# Carrier Weathermaker 9200



## yuri (Nov 29, 2008)

Make sure all the exhaust piping is sloped back to the furnace properly and has no sags in it which will collect water. Then it backs up and blocks the pipe and starts tripping a pressure switch. Add more hangers with perforated nylon coated strapping if necessary.


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## klrz28 (Jan 18, 2011)

I fixed the pipe issue no more gurgling. All though the furnace still continued to shut off and on while heating, so I cut in a extra cold air return vent and went with a thinner furnace filter. The heat exchanger was getting too hot and shut down, problem solved, Thanks,
:thumbsup:


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## yuri (Nov 29, 2008)

Glad to hear you got it going. We don't always get the positive results/outcome here.


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## klrz28 (Jan 18, 2011)

Now its having a issue with staying running. It fires up runs for a few minutes then the burner shuts down, blower cools down the heat exchanger then shuts off and then fires back up again. Flashes 33 is there a bad sensor? What can it be? Is it getting too hot? Not enough cold air return? Weak blower motor? A coil is clean. What can it be?


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## HVACDave (Oct 16, 2007)

Have you tried a temperature rise test accross the heat exchanger to see if the unit is actually overheating or if you have a bad limit switch? Take a thermometer and check the discharge air temp and then check the temp. in the return air duct and calculate the difference, then check the rating plate inside the furnace for the heat rise (it will be a range) (typically 40-70 degrees F) and see if you are in that range. If you are outside (above the range) in temp. difference then you have an airflow issue and the furnace is in fact overheating. Have you by chance been running it without a filter for a period of time? If so you may have a restricted secondary heat exchanger which can plug up just as you suspected your A/C coil may have been. If this is the case, you must remove the blower assembly and sqirm in on your back and look up to the heat exchanger and see if it is restricted and clean that coil if it is.


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## klrz28 (Jan 18, 2011)

The heat exchangers look clean. This house is on a crawlspace. The crawlspace walls are insulated. the duct work is insulated as well. Should I remove the insulation from the ducts to help disperse the heat from the trunk? I am almost positive its the limit switch tripping from excessive heat.


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## klrz28 (Jan 18, 2011)

Or Can I add a duct and Bring in Fresh air from the outside of the house to help, maybe add a damper to it to adjust air flow coming in? I know most homes air inside the home is 4-5 times dirtier than the outside air. Any thoughts are greatly appreciated.


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## HVACDave (Oct 16, 2007)

Has this been an ongoing problem, or has it become more noticable just lately? How large is the furnace (btu's) and how much ducting do you have connected?


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## klrz28 (Jan 18, 2011)

I believe its been doing it for some time just haven't noticed.


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## klrz28 (Jan 18, 2011)

I believe its a 80,000 btu


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## klrz28 (Jan 18, 2011)

I believe there is 13 supply ducts and 7 cold air ducts.


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## klrz28 (Jan 18, 2011)

It has to be starving for cold air. If I take out the .99 cent air filter and leave the cover off it will run all day long and not hit the high limit. So it has to be starving for more air. The furnace is up side down. The cold air return is on top of the furnace and pushes the heat down under the house thru the trunk. The a/c coil is clean. So now I dont know what to do to get more air to it. There already is a Cheater duct above the furnace that seemed to help a little but its still not enough air. One other thing. All of the crawlspace perimiter walls are insulated and visquine is laid on the floor.


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## kenmac (Feb 26, 2009)

Hard to believe that a new 99 cent filter is enough restriction to limit air flow.Duct must be way undersized. Are all the return vents clear / have no restrictions ?


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## klrz28 (Jan 18, 2011)

The previous owners had the 4 inch thick filter in there and I noticed it hitting the high limit. It would shut down and fire back up. I think the furnace is too many btu's for the house. Im no hvac expert.


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## klrz28 (Jan 18, 2011)

Everything is clean and clear also.


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## klrz28 (Jan 18, 2011)

So I found another issue. The supply that comes from the furnace isnt a sweep elbow. Its just a box then the trunk ties into it. Im Pretty sure thats restricting air flow quite a bit. We installed a famco. And that helped out some. Especially air quality having pets. Is installing a sweep elbow going to help quite a bit? Whats your thoughts guys?


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## yuri (Nov 29, 2008)

Sweep elbows are VERY rare where I am if the furnace is a vertical upflow. Square box/plenum and horizontal take off into it is most common. Most problems are due to undersizing. Increasing your return air duct size that drops down and into the side of the furnace helps a lot. If the AC coil is jammed high up into the plenum blocking the horz takeoffs rather than sitting low down to the furnace that causes weird airflow thru it and extra resistance. Is the furnace installed vertical or horizontal?


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## klrz28 (Jan 18, 2011)

The furnace cold air return is above the furnace and the supply goes down under the floor into a 19"x24'' box and has the trunk 8''x24" tie into the side of it. This is in a crawlspace aswell.


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## klrz28 (Jan 18, 2011)

The furnace is on the 1st floor, supply going under the house.


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## yuri (Nov 29, 2008)

Not a setup I am familiar with. 95% of my units are vertical, 3% horz and 2 % counterflow. 5% of our homes don't have full basements.


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## Chris4mx (Mar 3, 2011)

What model is the furnace? It's on the tag inside the upper competent on the left side. Is the flame blue and consistant?


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## klrz28 (Jan 18, 2011)

MODEL 58MXA080 Weathermaker 9200 flames are nice and blue.


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## Chris4mx (Mar 3, 2011)

Could be a bad limit. That furnace might have a few limits. Prob some on the blower housing and one in the heat exchanger.


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## klrz28 (Jan 18, 2011)

It is a downflow furnace..


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