Safe to run circulation fan all night?

Discussion in 'Home Repair' started by M, May 27, 2008.

  1. M

    M Guest


    I have central air and a gas furnace for heating, and I believe one
    system controls the air circulation. When it gets hot out, the a/c
    doesn't cool the upstairs well. My thermostat has the option to keep
    the circulation fan on all the time, not just when the AC (or heat)
    turn on. I believe this will help a great deal, but hubby says it
    isn't built for that and we will break something. Is it safe to run
    the circulation fan all night, or should I save that for more
    conventional house fans?

    M, May 27, 2008
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  2. M

    mark Guest

    Hubby is wrong. I do it all the time, and nothing has broken for years.
    It's suggested to run the fan all the time during the heating season, this
    eliminates the high and low temps when the system is cycling on and off. Run
    it. Mark
    mark, May 27, 2008
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  3. M

    Clint Guest

    It might be safe but it could also be more expensive.
    Clint, May 27, 2008
  4. It's harder on a motor to turn it on/off than it is to keep it running.
    Also starting a motor takes more power. If you find it OK to run during
    daylight, why wouldn't it be OK to run at night?
    franz fripplfrappl, May 28, 2008
  5. M

    Calab Guest

    I have central air and a gas furnace for heating, and I believe one
    I've always wondered how much it would cost to run the fan 24/7...
    Never did investigate much as I don't have a "Kill-A-Watt" or clamp on

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    Calab, May 28, 2008
  6. M

    Big_Jake Guest

    It is fine to do that, but another option would be a t-stat that has a
    "circ" option for the fan, where it runs the fan around 30% of the
    time to even out the temp throughout the house. The Honeywell
    VisionPro has the option, and I'm sure others do to.
    Big_Jake, May 28, 2008
  7. M

    ransley Guest

    Starting the motor is hardest on it, its made to run. You will even
    out the temp upstairs which I guess is where you sleep. It might pull
    400 watts but not add alot to your bill in the hottest days by itself,
    but cooling more upstairs can add more, run it and be comfortable.
    ransley, May 28, 2008
  8. M

    Mikepier Guest

    During hot spells, I always leave the fan on. Last year when I checked
    with my amprobe, I think the fan used about 6 amps@110V amps. My CAC
    compressor uses 14 amps@220V.
    So thats 660W vs 3800W. Big difference. You obviously save more
    electricity running the fan more and the CAC less.
    Mikepier, May 28, 2008
  9. M

    Rick Brandt Guest

    Our system has a continuously variable blower and the specs require that the
    fan switch on the thermostat be left in the "On" position all the time.
    Then the board on the furnace controls everything to do with the fan.

    There might be times when it goes completely to off, but most of the time it
    is always turning at a low speed.
    Rick Brandt, May 28, 2008
  10. M

    Nate Nagel Guest

    In my house the basement is consistently cooler than the second floor.
    Keeping the fan running makes both more comfortable. Certainly beats
    running the A/C cost wise. I left the fan running when I left for work
    this AM and it was close to 80 degrees out when I got home. The house
    was about 70 degrees inside, had the A/C set for 77 degrees, so
    obviously it never kicked on all day. (I must admit that it was cool
    last night so the inside temp. was about 66-67 degrees when I left,
    because I'd had the windows open and a big window fan running to cool it
    off before I went to bed.)

    I'm sure that if I *hadn't* had the fan running it would have been at
    least 75 upstairs if not higher - I can say this because I didn't have
    the central A/C last year and just had a mercury thermostat with no fan
    switch, so I didn't have the option of leaving the fan running.

    Nate Nagel, May 30, 2008
  11. M

    ransley Guest

    Humid air even if cool is uncomfortable, a basement can add a big load
    to the AC even if its cool because of its humidiy, but every house is
    ransley, May 30, 2008
  12. M

    Pat Guest

    Okay, this makes a bunch of assumptions, so don't freak, people.

    The usage of the work "upstairs" implies there is a "downstairs". So
    it seems like a 2 story house.

    AC keeps the downstairs cool but not the upstairs. So, heat rises
    (funny how that happens) and there is insufficient air movement to get
    keep the temps even. So there is an air circulation problem in the

    There could be a couple of solutions. Most 2-story homes have an
    upstairs bathroom. It might be simpler to keep the bathroom exhaust
    fan on and vent out the hot air. That will allow the cool air to get

    A second solution, in a more temperate climate would be to shut down
    the system at night and use an fan to blow cool air IN to the second
    floor during the night. That's what I do and it works VERY well.

    For heat, the solution is a bit more complex. I had the same
    problem. I have an open stairway and I have ALL of the upstairs heat
    shut off because I don't need it (and I am in the snowbelt outside of
    Buffalo). The solution was to go to the end of the stairway and cut a
    small vent (2 x 6 or whatever standard ducting and covers are) in the
    floor and into the ceiling of the floor below. Before, the air
    couldn't rise up the stairs because the upstairs air was trapped.
    With the small vent, the warm air can come up the stairs, move down
    the hall, and the cold air exits through the vent and goes downstairs
    to be rewarmed. It works tremendously well and doesn't require any
    fans or anything.

    Now, granted, this is "old school" but it works. That's why the old
    houses had floor vents.
    Pat, May 30, 2008
  13. M

    Pat Coghlan Guest

    Sounds like you're talking about an older, 2-storey house.

    Whether heating or cooling, you need to push cold (or warm) air to where
    it's needed, and then have it flow back to the furnace. In the summer,
    that usually means closing most of the floor vents on the main level and
    drawing warm air from the top level (near ceiling, if there's an air
    return there).

    In the winter, you want to push most of the warm air to the main living
    areas on the main floor, plus a certain amount upstairs. Cold air needs
    to be returned to the furnace.

    Every house is a bit different and requires its own fine tuning at the
    start of each season - which reminds me- it's almost time to get ready
    to switch from heating to cooling in our house :)
    Pat Coghlan, May 31, 2008
  14. M

    DerbyDad03 Guest

    I believe that Pat hinted at something that no one else has said. Many
    people have commented on your question about running the fan 24/7, but
    no one specifically addressed the issue of "When it gets hot out, the
    a/c doesn't cool the upstairs well."

    Besides the runing the fan 24/7 (which has been recommended to me by
    more than one HVAV contractor) there is also a need to rebalance
    (unbalance?) the system when you switch from heating to cooling. I
    close just about all of dampers in the ductwork for the basement and
    first floor ducts during the cooling season.

    This forces the cold air to the registers on the second floor where it
    cools the bedrooms and bathrooms and then naturally sinks to the lower
    DerbyDad03, Jun 21, 2008
  15. M

    Mikepier Guest

    Besides the runing the fan 24/7 (which has been recommended to me by
    In addition to opening up the upper supply vents and closing the lower
    ones, you should do the same for the return grilles. By opening up the
    upper ones and closing the lower ones, you are pulling more heat and
    humidity out of the room. And since hot air naturally rises, it makes
    sense to have th upper ones do most of the work.
    Mikepier, Jun 21, 2008
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