Occupancy Sensor and CFL light bulbs

In the post I wrote a few months ago on picking the right lighting occupancy sensor I thought the old Leviton sensor I was using had gone bad when I wrote the following:

And this worked well and good up until October 2010 (it was 2.5 years old) when the sensor started acting up.  As you can see in the picture on the right, the sensor has three modes: Off/Auto/On.  Off and On work just like a standard light switch would.  Auto mode is where the sensor controls the lights.  While in “Auto” mode, when nobody was in the kitchen and the lights were off, they would start flickering like strobe lights.  Or the lights would be on and they would buzz and only come on half the normal brightness.  Or they just wouldn’t come on at all.  If the mode was turned to “ON” the lights would look fine and work perfectly, so I determined either the sensor had gone bad…..or we had ghosts.

Well, it turns out the sensor hadn't gone bad...and we didn't have ghosts.  

After installing the new Legrand occupancy sensor I discovered a feature that wasn't too popular in my household:

But there is a downfall to this new sensor!  You can’t set it so the lights will stay in the “On” mode.

So if we were in the dining room working or eating and we wanted a little extra light, we couldn't put the kitchen lights in manual mode so they would stay on.  I was doing some research on occupancy sensors when I discovered this comment on the review of the Leviton occupancy sensor on Amazon that I had previously removed:

(2) Flickering fluorescents - With the widespread conversion to fluorescent lighting, there is a new problem. The small screw-in spiral bulbs that replace incandescent lights have electronic "ballasts", which are totally different from those on the long fluorescent tubes. This motion-sensing light switch does not go completely OFF when there is no motion. A sensitive VOM will measure about 30+ volts on the hot line. However, there is little current available. The 30+ volts is enough to trigger the ballast on the spiral fluorescents, and it tries to light the lamp, however there is not enough current available and the light tries to go on, drains the minimal charge on the line, and then goes out. This repeats and you get a flicker. ---- You can solve this by replacing one of your lights with an incandescent lamp. This will constantly drain the charge trickle through the switch and prevent the voltage building up to trigger the ballast. I have used 45W and 60W bulbs, and both work. They just go in parallel with your spiral fluorescents. And you should no longer have any flicker.

I thought back to the time when I started having problems with the Leviton lighting sensor and I remembered that out of the 10 spots for recessed light bulbs, I had left 2 incandescent lights in while I replaced 8 with CFLs.  A few days before I started having problems with the sensor I had finally changed the incandescents to CFLs!

So I took out the new occupancy sensor and put back in the Leviton after putting an incandescent light back in the circuit and....WA LA!  Everything works great.

Bottom Line: If you are using an occupancy sensor, make sure it is compatible with CFLs.  If not, use an incandescent in the circuit!

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Occupancy sensors is a very interesting concept. They save a lot of power but have some disadvantages; of not having manual mode in some of them.
Occupancy sensor sound very interesting. They save a lot of power but have some downfall to them; not having manual mode in some of them. We have been getting ideas about a normal howsehold upgrading to be more energy effecient. You are welcome to come and bring your ideas at
ckmapawatt's picture
I actually adjusted my time delay last night on my sensor. I had it set to 30 seconds (if it doesnt sense motion in 30 seconds, it goes off) but this was way too short and driving my wife and me crazy. For instance, if you are reading the mail and not making many movements, the lights would go off. The problem with the current sensor (Leviton) is that the time delay is behind the wall plate, and it is just a dial with no markings on it, so you have to play with it to get the right time. I would prefer a dial that you could adjust without removing the wall plate with time increments marked on the dial!
I ran a few tests and found that a <a href="" rel="nofollow">7.5W incandescent bulb</a> in the circuit was not enough to prevent <a href="" rel="nofollow">13W CFL</a> flicker, but a <a href="" rel="nofollow">10W bulb</a> was. The bulbs that I am currently using are rated for 11W at 130V (85mA), which works out to about 10W at 120V. I have not found any bulbs between 7.5W and 10W to test. These rules may help narrow things down for the resistor project.
ckmapawatt's picture
Great feedback!
Andy, your resistor calculation is fine. Just make sure that the resistor is rated at for at least twice the power you expect to draw. In you example your 15000 Ohm resistor is going to dissipate 0.96 Watts of heat when dropping 120 Volts. So go with a resistor rated for at least 2 Watts. A 3, 5 or 10 Watt resistor would be even better. Please let us know how your experiment works out.
ckmapawatt's picture
Andy, please don't do any experiments that will electrocute yourself if you don't know what you are doing.
I'm glad people are aware of products like this. I think what would help, us all, a lot is the tip on how to add a regular bulb to a CFL light. What I mean is that most people have more than one CFL so they put a normal bulb in the string and their sensor works. One person said they had used 60w and 45 watt. It would be really useful if something like 1watt (that would be a resistor) or a 4 watt (nightlight) bulb would work to make CFLs operate. I haven't had the ability because I've not bought any sensors knowing they don't work with CFL lamps. But if I get a chance to try one I will be putting a 1watt resistor (that would be a 15,000 ohm resistor to get 1 watt* across 120 volts. Someone check my ohms law ok?*
For situations where you don't have access to the neutral wire, Black &amp; Decker makes a battery operated "add-on" to your convention (toggle type) light switch called the SW100 Energy Saver Series Lights Out Auto Switch. I don't own one, nor have I ever seen one in action. The following link has a review of this product that includes an example of what savings this gadget might offer that's worth reading: I see that is currently offering the SW100 for just under $20.00 and it's getting mixed reviews from buyers at this link:
A lot of the older sensors were 2-wire devices and you could install them anywhere as long as it was controlling incandescent or florescent lamps with magnetic ballasts. To accommodate CFL lamps, most of the newer occupancy sensors, like the one Eric mentioned, are 3-wire devices. This means that you can only install these sensors in locations where the device will have access to the "neutral" wire. In situations where power from your breaker panel was terminated at the light fixture(s) first and then just 2 wires were brought down to the switch box, you're out of luck.


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