 Low voltage cabling layout
Most
good garden lighting works at 12 volts, so you need to locate transformers
in the garden and use flexible low voltage cable from the transformer
to the lights themselves. Cable loses voltage according to its
length and the number & power of lights you connect to it,
so keep low voltage cable runs as short as possible to optimise
the performance of your lights. We use 2 types of low voltage cable
as standard;
- 2.5mm2 ground burial low voltage cable for spike
mount spotlights, recessed uplights and other ground mounted
light fittings. The cable is run under bark or gravel mulch to
aid flexibility in locating lights. Protective conduit may be
used where cable might be vulnerable. (TIP - garden with a
fork rather than a spade until you are sure there are no lighting
cables or irrigation pipes where you want to plant your new shrub!) It
is supplied in 50 metre reels (part number T9912) or 25m reels
(T9913). Cable clips are available in boxes of 100 (part number
T9951)
- 2.0mm2 exterior low voltage cable for surface mount
spotlights fixed on pergolas, in trees & on walls. This flat
cable can be installed more unobtrusively up structures than
the thicker ground burial cable. It is supplied in 100 metre
reels (part number T9920), 50 metre reels (T9921) or 25m reels
(T9922). Cable clips are available in boxes of 100 (part number
T9952)
Observe the following maximum cable runs (in metres) to limit
voltage drop within these cables;
|
Lamp watts
|
20
|
20*
|
20*
|
20**
|
20**
|
35
|
35*
|
35**
|
35**
|
50***
|
75***
|
100***
|
|
Number of lamps
|
1
|
2
|
3
|
2
|
3
|
1
|
2
|
2
|
3
|
1
|
1
|
1
|
|
Ground burial cable run
|
20
|
10
|
6.7
|
13
|
10
|
12
|
5.7
|
7.6
|
5.7
|
8
|
5.3
|
4
|
|
Exterior cable run
|
15
|
7.5
|
5
|
10
|
7.5
|
8.6
|
4.3
|
7.6
|
5
|
6
|
4
|
3
|
*lamps at end of the cable ** lamps equally
spaced along the cable
*** lights with lamps of 50 watts or higher should
be individually wired from the transformer in most installations
Tips on transformer location and cabling
- Keep cables runs from transformers to light fittings as short
as possible to ensure optimum performance
- Locate a transformer centrally amongst a group of lights it
is to power; for example, with lamps of up to 50 watts a radius
of 8 metres defines the area of coverage for spike mounted lights
from one transformer.
- If you want 2 sets of lights in an area to be operated by separate
switches, you must provide a separate transformer for each group
of lights and a separate mains supply to each transformer.
- If the distance from the proposed transformer position exceeds
the maximum cable route for a single light, either revise the
transformer layout, increasing the number of transformers to
reduce the low voltage cable runs, or use thicker cable.
- If the cable run for multiple lights connected to a single
cable exceeds the maximum shown, divide the lights onto individual
cables.
Copyright 2003; Lighting for Gardens Limited.
Light fittings can become hot in use; exercise appropriate precautions.
Exterior electrical installations should be undertaken
by a qualified electrician
|
