Cartridge fuses of the renewable type are allowed for replacement only in existing installations if which condition is met?

Cartridge fuses of the renewable type can only be replaced in existing installations if there is no evidence of over-fusing. This is crucial because over-fusing occurs when a fuse rated for a certain amperage is replaced with one rated for a higher amperage than appropriate for the wiring and devices connected to the circuit. Over-fusing can lead to overheating and potential fire hazards, as the circuit is not protected adequately against overcurrent.

In this context, confirming that there is no evidence of over-fusing ensures that the electrical system is being maintained safely and in accordance with the electrical code. It is a measure to guarantee that the system continues to provide the necessary protection without compromising safety.

The other options do not address the critical safety and code compliance factors related to the replacement of fuses, which is why they are not considered valid conditions for replacement in such contexts.