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High limit temp sensor

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by Mike M57, Feb 19, 2013.

  1. Mike M57

    Mike M57 New Member

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    Stove was out when I got up this morning and would not restart, the auger was not turning. When I got home from work I checked for auger jams, tested motor, bypassed vacuum switch and finally noticed high limit sensor had tripped. Reset sensor and stove started up. Is this an indication the convection blower is going or could it be 160 temperature sensor. Is there a way to test.

    Thanks

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  2. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    The first place to start is with the convection blower, clean it and pay attention to the motor and its cooling fan they need to be kept clean as well, then oil the blower motor if it is an oil able motor the makers plate should tell you if it is and what oil to use. They frequently need oiling every six months. Sometimes the oil ports are pointing down and that should be corrected if possible.
  3. Bioburner

    Bioburner Minister of Fire

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    How old of stove? Cleaned and oiled the fans lately? Without a accurate temperature gauge or IR gun its hard to check the snap.
  4. Mike M57

    Mike M57 New Member

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    By end of heating season last year motor was sounding a bit loud. I took out convection blower in the fall, oiled it and cleaned the blades, after that motor sounded quieter. After about 1&1/2 tons I did same. Oil ports are on top. Stove is 5 years old. I ordered some oil for furnace just to be safe, will cry when I have to write oil company the check. If I have to replace fan do they make one that fits my stove that has a higher cfm.
    Thanks for your expertise.
  5. Bioburner

    Bioburner Minister of Fire

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    I was making general questions on the service of the stove. You may well have your fans bearings going. Five years without its annual oil may have sealed its fate prematurally. Maybe someone with more knowledge on your stove model will join in. Maybe the fans bearings can be replaced?
    Good luck
  6. Mike M57

    Mike M57 New Member

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    I have oiled the convection blower multiple times each year. This was the first season that I pulled the motor to clean the blades. The combustion fan seems louder to me. Would that trip the sensor? I am certainly not the most mechanically gifted of individuals so this forum is of great help to me.
  7. Bkins

    Bkins Feeling the Heat

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    When was the last time the exhaust pathways were cleaned? Also the exhaust pipe its self? You need to look in all areas that can/could slow down the exhaust gases. The snap disc could just be bad also. Have you ever had to reset it if its a resetable one? The bearings going bad could cause the rpm's to drop enough on the fan to cause the temps to rise enough to trip the disc. I'm thinking your bearing are shot and need to be replaced mainly because you asked about increasing your CFM, and yes, I know that may just be something else you would like addressed.

    I would clean the stove/exhaust if it hasn't been done recently.
    Replace the snap disc.
    Replace the bearings or motor.

    I feel that if you do the above you will have covered all bases. Others will chime ion if I've forgotten something which I'm sure I have.
  8. Bioburner

    Bioburner Minister of Fire

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    I don't think a failing combustion fan-motor would cause the high limit switch to trip as the exaust is not flowing it would be getting cooler if the convection fan is doing its job and extracting the heat. Combustion fan is probably due to get pulled and cleaned properly. Most models will need a new gasket after removing the fan unit though. I am surprized no one with this model of stove has chimed in.
  9. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    What trips the sensor assuming the sensor is good is insufficient air flow to keep the heat exchanger's temperature below the trip point.

    There are two air flows that count the convection air flow which removes heat from the exchanger and dumps it in the room a dirty or failing or unmaintained convection blower is the leading cause of high limit trips provided the stove is not overfeeding pellets (improper feed gate setting if any, burning other than approved fuel, incorrect auger motor replacement, etc ...)

    Then there is the combustion air flow here the primary culprits are a dirty exhaust system, a failing combustion blower, or an improperly installed vent system.

    It is possible for both air flows to contribute to the sensor tripping.

    The high limit sensor I'd trust.

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