Yes, it is generally recommended to replace the sockets when changing out lights from T12 to T8. Here are a few reasons why

Different Electrical Requirements:

T12 and T8 bulbs have different electrical requirements. T12 bulbs operate at a higher voltage and lower amperage than T8 bulbs. The sockets are designed to match the electrical characteristics of the specific bulb type. Using an incompatible socket can lead to electrical problems, such as flickering, overheating, or premature bulb failure.

Shunted Sockets

As you mentioned, some T12 sockets are shunted, meaning they have a metal jumper connecting the two pins of the socket. This jumper provides a complete circuit when a T12 bulb with a single-ended base is used. T8 bulbs, on the other hand, have a double-ended base and do not require a shunted socket. Using a shunted socket with a T8 bulb can create a short circuit, damaging the bulb or the ballast.

Ballast Compatibility

The ballast, which is the device that provides the electrical power to the bulbs, must be compatible with the type of sockets being used. Ballasts for T12 bulbs are typically different from ballasts for T8 bulbs. Replacing the sockets ensures compatibility with the new ballast.

Safety

Using incompatible sockets or a mismatched ballast and bulb combination can create electrical hazards, including the risk of fire or electric shock. Replacing the sockets with the correct type for T8 bulbs helps ensure the safety of the lighting system.

Note: The ballast diagram should indicate whether the sockets are designed for T12 or T8 bulbs. If the diagram does not specify, it is best to replace the sockets to avoid any potential issues. Flag for review