OFF - HI - MED - LO

June 14, 2005 5:33 PM

Just a stupid question that's puzzled me for years: Why is it that, on electric fans, the order of the settings on the switch is OFF - HI - MED - LO? I'm sure there's an electrical reason for this, but I don't know what it is, since I know nothing about circuitry. One would think that OFF - LO - MED - HI would make more sense. Can someone explain this to me?
posted by Dr. Wu to Technology (23 answers total)

Just a guess: Maybe people generally like their fans going at full speed, and putting HI next to OFF makes this easier?
posted by Turd Ferguson at 5:43 PM on June 14, 2005

My fan is off-low-med-hi. And I like it that way.
posted by recurve at 5:55 PM on June 14, 2005

My understanding is that a fan is switched to HI first, so when the fan is starting up the motor is working at highest power to overcome the inertia of the blades. I have been told that starting a fan in LO can burn out the motor. Might be BS though.
posted by phatboy at 6:09 PM on June 14, 2005

Well, the cheapass way to wire the switch would be to have off in the middle.

You would wire the two centre poles of a DPDT (centre off) switch to hot. One side would have winding A connected to one point, and the other point open. The other side has winding B connected to one point and winding A connected to the other. The other ends of the windings would be tied to ground.

That creates a switch like this:

LOW -- OFF -- HIGH

Which is exactly how my $9.99 fan operates.
posted by shepd at 6:11 PM on June 14, 2005

I'm with Turd. Most people want High power right away. That's how my fan works, and I hate it.
posted by rschroed at 6:13 PM on June 14, 2005

Popping in to confirm from Vietnam that the OFF-HI-MED-LOW ordering doctrine is indeed universal. The ceiling fans in my home have big, plastic VINAWIND controller boxes on the wall. They have six settings on a half-circle dial: OFF, and then five decreasing steps.

My gut tells me the reason is electrical. Or was once a matter of electrical necessity, and remains a convention.

The newer wall fans have a full-circle dial that goes around and around, so you can always get to any setting by going either direction.
posted by squirrel at 6:15 PM on June 14, 2005

Now that I think about it, my ceiling fans have always been wired the same way: one pull on the cord for high, the next for medium, one more for low, and the fourth turns it off. I never noticed that it was the same as the box and reciprocating fans.
posted by tew at 6:24 PM on June 14, 2005

I've wondered this myself for a long time. I don't buy the "most people want their fans on high" response.


I like the inertia explanation, but it makes me scared that I'm burning my motor by always turning the dial all the way to "LO" and skipping the warm-up.
posted by rafter at 6:32 PM on June 14, 2005

Best answer: I have always taken this as an indication that there is something deeply wrong in the world. Thank you for asking this question and bringing it into the light of day.
posted by alms at 6:35 PM on June 14, 2005

Maybe (and this is a pure guess), it's a safety feature. If l'enfant terrible turns the fan on, most likely it'll be a full switch, and 'lo' would seem to be less likely to cause injury than 'high'.
posted by lowlife at 6:35 PM on June 14, 2005

Response by poster: Thanks for the answers so far, ever'body.

I don't buy the "we like our fans on HI" explanation, either, and am convinced there's some honest-to-god reason for arranging the switches in this seemingly illogical fashion. The inertia thing doesn't make that much sense to me, either, as, even at LO, the fan is spinning pretty darn fast - fast enough to overcome any inertia, I'd figure.

shepd, I know literally NOTHING about circuitry, and therefore don't totally understand your answer. Can you clarify? Like, as if you were talking to a nine-year-old?
posted by Dr. Wu at 6:39 PM on June 14, 2005

Best answer: It's the "inertia" reason. This thread on the Straight Dope Message Boards explains it thus:

When you first apply power to an electric motor (with a load attached to it), the motor must overcome the rotational inertia necessary to get it up to speed. During this startup time the motor’s impedance is fairly low, and it draws quite a bit of current. And to make matters worse, there’s not much air flowing across the motor windings during this time. Once it gets up to speed the motor’s impedance increases, and thus draws less current. There’s also a lot more air flowing across the motor windings once it is up to speed. It makes sense, then, that you do not want the motor to spend much time in the startup phase, since the motor draws lots of current, the windings are getting hot, not much cooling air for the motor windings, etc. If you’re the designer, this phase will make you “nervous,” and you will want the fan to spend as little time in it as possible. Starting the fan on high minimizes the amount of time the fan spends in this phase.

posted by Johnny Assay at 7:06 PM on June 14, 2005

answerbag had the same question and they concur with the inertia speculation, wonderquest concurs with them
posted by jessamyn at 7:09 PM on June 14, 2005

So you don't mistakenly turn the dial to 'low' instead of 'off' and leave the fan running just because the blades were slowing when you last saw them?

That had always been my guess, though Johnny Assay's quote is a pretty compelling argument for the "fast startup" explanation.
posted by Eamon at 7:10 PM on June 14, 2005

I believe Imponderables covered this. I believe they also said it's a combination of inertia and that most people want it on high.
posted by abcde at 8:13 PM on June 14, 2005

If anything, heavily influenced by less efficient motors of old, with which one would have to have selected "hi" to get the thing started and waited a moment for the speed to pick up then to a lower setting to conserve electricity.
posted by five fresh fish at 10:08 PM on June 14, 2005

[conjecture]
posted by five fresh fish at 10:08 PM on June 14, 2005

Response by poster: Thanks, all!
This is very interesting. AskMe solves another one!
posted by Dr. Wu at 10:16 PM on June 14, 2005

I too had wondered about this and am glad you asked the question.

I'd just like to point out that the "best answer" check for alms is one reason I have no patience with people who want to use "best answer" ratios as some sort of measure of poster quality. No offense, and of course you have the right to mark whatever you want, but there's a lot of noise in the system.
posted by languagehat at 6:56 AM on June 15, 2005

Odd - it's defnintely not universal, as the desk fan sitting next to me is 0-1-2-3 (where 3=fast)...

The straight dope answer sounds - as ever - pretty convincing, though :-)
posted by Chunder at 7:11 AM on June 15, 2005

Response by poster: languagehat: I hear ya. However, honestly, I think that the "best answer" feature is a little ... dopey. Makes it out to be too much of a contest. This is the first time I've used it, actually. So I marked the actual most helpful answer, but also the one I thought was "best" because it was funniest.
posted by Dr. Wu at 7:12 AM on June 15, 2005

Oh, I agree with you. I wasn't coming down on you for doing it, just pointing out that that's why it's so dumb for people to start those MetaTalk threads about how people shouldn't be allowed to use AskMe unless they've proven their worth through a sufficient percentage of Best Answers.
posted by languagehat at 12:46 PM on June 15, 2005

Response by poster: Gotcha - I misunderstood. We is all agreein'-like.
posted by Dr. Wu at 4:43 PM on June 15, 2005