DOUBLE-ENDED LIGHTING
Working in a hydroponics shop,
I am frequently asked by customers how the new range
of double-ended, high
pressure sodium (HPS)
globes are different than
their single-ended, HPS
counterparts and why they
do not work effectively with
that circa 1996 magnetic ballast
they found in the basement.
Horticultural lighting has come
a long way in a short period of
time and to understand why
these updates are worth the
expense, it is helpful to illuminate a bit more about HPS
globes in general.
Single-ended HPS globes have
been the industry standard
when it comes to grow lights
for decades. They have a typical
E40 Edison screw thread and
produce a warm, yellow light,
making them exceptionally
good for flowering or fruiting
plants or as supplementary
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“SINGLE-ENDED HPS GLOBES HAVE BEEN
THE INDUSTRY STANDARD WHEN IT
COMES TO GROW LIGHTS FOR DECADES.”
lighting when combined with
the sun. HPS globes are part
of the high intensity discharge
(HID) family of lamps that
produce bright light by heating
an electric arc contained inside
a tubular housing. An electric
current flows between electrodes
on either end of the arc tube,
vaporizing mercury and sodium
into a gas to generate heat and
light. These high-powered lights
require a ballast to provide a
burst of high voltage to initiate
the arc and once established, it
swiftly reduces the energy and
regulates the electric current
to produce a consistent light
Maximum Yield USA | November 2015
output. HPS lamps are designed
to operate at extremely warm
temperatures and sustaining an
optimal electrode heat is the key
to long lamp life.
The DE Difference
So how are double-ended HPS
lamps different than single-ended
HPS lamps? Double-ended HPS
lamps, used by commercial
growers for about 10 years, have
rapidly grown in popularity with
hobby growers over the past five
years. The physical differences
to single-ended lamps start with
their attachment to the reflector.
Unlike the Edison screw thread of