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Role-out switch trips on forced hot air system, help!

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Hector V
Hector V Member Posts: 1
in Thermostats and Controls
I am looking to see if anyone has had this problem with a home heating system. The system is a gas, forced hot air heating system. Goodman Manufacturing Co., "Dependable 92", model no. GMN100-4, 9 years old.

The symptom is that the system turns on when heat is called for. The operation to start up is as follows. The direct vent fan turns on. Then the ceramic gas ignitor turns on and the gas valve opens and flames ignite into the heating tubes of the furnace. Then the main fan turns on and the system begins to send warm air to the whole house. The problem begins here, the top of the furnace begins to get very hot to the touch, something that didn't happen before a few weeks ago. About 6 minutes into the operation, the top portion of the furnace gets too hot and a rollout switch near the ceramic gas ignitor trips. I was able to reset the first time, thinking it was a odd happening, but after resetting I now see that it trips because it gets too hot. I wanted to know if anyone has had this problem, and what did you do to resolve.

I did the following: Opened up the A-coil for the cooling above and vacuumed out the coils, replaced the air filter with a new one, reset the rollout switch.

I will do this next: Check the power vent exhaust vent pvc piping to see if there is any obstruction in that pipe causing air flow obstruction.

After this, I don't know what else to look at. Need some suggestions.

Hector

Comments

  • ed wallace
    ed wallace Member Posts: 1,613
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    rollout switch

    check the the blower motor sounds like the motors not working

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  • Jon_2
    Jon_2 Member Posts: 109
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    Roll-out limit tripping

    1. Check the direct vent draft motor and vent line. Sometimes on the draft motor the impeller seperates from the shaft. And any blockage of the vent line will cause roll-out. All so sometimes the plastic cover on the secondary heat exchanger cracks, you have to tear the front off the furnace to check that. You have to find out why the draft motor is not sucking the flame down the burner tubes. The three items I mentioned are nearly all ways the cause. Jon
  • Glenn Harrison_2
    Glenn Harrison_2 Member Posts: 845
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    I'll bet it's a bad Heat Exchanger

    Goodman/Janitrol has had problems with the primary heat exchangers coming apart. In the manufacturing process, they would drill holes in the HX and crimp the metal over thru the holes to hold the two halves of each cell together. Over time, these crimps, wich look just like rings about the size of a dime, would snap off, and the cell halves woul separate causing the flame to back upp and trip the rollout. If you can, look down from the top of the HX and look for these rings laying on top of the secondary HX. Otherwise, you'll have to pull the HX to confirm the HX coming apart.

    Sorry for the bad news. Hope it's helpfull tho.

    Glenn
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