Can a one-way CFL bulb be used in a three-way socket?

June 8, 2008 5:38 PM

Can I use a one-way CFL bulb in a three-way socket?

I bought a lamp with a three-way socket that vaguely warns against using a one-way bulb. I quickly discovered that three-way CFL bulbs are incredibly expensive, so can a one-way CFL be used in it? Is this safe, and will the life of the bulb be affected?

posted by binary to home & garden (6 comments total)

We use one in our (oldish) 3-way lamp. It's fine, and is still going strong after...I want to say 3 years? We've had no problems with it.
posted by phunniemee at 5:43 PM on June 8

General Electric says you can:

GE CFL FAQ on three-ways.

Don't use a regular CFL on a dimmer, though.
posted by Justinian at 5:46 PM on June 8

The way that three way sockets work is they have one neutral (the socket threads) and two hots. The two hots are only different in that the four positions of the switch are: Off-Off, Off-On, On-Off, and On-On. If you look at the business end of a 3-way bulb, you'll see that the two hots are a ring contact and a center contact. A normal 3-way bulb has two elements in it, one that's a low number of watts and one that's a high number.

A regular bulb (CFL, halogen or regular incandescent) only has the center contact for a hot, so it completely circumvents the ring contact.

End result, the four positions of the switch result in the following behavior when you have a regular bulb installed: Off, Off, On, On.

The reason the warning is there is because if the contacts are just out of alignment, there could be some sparking from intermittent contact between an oversized center contact and the socket's ring contact.

YMMV, but I've used many single-way bulbs (CFL and otherwise) in 3-way sockets and not had issues.
posted by tomierna at 5:52 PM on June 8

I've had a CFL in a three-way lamp for years with no ill effects (literally the same bulb for 3+ years).

The only quirk is that, due to the 3-way mechanism, there are two "off" and two "on" positions, meaning you have to twist the knob twice instead of once.
posted by CrayDrygu at 5:59 PM on June 8

Yup, there's nothing wrong with it. The switch on the lamp will just be "weird" when you go to turn it on and off. Instead of off-low-med-high-off, as you turn the switch, it'll be off-on-on-on-off. So you'll just have to "click" it a few extra times to get it to turn off (assuming you use the switch in the lamp and don't plug it into a switched wall outlet).
posted by Kadin2048 at 8:37 PM on June 8

I also have not had any problem in my 3 way lamp.

Point of fact: I originally bought the three way CFL for the lamp, and went through two or three in a week before I went 1-way. Haven't had to change the bulb since, and that was in 2003.
posted by absalom at 10:22 AM on June 9