# Electrical question regarding CF bulb use **URL:** \ **Category:** Factual Questions\ **Created:** [December 12, 2007, 3:45pm UTC](https://boards.straightdope.com/t/electrical-question-regarding-cf-bulb-use/429747 "2007-12-12T15:45:26Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![BwanaBob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bwanabob/32/2985_2.png) [@BwanaBob](https://boards.straightdope.com/u/BwanaBob)\ **Post date:** [December 12, 2007, 3:45pm UTC](https://boards.straightdope.com/t/electrical-question-regarding-cf-bulb-use/429747/1 "2007-12-12T15:45:26Z")
We have a fixture that consists of 4 standard bulb sockets, each socket rated up to 60 Watts - no dimmer. I have no desire to burn 240W while eating, so I switched the bulbs to compact fluorescent (much like we have in the rest of the house). Now here’s the odd thing. If put in 4 CF bulbs, they will all flicker, enough to drive you mad, but if I replace any one of the 4 with a standard incandescent bulb, the flickering stops. (I’ve rotated the CF bulbs; I’ve swapped out each one individually with an incandescent one and get the same behavior). Any idea what could be happening here? For clarity, here is a list of all combos tried: CF-CF-CF-CF = flicker I-CF-CF-CF = no flicker CF-I-CF-CF = no flicker CF-CF-I-CF = no flicker CF-CF-CF-I = no flicker ---
**Author:** ![BwanaBob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bwanabob/32/2985_2.png) [@BwanaBob](https://boards.straightdope.com/u/BwanaBob)\ **Post date:** [December 12, 2007, 4:01pm UTC](https://boards.straightdope.com/t/electrical-question-regarding-cf-bulb-use/429747/2 "2007-12-12T16:01:23Z")
Forgot to mention that I also had swapped out each individual CF (from the original 4) with a fifth bulb to make sure I didn’t have a bum bulb; but I guess I could have had multiple bad CFs, but I didn’t think that likely. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 12, 2007, 4:07pm UTC](https://boards.straightdope.com/t/electrical-question-regarding-cf-bulb-use/429747/3 "2007-12-12T16:07:06Z")
My WAG is that there’s some kind of impedance-based smoothing going on in the bulb filament, or something like that. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [December 12, 2007, 5:03pm UTC](https://boards.straightdope.com/t/electrical-question-regarding-cf-bulb-use/429747/4 "2007-12-12T17:03:21Z")
One thing they all have in common is the phase of the power being applied. That’s very likely to be link to the observed flicker. 4 CFs is probably reaching some threshold of mutual effect (e.g. transient current draws from the instant of ionization damping ionization in other CFs in the fixture; enough UV leaking past the phosphor of three neighbors to influence each bulb in close proximity; etc.) To test this general mechanism, try using only 3 CFs (maybe rotating the empty socket).