12V fitting with 220V lamps

[Slow Blow]

Just to stir things up a bit, how many electricians attach an in line fuse to a 12 volt lamp fitting (between transformer and lamp), I once had to do this to an entire shopping mall.

[Leecatt]

Just to stir things up a bit, how many electricians attach an in line fuse to a 12 volt lamp fitting (between transformer and lamp), I once had to do this to an entire shopping mall.

Kindly expand on this story so that we can have an idea of the circuitry

[AndyD]

I'm guessing it was because the transformers that were installed had no fuse on the secondary side like they're supposed to.

[Leecatt]

I'm guessing it was because the transformers that were installed had no fuse on the secondary side like they're supposed to.

Andy as far as I am aware a 50 va transformer does not need a fuse.

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.

However, multiple circuits that are fed from a larger transformer must have overload protection on the secondary cables to protect the cable.
As an example: A 300VA transformer supplies 6 x 50 VA light fittings each supplied by a 1.5mm cable, 2 meters long.
One light draws 4.2 amps
Each cable must be protected via a 10 amp circuit breaker in order to protect the cable during a short circuit.
One common 10amp circuit breaker can be used to protect all the cables but this will be impractical as it will trip under load.
The transformer and circuit breakers must be housed in a ventilated box and all cable glanded individually.
See 7.9.3.2.2

It just seems a lot easier for each light to have it own transformer.

Additionally, the 50 VA transformer housing can not be used as a junction box, or a looping box, unless it is designed to used as such, which they are not.
A 3 way looping box must be used on the supply cable and a single cable feed into the transformer.

This is the correct way to install low voltage lighting

[Slow Blow]

Andy as far as I am aware a 50 va transformer does not need a fuse.

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.

However, multiple circuits that are fed from a larger transformer must have overload protection on the secondary cables to protect the cable.
As an example: A 300VA transformer supplies 6 x 50 VA light fittings each supplied by a 1.5mm cable, 2 meters long.
One light draws 4.2 amps
Each cable must be protected via a 10 amp circuit breaker in order to protect the cable during a short circuit.
One common 10amp circuit breaker can be used to protect all the cables but this will be impractical as it will trip under load.
The transformer and circuit breakers must be housed in a ventilated box and all cable glanded individually.
See 7.9.3.2.2

It just seems a lot easier for each light to have it own transformer.

Additionally, the 50 VA transformer housing can not be used as a junction box, or a looping box, unless it is designed to used as such, which they are not.
A 3 way looping box must be used on the supply cable and a single cable feed into the transformer.

This is the correct way to install low voltage lighting

Leecatt is correct, but, The Western Cape Approved Electrical Inspection Authority has made the local rule of having to put an in line 10 amp fuse between even a 50w transformer and the lamp, so I just do it anyway to avoid any legal complications in the event of an accident.
I don't know if this is approved by, err, who approves things electrical nowadays