Friday, May 22, 2015

3 Way Sockets Vs. 3 Terminal Sockets

Lamp sockets come in a variety of styles, colors, finishes, materials, and flavors. Note: Don't check the flavor of your socket while the lamp is plugged in! There are seriously a lot of things to choose from, but did you know there are also different socket interiors? The socket interiors sit inside the socket shell and come in keyless, push-thru, pull chain, and turn knob. Maybe the most complicated socket interiors are the 3 way and 3 terminal interiors. Begs the question....

What's the difference between 3 Way and 3 Terminal Sockets? 

3 Way Sockets

3 Way sockets have two contacts inside the socket and are made to burn 3 way bulbs. If you look at the bottom of the 3 way bulb there are two contact points on the bulb to match the contacts in the socket. 3 way bulbs have two filaments inside the glass. The 3 way socket allows the filaments to burn independently or in tandem.

3 Way Socket Ineriors
3 Way sockets will burn a standard bulb, but there will be an extra rotation from on to off. 3 way sockets are turn knob or pull chain sockets; they will never be keyless or push-thru. Mogul sockets are also 3 way, but require a mogul bulb.

3 Terminal Sockets

3 Terminal sockets are often confused with 3 way sockets but work completely different. They are designed to run an additional circuit; mostly used for another keyless socket. They are commonly found in 3 tier lamps or Gone-With-The_Wind style lamps. 3 terminal sockets have only one contact with the bulb.

3 Way Socket and 3 Terminal Socket Comparison
 The 3 terminal socket has 3 screws on the bottom for the wires to connect to the different bulbs. The broad headed screw connects the two smooth wires from the plug wire and the other socket. The brass screw connects to the smooth plug wire and the black screw connects to the smooth wire going to the other socket.

Wiring a 3 Terminal Socket Interior
Unlike the 3 way, a 3 terminal could be a turn knob socket or be keyless socket with a 2 circuit switch. Here are some examples of the type of lamps requiring a 3 terminal socket:

If you are repairing a lamp and come across one of these types of sockets, you have just entered the next level of repair. Congratulations!