degrees and overheating, sending it into protection mode and shutting the flames off.

I was told the most common cause for this is a blocked evaporator coil. I opened up the box to expose the coil and much to my surprise, both sides looked pretty clean. I mean, there was a little dust on the under side of the a-frame coil but nothing major. I could even see all the fins fine. Also, I noted that with the A/C on, the air output from the vents was just fine. I mean, more than sufficient airflow from the registers even on the top floor. So, I have declared this NOT to be the problem.

Before I pay someone else for a second opinion(money doesn't grow on any of the trees near my house) , what are some other things I may check?

problem: furnace overheating and shutting down

additional info:
-evap coils look good
-good airflow from registers
-air filter not very dirty/ almost new
-Carrier furnace model: 58YAV091

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https://picasaweb.google.com/lh/phot...eat=directlink
 
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Old 09-15-11, 04:22 PM
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gas pressure may be set wrong. Blower speed may be set wrong. Filter could be sized wrong/too restrictive. Ductwork could be undersized or not enough return/supply. Limit could be worn.

on a side note. With that model furnace and the age it may have cracked heat exchanger cells. Especially with main limit tripping.
 
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Old 09-15-11, 04:25 PM
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lol.... so second opinion. by a professional!

Thank you very much. I'm just wondering if this thing is worth fixing. I've got a buddy who knows a good HVAC contractor who installs Goodman. What's your opinion on that?
 
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Old 09-15-11, 04:32 PM
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Goodman is a much better brand now that they own Amana and use Amana's design. Now, having said that, it all goes back to the installing contractor. A system is only as good as the installer. Goodman, is a lower end brand though.... But it's still Amana's design. All in all, ok equipment. Get at least 3 contractors to quote you. Remember you get what you pay for.
 
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Old 09-17-11, 05:13 AM
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Any idea on the AFUE of this unit? I'm trying to educate myself a bit before I have someone else come out and have a look.

Also, I have not turned the unit on myself yet since the tech said it was overheating but, shouldnt I get a blinking error code?
 
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Old 09-17-11, 06:29 AM
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your current furnace is 80% efficient.

You would only get an error code while the unit is out on main limit if it were overheating. When the main limit trips, the furnace control board shuts off the burners and inducer and leaves the blower on until the main limit resets. Only while the main limit is tripped you would get an error code.
 
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Old 09-17-11, 08:22 AM
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Usually overheating conditions are easily corrected once the cause is identified. The cause is usually something that restrict airflow through the furnace, such as a plugged filter, return air vents obstructed, too many warm air vents closed off, collapsed ductwork and such.
 
 

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