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Technical Info

Low voltage garden lighting

The majority of modern garden lighting works at 12 or 24volts. To be able to operate these lights at 12 or 24 volts you will require a driver or transformer. These devices alter the voltage usually from 230 volts to 12 or 24volts. There is a very good reason for this reduction and that is safety. If the cable running to the light is damaged it will not harm anyone because the voltage is so low. However, if the cable were 230 volts and it became damaged it could quite easily kill someone (if an *RCD is not working properly or fitted).

*RCD is a Residual Current Device is a life-saving device which is designed to prevent you from getting a fatal electric shock if you touch something live, such as a bare wire.

Low voltage garden lighting still requires 230 volts (up until the transformer/driver) and this is fed by using steel wired armoured cable. This should be buried below the ground (regulation of 500mm/18 inches) and covered with a yellow warning tape. However due to the low voltage cable being 'safe', the cable can be covered with mulch or left just below the soil surface.

Depending on how many lights you are trying to illuminate will determine the size of the transformer. However, low voltage cable may reduce in voltage if the amount of lights fitted extends over a long distance (see voltage drop chart below) It is preferable to keep the number of lights used to a minimum, otherwise this will result in a voltage drop and the lights will become dim.

It is important to note that although these lights are low voltage, the halogen fittings can still become hot. This will depend on the wattage of the lamp used i.e. 50 watt will be hotter than a 20watt lamp. The material used for the fitting will also make a difference to the overall heat eg a stainless steel fitting will retain its heat for longer than a aluminium fitting. With any lighting it is advisable to be sensible when changing lamps or moving the fittings. Always wear gloves to change the lamp or when re-positioning the unit if it has been on for some time.


However, LED's create very little heat and are often warm to touch. Please note that if in doubt please do not touch any bulb/fitting if they have been switched on.

An approved quality light fitting should always carry an IP rating (as below). This indicates how well it will stand up to external conditions.

The installation of external lighting should be carried-out by a professional who knows the correct procedures and uses equipment that will keep it safe.

Voltage drop chart

Load in Watts
2.5mm cable
(metres)
4mm cable
(metres)
6mm cable
(metres)
10mm cable
(metres)
20w
40w
50w
60w
70w
80w
90w
100w
120w

40
20
16
13
11
10
8.5
8
6
65
32
25
20
18
16
14
13
10
97
48
38
32
27
24
21
19
16
164
81
65
54
46
40
35
33
27

 


Lighting IP Ratings

IP numbers are often quoted on lighting enclosures, connectors and fittings etc., to indicate protection from solids, liquids and impact. The table below gives a description of these ratings. Note that the third number, protection ainst impacts, is often omitted.
 

First Number
Protection ainst solids

Second Number
Protection ainst liquids

Third Number
Protection ainst mechanical
impacts (often omitted)

0

No Protection

No Protection

No Protection

1

Protected against solid
objects over 50mm

Protected ainst vertically
falling drops of water

Protected ainst impact
of 0.225 joules

2

Protected against solid
objects over 12mm

Protected ainst direct sprays
up to 15° from vertical

Protected ainst impact
of 0.375 joules

3

Protected against solid
objects over 2.5mm

Protected ainst direct sprays
up to 60° from vertical

Protected ainst impact
of 0.5 joules

4

Protected against solid
objects over 1mm

Protected ainst direct sprays
from all directions - limited
ingress permitted

Protected ainst impact
of 2.0 joules

5

Protected against dust -
limited ingress permitted

Protected ainst low pressure
jets from all directions -
limited ingress permitted

Protected ainst impact
of 6.0 joules

6

Totally protected
against dust

Protected ainst strong jets
from all directions -
limited ingress permitted

Protected ainst impact
of 20.0 joules

7
 

Protected ainst effects of
immersion from 15cm - 1m
 

8
 

Protected ainst long periods
of immersion under pressure