Date: Tue, 14 Apr 1998 07:59:20 -0400 From: carlstrom_rick@advmar.com To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1251$foo@default> Subject: Fixtures
Just to add my 2 cents worth.
The equation:
power = volts * amps
is really only true for DC circuits. If you have an AC circuit the
equation is fine if you use RMS volts and amps and have a PURE RESISTIVE
LOAD. Florescent lights are not pure resistive loads. In other words
the current and voltage are somewhat out of phase. This introduces a
power factor. For AC circuits that have some inductive component the
equation is:
power = volts * amps *power factor
Again using RMS volts and amps. FYI AC induction motors have a power
factor of about 0.6. A toaster (being a pure resistive load) has a
power factor of 1.0. The real problem with low power factors is that
they increase your amps and therefore increase your resistive line
losses in the circuit.
Anyway, all of this really does not matter since the florescent bulbs
are labeled with a wattage. More important, you must consider
efficiency. The new electronic ballasts are much more efficient than
the old magnetic ones. A new 34 watt (T-8) bulb hooked up to an
electronic ballast puts out more light (lumens) than an old 40 watt
(T-12) bulb hooked up to a magnetic ballast. They also loose less light
over their usable life span than the old 40 watt bulbs.
Oh and by the way the 40 watt bulbs can no longer be produced BUT the
manufactures simply stockpiled tons of them while it was still legal.
Also the environmental law only covers standard 40 watt bulbs, not any
specialty (aquarium, plant, reptile) bulbs.
To sum it all up, I would get a 4 tube fixture with an electronic ballast and
put new 34 watt T-8 bulbs in it.
Rick Carlstrom
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