What should be installed when replacing a transformer to address the original unit's failure?

When replacing a transformer, it is essential to install a fuse on either the primary or secondary side. This is because fuses are designed to protect the electrical circuits by breaking the connection when there is an excessive current flow, which can occur during short circuits or overload conditions. By installing a fuse, it helps prevent damage to the transformer and any connected components, addressing the underlying issues that may have contributed to the original unit's failure.

Fuses serve as a critical safety mechanism, ensuring that any faults in the electrical system can be isolated quickly and effectively. This safeguard helps in maintaining the integrity of the electrical systems and prolongs the lifecycle of the new transformer by reducing the risk of similar failures.

Other options such as circuit breakers, surge protectors, and overload relays serve different purposes. While circuit breakers also provide protection similar to fuses in the form of automatic interruption of the circuit during faults, they are not specifically required as an immediate fail-safe for a transformer replacement unless stipulated by specific design guidelines or codes. Surge protectors safeguard against voltage spikes, which may not directly relate to the cause of transformer failure. Overload relays monitor the motor's current and disconnect power under overload conditions but are typically used in conjunction with motors and not directly with transformers