Hardwire blower fan to run continuously?

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Old 06-05-15, 11:26 AM
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Hardwire blower fan to run continuously?

I installed a Honeywell Prestige Tstat using a 4 wire connection. I "borrowed" the fan wire to use as the common.

It works, but now I can't set the fan to run continuously.

Question - how do I hardwire the fan to run all the time?
 
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Old 06-05-15, 12:36 PM
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Best bet would be to pull a new cable in between furnace and Tstat,I would guess you removed the fan wire from the board at the furnace and connected it to common there,if you want the fan to be constant on jump a wire from Red on the board to Green on the board that should keep the fan constant.
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Old 06-05-15, 01:28 PM
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yes i did move the fan wire to common at the furnace. and then jumped the fan to Y.

question - should I remove the jumper from fan to Y, or leave it in place and also jump fan to R? is it okay to have Y to R to fan all jumped together? wouldn't this keep the A/C on all the time?
 
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Old 06-05-15, 02:49 PM
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You can't jump Y to R or the cooling will run continuously, if you jump R to G at the furnace that will keep the fan running continuously. The jumper from Y to fan won't matter as your fan will be already running.
Just curious, why do you want the fan running continuously ?
Geo
 
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Old 06-05-15, 02:53 PM
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we were advised by our HVAC contractor to have our fan on at all times (I think to prolong its life?). also, I'd like to keep air moving in the house and especially in basement where it tends to get dank and stale during times where neither heat or AC is running much.
 
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Old 06-05-15, 05:28 PM
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Running a blower continuously has good and bad points but the bad points outweigh the good.

Running the blower continuously will not prolong its life.
Running the blower continuously will return humidity back to the air once the A/C compressor shuts off. This is definitely not good in high humidity areas.
 
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Old 06-05-15, 06:00 PM
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If you have the Pro version Prestige thermostat ( Not from Home Depot) you could add an EIM.
This would allow you to run the stat with only 2 wires.

http://www.amazon.com/Honeywell-THM5...=honeywell+eim

Running the fan continuously would grow mold in the ductwork in my area.
 
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Old 06-05-15, 06:34 PM
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this is interesting. we are in Chicago. I've heard from several HVAC people that we should run the fan all the time. one was after we had a GE ECM programmable DC motor blow its inrush current limiting thermistor. I fixed it for about $2 (vs. the $1200 cost to replace the motor), but the HVAC place I worked with said it would never have happened had we kept the motor running??? they claimed the constant start/stops burned the thermistor.

I certainly don't want mold in my ducts. I do watch the humidity levels in my house like a hawk and run dehumidifiers when it gets above 45%.

The Tstat is the Pro version (my wife works for honeywell and I got it through their employee discount program). I probably will someday get the EIM when I add a whole house dehu, but for now I just needed to get the thing working.
 
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Old 06-06-15, 11:39 AM
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If you run the fan continuously in the cool mode it will act as a humidifier every time that the compressor cycles off.

The water that has condensed on the coils will evaporate and flow into the ductwork.

 
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