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Thread: Furnace

  1. #1
    Join Date
    Dec 2010
    Posts
    1

    Default Furnace

    I have an amana furnace that was installed in 1998. When I moved in 5 years ago, I replace the old thermostat with a programable one.

    Two years ago, the furnace blower would start but the furnace would not kick in. I replaced the igniter but there were still times it would not work. A repair person showed me how to rest a switch in side.

    This year, the furnace will kick in a go to the set temperature and kick out. However, the blower will continue to run, blowing cold air for several minutes.

    A few (approm. 5-7) minutes later, the furnace will kick back in again. I have also needed to reset the switch on several occations.

    The repair person says that the pipes are too small for the furnace. Is this possible?

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Furnace

    Quote Originally Posted by brutus View Post
    I have an amana furnace that was installed in 1998. When I moved in 5 years ago, I replace the old thermostat with a programable one.

    Two years ago, the furnace blower would start but the furnace would not kick in. I replaced the igniter but there were still times it would not work. A repair person showed me how to rest a switch in side.

    The blower to circulate the air should only come on after the igniter lights the burners and the heat exchanger comes up to a set temperature.
    Perhaps you might be describing the Induced Draft Fan which comes on first before the igniter. This is to provide ( induce ) a draft up the flue to ensure the furnace is properly exhausting. There is a pressure switch associated to this fan that sends a signal to the control module to turn on the igniter. If there is a fault with the pressure switch the igniter will not turn on ---nor will any fuel be supplied to the burners -- one of many saftey interlocks.

    This year, the furnace will kick in a go to the set temperature and kick out. However, the blower will continue to run, blowing cold air for several minutes.

    On the furnace there is a low , high and over temperature control device that controls the blower. Once the igniter lights the burners and the heat exchanger warms up , this controller measures the temperature and when an adjustable set value is reached , electrical contacts will close to engage the blower motor. When your thermostat is satisfied the burners shut off and the blower will continue to run until the low limit temperature in the heat exchanger is sensed by the controller -- opens the electrical contacts to the blower motor to shut it off.
    It's possible the set value for the low limit is set too low or the controller is sticking.


    A few (approm. 5-7) minutes later, the furnace will kick back in again. I have also needed to reset the switch on several occations.

    The thermostat controlls when the furnace comes on -- don't know what else to say here.

    The repair person says that the pipes are too small for the furnace. Is this possible?
    It's possible the ducting is too small for the amount of air flow needed.
    Though I don't believe that would have anything to do with the igner not working.

    Sounds as though you need to have an HVAC professional come out and evaluate the furnace for proper operation as well any concerns regarding the size of the ducting.

    Addition--- if the previous repair person showed you the reset on the furnace and you are regularily using it this indicates there is a problem that needs to be addressed --- you shouldn't need to be resting the furnace often if at all .
    Some other HVAC professional needs to properly troubleshoot your system.
    Last edited by canuk; 12-10-2010 at 06:59 AM. Reason: addition
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Feb 2008
    Posts
    175

    Default Re: Furnace

    Great post, canuk, as usual.


    Well done!

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