What's the optimal way to combine a fan with an air conditioner?

May 30, 2006 12:54 PM

What's the optimal way to combine a fan with an air conditioner?

I have an air conditioner (building supplied HVAC unit), but while the air coming directly out of the vent is cold, it doesn't do an effective job of cooling the room. I have a reasonably powerful vornado floor fan (more than one, actually, if needed).

Where's the best place to put the fan?

Should I blow air across the room to the air conditioner, or should I put the fan on top of the AC vent and blow the cold air into the room?

(Apologies if this has been asked before. The only similar question I could find was this, which doesn't really answer my question.

posted by Caviar to home & garden (12 comments total)

Considering the way ceiling fans help to mix the vertical layers of air: do your freestanding fans angle upwards at all?
posted by voidcontext at 1:00 PM on May 30, 2006

Is the AC vent near the floor or the ceiling? Cold air is heavier than warm, so a vent high up is better for cold air.

Try to blow the cold air up.

A ceiling fan might do a better job to circulate air. It will also be good in the winter, when you would run the fan in the opposite direction.
posted by cahlers at 1:02 PM on May 30, 2006

The AC vent is about 2.5-3 feet off the ground.

A ceiling fan is not an option in this room.

I can angle the fans up.

If I have multiple fans, should I cluster them all together, or put them on opposite sides of the room?
posted by Caviar at 1:08 PM on May 30, 2006

Place fans throughout the room at the level where the cold air is coming out of the vent. Angle the fans upwards as much as possible. Your goal is to blow the cold air up, it will fall down on its own.

A ceiling fan is not an option in this room.

Is this because you rent? A ceiling fan would save cooling and heating costs, a plus for you or your landlord, whoever is paying the bills. It is not that difficult to install a ceiling fan.
posted by cahlers at 1:30 PM on May 30, 2006

Ceiling fans are wonderful, but not all landlords are cool with their tenants installing appliances in the ceiling, and not all landlords care about their tenants heating and cooling bills.

A window fan set to exhaust at the other end of the room (or in the next room, if the windows at least kinda line up) can help pull the cooler air through a room. I find that the old-fashioned clunky window box fans work better than the cuter, newer twin-fan style.
posted by desuetude at 1:54 PM on May 30, 2006

Not sure if "exhausting" cool air makes sense, but maybe for the first half hour to cool off the room.
posted by cahlers at 2:02 PM on May 30, 2006

Not sure if "exhausting" cool air makes sense, but maybe for the first half hour to cool off the room.

Window fans aren't generally powerful enough to actually "exhaust" the cold air from the air conditioner on the other side of the room. Unless it's a very small room. In which case one doesn't need fans to get the room cool quickly.

Any and all fans used in conjunction with the air conditioner may be turned down or off if no longer needed, at the discretion of the air conditioner/fan-combination-user. Sheesh.

Caviar, I feel more comfortable with multiple fans spaced out within a room, but YMMV. Without knowing the shape and size of the room in question, I bet even the physics-inclined around here couldn't figure out optimal air flow for you.
posted by desuetude at 8:22 PM on May 30, 2006

The AC is under the window, which extends from the top of the AC to the ceiling, so there's really no exhaust possibility there.

Rather than trying to figure out optimal airflow, I guess my question is - will I do better pushing cold air away from the AC, or hot air to the AC, or does it not make a difference?
posted by Caviar at 5:46 AM on May 31, 2006

I think because the hot air is always going to rise, the best use of the fans will be in pushing the cold air away from the AC towards the middle of the ceiling, where it can spread out and be pushed down by air that is warming up.
posted by cCranium at 8:23 AM on May 31, 2006

Right, fan in front of AC unit, blowing at a 45 degree angle up and away from it. Blowing hot air towards the unit is almost impossible, it's easier to spread something out from a point source than to do the opposite.
posted by voidcontext at 7:52 AM on June 1, 2006

Why do I want to blow cold air at the ceiling? Won't that just redistribute the hot air that's already there? Don't I want to leave it there instead?
posted by Caviar at 4:29 PM on June 3, 2006

You want to make sure it all mixes up. Naturally the cooler air would tend to hug the floor, and you want to move it up into the middle of the room. You also want to disrupt the pocket of warm air that takes up the top part of the room, so that it gets circulated out.
posted by voidcontext at 1:55 PM on June 4, 2006