Sockets, also known as tombstones, come in two varieties: shunted and non-shunted. Knowing which kind of socket your lighting needs is important, using the wrong kind socket can cause electrical shorts, melting, and even fires.
Telling the Difference:
Shunted sockets have internally connected electrical contacts, which provides a single track for the current to travel through the ballast to the socket and then to the lamp’s pins. Non-Shunted sockets use two tracks for the current to travel, and their contacts are not connected. Shunted tombstones get voltage from a single set of wires that get spread to two contacts. While non-shunted tombstones use two wire tracks to send voltage to each contact.
When to Use Shunted vs. Non-Shunted Sockets: Bi-Pin Lamps
Shunted: T8 (Instant-Start Ballast), T8 (Plug-and-Play), T5 (Plug-and-Play
Non-Shunted: T12, T8 (Rapid-Start/Programmed-Start/Dimming Ballast), T5 (Rapid-Start/Programmed-Start/Dimming Ballast), T8 (Direct Wire), T8 (Remote Driver), T8 (Magnetic Ballast)
Don’t be shy about talking to an electrical expert if you’re unsure about which kind of socket to use.