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Day & Night Gas Furnace turns on and off twice after completing heating cycle

Day & Night Gas Furnace turns on and off twice after completing heating cycle


  #1  
Old 12-08-13, 09:58 AM
J
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Day & Night Gas Furnace turns on and off twice after completing heating cycle

I have a Day & Night gas furnace. It heats the house fine but after a heating cycle is complete and the fan shuts off, the fan will start up for a second then shut down and a couple seconds later it will do it again. This seems to be more of an irritation than anything but could this be a warning of future problems?

I tried changing batteries in the thermostat and the limit switch with no change in operation.

Any ideas?
 
  #2  
Old 12-08-13, 10:09 AM
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Welcome to the forums.

That's not an un-common problem. It happens when there is extra heat left in the heat exchanger.
It's not controlled by the thermostat but by a limit switch.

You mention limit switch.... is it an adjustable one for the blower ?
 
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Old 12-08-13, 10:17 AM
J
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Thanks for the reply PJ.

The switch I changed is installed just above the burner inside the heat exchanger. Its a non-adjustable 180 140 degree switch, it turns on the fan at 180 and shuts it off at 140.
 
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Old 12-08-13, 01:50 PM
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PJmax meant to say fan switch. Sounds like you changed the limit. If this old enough to have a fan switch and not a fan timer board, I believe it probably has a Camstat fan switch. Look for it close to the limit. If it does have this it will have a red face as I recall and it is adjustable. However those were known to short cycle after they became old. This happens mostly on counterflo models
 
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Old 12-08-13, 01:53 PM
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His unit doesn't have an adjustable fan control. It's a preset control that looks like a limit switch (clixon)
 
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Old 12-08-13, 03:01 PM
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The only fan control I've noticed beyond the limit switch is a terminal board used to adjust the fan speed. A sticker on the lower access panel mentions three speeds and moving a wire accomplishes this task.
 
 

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