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Heating & Air Conditioning

Fan on my Air Conditioner

12 years ago

I have a question about my whole house fan. When I turn on my fan from my thermostat,the fan from my air conditioner turns on. Maybe this is correct I'm not sure. Is the Air conditioner fan powering the air that moves throughout the ductwork? I thought the furnace fan would have done that. There is a fresh air intake that comes from outside of the home directley to the furnace as well. I have not put the setting to "cool" on the thermostat yet because of how cool the central fan air has been out of the ductwork. It seems that the air coming through the ductwork (with just the fan on) is just as cool as if I were using the air conditioner. Maybe because It's running through the cool basement. Does this sound right or no? Thank you..

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Comments (8)

veesubotee
12 years ago
Where are you located (nearest big city)? What is the temperature/humidity of your outside air? What is the indoor temp (at the thermostat)?

I can't imagine where you are, that pulling in outside air at this time, is not causing discomfort.

Is the fresh air duct equipped with a damper to shut it off?

While the basement may seem cool, the air traveling in the ducts will pass through quickly and will not cool very much.

V
murph7811
Original Author
12 years ago
Mpls is the nearest big city.. The temp has been in the mid 90's with the humidity pretty high as well the last couple of weeks.. There is no damper on the fresh air intake to the furnace.. Indoor temp at the thermostat will stay around 72 with the fan turned on at the thermostat. Is it normal for the fan to run on the AC unit with just the "fan" switched on at the thermostat and NOT on "cool"? Thank you..
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Thanks so much for responding Mike. I cannot talk anyone into doing a Manuel J calculation so I am so very grateful for your time. I’m feeling out of my depth and loosing sleep on this one. In my temperate area the summers are long, warm, arid, and mostly clear and the winters are short, cold, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 39°F to 81°F and is rarely below 31°F or above 91°F. A handful of days each summer reach 100. I trust the Fraser Johnson guy the most as he was the only one willing to actually look at my system and ductwork but I’m worried 5/4 tons is too high. Here are my two most trustworthy contractors. I’d pay more for what is right for my house but 5k more and the heater is only 80% AFUE seems excessive. But your comment about 96% makes me think I’m mistaken that this is standard- just what all my other quotes were. We have solar so gas for heat costs us more than air. House built in 2000 has “cool roof” and pretty good insulation but the 9 foot ceilings downstairs (with large room with 15 foot ceilings) and 11 foot upstairs makes for more cubic feet. Pretty well shaded and lots of double pained windows.
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brickeyee
12 years ago
"Is it normal for the fan to run on the AC unit with just the "fan" switched on at the thermostat and NOT on "cool"? "

Most systems have a separate setting for the fan mode (AUTO or ON) and the heating/cooling mode.

If the fan is set to ON it runs continuously.
If the fan is set to AUTO it only runs when the set point has NOT been reached, then shuts off until the heat/cool is called for by the temperature.
murph7811
Original Author
12 years ago
Thank you I appreciate your feedback...
weedmeister
12 years ago
There are two fans. one is inside and one is outside on the AC condenser unit. When the Fan switch on the tstat is set to ON, the inside fan should turn on and stay on. The outside fan should not come on.
murph7811
Original Author
12 years ago
Hmm ok, well in that case that's not good because when I switch the thermostat to "fan" the fan on the air conditioner unit turns on. I cannot here the condenser turn on just the fan. When I switch it to "cool" I can hear both the condenser and the fan turns on?
dadoes
12 years ago
Murph, all air conditioning units have two fans.

One is inside the house in the air handler (also referred to as the blower coil, which may be mounted in the attic, a closet, or crawl space under the house) and pulls indoor air through the return-air grill (and filter) and blows it through the evaporator (cooling coil) and out the ductwork and registers.

The other fan is part of the compressor unit outdoors and circulates outside air through the condensor coil (which ejects heat outdoors).

The indoor/airhandler/evaporator fan should run 1) when the Fan switch on the thermostat is set to AUTO and the system/compressor cycles on to cool the house; and 2) any time the Fan switch is set to ON even if the compressor is not running.

The outdoor fan on the compressor unit is not controlled by the Fan switch. It turns on only when the compressor is running. If, for example, the temp inside the house is 72F and the thermostat is set at 80F, then the compressor is not going to run. Setting the Fan switch to ON in such a circumstance will run the indoor fan for circulating air through the ducts, but the outside fan and compressor will remain off.

Setting the FAN switch to ON will (or should) also circulate indoor air if the System switch (Off/Cool/Heat) is set to Off ... in which case the compressor will not run regardless of how the thermostat temp is set.
murph7811
Original Author
12 years ago
Thanks Dadoes! Ok then I definatley have a problem. Because when only the fan switch is on, the air conditioner fan turns on. Any advise as to what could be causing that? Bad wiring etc..? Again I appreciate your feedback! Thanks!

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