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  1. #1
    Join Date
    Aug 2012
    Location
    SE Oklahoma, USA
    Posts
    13

    At What Setting is my window AC most efficient ?

    I posted a quiery here recently about a Fedders window unit, that I had cleaned up a good bit, and installed. http://hvac-talk.com/vbb/showthread....473&p=13943811 You guys did answer my question, enough to where I could finally figure it out, and I thank you for that. The settings turned out to be (CC) TOP-OFF (to the left) 1st-low fan, 2nd-low cool, 3rd-med cool, 4th-high cool, 5th-high fan, Top-OFF. It is working very well, although I only use it when it seems totally necessary, and only then until it doesn't.
    I have another question, if you guys don't mind. At what setting is it the most efficient? The lower settings as you'll know produce the lower temps(at the discharge), I've seen it down in the 50's, BUT, the higher settings(although not producing as low of temps) cast it farther.
    Does the compressor turn at the same rate, use the same amount of juice, produce the same amount of "cool", on low fan, as it does on high fan??(it seems to sound the same on both settings?
    If you are not familiar with my first post(above link), you'll see it has pics of the unit label, the compressor label, and fan label too. It is rated at 7500 btu and 9.5 amp, and i suppose that is an "on high" rate?
    Any idea what the low cool, med cool settings will be drawing? and at which setting I can achieve the most "cool" per kwh?
    I sincerely appreciate your expertise, and any helpful suggestions

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,064
    Off is the most efficient setting... Just kidding. It really won't make much difference. Window units do not have variable or staged compressors and the compressor is the main energy hog of the unit, it will pull the same amount of power in any fan mode

  3. #3
    Join Date
    Aug 2012
    Location
    SE Oklahoma, USA
    Posts
    13
    lol! Thanks, JT, I'll turn it off ; )

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    While "off" uses the least electricity, having the fan on its highest speed will result in the highest total cooling capacity for the electricity used.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Aug 2012
    Location
    SE Oklahoma, USA
    Posts
    13
    Aha! so... the only variance in energy used will be the fan draw?

  6. #6
    Join Date
    Aug 2012
    Location
    SE Oklahoma, USA
    Posts
    13
    (i'm thinking keep it on low, and put a more energy concious fan in front? like a super-charge maybe?

  7. #7
    Join Date
    Aug 2012
    Location
    SE Oklahoma, USA
    Posts
    13
    Thank you so much, Mark, I'm turning it back to high. As well, with what JT said, I'm also thinking put a pedestal fan in front to toss the cold air into the room, while the (bigger draw) AC fan is on low. Could that be more energy efficient?

  8. #8
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,195
    I'm fairly certain that the unit as a whole will use the most electricity at the highest setting, but lowering the fan speed may not make a significant cost saving over the cooling it gives to the house.

    if it cools well at the lowest setting, then that is the most efficient. if the high setting is required to cool the area needed, then That is the highest efficiency for the room.

    running the fan higher speed introduces more heat for the condenser to remove, so the pressures and energy draw of the compressor will be higher. lower fan speeds also reduce the energy demands of the blower, but half of 3 amps is not significant, like half of 11 amps would be for the compressor.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
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    Dwane Johnson
    The A/C repairman

  9. #9
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295
    Quote Originally Posted by Le_Bear View Post
    Thank you so much, Mark, I'm turning it back to high.
    ALL KIDDIN ASIDE -
    _ Talking abOUT window units and efficiency is Truly a misnomer.

    + The most BTU/ kW will be realized at high fan & the T-stat setting of 80'F in comparison to 74'F BASED ON THERMODYNAMICS.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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