Does any know if using the fan on your central A/C unit, use as much energy as when it is cooling?
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September 1st, 2011
Central A/C units always have the option of using the fans. Does it waste as much energy as a regular fan or does it waste a bit more or would it be the equivalent of running your cooling system non stop?
I ask this because sometimes I like to air out the house. But if there is no breeze it would be nice just to run the fan to push the trapped air out.
I don’t want to run the cooling system and push my electric bill up.
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The actual calculation would depend on the particulars of your unit, but remember that when the AC is on its cooling cycle, both the fan and the compressor unit are running. The compressor uses roughly the same amount of electricity as the fan does. So running the fan alone will use only about half the power as running the fan and compressor together. Make sense?
Here’s an example for a typical home central AC unit (from here):
“Let’s look at the central AC energy use for a 3 ton air conditioner with an SEER rating of 14.5, which is the new minimum required standard for an ENERGY STAR qualified central air conditioner as of January 2009.
Assuming the air conditioner runs 8 hours a day, 125 days a year, its thermal output is 30 million BTUs. At SEER 14.5, that means it will consume 2069 kilowatt hours per year. At $0.10 per kwh that would cost you about $207 in energy costs.
The inside blower on a 3 ton air conditioner is typically ½ horsepower. Multiply horsepower by 746 to get watts, so your fan consumes 373 watts on full-power mode.
If you run a 746-watt fan 24 hours a day during that same 125 days, your usage is:
746 watts x 24 hours x 125 days / 1000 watts per kilowatt = 1,119 kilowatt hours, at $0.10 per kwh makes $111.90.”
Besides the obvious fact that fan plus compressor uses way more power than fan alone, most HVAC systems circulate air throughout the house (from the return to the various registers), and maybe filter the air, but they don’t bring in fresh air from outside. For that you need to open windows & doors—or a system with an outside intake.
The fan just circulates the air through the house, and uses no more energy than any other type of fan (negligible). It’s the A/C compressor that gobbles up electricity at a ferocious rate because it takes a lot of strength to compress the A/C fluid.
I don’t think so. If cooling is not on, that means compressor is sitting idle. So it should consume less power.
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