Why is it that the installation instructions for fluorescent light fixtures say not to control the light with a photocell switch?

Cliff

Cliff,
I can't see anything wrong with controlling fluorescent lighting with a photocell.
But, I would be careful with selecting the photocell, to make sure that the contacts in the cell can safely make and break the Inductive currents that fluorescent lights generate.

Trunpy,

AHA! Now I understand...

Thanks.

Merry Christmas and a Happy New Year.

Cliff

I believe that there are photo controls out there that do not use a relay but rather a triac in the same way a dimmer does. They only go full on and full off however the waveform can be distorted like that of a dimmer and this is not suitable for fluorescent ballasts.

I think that the ballast manufacturer is just being cautious. Make sure that your photocontrol uses relay contacts and you will be OK.

-Hal

I 2nd Hal's opinion. I've seen several of the photo units that "flicker" an incandescent in the twilight hours. I can only imagine the havoc that would cause with some of the cheaper imported fixtures...

I had an $8 photocell go bad that was controlling some fluorescent lights. I hacksawed the thing open, and sure enough it was the relay type.

For some reason, the neutral connection had vaporized, and that's why it went bad.

Peter

Personally I'd switch any decent sized Fluorescent installation through a Contactor by cascading the control switch or relay contact with the Contactor coil.
Sure, more expense, but less worries!.