Why was a fluescent light wired this way

[EFLImpudence]

Although the short circuit current with a 6 A protective device is not 6 A but something higher time is also reduced so the likely hood of welding contacts with 6 A is less than with 10 A or 16 A

Is it?

so although it is permitted to have 16 A protective device a 6 A one is far better.

It may be 'better' in the sense you mean it, but if a 10A or 16A MCB were required for valid reasons then fitting a 6A is not possible.

As to speed that depends on protective device and the loop impedance and with a MCB if within the limits then it should not make any difference, however although short circuit when found do not know if it went full short circuit straight away?

Yes, but the loop impedance of the circuit isn't altered by the protective device you choose to install.

If it is low enough for a 10A or 16A then that might be 'better' than a loop impedance just low enough for a 6A.

Are you contemplating fitting lower rated MCBs (than the cable will allow) on socket circuits?

 

[JohnW2]

It may be 'better' in the sense you mean it, but if a 10A or 16A MCB were required for valid reasons then fitting a 6A is not possible.

Quite. There is an argument that it makes sense to use an MCB rated not much more than the anticipated loads (even if it would then be lower-rated than the cable would allow), so as to catch at least some of eric's more-than-negligible-impedance faults. If one took that approach, one probably would usually protect a standard 'lighting' circuit with a B6 (or maybe, these days, even a B3, or lower, if available), but if one wanted to put 13A socket(s) on the circuit, then use a B16 (cable allowing).

Are you contemplating fitting lower rated MCBs (than the cable will allow) on socket circuits?

Indeed, as I say, once one starts considering more-than-negligible-impedance faults, then one presumable would consider down-rating the OPDs on most types of circuit.

Kind Regards, John