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  1. #1
    Join Date
    Apr 2005
    Posts
    9
    I am working on a Reznor FE-100 power vented hanging heater with electronic ignition. When I turn on the unit, the burner lights and goes through the proper sequence and the blower fan will turn on after approximately 6 minutes.

    It works fine for the first cycle. The next time the thermostat calls for heat, it will proceed through the proper cycle but the blower fan does not turn on and then the high limit switch shuts down the unit.

    My thought was the thermac disk fan control switch was bad so I removed it and connected an ohm meter across the terminals. I then heated the switch with a heat gun and I could hear it click and the meter showed continuity. After the switch cooled, it opened and the meter showed infinite resistance. I repeated this several times and concluded that the fan control switch was OK. I reinstalled the switch making sure that the mounting springs were compressed and that the unit was preloaded against the heat exchanger.

    What should I check next?

  2. #2
    Join Date
    Oct 2004
    Posts
    3,400
    That's not the right way to test the fan switch.

    Test it in place, with a thermometer & voltmeter.

  3. #3
    Join Date
    Apr 2003
    Location
    Eugene, Oregon
    Posts
    1,209
    Motor overload
    Proud supporter of Springfield Millers and Oregon Ducks.

  4. #4
    Join Date
    Apr 2005
    Posts
    9
    Thanks for the responses.

    The motor is fine - when it does not turn on, I can jump the thermac switch and the motor will run. Measuring the current draw with an Amprobe shows the motor to be performing to the specs.

    I'll hook up a meter across the motor leads and monitior the temp. of the heat exchanger with a thermometer and see if the thermac switch closes.

    My gut feel is that the thermac switch is not closing as I do not hear the distinctive "click" when it operates properly in the first cycle.

  5. #5
    Join Date
    Apr 2005
    Posts
    9
    Correction to the last sentence in my response: I hear the thermac switch closing during the first cycle (when the fan operates properly) but not on subsequent cycles when the fan does not turn on and the unit shuts down.

  6. #6
    Join Date
    Apr 2005
    Posts
    9

    UPDATE

    The thermac switch is OK. The problem is 3 of the 5 burners are not lighting all the time. Most of the time, the heater was running on two burners and before the fan would turn on, the high temp cut-out switch would shut the unit down.

    I checked the orifices for restrictions and there were not any. I then removed the burners and cleaned them and reassembled the unit. When all 5 burners light ,after 2 minutes, the fan turns on.

    What would cause 3 of the burner sections not to light? When it does not light, if I create a draft, they will then light and everything works properly.

  7. #7
    Join Date
    Oct 2004
    Posts
    3,400
    Dirt, dust, rust, etc...

    Other things as well, but that's a good place to start.

  8. #8
    Join Date
    Apr 2005
    Posts
    9
    With the burners cleaned and the burner tray installed and all the shields in place, the unit appears to function properly.

    The pilot lights the closest two burners and after about 1 minute, the remaining three light. The blower fan turns on approximately 1 minute later (approximately 2 to 2-1/2 minutes after turning on the master power switch). It was taking 6 minutes for the fan to operate when three of the 5 burners were not lighting.


  9. #9
    Join Date
    Oct 2004
    Posts
    3,400
    Originally posted by willie2
    With the burners cleaned and the burner tray installed and all the shields in place, the unit appears to function properly.

    The pilot lights the closest two burners and after about 1 minute, the remaining three light. The blower fan turns on approximately 1 minute later (approximately 2 to 2-1/2 minutes after turning on the master power switch). It was taking 6 minutes for the fan to operate when three of the 5 burners were not lighting.

    Why do the others take a minute to light?
    Is this some type of 2 stage?

  10. #10
    Join Date
    Apr 2005
    Posts
    9
    I don't know why the other 3 burners take an extra minute to light....I an going to speak with the Reznor rep. in the morning. I'll post back my findings...

  11. #11
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Have you checked manifold pressure?

    Are the burners lined up properly so that the flame can jump across from one burner to the other?

    Did you make sure orifices were clean when the burners where removed and cleaned? (spider web)


  12. #12
    Join Date
    Feb 2004
    Posts
    2,474
    Clock input-- sounds like undergassed, if so there are several reasons to explore. Is this actually a reznor or just using to describe a unit heater? The reason I asked is some of the older carrier products had a shipping strut that held burners in place and if it wasn't removed delayed ignition may occur

  13. #13
    Join Date
    Apr 2005
    Posts
    9
    It is a Reznor FE-100 unit - built in 1991. The burners are lined up and I made sure the orifices were not obstructed when I cleaned the burners. It just takes an extra minute for the flame to jump across to the other three burners. I think that should happen almost instantaniously.

    I do need to check the manifold pressure though. That will be my next step in the process.

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