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Thread: Thermostat or Furnace? Which one is screwing up ...

  1. #1

    Red face Thermostat or Furnace? Which one is screwing up ...

    Hey everyone,

    Have one for you guys. Here's the situation:

    -Rented apartment
    -Basic heat-only furnace (WeatherKing brand, no other info available on the unit)
    -Two wires coming out of furnace:
    -Black: appears connected to a ground
    -Brown: appears connected to the on/off valve
    -Original thermostat was a simple mercury switch model
    -Current thermostat Hunter Model 44260, mounted in a separate room
    -Black -> W/B
    -Brown -> RH with jumper to RC

    The furnace is doing some very strange things. In general, it seems to come on when it's cold and turns off when it's hot - but there are serious quirks. When the thermostat is in 'on' mode (I can hear it click when the temp falls under the programmed temp), the furnace clicks on, warms up, runs for about 5-10 seconds, then turns off. A couple minutes later the furnace will spin up again and usually heat the apartment until it hits the programmed temp - however, sometimes it will keep turning on and off and on and off until it gets to temp.

    The problem here is my gas bill is ridiculous! I think my furnace is wildly inefficient and the way it's running with these rapid cycles just makes things even worse. What can I do for this thing? Is it a bad tstat? Something in the furnace itself? This is a VERY old apartment with very mediocre upkeep. The windows are very very leaky so I lose a lot of heat that way (recently sealed things up with the plastic shrink wrap stuff).


    Thank you!

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    The biggest problem may be your heat loss, but there may be some controls in the furnace having problems.

    Most likely, by design the furnace should work like this: t-stat says it's cold, signals furnace. Igniter or intermittent ignition sparker comes on. Gas comes on, burner ignites. If sensing circuit confirms flame, the burner keeps going, other wise the "try to start" sequence is repeated. Once the burner is going, in a minute or three, the duct sensor feels that it is warm enough and turns on the forced air blower.

    Depending on the age of your furnace, the exact type of ingnition and sequencing may vary.

    You should not mess with this in a rented apartment. The landlord should have a technician check it out.


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