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  1. #1

    Hmm Save Energy By Keeping Fan On?

    Among other energy saving recommendations, Florida Power and Light asks that its residential customers set thermostats two degrees higher (for AC) and leave the air handler fan on ON, not AUTO. I have no problem with doing that. However, FPL can't/hasn't given me a straight answer on the average/hypothetical/potential energy savings or possible benefit in avoiding surges in use.

    Does anyone have an idea what, generally, the energy consumption trade-off might be for setting thermostat two degrees higher with fan on ON?

    (3300 sf house is in south Florida, using AC nine months of the year, heat pump maybe three weeks a year. System is well-preforming, five-year-old SpacePak HV, one two-ton and one three-ton, retrofit in single-story flat-(insulated)roof, CBS house with large low-e impact windows, half of them on the southern elevation. Total average FPL bill is $200/month; judging from last three years' bills in no-AC/no-heat months, average energy cost to AC/heat is about $130 of that $200.)

  2. #2
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    The first thing you'll get for responses will be to begin the debate about constant fan vs. auto fan and re-evaporating moisture removed from the system, a wet AC coil, blah, blah, blah.

    I can't speak for the rational from FPL but from my own experience here's the deal. The human body is normally many degrees warmer than the surrounding air in a cooled room. Heat flows from warmer to cooler, so your body feels cooled as moisture on your skin evaporates into the drier, cooler air. When the thermostat is satisfied (set-point) and turns off the outdoor unit and the indoor blower turns off simultaneously, the circulation of air naturally stops. If your warm body is sitting watching T.V., reading the paper, working at a computer or whatever not moving around, then in short order your body begins to warm the layer of air surrounding your body. This leads to discomfort and you're apt to lower the t-stat setting.

    By keeping the blower running, it continues to break up the air layer surrounding your body and so you continue to feel the overall cooler temperature in the room, thus being more comfortable and not lowering the t-stat.

    Your energy savings using such a methodology is arguable. If you've got a variable speed blower, you'll not use much more electricity than you do with the fan on auto. If you've got a standard PSC motor and the blower is properly sized for the application, you'll use more electricity to power the blower but overall less running a 2-degree higher temperature.

    Frankly I think the blower issue is smoke and mirrors and the real issue is to get you to raise the indoor temp 2-degrees.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  3. #3
    Join Date
    Jul 2010
    Posts
    26
    i agree sounds like BS to me. If u want airflow install ceiling fans

  4. #4
    "blower issue is smoke and mirrors."

    Thank you.

    (Politicos don't learn; neither do voters. We are, in historic terms, well into irreversible decline; our political and economic systems permit mediocrity at best.)

  5. #5
    Join Date
    Jul 2003
    Location
    Philadelphia Pa.
    Posts
    461

    Tried continuous fan during summer several years ago and.....

    Didn't like it. I'm in Pennsylvania not Florida.

    What I found was that the compressor cycles per hours were less..The compressor didn't run as many times an hour...so I guess this would save some electric.....But during the "off" time the house became uncomfortable. At first I couldn't understand why but after a day or so I realized the problem was coming from the air feeling sticky. Temp stayed the same but the air felt sticky. I guess this is the humidity issue.

    Raise the Tstat two degrees from what? What you have it now? I currently have mine at 80F during the day....don't think I am going to raise it to 82F

  6. #6
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
    1,555
    If you live in a humid environment, you don't want your fan to run in the "on" position. It will pick up moisture from a wet coil and make the air heavy with moisture/humidity.

    If you want air circulation, use an external fan in the room.
    Doug

  7. #7
    Join Date
    Sep 2010
    Location
    Chicago
    Posts
    218
    Chicago has bad humidity most of the summer so leaving the fan on will make things worse so I guess comfort wise the idea is ok if you live in a desert environment.


    EPA 608 certified: Universal

  8. #8
    Join Date
    Oct 2009
    Posts
    977
    FPL has power to spare and must strike a balance, and collect tax credits. The meter spinning is still number one in their business.

  9. #9
    Join Date
    Nov 2010
    Location
    Canada
    Posts
    59
    A ceiling fan may offer some help - I have recently replaced my old fan with a new generation of variable speed fans, and at the max speed it only uses 60W - since max would be way too much for me, I suspect I am well below 60W.

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