What is the difference between a transformer and a power supply ?
A transformer provides alternating current (a.c.) output of 12 volts; 12v ac from a wire-wound (magnetic) transformer is used to
power halogen lights in the
Elipta
range. A dc power supply provides direct current (d.c.) which is compatible with
Elipta
l.e.d.
lights: use a regulated 12v DC power supply to ensure stable voltage to a group of
Elipta
l.e.d. Lights. The power supply should
be installed close to the lights as long cable runs can induce instability in l.e.d. lights run from a dc power supply. For larger l.e.d.
installations, a 12v ac wire-wound transformer may be used provided it is loaded to at least 80% of it’s nominal rating, eg 32w on
a 40va transformer.
Electronic transformers should not be used with l.e.d. lights and lamps.
What size of transformer do I need for halogen lights?
A frequently asked question is “how many lights can I run from one
transformer”? In fact, transformers are available in a wide range of
wattage ratings, so look at the question in reverse: “what size of
transformer do I need to power a group of lights”? This is simply a
matter of multiplying the wattage and numbers of the lamps used in the
lights to be connected to the transformer, as shown in the examples. In
most cases, consider some spare capacity within the transformer
rating to allow scope to increase some lamp wattages as plants grow,
or to allow flexibility in adding a light in the future. Use
Powersaver
energy saving l.e.d. lamps which use a third less power for the same
light output to reduce transformer size.
!
Multiply the lamp wattages for each type of light as in the examples
>
!
Allow up to 30% spare capacity in the transformer to allow brighter
halogen lamps as plants grow, or for addition of extra lights
!
Transformers are available in 20, 50 or 100 watt steps, so choose
the next step up from the total wattage you have calculated
!
Check that the total load of halogen lights is at least two-thirds of the
transformer rating you propose to use; avoid using a big
transformer with only a small load (few lights and low lamp
wattages) as this can result in “overvoltage” which reduces lamp
life and causes premature failure.
What size of power supply do i need for l.e.d. lamps?
Look at the question in reverse: “what size of power supply do I need to
power a group of l.e.d. lights”? This is simply a matter of multiplying the
power consumption in watts numbers of l.e.d. lights or lamps to be
connected to the power supply, as shown in the examples. Consider
some spare capacity within the power supply rating to allow scope to
add a light in the future: dc power supplies provide a regulated output
voltage, avoiding “overvoltage” which causes premature l.e.d. failure
!
Multiply the lamp wattages for each type of light or the l.e.d. power
consumption as shown in the examples (right)
!
Power supplies are available in 2 sizes - 10w and 25w - choose the
next step up from the total wattage you have calculated
!
You can use a 12v wire-wound transformer, which is less expensive
than a power supply, if the total load of for l.e.d. lights and l.e.d.
lamps is at least 80% of the transformer rating you propose to
use. Do not use a big transformer with only a small load as this will
result in “overvoltage” and cause premature l.e.d. failure
!
For l.e.d loads of less than 16w, use a 12v dc power supply
!
Do not use an electronic transformer with Elipta l.e.d. products
!
Do not use constant current l.e.d. drivers with Elipta l.e.d. products
Tips on transformer location and cabling
!
Keep cable runs from transformers to lights as short as possible to ensure optimum performance - see
Help
page for advice
!
Locate a transformer centrally amongst a group of lights; 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. Most transformer models have a single low voltage
output cable: use an exterior junction box of appropriate size alongside the transformer to connect to cables running to
individual lights or groups of lights.
!
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 transformer position exceeds the maximum cable length recommended for a single light, revise the
transformer layout ( increasing the number of transformers to reduce the low voltage cable runs) or use thicker cable such
2
2 2
as T9910 4.0mm . To connect a light to 4.0mm cable use a T9963 cable splice kit; to connect 2 or more lights to a 4.0mm
cable use an exterior junction box of appropriate size for above-ground connections or a T9969 underground joint kit.
!
Use
Powersaver
energy-saving halogen lamps to reduce power consumption, which increases the permissable cable length
!
Use l.e.d. lamps instead of halogen lamps to reduce power consumption, which increases the permissable cable length & size
!
If the cable run for multiple lights connected to one cable exceeds the maximum shown, divide the lights onto individual cables.
!
In gardens with lighting or irrigation, 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!
Recessed uplight
1
50
50
Underwater light
1
35
35
Steplight
2
20
40
Wall spotlight
2
20
40
Total
7
165
Spare capacity
35
Transformer rating
200
Spike spotlight
2
50
100
Wall up/downlight
2
40
80
Wall spotlight
1
20
20
Spreadlight
2
20
40
Total
7
240
Spare capacity
60
Transformer rating
300
Naviagtor Minor
10
0.5
5
Navigator Major
5
1
5
Navigator Eye
2
2
4
Half eyelid steplight
2
0.6
1.2
Total
19
15.2
Spare capacity
4.8
Transformer rating
20
3 x 1w MR16 blue
2
5
10
3 x 2w MR16 white
4
6
24
1w MR11 white
2
2.4
4.8
MR16 colour change
2
2
4
Total
10
42.8
Spare capacity
7.2
Transformer rating
50
Low voltage
halogen lights
Number
of lights
Lamp wattage
Total
wattage
Number
of lights
(W) Power
consumption
Total
wattage
Lights with led
modules fitted
Examples: transformer & power supply selection
LED lights
Number
of lights
Total
wattage
(W) Power
consumption
Low voltage
halogen lights
Number
of lights
Lamp wattage
Total
wattage
45