CFL Bulbs & Photocells

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Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Why aren't CFL bulbs recommended for use with a photocell? Also, would a lamp post type exterior light be considered exposed to the weather?
 

Little Bill

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Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Lots of photocell units use off-mode current flow through the incandescent lamp to derive their operating power. No flow, no operation.

I have several post lamps that I take care of. The property manager told me to use CFL bulbs in the lamps, because he wants them to last longer and that's what he has been using. They are all controlled by a photocell. I haven't seen any problems with the CFLs controlled by the photocell but I saw on the package that they weren't recommended for use with a photocell. I just wondered why. It also said not for use where exposed to weather. They are in an enclosed housing with plexiglass sides. I haven't had any problems there either. I just don't want problems down the road.
 

broadgage

Senior Member
Location
London, England
In practice it seems to depend on the type of photocell.
Some small ones use a solid state circuit, and these generally dont work correctly with CFLs

Others use a relay, these normally work fine.

On large installations it is usuall to switch the lamps by a contactor, controlled by a photocell. That will be fine, the lamps dont "know" what controlls the contactor.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
In practice it seems to depend on the type of photocell.
Some small ones use a solid state circuit, and these generally dont work correctly with CFLs

Others use a relay, these normally work fine.

On large installations it is usuall to switch the lamps by a contactor, controlled by a photocell. That will be fine, the lamps dont "know" what controlls the contactor.


Thank you broadgage. The lights have been working fine, I just saw this info on bulbs spec sheet and didn't know why they weren't recommended to be used with a photocell. This makes sense to me. :thumbsup:

As far as them lasting outdoors in the enclosed post lamps, time will tell.
 
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