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GBlist: Re: greenbuilding-digest V1 #273

Fluorescent Lighting Discussion

The gentleman from New Zealand was absolutly correct.  The inrush of current
happens so fast that this spike does not affect your electric bill.  Hook a
fluorescent up to a watt meter and you can see the spike only monentarily.

In regards to the affect on lamp life, fluorescent tubes are rated for lamp
life based on a 3 hour start.  The lamp is turned on for 3 hours, turned
off, allowed to cool down and then restarted.  Most linear fluorescents are
rated with a lamp life of 20,000 hours.  This means that if the lamps were
started every 3 hours then at 20,000 hours of life, 50% of the lamps would
still function the other 50% would be burned out.  If you turn the lamp on
and off more often lamp life is shortened, if it is turned on and off less
often lamp life is increased.  Economically it is still best to turn the
lamps off.  Life cycle costing (LCC) analyses of fluorescent lighting
systems shows that the cost of the tubes is about 1% the LCC.  Energy is 80%
to 90% of the LCC.

In regard to the ballasts, a rapid start electronic ballat should be used in
combination with motion sensors.  Rapid start ballasts will provide about
20,000 starts.  Instant start ballasts will provide about 5,000 starts but
slightly greater efficiency.  

Many years ago the Navy performed a study that demonstrated that fluorescent
tubes should be turned off whenever possible.  Their results showed an
economic threshold of 30 seconds.  This was the point at which the energy
savings offset the loss of tube life.  I don't recommend 30 seconds, but
certainly if you will be out of the room for 5 or 10 minutes, turn off the

Marcus Sheffer, Energy Consultant
Energy Opportunities
1200 E Camping Area Rd
Wellsville, PA  17365
717-292-2636 v

>> Ken:
>> About the motion sensor thing with fluorescents - my understanding is
>> that it takes the amount of power that it would take to run a
>> fluorescent tube for 3-4 hours in order to turn it on
>> My father, who worked with lighting a lot had told me this, and when
>> I checked recently with my local power company they said no, but then
>> I checked with the engineering dept at Philips, and they said yes,
>> this was still a fact.
>> What is your understanding of the situation?
>> Marilyn
>> Keep on keepin' on.

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