Low Voltage
Landscape Lighting Design Notes
A low voltage
lighting system will consist of light
fixtures, one or more transformers (to
convert line voltage to 12V), and one or more timers.
The first decision
to be made is simply what to light. There are a good
variety of landscape lighting fixtures designed to
suit different situations, available in various wattages
or brightness levels. Walkway
lights are generally
designed to cast light downward to provide enough
light to see one's footing on a path. Spotlights and floodlights are
higher wattage and can project a directed beam on
a shrub, pond, statue or other garden feature (a
spotlight will have a more focused beam than a flood).
Various wattage accent
lights can be placed
throughout the garden for interest. Low wattage
surface mount deck
lights provide subtle
lighting on deck posts or safety lighting on stairs.
If there are to
be only a handful of lights, they can be combined
on a single circuit provided
that wattage limits are not exceeded. If there are
to be a large number of lights or several geographically
distant locations, areas or light types (i.e. walkway
or garden accent) can be divided off into separate
circuits, or zones.
If the system is controlled by timer(s), this also
allows for greater control over the light display.
The sum of the
wattage consumption of all lights on a zone or circuit
should ALWAYS BE BELOW the rated voltage of the transformer.
The most control
comes from creating many smaller zones with accompanying
smaller wattage transformers (can be especially effective
if a remote control is used).
Proper outdoor-rated low
voltage lighting wire should
be used, typically 12 or 10 gauge. This wire is specifically
designed for the rigors of outdoor existence. Use
of household wire or speaker wire is not recommended,
nor is the use of smaller gauges. The wire can be
placed in a conduit between lights or can be left
on the surface and mulched over.
All wires experience
losses over distances due to internal friction. This
means that in a long run of lights connected sequentially
on a single wire, the lights furthest from the transformer
will be noticeably dimmer than those closest. For
this reason, it is best to design any circuit like
a tree rather than like a string, balancing the amount
of wattage draw on each branch.
The General Rule:
100 watts, 100 feet. On any given circuit path from
the transformer to the most distant light on a branch,
the total distance should not exceed 100' and the
power draw should not exceed 100W. This is just a
rule of thumb but it provides a good benchmark to
work from.
Not all low voltage
transformers are approved for use with lights situated
near water (i.e. pond, spa). All lighting transformers
should be connect only to a GFCI protected
electrical outlet.
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