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What is the flame rollout switch for?

californian
13 years ago

I have a Carrier 58wav070-1-12 gas furnace and the induced draft blower motor is not turning. The LED fault code is three short flashes followed by three long flashes (33), which is supposed to mean limit or flame roll out switch is open.

I know the blower is good because it turns if I disconnect the wires and apply 120 volts AC directly to it.

There is also supposed to be a manual reset on some limit switch, but I don't see any switch with a reset on it. And it doesn't say what the limit switch is for or where it is.

Another symptom is the main blower is always running.

My guess is the problem may be the computer that controls everything because the component self test doesn't run.

I guess a defective low gas pressure sensor switch could also inhibit the furnace turning on because that is not tested by the self test.

Comments (12)

  • johnhvac
    13 years ago

    In the link below is your operating manual

    There is a drawing showing approximate locations for the various limits etc depending if it is a upflow,Downflow furnace etc

    The switch is also called a flame roll out switch, if you reset it and it shuts off again, Get a tech in there to determine the cause of the failure. I cannot stress this point enough!

    This is from the Carrier Manual

    Check the manual reset limit switch(es) located near the
    burners. If the furnace has experienced a high-temperature condition due to inadequate combustion air, these switches will shut off the furnace. Reset the switch(es) by pushing the button on the switch. If the switch trips a second time, turn off the furnace and call for service.

    http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/om58-93.pdf

  • ionized_gw
    13 years ago

    Yes, but inquiring minds want to know what it is for.

  • brickeyee
    13 years ago

    "Yes, but inquiring minds want to know what it is for."

    If for ANY reason the gas flame comes out forward it kills everything.

    It could be due to delayed ignition and gas buildup, a partially blocked flue or passages in the unit, etc.

  • californian
    Original Author
    13 years ago

    I spent about four hours yesterday researching my problem and flame rollout switches. In case anyone is interested the flame rollout switch detects something called flame rollout, which is where the flame goes somewhere it shouldn't like through a cracked heat exchanger or out the front of the furnace.

  • berlin
    13 years ago

    well, it won't sense it if it goes "through" a cracked heat exchanger, but when the blower kicks on, if your heat exchanger has a large enough perforation, the conditioned air blower will blow the flame back onto the sensor.

  • ionized_gw
    13 years ago

    Thanks for the explanation. This is one case where the name of a device corresponds pretty well with its function, but one can never be sure.

    One more question if someone will indulge me. When did such safety devices become common in residential heating devices?

  • Doug Duchesne
    7 years ago

    Teledyne Laars jvt50. Roll out switch. Had to jump out to fire


  • Doug Duchesne
    7 years ago

    Any input

  • mike_home
    7 years ago

    What is the question?

  • PRO
    Austin Air Companie
    7 years ago
    last modified: 7 years ago

    Flame roll out is a safety device that is wired within the control circuit of the gas valve. There is more than one such safety device but for the purpose of this thread won't get into those.

    If the flame (from the burners) rolls out of the cabinet without a flame rollout safety switch you're probably looking at a 5 alarm fire in your attic, closet or crawlspace.

    If the flame rollout is tripped (IE not sending power to gas valve) the furnace (heating portion) can not run or in the event it is running - it shuts off power to the gas valve which in turn kills the live flames. Most manufacturers of heating equipment today, pass this circuit thru the board before going on to the gas valve... you know to give a hint to the less fortunate / uneducated (which ever you prefer) in this field.

    Sometimes hints can be deadly. (IE see 5 alarm fire mentioned above.)

  • PRO
    John Sparrow Landscaping
    6 years ago

    can excessive heat transfer cause the roll out switch to trip. The roll out held was so Hot I could not handle it or the switch without gloves. I do not think a blow back/roll out could make that metal so hot. I tested the situation by jumping out the switch and let the boiler run for 30 min or so while I stayed in the room. when I determined that was the cause I went to remove the shield switch assembly and could not handle ti. Questions can the excessive heat rather than roll out burn out the switch, what could be causing this the boiler was just completely cleaned by a "professional "