Air output of vents when compressor is on vs off

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Old 07-21-19, 11:51 AM
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Air output of vents when compressor is on vs off

Hello everyone. I am baffled when trying to understand why when I have my blower set to "on," the air flow out of vents is noticeably less compared to when the compressor kicks on. In other words, I like to keep my blower on to circulate air but the air barely comes out the vents. But when the A/C compressor kicks on, the air comes out of the vents as expected. Any ideas why this would be the case and if it is possible to have the same air flow regardless of whether the compressor is running or not? I figured it would/should be the same air output.

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Old 07-21-19, 12:25 PM
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You have a variable speed blower on your system,possibly also a two-stage burner on the furnace. When in cooling mode the blower runs at a higher speed but when the thermostat switch for the FAN (only) is in the on position the blower runs at a very low speed.

I don't know if there is any practical way to alter this operation. You can probably get the blower to run at the cooling speed if you set the thermostat for cooling, set the temperature lower than the room temperature and pull the local disconnect for the A/C outside unit to prevent its operation.

One thing to remember, if you are running the A/C you should NOT be using continuous air circulation as it will tend to raise the relative humidity in the house.
 
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Old 07-21-19, 12:29 PM
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Thank you so much! I just could not wrap my head around why there was a difference but that makes perfect sense. I really appreciate it. Have a great day.
 
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Old 07-21-19, 03:42 PM
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On my York furnace with a variable speed blower motor, there are jumper settings that allow me to control the speed of the fan when in ON mode. If I recall correctly, there are 3 or 4 speed settings. I have my ON fan speed set to the lowest setting (probably where yours is set).

I leave my fan set to ON when the compressor begins to come on and cycle (during the day). I think it extracts all of the cooling from the evaporator coil, since otherwise, as soon as the compressor turns off, the blower turns off. If the condensate is draining properly from the furnace/air handler, there shouldn't be much water present to add to the humidity level. Personally, I like having the constant flow of air, albeit low, to help keep air moving in the house.
 
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Old 07-21-19, 08:49 PM
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It doesn't really matter how fast the water drips off...... the coil is wet and running the air continuously will bring some moisture back into the house. You don't need to extract all the cold out of the coil as it is contained within the duct.

Many systems have three operating speeds...... A/C is high, FAN ON is medium, heat is medium low.
Most can be changed by moving jumpers or wires to different terminals.
 
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