downlighters

[murdock]

12 volt and 230 volt downlighters.

mounting the transformer?

exposed wiring?

fuses for the output side?

distance from the transfomer to the lamp?

using a 300 va transformer and sizing the conductors?

[AndyD]

Hi Murdock,
Have you a particular installation you are enquiring about or are you just asking about the general rules that apply?

12 volt and 230 volt downlighters.

You can't really lump the 12v and 230v lighting systems into one question because they fall under a completely different set of rules.

mounting the transformer?

There's various rules covering the mounting and positioning of transformers.

7.9.3.1.1 Components shall be mounted in an enclosure, ventilated
where necessary

7.9.4.4 Transformers, protective devices or similar equipment mounted
above false ceilings that are moveable, or easily accessible, or in a
similar place, shall be mounted on a fixed part of the building such as a
beam, and information shall be given about its presence and location

7.9.3.3.1.4 The ELV power source shall not be installed above the lamp
or within 200 mm from the lamp to any side unless a heat barrier is
installed between the lamp and the power source.

exposed wiring?

On the primary side (LV) or secondary side (ELV) ??

7.9.4.1 Primary terminals of the supply source shall be in an enclosure.

7.9.2.4.1 Bare conductors may only be used in an extra low voltage
lighting installation system if
a) the nominal voltage does not exceed 25 V a.c. or 60 V d.c.,
b) the wiring system is made up of compatible components and complies
as a complete unit with SANS 60598-2-23/IEC 60598-2-23
(SABS IEC 60598-2-23), and
c) the conductors are at least 1 m from the thatch under a thatched roof.

7.9.2.4.2 If both circuit conductors are uninsulated and supplied from a
convertor that complies with SANS 61347-2-2/ IEC 61347-2-2
(SABS IEC 61347-2-2)), the power of the convertor shall not exceed
200 VA. Amdt 1; amdt 3

fuses for the output side?

It depends...

7.9.3.2.2 Each secondary circuit of a safety extra low voltage (SELV)
supply source (transformer or convertor) shall have overcurrent protection
(see 6.7.1 and 6.7.2). The overcurrent protection may be either by a
common protective device, or a protective device for each SELV circuit.

7.9.3.2.3 A protective device shall be readily accessible unless it is built
into the supply source and is of the automatic resetting type.

7.9.3.2.4 Secondary overcurrent protection is not required where the
maximum output of the SELV transformer is 50 VA, the secondary circuit
conductor is at least 1,5 mm2, not exceeding a length of 2,5 m, and at
least one conductor and its terminals are insulated to prevent a short
circuit. Amdt 1

distance from the transfomer to the lamp?

Can vary but cable must be sized accordingly, see attached table. Also last 200mm must be class H;

7.9.3.3.1.3 At least 200 mm of the conductors leading from an ELV lamp
holder shall be 180 °C (class H) flexible conductors such as siliconrubber-
insulated conductors. The lamp holder shall also be suitable for an
operating temperature of at least 180 °C. Amdt 3

using a 300 va transformer and sizing the conductors?

Again see attached table, depends on length.

[murdock]

lets start with components should be mounted in an enclosure and ventilated?

the question...is the transfomer regarded as being in an enclosure as it is supplied...because if not then i could spend the rest of my working life going around condeming all the installations?

the second question...twin and earth suppling the transformers on top of the battens or under the battens?

if on top do they need to be mechanically protected form people climbing and working in the roof?

[Jacques#1]

The roof is deemed a "traffic free" environment. The twin and earth does not have to be suitably stayed, it can just lie on the ceiling. Secure the connections by adding a clip to the wire/on the beam at the point of exit and the point of entry in the length of the cable.

Transformers has its own specific section in the book, so they fall under their own specific category. I would assume that the black transformer which comes with a small cover that fits over the supply side terminals is fine as is....so is the single 50VA transformers, also have the cover (they are also double insulated if I am not mistaken?).....if using an uninsulated transformer like one you would find in a swimming pool, then I would say no, that must go in an enclosure.