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RE: [hreg] motion switches and cfl's question

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  • Robert Johnston
    I have a motion-sensing switch for the light in my back entryway/laundry room. Since it is only on for about 1 minute each time it triggers, I just use
    Message 1 of 4 , Jul 8, 2007
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      I have a motion-sensing switch for the light in my back entryway/laundry room.  Since it is only on for about 1 minute each time it triggers, I just use regular incandescent lightbulbs.  (CFLs generally don’t reach full brightness for several seconds, and this is just a walk-through area).  It is a Heath-Zenith controller, and has been working great now for several years.  I just installed 2 motion-sensing light fixtures a week ago—one as a security light over my driveway, and one as a porchlight.  I now have light when I return home at night and used to fumble with keys in the dark.  Can’t comment on CFLs because I haven’t tried them in this application for the reason cited above.  I really don’t see the need for CFLs in such applications as mine.  Besides the irritation of gradual warm-up on CFLs, which make them a poor choice for such a quick walk-through application (in my opinion), there just isn’t an economic driver or significant environmental benefit.  For example, in my application, I set my lights to come on for only 5 minutes (I may change it to 1 minute later if I find 5 minutes unnecessary).  If I average 2x per evening, 365 days a year, that is only 3650 minutes per year, or 61 hours (if I reduce the timer to 1 minute this will be 12 hours!).  Since incandescents are rated for 1000-2000 hours, one bulb should last for 15 years--there is clearly no significant benefit from a CFL’s longer lifetime (assuming it DOES have a longer lifetime in this application; my own experience suggests a power spike or lightning or something will kill it first).  What about the energy savings?   Assume a 60w bulb.  That would be 3.65 kwh per year.  At current utility rates, that is about $0.50/year ($0.10/year if I switch timer to 1 minute, as I may).  A CFL might save you $0.40/year in energy costs, then.  Assume the CFL costs $3 and the incandescent 50 cents.  You are looking at about a 5+ year payback.  But I think this is questionable, as I really am coming to the viewpoint that CFLs should only be used in applications where they are on for several hours a day.  My experience of CFL failures from power spikes etc. makes me think that if you are only using them a few minutes a day, they will probably fail before their payback time.  I thus don’t use CFLs in walkthrough applications or closets.  (I do use some in areas where lights are on several hours a day, but as I’ve mentioned several times before, my track record with CFLs hasn’t been very good—they always fail way before their rated lifetimes).  If your CFL fails well before its payback time, then not only do you have an economic loss, but there is probably no benefit to the environment either, considering the mercury in the bulb, the manufacturing energy and material consumption, etc.


      On another note, I once stripped most of the switches in my home out and put in the power line controller X-10 switches, with a computer interfaced controller that set the lights on and off at optimum times, turned off lights in kids rooms when they were unlikely to be in there, etc.  I thought it would save energy.  In the end it was a total aggravation.  The switches failed quickly, and I was having to replace them after 1-2 years.  That is unacceptable.  After replacing several, I concluded that the technology just wasn’t ready and I gradually replaced them all with conventional switches.  An expensive lesson.






      From: hreg@yahoogroups.com [mailto: hreg@yahoogroups.com ] On Behalf Of H.C. Clark
      Sent: Friday, July 06, 2007 5:29 PM
      To: hreg@yahoogroups.com
      Subject: [hreg] motion switches and cfl's question



      I went to a meeting in a building where all the light switches had been replaced by motion switches as an energy saving measure.  I went straight to Home Depot and bought a switch to try, and it works fine, but it's expensive and the box notes that it only works with standard lightbulbs.  Any thoughts on switches, prices and compatibility with cfl's would be appreciated.  Thanks.

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