Fixture Selection
Once all of the lamps needed for
the system have been identified you need to select the fixtures that
will hold and protect the lamps. There are several factors to consider
when selecting fixtures:
·
Lamp Type. The fixture
selected must accommodate the lamp we have selected in both the lamp
connector and the physical size of the lamp. MR16 and MR11 lamps have a
2 pin base, but the 2’ wide MR16 will not fit into fixtures designed for
the 1 3/8” MR11.
·
Mount. The fixture must
have a way to be mounted in the location where it is to be used.
Additionally, if the fixture is stake mounted you need to be sure that
the correct length is available.
·
Materials. Fixture
bodies are made with a wide choice of materials: copper, brass, bronze,
aluminum, steel, composites, and plastics or a combination of two or
more of these materials. Durability and appearance varies considerably
between these materials. If the fixture is to be used in a harsh
environment such as a coastal location, copper or brass fixtures may be
worth the additional investment. Replacement not only involves the cost
of the fixture but also the labor to remove the old fixture and install
the new one.
·
Aesthetics. Fixtures are available that are as plain as a
soup can and they are available as pieces of art. There’s no right or
wrong answer here – “beauty is in the eye of the beholder.” Manufactures
have designs that project various themes such as garden, Oriental,
Contemporary, and Craftsman styles. This allows the designer to include
the lighting in developing the overall look of the project.
·
Budget. Fixtures range in price from a few dollars to several
hundred dollars. Quality fixtures can be found in the range from $30 to
$150. Spend less than that and you should expect quicker replacement and
perhaps disappointing results. More than that and you are showing a lot
of art appreciation.
For path and area
lighting the fixture plays a more important role in how much light is
projected and where it will illuminate. Manufacturers of these types of
fixtures often provide photometric data for the fixture with the
recommended lamp that can be used in the fixture. Although the amount of
detail provided varies, manufacturers usually list the lamp used, and
the illumination levels at various distances from the fixture measured
in footcandles. Often there is a significant difference between similar
fixtures as in the example below.
 
Source: Hadco Nightlife Catalog HNL02300
Both of these Hadco
path Lights are similar in design and both are copper fixtures. However
the GATL1-AC uses a 12 volt, 27 watt, 1156 bulb and GAL1-AC uses a 12
volt, 20 watt, T3 bulb. Although the GAL1-AC has the higher wattage lamp
and produces 16 footcandles at a distance of 1 foot, the light output
falls below 1/10th footcandle at less than 6 feet. The lower
wattage GATL1-AC provides more than 1/10th footcandles all
the way out to 8 feet.
There can also be a
significant difference between similar fixtures with the same lamp.
 
Source Kim Lighting
The two charts above
are for path lights manufactured by Kim Lighting. They both use 25 or 50
watt A19 lamps. The KLV110 is approximately 30” high while the KLV115 is
only about 16” high. However, with lamps of the same wattage, the KLV110
has twice the illumination of the KLV115 at 2’. However the light falls
off more rapidly with distance for this fixture than the KLV115. This is
because the KLV110 fixture globe focuses the light more directly towards
the ground. The light from the lamp in the KLV115 is reflected by the
top of the fixture over a broader area.
The final example shows
that increasing the wattage of the lamp increases the level of
illumination of the fixture but it is basically in the same area.
Source Kim Lighting
This chart is for Kim
Lighting’s KLV60 path light. As you can see from the two right hand
columns the 50 watt MR16 lamp produces 6.2 footcandles at 2 feet while
the 20 watt lamp (inside right column) produces only 1.6 footcandles at
the same distance. However when you get to 6-8 feet out, neither wattage
provides very much illumination.
To select the fixtures
that best meets your needs will require browsing through several
lighting catalogs or visiting websites. All of the major manufacturers
and suppliers have websites that have photos and technical information
for their products.
As you identify the
fixture for each application write down the name of the manufacturer,
model number, lamp model, wattage, and cost: |
