What must be installed according to the manufacturer's instructions regarding SPD?

The correct choice relates to the grounding conductor, which is essential for the safe and effective functioning of surge protection devices (SPDs). When installing SPDs, adherence to the manufacturer's instructions ensures that these devices can properly channel any surge energy, such as from a lightning strike, away from sensitive electronic equipment. A grounding conductor provides a crucial path for this energy, allowing it to dissipate safely into the ground and thereby protecting the electrical system and connected devices.

In the context of surge protection, an effective grounding system is vital because it minimizes the risk of equipment damage and electrical hazards. If the grounding conductor is not correctly installed according to the manufacturer's specifications, the entire SPD system may fail to operate as intended, leaving equipment vulnerable to surges.

The other options, such as lightning rods, circuit breakers, and surge protection devices, are important components of an overall lightning protection system, but the grounding conductor specifically must be installed following precise instructions to ensure that the SPDs function correctly. This emphasizes the importance of grounding in protecting electrical systems from transient overvoltage events.