How To Wire Lights in Series? Basic Electrical Wiring Disadvantages of Series Lighting Circuit. The break in the wire, failure or removal of any single lamp will break the circuit and cause all.. If more lamps are added in series lighting circuit, they will all be reduced in brightness. Series Wiring is "ALL or NONE" type wiring mean all the Wiring Lights in Series : Electrical Online Wiring Lights in Series. Each fixture is connected to the hot conductor and the neutral conductor so that each fixture has the source voltage present. One example of wiring lights in series was some Christmas light strings that used to be fairly common. Again, the major negative drawback to these was when one bulb failed,..