DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Blower operates continuously

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Old 11-29-2007, 05:11 PM  
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Default Blower operates continuously

I have a Bryant (Model: 396G036075) Gas Furnace. I recently replaced the thermostat with a Rite Temp (Model: GPMG8035C) 7 day programmable thermostat. The furnace blower runs continuously. The furnace still kicks in and warm air emits from the vents until the house reaches the set temperature. However the fan is still running after the furnance acheves the set temperature. It stops blowing warm air and just blows room temperature air thru the house vents. When I first moved into the house there was a manual thermostat installed. I then replaced the manual with a used Rite Temp thermostat that just died. I then just recently purchased a brand new Rite Temp described above. The old Rite Temp thermostat never had this issue. The thermostat fan is set to auto and even if the thermostat is set to off the blower continously runs. Here is what I've tried to fix it:

1) The air filters were dirty so I replaced them with fresh ones.

Powering Furnance OFF steps: turned off the furnace power switch, flipped the furnace breaker to off, set thermostat to off and fan to auto

Powering Furnace ON steps: flipped furnace breaker to on, turn on furnance power switch with the thermostat set to off and fan to auto.

As soon as I power the furnance up the blower starts running and never stops like its supposed to after the house reaches the set temperature.

Do I need to buy another thermostat or is there something faulty on the furnace?

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Old 11-29-2007, 07:19 PM  
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It sounds like the issue started when you replaced the thermostat. Either the new thermostat is wired incorrectly or the thermostat is defective.

Do you have access to a different thermostat to try it?

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Old 11-29-2007, 08:24 PM  
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I intentionally run my fan constantly when in the heating season.
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Old 11-29-2007, 11:33 PM  
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The fan on my geothermal unit has been running from the day we installed it... 11 years ago.
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Old 11-30-2007, 07:33 AM  
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The T 'stat you have may be wired WRONG as continual high speed running of the blower is NOT efficient in either heat or cool mode. In the heat mode a fan should start up when the plenum is up to temp(120-130) and continue to run in heating speed until the plenum temp is say down to approx 90-95, then if equipt with such it may go into a continuous LOWER speed to lightly circulate thru the home.(hi speed continuous running is NOT desired because of drafts,etc.)
And running the blower continuously in the cooling mode is also a no-no because when the outside compressor unit shuts off and the inside main unit blower continues to run, it just brings back into home more humidity that has saturated the inside evap coil.

check the t'stat for a wrongly 'jumped' wire ,especially green (fan relay)
Make sure you re-check the manual that came with this stat
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Old 11-30-2007, 05:28 PM  
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not all tstats will call for fan based on temp. I have a baysys and it will run the fan for 2 minutes prior to firing the burners. There are also new stats on the market that will randomly come on to circulate air in the home (sweet).
another problem is that the tstat wires could be shorting the hot to the fan circuit, in which case any tstat will seem to be malfunctioning. disconnect the red and the green at both ends of the wires (furnace and tstat) and check for continuity between the two. if continuity exist then the wires are shorted. repair or replace as necessary.
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Old 11-30-2007, 08:15 PM  
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Mudmixer is right.

If you continously run the fan in heating mode, it recirculates the air inside your house, keeping the temperature constant throughout the house.

The air in your home will recirculate 2500 times in a month if you have your fan on "ON" position. This is also helpful if your family has pets or allergies because it will filter out contaminents constantly....That is if you have a good filter, NOT A "ROCK CATCHER" ( a filter that you can read a newspaper through...not good at eliminating pet dander, and pollen)

If you have allergy problems, the electrostatic, or an electronic air cleaner is the way to go.
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Old 12-03-2007, 10:49 AM  
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In the majority of cases, a furnace fan operating set to "on" instead of "auto" will most certainly cause a draftiness in the Winter and a high humidity in the Summer.
In the heating season, if the furnace is equipt with a "low " speed fan feature that enables the fan speed to drop when the majority of the heat has been delivered, this low speed will kick in to circulate air thu-out the home. Draftiness is not as much as with the higher fan speed.

In the Summer cooling season, the fan should be set to "auto", which will turn on when the outside compressor unit starts up ,and then when the outside compressor unit shuts off ,the fan will also shut off. This eliminates the entry of humidty that is still not evaporated from the inside coil and water pan area.

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