In article ,
ARW writes:
On 21/04/2018 12:44, Andrew Gabriel wrote:

Occupancy sensors driving flouresents is not ideal, but if you just
accept you'll get shorter tube life, and they won't have run up to
final output before you finish using the room, then it can be done.
I have 3 x 58W fluorescents in my internal garage where the freezer
is on occupancy sensor. I replaced the ballasts with electronic
instant start (that's real instant start, not even a few milliseconds
preheat), and they're on a 20 min timer. I think they're on their
second tubes in 15 years, although the total 'on' duration wouldn't
come close to merit that. If I was doing it now, I would use LEDs
of course.

How long would you set the timer for if they were LED?

Long enough not to go off while you are in the room, and add
a bit for good measure. The power rating would only be around
half, so any wasted 'on' time costs correspondingly less anyway.
Frequency of switching has no effect on LED life, and probably
just a tiny amount on the driver, which you can ignore.

--
Andrew Gabriel
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